The effect of the introduction of ICD-10 on cancer mortality trends in England and Wales

Transcription

1 The effect of the introduction of ICD-10 on cancer mortality trends in Anita Brock, Clare Griffiths and Cleo Rooney, Offi ce for INTRODUCTION From January 2001 deaths in have been coded to the Tenth Revision of the International Classification of Diseases (ICD-10), although cancer incidence data have been coded to ICD-10 since This is the first change in ICD revision used to code mortality data in since 1979, and the most important International change in codes since Although a deliberate broadening of the application of ICD-9 selection rule 3 by OPCS (now ONS) from 1984 to 1992 also had an impact on mortality statistics. 1 Information on the main changes in classification between ICD-9 and ICD-10, and changes to the mortality coding rules (including selection rule 3) have been published by ONS. 1 3 These are summarised in Boxes 1 and 2. Previous work has shown that the main changes that affect the assignment of deaths to malignant and non-malignant neoplasms are: This article examines changes in deaths assigned to malignant and non-malignant neoplasms resulting from the introduction of ICD-10 in. In particular the Government s target of reducing mortality rates from malignant cancers on those aged under 75. The main changes are highlighted and the article explains how data can be adjusted to take account of these changes so that trends in mortality rates over time can be analysed. the new interpretation of selection rule 3, which affects neoplasms Chapter II as a whole and some specific sites; the introduction of new codes for mesothelioma and Kaposi s sarcoma; a new code for malignant neoplasms of independent (primary) multiple sites; the transfer of deaths previously coded to Chapter IV (diseases of the blood and blood-forming organs) in ICD-9 to codes in Chapter II specifically to non-malignant neoplasms in ICD-10; the transfer of deaths between malignant melanoma and other malignant skin cancer; and a gain in deaths coded to malignant neoplasms of lymphoid, haematopoietic and related tissue in ICD-10. 7

2 This article looks specifically at the effect of the introduction of ICD-10 on deaths assigned to malignant neoplasm by site, and to non-malignant neoplasms, in more detail. Neoplasms accounted for a quarter of all deaths in between 1993 and The Government has set a number of health targets, one of which is to reduce malignant cancer death rates in those aged under 75. Monitoring progress towards this target depends on having comparable mortality trend data. Box one Main changes in ICD-10 including selection rule 3 ICD-10 represents the greatest change in the ICD in over 50 years. The main changes are: Box two Bridge coding study: methods To understand trends in cause-specifi c mortality spanning the change from ICD-9 to ICD-10, we need to measure the impact of this change on the number of deaths attributed to different causes of death. This is done using bridge coding, that is coding a sample of death certificates independently to both ICD-9 and ICD-10, and comparing the resulting underlying causes of death. The fi rst step in this process is to identify equivalent codes or code groups in the two revisions which represent the same causes. In most cases this is not contentious, and the same groupings have been used by various authors and national statistics offi ces. The fi rst character of each code is now alphabetic rather than numeric this has enabled the expansion of the number of codes to provide for recently recognised conditions and more detail about common diseases. Some diseases and groups of conditions have been moved between broad groups (ICD Chapters) to reflect current ideas of aetiology and pathology. There have been several changes to the rules governing selection of the underlying cause of death. There are now only 5 rules instead of 9. The changes in the application of rule 3 have the biggest impact. This rule allows a condition which is reported in either Part I or II of the death certifi cate to take precedence over the condition selected using the other coding rules if the latter is obviously a direct consequence of that condition. In ICD-10 the list of conditions affected by rule 3 is more clearly defined than in ICD-9 and is also broader in scope. This internationally agreed interpretation is used in the automated coding software produced by the National Centre for Health Statistics (NCHS) in the USA, used in, Scotland and an increasing number of other countries. The impact of this is to reduce the number of deaths assigned to conditions such as pneumonia and to increase the number of deaths assigned to