Lung cancer and asbestos

Transcription

1 Lung cancer and asbestos Bureau Veritas Training Bill Sanderson For the benefit of business and people

2 To begin with.. There are known knowns, that is there are things we know that we know. There are known unknowns, that is to say there are things we now know we don t know. But there are also unknown unknowns, that is there are things we don t know we don t know and each year we discover a few more of those unknown unknowns. D Rumsfeld, 2002 Bureau Veritas Training Title of Presentation 1

3 Lung cancer First links made in 1930 s? Evidence suppressed by asbestos companies Reports published in Germany in early 1940s Factory Inspector notes high incidence in asbestos workers ? Doll establishes link in 1955 paper IARC classifies asbestos as Group 1 carcinogen in 1979 Confirmed carcinogenic to humans Bureau Veritas Training Title of Presentation 2

4 Lung cancer The most common cancer in the UK for both males and females Deaths in 2005:- Males 19,500 Females 14,000 Bureau Veritas Training Title of Presentation 3

5 Male lung cancer death rates Bureau Veritas Training Title of Presentation 4

6 Female lung cancer death rates and over Rate per 100,000 population Year of death Bureau Veritas Training Title of Presentation 5

7 Lung cancer & asbestos Questions to be asked / answered? Effect of type of asbestos amphibole vs. chrysotile Link with asbestosis? Is there an exposure threshold for lung cancer? Presence of pleural plaques? Relative contributions of smoking? Do the multiplicative effects still hold at low asbestos exposure levels? Effect of cessation of smoking? Effect of extended life expectancy? Bureau Veritas Training Title of Presentation 6

8 Lung cancer Lung cancer Small cell lung cancer (SCLC) ( Oat cell ) Non-small cell lung cancer (NSCLC) Squamous Adenocarcinoma Large cell Bureau Veritas Training Title of Presentation 7

9 Lung cancer Although about 20% of lung cancers are small cell, asbestos related lung cancers appear in all forms cannot determine causality from location in the lung or cancer type Strictly, lung cancer is a carcinoma of the epithelial cells of the (usually upper) bronchus bronchial carcinoma Hence, completely different disease mechanism to either asbestosis or mesothelioma Lung cancer is very aggressive and does not respond well outlook for treatment is very poor Bureau Veritas Training Title of Presentation 8

10 Mechanisms of carcinogenesis Incomplete knowledge, but:- (a) oxygen free radicals lead to cellular and DNA damage (b) chromosomal deletions and rearrangements, and found to be strongly mutagenic in mammalian cells Bureau Veritas Training Title of Presentation 9

11 Latency period Latency or induction period between years or longer possibly as short as 5 9 years Not thought to be dose dependent (i.e. higher dose leads to a shorter induction period) Possible genetic link (as for other cancers) Bureau Veritas Training Title of Presentation 10

12 Lung cancer Complicating effects of smoking not connected with either asbestosis or mesothelioma Lung cancers clinically identical from smoking and asbestos Very difficult to establish exactly how many lung cancers are attributable to (a) asbestos (b) smoking (c) both, or (d) neither (e.g. chromate ores, Ni compounds, As compounds, Be, radon, etc.) Bureau Veritas Training Title of Presentation 11

13 Asbestos type Clearly the amphiboles are more potent than chrysotile Amosite / crocidolite Chrysotile 1 Do the same ratios apply at low exposure levels? Expect a higher ratio because of the more rapid clearance of chrysotile? Bureau Veritas Training Title of Presentation 12

14 Link with asbestosis? At one stage, it was asserted that lung cancer only appeared where there was sufficient exposure to induce asbestosis Evidence now moving to accept there is a raised risk of lung cancer even in absence of asbestosis Asbestosis deaths 134 in 2005 Asbestosis IIB compensation ~800 in 2005 Asbestos-related lung cancers 80 in 2005??? Bureau Veritas Training Title of Presentation 13

15 Asbestosis Deaths to 2005 Deaths per year Year Asbestosis Asbestosis deaths Bureau Veritas Training Title of Presentation 14

16 Asbestosis It is now generally accepted that there is a threshold exposure below which asbestosis does not occur Threshold is much lower for amphiboles than for chrysotile (~25 f/ml-yrs) [Ontario Royal Commission] 2 f/ml-yrs for amosite? If there is a threshold exposure for asbestosis, is there also a threshold exposure for lung cancer? Agreed not or very low indeed (if at all) Bureau Veritas Training Title of Presentation 15

17 Lung cancer rates Current view is that the number of lung cancers is much closer to the mesothelioma rate General view was that there were between one and two lung cancers per mesothelioma Darnton, et al (2006) suggested the number of lung cancers to be approximately case per mesothelioma At current mesothelioma rates = 1,400 2,000 per year Bureau Veritas Training Title of Presentation 16

18 Pleural plaques Hillerdal (1994) reported increased risk of lung cancer for patients with pleural plaques but no evidence of asbestosis Pleural plaques could be regarded as indicative of exposure (with a history of asbestos exposure) but other authors do not regard pleural plaques as predictors of lung cancer i.e. pleural plaques do not predispose towards lung cancer Any evidence of increased risk of mesothelioma? Bureau Veritas Training Title of Presentation 17

19 Asbestos and smoking Established early on that smoking and asbestos are linked Consensus now that effect is multiplicative or nearly so Relative risks for chrysotile and amphiboles? Bureau Veritas Training Title of Presentation 18

20 Asbestos and Smoking [Kjuus et al (1986)] No Heavy Increased Smoking asbestos asbestos risk Light 3 12 x 4 Heavy x 4 Increased x 30 x 30 risk Bureau Veritas Training Title of Presentation 19

21 Asbestos and Smoking Smoking is a far more significant factor than asbestos If smoking ceases, lung cancer risk falls After 15 years, risk is the same as for a person who has never smoked Does the same reduction apply for asbestos? What would be the risk factors for light smoking and light asbestos exposure? Bureau Veritas Training Title of Presentation 20

22 Smoking rates Figure 6.1: Percentage of persons aged 16 and over, who smoke cigarettes, Great Britain, % of adult population who smoked manufactured cigarettes Men Women Unweighted data weighted data Year Bureau Veritas Training Title of Presentation 21

23 Asbestos and Smoking UK Smoking trends Percentage of group Male (manual) Male (non-manual) Female (manual) Female (non-manual) Year Bureau Veritas Training Title of Presentation 22

24 Asbestos and Smoking Smoking trends are consistent Males smoke more than females Manual workers smoke more than non-manual workers Unfortunately, most asbestos exposure is for male manual workers the group with the highest smoking rates What are the implications for future lung cancer trends? The smoking effect clearly supports HSE s view that education of asbestos-exposed workers is vital Bureau Veritas Training Title of Presentation 23

25 and finally.. The absence of evidence is not the evidence of absence. It is basically saying the same thing in a different way. Simply because you do not have evidence that something does exist does not mean that you have evidence that it doesn't exist." "Learn to say 'I don't know.' If used when appropriate, it will be often." D Rumsfeld Bureau Veritas Training Title of Presentation 24