Radio-iodine Therapy and Helicobacter Pylori: A Preliminary Concept

Transcription

1 Radio-iodine Therapy and Helicobacter Pylori: A Preliminary Concept

2 Background Helicobacter pylori (H.pylori) infection has been one of the most important causes of the gastritis during the past two decades. The prevalence of H.pylori infection is more than 90% in some areas such as developing countries. The unpleasant effects of this infection (such as gastritis, dyspepsia, gastric ulcer, ) have led scientists to pay more attention to its treatment. Several drugs have been examined and fortunately they were highly helpful.

3 Background On the other hand, radioactive treatment in conjunction with surgery forms the basis of treatment for patients suffering from differentiated thyroid cancers (DTC).

4 Background In the present practice of nuclear medicine, it is not infrequent that post-treatment imaging is requested for such patients. These images reveal the distribution of radio-iodine throughout the malignant tissues as well as those normal tissues which possess sodium/iodine (Na/I) symporter, naturally.

5 Background Normal distribution consists of radio-iodine uptake by the remaining thyroid tissue, salivary gland, and more considerable uptake by the stomach. Reviewing of the images shows that there is a remarkable radioactivity in the gastric area, mouth, and sometimes intestine of patients treated with radio-iodine in fact, a distribution similar to that of H. pylori infection.

6 Aim We decided to find whether the high radiation induced by radioactive iodine has any eradicative effect on H. pylori infection.

7 Method All consecutive patients afflicted with differentiated thyroid carcinoma (DTC), who had been admitted for radio-iodine ablation therapy were enrolled in our study. All of them had the previous history of total thyroidectomy. At the admission time, 1-2 hours before radioiodine administration, Urease Breath test (UBT) was performed for all patients. Thereafter, the previously determined dose of radioiodine (which was calculated based on disease extension) was administered to the patients (Range: GBq) and all of them were hospitalized for 3 days.

8 Method In fact in our study, in order to detect H. pylori infection the UBT test was performed at the time of hospitalization. The test was repeated again two months after the radioiodine treatment for the determination of the radioactive iodine effect on the H. pylori infection. We asked patients to avoid consumption of drugs that might conceal H. Pylori activity (bismuth and antibiotics for 4 weeks, or omeprazole or similar for 7 days before hospital admission and also during the two months period between the first and second UBTs).

9 Result 88 patients (70F, 18M) were entered in the final analysis. The mean age of these patients was 37.8±13.4 years (range: 12-72). Eighty one patients had papillary type, 5 patients had follicular type and 2 patients had mixed type (follicular and papillary) DTC.

10 Result Out of 88 patients, 71 patients had pre-treatment positive UBT. 23 patients had negative post-treatment result, which means a significant reduction (26.1%, 95% CI: 16.8% -35.5%) in the number of positive UBT results with treatment (p<0.001)

11 Result On the other word: 32.4% of patients with positive UBT result became UBT negative after radio-iodine consumption.

12 The pre and post-treatment UBT results There was a significant decrease in the number of patients with positive UBT after radio-iodine therapy (p<0.001)

13 Discussion It is a long time that physicians are concerned about gastric side effects of radio-iodine therapy on patients treating for DTC. Transient gastritis following radio-iodine therapy and doubts about the risk of gastric cancer after radio-iodine treatment are the main evidence of physicians concerns about the unpleasant gastric effects of radio-iodine therapy

14 Discussion These concerns emphasize the fact that physicians are aware of high radiation dose to the gastric tissue following radio-iodine therapy. For example, it has been confirmed that of the extrathyroidal iodide compartment, 15% is located in the stomach. It is established that outside the thyroid gland the highest absorbed doses per MBq of administered 131 I is for the urinary bladder, followed by stomach.

15 Evidences from the previous studies Estimated dose to the stomach wall is at 1.2mGy/MBq. Also it seems that the residence time of radioactive iodine in the stomach is long enough to have remarkable biologic (or therapeutic) effects. This time has been calculated to be 1.23±0.31hr ( ) in euthyroid state and 0.9±0.08hr ( ) in hyperthyroid state.

16 Discussion The 32.4% reduction of positive cases in UBT tests can be assumed as an indirect clue in radio-sensitivity of H. Pylori bacteria. Anyway, further direct clues for this matter is required which should be provided by future studies (such as external irradiation of H. Pylori cultures to determine the lethal dose).

17 Discussion Systemic prescription of radioactive iodine is not rational and logical for the treatment of the patients suffering from adverse effects of H. Pylori infection, because it will be followed by some more unpleasant troubles such as hypothyroidism and etc. However this finding should not be simply neglected. For example, this finding can be useful for the food industry where radiation is use widescale to sterilize food.

18 Discussion In view of the high prevalence of reinfection in our country, it should be kept in mind that it is possible the patients, in whom the H. Pylori infection had been eradicated, were afflicted again during the intervening 2- months between the first UBT and the second one. Then we are convinced that if the second test had been performed earlier, may be the negativity of the second tests would have been more than 32.4%. In fact, the therapeutic benefit would be more considerable if the second UBT was done with a lag time of less than two months.

19 Conclusion Another explanation is that radioactive iodine may suppress H. Pylori infection and therefore make the results of UBT false negative. In fact, radioactive iodine may suppress H. Pylori infection (like as antibiotics) or gastric acid secretion (like as PPI) and therefore make the results of UBT false negative. Hence, we recommend not using UBT for screening H. Pylori infection at least within two months following radio-iodine therapy.

20 r o f g n i k n a h d T n i K r u Yo n o i t n e t t A