chronic debilitating diseases. In England and Wales, about 20 per cent of deaths mention pneumonia so the effect of this rule change is large. The results are then presented as comparability ratios of the numbers of deaths assigned to a given disease or group of diseases in the two revisions. These are simply the ratio of the number of deaths coded to a cause in ICD-10 to the number coded to the equivalent cause in ICD-9. They measure the net effect of all changes to a particular cause of death, so if the comparability ratio equals 1 this means there is no net effect. A comparability ratio of more than 1 means a net gain has occurred, and less than 1 means a net loss. Confi dence intervals have also been produced for these ratios; the method used to do this has been described elsewhere. 2 These comparability ratios can then be used to adjust comparisons of cause-specifi c mortality rates. In, all deaths registered in 1999 were bridge coded and comparability ratios with confi dence intervals were produced. 2 They should not be used before 1993, as ONS used a different interpretation of the rules to select the underlying cause of death from the international interpretation from 1984 to For a particular cause, the number of deaths coded to the equivalent cause in ICD-9 in the years being compared should be multiplied by the comparability ratio in order to give an expected number of deaths which would have been coded to this cause in ICD-10. The ratio can also be applied directly to rates, to give an expected rate. Age-specifi c ratios have been produced for three broad age groups under 75, and 85 and over. These are only presented in this article where there is a signifi cant difference in the comparability ratios by age. Table 1 Comparability ratios for selected causes of death by broad age band and sex, 1999 Age group Females Under and over All ages ICD-10 code ICD-9 code Name 10/9 ratio 10/9 ratio 10/9 ratio 10/9 ratio C00 D Neoplasms * * * * C00 C Malignant neoplasms * * * * C Breast cancer * * * C81 C Cancer of lymphoid, haematopoietic and related tissue * * * * D00 D Non-malignant neoplasms * * * * Males Under and over All ages ICD-10 code ICD-9 code Name 10/9 ratio 10/9 ratio 10/9 ratio 10/9 ratio C00 D Neoplasms * * * * C00 C Malignant neoplasms * * * * C Cancer of larynx * * * C Prostate cancer * * * C81 C Cancer of lymphoid, haematopoietic and related tissue * * * * D00 D Non-malignant neoplasms * * * * 8

3 RESULTS All neoplasms Overall mortality from neoplasms (Chapter II of the ICD) increased by 3.3 per cent (almost 4,500 additional deaths) when ICD-10 was used to code cause of death instead of ICD-9. This increase varies by age, with rates in older age groups generally being affected more than those at ages under 75. Table 1 shows the comparability ratios by age group for the main neoplasms for which an age-specific pattern was evident. Three-quarters of these additional deaths had previously been coded to Chapter VIII diseases of the respiratory system and a fifth coded to Chapter IV diseases of the blood and blood-forming organs. The vast majority of deaths previously coded to respiratory diseases were pneumonia deaths that are affected by the new interpretation of rule 3. These deaths were dispersed throughout the neoplasm chapter. Almost all of the deaths previously coded to the blood diseases chapter, however, came from one specific code ICD other diseases of blood and blood-forming organs. These were all coded to non-malignant neoplasms in ICD-10. Although over 99 per cent of deaths coded to neoplasms in ICD-9 were also coded to neoplasms in ICD-10, there was a small percentage that were coded to other causes. Table 2 Malignant neoplasms a) Number of deaths coded as due to malignant neoplasms in ICD-10 (C00 C97), and their underlying cause of death chapter in ICD-9, 1999 ICD-9 code Number of deaths % of total deaths Malignant neoplasms , Respiratory diseases , Non malignant neoplasms Circulatory diseases Other causes All malignant neoplasm deaths in ICD , b) Number of deaths coded as due to malignant neoplasms in ICD-9 ( ), and their underlying cause of death chapter in ICD-10, 1999 ICD-10 code Number of deaths % of total deaths Malignant neoplasms C00 C97 133, Non malignant neoplasms D00 D Respiratory diseases J00 J Circulatory diseases I00 I Other causes All malignant neoplasm deaths in ICD-9 133, Comparability ratio 1.023* Table 3 Non-malignant neoplasms a) Number of deaths coded as due to non-malignant neoplasms in ICD-10 (D00 D48), by their underlying cause of death chapter in ICD-9, 1999 ICD-9 code Number of deaths % of total deaths Non-malignant neoplasms , Diseases of the blood and blood-forming organs Respiratory diseases Malignant neoplasms Other causes All non-malignant neoplams deaths in ICD-10 3, b) Number of deaths coded as due to non malignant neoplasms in ICD-9 ( ), by their underlying cause of death chapter in ICD-10, 1999 ICD-10 code Number of deaths % of total deaths Non-malignant neoplasms D00 D48 1, Malignant neoplasms C00 C Congenital malformations Q00 Q Other causes All non-malignant neoplasm deaths in ICD-9 2, Comparability ratio 1.675* 9

4 Deaths coded to malignant neoplasms increased by 2.3 per cent in ICD- 10. Table 2 shows the number of deaths coded to malignant neoplasms in both ICD-9 and ICD-10. The effect of the new interpretation of rule 3 can be seen in the number of deaths that were previously coded to respiratory diseases in ICD-9 almost 3,000 (2.2 per cent of total malignant neoplasm deaths) in ICD-10. Nearly 200 deaths previously coded to other and unspecified classifications within non-malignant neoplasms, were subsequently coded to site unspecified malignant neoplasm codes in ICD-10. When these data were examined by age the new interpretation of rule 3 was seen to increase with age as the number of deaths previously coded to respiratory diseases (specifically pneumonia) was much higher in older ages. However, the proportion of deaths previously coded to non-malignant neoplasms decreased with age. Although over 99 per cent of deaths coded to malignant neoplasms in ICD-9 were also coded to malignant neoplasms in ICD-10, there was a small percentage that were coded to other causes (Table 2b). The number of deaths coded to non-malignant neoplasms increased by 68 per cent in ICD-10. Most of the extra deaths coded to nonmalignant neoplasms in ICD-10 came from ICD other diseases of the blood and blood-forming organs and were coded to D46 myelodysplastic syndromes (81 per cent) and D47.1 chronic myeloproliferative disease (17 per cent) in ICD-10 (Table 3a). These diseases, in which production of selected blood cell lines increases out of control, have been moved to Chapter II neoplasms to reflect their classification as blood cell neoplasms, rather than merely disorders of bone marrow. Of the deaths previously coded to malignant neoplasms a third were coded to 191 brain cancer in ICD-9. These were coded to neoplasm of uncertain behaviour of brain in ICD-10. Intracranial neoplasms can lead to death through their effects on the surrounding brain without showing any of the characteristic features of malignant tumours (invasion into other tissues, spread to lymph nodes and metastasis to distant sites). The ICD-10 classification reflects their benign morphology. As with malignant neoplasms, the effect of the new interpretation of rule 3 can also be seen and was found to be agespecific. Nearly 89 per cent of deaths coded to non-malignant neoplasms in ICD-9 were also coded to these sites in ICD-10. However, 9 per cent of deaths coded to these sites in ICD-9 were coded to malignant neoplasms in ICD-10. These deaths were associated with a broad range of cancer sites in ICD-10, with a fifth being coded to C80 malignant neoplasm without specification of site and just under a fifth to C71 malignant neoplasm of brain. Cancers by site The three most common malignant neoplasm mortality sites are breast (18 per cent of all cancers between 1993 and 2002), lung (17 per cent) and colorectal (11 per cent) in females, and lung (27 per cent), prostate (12 per cent) and colorectal (11 per cent) in males. Female breast, prostate and colorectal cancer all gained deaths in ICD-10 whereas the number of lung cancer deaths fell. The cancer sites with better survival tended to be affected by the new interpretation of rule 3 more than cancer sites with low survival. In these cases a cancer, for which the patient was treated many years before death, may be recorded in Part II of the death certificate, but be selected in preference to pneumonia recorded in Part I. Female breast cancer (C50) There was a 2.7 per cent increase in the number of deaths with an underlying cause of female breast cancer in ICD-10. Most of the increase in deaths coded to breast cancer in ICD-10 came from deaths which were previously coded as pneumonia, as a result of the new interpretation of rule 3 (Table 4a). There were also a small number of deaths coded as female breast cancer in ICD-9 which were not coded to this site in ICD-10 (Table 4b). These were mostly transferred to C97 cancer of multiple primary independent sites or to other cancer sites (mainly C80 unspecified site). This may also reflect high survival rates and advanced age at death, with patients living long enough to develop second independent cancers before they die. When these data were examined by age (see Table 1) it could be seen that this effect was age-specific, with the ratios increasing with age. Table 4 Female breast cancer a) Number of deaths coded as due to female breast cancer in ICD-10 (C50), by their underlying cause of death in ICD-9, 1999 ICD-9 code Number of deaths % of total deaths Female breast cancer , Bronchopneumonia and pneumonia, organism unspecified Other malignant neoplasms x Other causes All female breast cancer deaths in ICD-10 11, b) Number of deaths coded as due to female breast cancer in ICD-9 (174), by their underlying cause of death in ICD-10, 1999 ICD-10 code Number of deaths % of total deaths Female breast cancer C50 11, Malignant neoplasm of multiple independent primary site C Other malignant neoplasms C00 D96 xc Non-malignant neoplasms D00 D Other causes All female breast cancer deaths in ICD-9 11, Comparability ratio 1.027* 10

5 Prostate cancer (C61) There was a 3.8 per cent increase in the number of deaths with an underlying cause of prostate cancer as a result of changing to ICD-10. Most of the increase in deaths coded to prostate cancer in ICD-10 came from deaths previously coded as pneumonia (Table 5a). As prostate cancer has a relatively high survival rate this is mainly an effect of the new interpretation of rule 3. There were also a small number of deaths which were coded as prostate cancer in ICD-9 which were not coded to this site in ICD-10 (Table 5b). As with female breast cancer, most of these were transferred to C97 cancer of multiple independent primary sites or to other cancer sites (mainly C80 unspecified site). The incidence of prostate cancer rises very steeply with age, and large proportions of older men may die with prostate cancer. This may include many who die from another cancer in a different organ system. When these data were examined by age (see Table 1) it could be seen that this effect was age-specific, with the ratios increasing with age. Lung cancer (C33 C34) There was a decrease of 0.4 per cent in the numbers of deaths with an underlying cause of lung cancer in ICD-10. This decrease is mainly a consequence of deaths previously coded as cancer of lung in ICD-9 being coded as C97 cancer of multiple independent primary site as Table 5 Prostate cancer a) Number of deaths coded as due to prostate cancer in ICD-10 (C61), by their underlying cause of death in ICD-9, 1999 ICD-9 code Number of deaths % of total deaths Prostate cancer 185 8, Bronchopneumonia and pneumonia, organism unspecified Other malignant neoplasms x Other causes All prostate cancer deaths in ICD-10 8, b) Number of deaths coded as due to prostate cancer in ICD-9 (185), by their underlying cause of death in ICD-10, 1999 ICD-10 code Number of deaths % of total deaths Prostate cancer C61 8, Malignant neoplasm of multiple independent primary site C Other malignant neoplasms C00 C96, xc Non-malignant neoplasms D00 D Other causes All prostate cancer deaths in ICD-9 8, Comparability ratio 1.038* Table 6 Lung cancer a) Number of deaths coded as due to lung cancer in ICD-10 (C33-C34), by their underlying cause of death in ICD-9, 1999 ICD-9 code Number of deaths % of total deaths Lung cancer , Bronchopneumonia and pneumonia, organism unspecified Other causes All lung cancer deaths in ICD-10 29, b) Number of deaths coded as due to lung cancer in ICD-9 (162), by their underlying cause of death in ICD-10, 1999 ICD-10 code Number of deaths % of total deaths Lung cancer C33 C34 28, Other malignant neoplasms C00 C96 xc33 C Malignant neoplasm of multiple independent primary site C Mesothelioma C Non-malignant neoplasms D00 D Other causes All lung cancer deaths in ICD-9 29, Comparability ratio 0.996* 11

6 a new code C45 mesothelioma or as other cancer sites (mainly C80 unspecified site) (Table 6b). Only a small proportion of deaths coded as lung cancer in ICD-10 came from deaths coded as pneumonia in ICD-9 (Table 6a). This reflects high fatality, with only 20 per cent of lung cancer patients surviving a year 4 and most dying directly from the cancer. No significant pattern by age was found. Deaths coded to C80 unspecified site are mainly cases for which the certifier stated that the primary site was unknown. However, it also includes certificates with more than one tumour site mentioned, with no indication whether one is primary and the other secondary, or with site(s) described as metastatic without specifying whether to or from the stated site(s). Colorectal cancer (C18 C21) A previous analysis 3 examined colon and rectum separately and found that colon cancer (C18) increased by 1.6 per cent and rectal cancer (C19 C21) increased by 1.2 per cent in ICD-10. As the two sites are very close to each other and invasive neoplasms often spread from one site to the other they have been analysed together as colorectal cancer (C18 C21) in this article. There was a 1.5 per cent increase in the number of deaths coded as colorectal cancer as a whole in ICD-10. The increase in the number of deaths coded as colon, rectal and colorectal cancer in ICD-10 came from deaths that were previously coded as pneumonia (Table 7a). As with the other sites examined above there were also a small number of deaths which were coded as colon or rectal cancer in ICD-9 which were not coded as these sites in ICD-10 (Table 7b). Most of these were coded as C97 cancer of multiple independent primary site or to other cancer sites (mainly C26 other and ill-defined digestive organs and C80 unspecified site). There was some interchange as deaths previously coded to colon cancer in ICD-9 were coded to rectal cancer in ICD-10 but not vice versa. This is mainly due to changes in indexing of vaguely specified or overlapping sites. No significant pattern in comparability ratios was found by age. Mesothelioma (C45) A specific code for mesothelioma was introduced in ICD-10. In ICD- 9, mesothelioma was coded to the exact organ site, if specified, for mortality. Cancer registries, using the International Classification of Table 7 Colorectal cancer Number of deaths a) Number of deaths coded as due to colorectal cancer in ICD-10 (C18 21), by their underlying cause of death in ICD-9, 1999 ICD-9 code Colon Rectal Colorectal Colon, rectal or colorectal cancer ,709 4,600 14,324 Bronchopneumonia and pneumonia, organism unspecified Other causes All colorectal cancer deaths in ICD-10 10,038 4,740 14,778 Number of deaths b) Number of deaths coded as due to colorectal cancer in ICD-9 ( ), by their underlying cause of death in ICD-10, 1999 ICD-10 code Colon Rectal Colorectal Colon, rectal or colorectal cancer C18 C21 9,709 4,600 14,324 Malignant neoplasm of multiple independent primary site C Other causes All colorectal cancer deaths in ICD-9 9,880 4,684 14,564 Comparability ratio 1.016* 1.012* 1.015* Table 8 Number of deaths coded as due to mesothelioma in ICD-10 (C45), by their underlying cause of death in ICD-9, 1999 ICD-9 code Number of deaths % of total deaths Cancer without specification of site Cancer of pleura Lung cancer Cancer of peritoneum Other malignant neoplasms Other causes All mesothelioma deaths in ICD-10 1,

7 Diseases for Oncology, were able to code incident cases of mesothelioma to specific codes for morphology and site. The sites most often affected are the pleura (the lining of the chest cavity and lungs) and the peritoneum (the lining of the abdominal cavity and organs). However, certifiers often did not specify the site, or specify that the mesothelioma involved the lung. Mesothelioma is largely due to inhaling asbestos fibres but the cancer does not appear until approximately 10 to 40 years after first inhalation. The number of mesothelioma deaths is rising steeply, reflecting historical patterns of occupational exposure. 5 Most of the deaths coded as C45 in ICD-10 during 1999 (see Box 2) occurred in men, two thirds of which occurred in those aged under 75. Table 8 shows the number of deaths coded as mesothelioma in ICD-10 according to where these deaths were coded in ICD-9. Over half of the deaths were coded as ICD cancer of unspecified site and a third were coded as ICD cancer of the pleura. Not all of the deaths coded to these sites in ICD-9 were coded to mesothelioma in ICD-10, however. Kaposi s sarcoma (C46) There were seven deaths in 1999 which mentioned Kaposi s sarcoma (C46 in ICD-10) on the death certificate. Only one of these deaths also mentioned HIV and this was coded as the underlying cause for this death in both ICD-9 and ICD-10 which accords with ICD rules. The remainder had code other malignant neoplasm of skin as the underlying cause of death in ICD-9 and Kaposi s sarcoma as the underlying cause of death in ICD-10. Kaposi s sarcoma is associated with HIV infection in young men but a rarer form of the disease (not associated with HIV) affects older adult men. Previous research has shown that doctors sometimes omit mention of HIV/AIDS and AIDSrelated illnesses on death certificates, because of the stigma involved. 6 The numbers of deaths from Kaposi s sarcoma reported here are almost certainly an underestimate of its true contribution to mortality in Statistics on AIDS-related illness reported to the Communicable Disease Surveillance Centre (CDSC) are more complete. 8 Multiple independent primary tumours (C97) A new code (C97) was introduced in ICD-10 to code deaths that are certified as due to two or more cancers. In ICD-9, if there was no indication of which cancer was primarily responsible for the death on the death certificate the first site mentioned was selected as the underlying cause, unless it was a site at which metastases commonly occurred, and the other was not. 9 In ICD-10, selection of the primary site is not determined by order of entry on to the death certificate. So, when two primary sites from different organ systems are listed in Part I of the death certificate, and it is not clear which was responsible for the death, the underlying cause is coded to C97. Table 9 shows numbers of deaths coded as C97 in ICD-10 by their underlying cause of death codes in ICD- 9. These deaths were coded to a variety of cancer sites in ICD-9 and five per cent were previously coded to pneumonia. When these deaths were analysed by cancer site mentioned on the death certificate, nearly 60 per cent of deaths had 3 or more independent primary sites mentioned, and 12 per cent had 4 or more. Of deaths with two independent primary sites mentioned (410 deaths) the most common combinations were prostate and bladder (11 per cent of deaths with two independent primary sites mentioned), colon and prostate (3 per cent) and breast and colon (2 per cent). Of deaths with three independent primary sites mentioned (453 deaths), the most common were always two cancer sites in combination with code C80 cancer without specification of site. The most common pairs of cancer sites appearing with code C80 were prostate and bladder (7 per cent of deaths with three independent primary sites mentioned), lung and prostate, and lung and breast (4 per cent each), colon and prostate, and colon and breast, and breast and ovary (3 per cent each). Malignant melanoma (C43) and other malignant neoplasm of skin (C44) There was a decrease of 3.9 per cent in the number of deaths coded as malignant melanoma when ICD-10 was used instead of ICD-9. The decrease mainly occurs because deaths previously coded as malignant melanoma in ICD-9 were coded instead as C44 other malignant neoplasm of skin to new code C97 neoplasm of multiple independent primary sites or to other cancer sites in ICD-10 (Table 10b). Only a small proportion of the deaths coded as malignant melanoma in ICD-10 were coded to pneumonia in ICD-9 (Table 10a). The number was not sufficient to counterbalance the number coded to other conditions. Table 9 Number of deaths coded to multiple independent primary site tumour in ICD-10 (C97), by their underlying cause of death in ICD-9, 1999 ICD-9 code Number of deaths % of all deaths coded to C97 Female breast cancer Prostate cancer Bladder cancer Lung cancer Colon cancer Bronchopneumonia and pneumonia, organism unspecified Non-Hodgkin s lymphoma Ovarian cancer Stomach cancer Kidney cancer Rectal cancer Leukaemia Cancer of connective tissue Cancer of ill-defined sites within digestive organs Malignant melanoma Oesophageal cancer Tongue cancer Other malignant neoplasm sites Other causes All deaths coded to multiple independent primary tumour in ICD

8 Table 10 Malignant melanoma a) Number of deaths coded as due to malignant melanoma in ICD-10 (C43), by their underlying cause of death in ICD-9, 1999 ICD-9 code Number of deaths % of total deaths Malignant melanoma 172 1, Bronchopneumonia and pneumonia, organism unspecified Other malignant neoplasms x Other causes All malignant melanoma deaths in ICD-10 1, b) Number of deaths coded as due to malignant melanoma in ICD-9 (172), by their underlying cause of death in ICD-10, 1999 ICD-10 code Number of deaths % of total deaths Malignant melanoma C43 1, Other malignant neoplasm of skin C Malignant neoplasm of multiple independent primary sites C Other malignant neoplasms Other causes All malignant melanoma deaths in ICD-9 1, Comparability ratio 0.961* Table 11 Other malignant neoplasm of skin a) Number of deaths coded as due to other malignant neoplasm of skin in ICD-10 (C44), by their underlying cause of death in ICD-9, 1999 ICD-9 code Number of deaths % of total deaths Other malignant neoplasm of skin Bronchopneumonia and pneumonia, organism unspecified Malignant melanoma Other malignant neoplasms Other causes All other malignant neoplasm of skin deaths in ICD b) Number of deaths coded as due to other malignant neoplasm of skin in ICD-9 (174), by their underlying cause of death in ICD-10, 1999 ICD-10 code Number of deaths % of total deaths Other malignant neoplasm of skin C Cancer of other and ill-defined sites C Cancer without specification of site C Kaposi s sarcoma C Cancer of multiple independent primary sites C Other malignant neoplasms Other causes All other malignant neoplasm of skin deaths in ICD Comparabilty ratio 1.097* 14

9 The number of deaths coded to other malignant neoplasm of skin increased by 9.7 per cent. Most of the increase in deaths coded to other malignant neoplasm of skin in ICD-10 came from deaths that were previously coded to pneumonia and to malignant melanoma in ICD-9 (Table 11a). There were also a significant number of deaths which were coded to other malignant neoplasm of skin in ICD-9 which were not coded to this site in ICD-10 (Table 11b). Most of these were coded to other and ill-defined sites or cancer without specification of site, but some deaths were assigned to Kaposi s sarcoma. No significant pattern by age was seen for either malignant melanoma or other malignant neoplasm of skin. Cancer of lymphoid, haematopoietic and related tissue (C81 C96) There was a 5.1 per cent increase in deaths coded to these conditions in ICD-10. Most of the increase in deaths coded to cancer of lymphoid, haematopoietic and related tissue in ICD-10 came from deaths previously coded as pneumonia, but also because deaths from Waldenstrom s macroglobulinaemia, a disease previously classified in Chapter III endocrine, nutritional and metabolic diseases in ICD-9, were coded to the neoplasms chapter in ICD-10 (Table 12a). This reflects a change in the index assignment for macroglobulinaemia from ICD to ICD-10 C88.0. There was also a small number of deaths which were coded to these diseases in ICD-9 which were coded elsewhere in ICD-10 (Table 12b). Most of these were moved to C97 cancer of multiple independent primary sites, but there was also movement from leukaemia in ICD- 9 ( ) to myelodysplastic syndromes in ICD-10 (D46) which is classified under non-malignant neoplasms. When these data were examined by age (see Table 1) it could be seen that this effect was agespecific, with the ratios increasing with age. Within this disease group, deaths from leukaemia and multiple myeloma were most affected. The numbers of deaths coded to both diseases increased by over 5 per cent in ICD-10. Most of these deaths were coded as pneumonia in ICD-9, but all of the deaths previously coded as hairy cell leukaemia (ICD excluded from the leukaemia group) and some deaths from other lymphomas (ICD ) were coded to leukaemia in ICD-10, whilst all of the deaths previously coded to neoplasms of plasma cells (ICD plasma cell neoplasm of uncertain behaviour) were coded to multiple myeloma. GOVERNMENT TARGET ON MORTALITY FROM CANCER The Government set a target in its Our Healthier Nation strategy to reduce mortality rates from malignant cancer among those aged under 75 by at least two-fifths by 2010 (compared with the rate for ). 10 In any assessment of progress against the Government s target for these diseases, adjustment is needed to the baseline figure to account for the change in ICD revision. The comparability ratios for people aged under 75 are for males and for females. Although the impact on the rate is small, it is important to examine trends against the corrected baseline. Table13 shows the age-standardised mortality rate by sex for the 20 most common malignant neoplasm sites adjusted, where necessary, to be comparable with ICD-10, from 1993 to Rates have been directly age-standardised to the European Standard population. Table 12 Cancer of lymphoid, haematopoietic and related tissue a) Number of deaths coded as due to malignant neoplasm of lymphoid, haematopoietic and related tissue in ICD-10 (C81 C96), by their underlying cause of death in ICD-9, 1999 ICD-9 code Number of deaths % of total deaths Cancer of lymphoid, haematopoietic and related tissue , Bronchopneumonia and pneumonia, organism unspecified Endocrine, nutritional and metabolic diseases Other malignant neoplasms Non-malignant neoplasms Other causes All cancer of lymphoid, haematopoietic and related tissue deaths in ICD-10 10, b) Number of deaths coded as due to malignant neoplasm of lymphoid, haematopoietic and related tissue in ICD-9 ( ), by their underlying cause of death in ICD-10, 1999 ICD-10 code Number of deaths % of total deaths Cancer of lymphoid, haematopoietic and related tissue C81 C96 9, Malignant neoplasm of multiple independent primary site C Myelodysplastic syndrome D Other non-malignant neoplasm D00 D48 xd Other malignant neoplasms Other causes All cancer of lymphoid, haematopoietic and related tissue deaths in ICD-9 10, Comparability ratio 1.051* 15

10 Table 13 Age-standardised mortality rates by most common cancer death site, adjusted for change in ICD, ICD codes Age-standardised rate per 100,000 to the European standard population (adjusted where comparability ratio is significant) Rank Rank Site ICD-10 ICD All ages as of as of comparability ratio Males 1 1 Lung C33 C * 2 2 Prostate C * 3 3 Colorectal C18 C * 4 5 Oesophagus C * 5 4 Stomach C * 6 7 Pancreas C Bladder C Non-Hodgkins lymphoma C82 C85 200, Leukaemia C91 C * Kidney, except renal pelvis C Brain C n/a Mesothelioma C45 n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a Liver and intrahepatic bile ducts C Multiple myeloma C * Lip and mouth C00 C Other digestive C * Malignant melanoma C * Larynx C * 19 n/a Multiple independent primary sites C97 n/a n/a n/a n/a n/a n/a n/a n/a n/a n/a Connective and other soft tissue C47, C Non-malignant neoplasms D00 D * Malignant neoplasms C00 C * Neoplasms C00 D * Females 1 1 Breast C * 2 2 Lung C33 C * 3 3 Colorectal C18 C * 4 4 Ovary C Pancreas C Oesophagus C Stomach C Non-Hodgkins lymphoma C82 C85 200, Leukaemia C91 C * Bladder C * Uterus C54 C55 179, * Brain C Multiple myeloma C * Other digestive C * Kidney, except renal pelvis C Cervix uteri C Liver and intrahepatic bile ducts C * Malignant melanoma C * Lip and mouth C00 C * Other female genital C51 C52, C Non-malignant neoplasms D00 D * Malignant neoplasms C00 C * Neoplasms C00 D * 16

11 DISCUSSION This article has presented detailed information on the impact of introducing ICD-10 on the analysis of trends in mortality from cancer as a whole and of specific sites. This is particularly important as deaths from neoplasms account for a quarter of all deaths in annually. The main findings of the analysis were that the number of deaths assigned to all malignant neoplasms increased by over 2.3 per cent as a result of the introduction of ICD-10 and the number of deaths assigned to non-malignant neoplasms increased by 68 per cent. Most of the increase for all malignant neoplams came from deaths previously coded to pneumonia, which is as an effect of the new interpretation of rule 3 on selection of the underlying cause of death. The increases were greater in deaths at higher ages. Most of the increased numbers of deaths assigned to non-malignant neoplasms came from deaths previously coded as diseases of the blood and blood-forming organs (mainly from ICD ). Not all malignant cancer sites had increased numbers of deaths coded to them in ICD-10. The numbers of deaths from cancer of the lung, brain, liver, lip and mouth, and melanoma of skin in men, and lung, ovary, pancreas, cervix, liver, lip and mouth, and melanoma of skin in women, all decreased in ICD-10. In ICD-10, there is a statistically significant increase in the number of deaths assigned to malignant cancer in those aged under 75 of around 1 per cent. In any assessment of progress against the Government s target for these diseases, adjustment is needed to the baseline figure to ensure comparability. When monitoring the impact of specific interventions, it is important to take account of the impact of ICD-10 on each cancer. REFERENCES 1. Rooney C and Devis T (1996) Mortality trends by cause of death in : the impact of introducing automated cause coding and related changes in Population Trends 86, Rooney C, Griffiths C and Cook L (2002) The implementation of ICD-10 for cause of death coding some preliminary results from the bridge coding study. Health Statistics Quarterly 13, Office for (2002) Report: Results of the ICD-10 bridge coding study, Health Statistics Quarterly 14, Quinn M, Babb P, Brock A, Kirby L and Jones J (2001) Cancer Trends in , TSO: London. 5. Health and Safety Executive (2003) Mesothelioma mortality in Great Britain: estimating the future burden, HSE Books: Suffolk. 6. McCormick A (1994) The impact of human immunodeficiency virus on the population of. Population Trends 76, Brock A, Griffiths C (2003) Trends in the mortality of young adults aged in, 1961 to Health Statistics Quarterly 19, Communicable Disease Surveillance Centre (2002) HIV and AIDS in the UK in An update: November 2002, CDSC: London. 9. World Health Organization (1977) Manual of the International Statistical Classification of Diseases, Injuries and Causes of Death. Volume 1, Pg , WHO: Geneva. 10. Department of Health (1999) White Paper, Saving Lives: Our Healthier Nation, TSO: London. Key fi ndings There was an overall increase of 3.3 per cent (4,500 deaths) in deaths assigned to neoplasms as a result of ICD-10 replacing ICD-9. The number of deaths assigned to malignant neoplasms increased by 2.3 per cent (3,000 deaths), mostly as a result of the new interpretation of selection rule 3 to deaths previously coded as due to pneumonia. However, the number of deaths assigned to non-malignant neoplasms increased by 68 per cent (1,400 deaths). Most of this increase came from deaths previously assigned to other diseases of the blood and blood-forming organs ICD In those aged under 75, the number of deaths assigned to malignant neoplasms increased by per cent for males and per cent for females as a result of introducing ICD