Relative risk (RR) of second malignancies (SM) in patients treated by “risk” radiotherapy (RT) or “risk” RT plus chemotherapy (CT) in comparison with patients treated by CT ± “non risk RT” for Hodgkin's disease (HD)

Abstract

6695 Background: Late effect, in particular second malignancies, kill more patients with HD then the disease itself. The most of published studies compare observed and expected numbers of cancers in the cohort with use of age-specific national incidence rate. Aim of our study was quantification of RR of SM in patients treated by “risk” RT ± CT (mantel field for breast cancer, and thyroid cancer, upper abdomen for stomach cancer, inverted Y or total nodal irradiation for colon cancer, inverted Y for gynecologic cancer) in comparison with patients treated by CT ± “non risk” RT. We wanted to assess if there is a reason to provide different follow up to this two different groups of patients. Methods: 851 patients (475 men and 376 women) with survival time after HD diagnosis >1 year were treated in MOÚ during 1967–1995. 337 patients were treated only by RT, 182 only by CT and 332 by RT+CT. Median age at RT was 33 years, median follow-up 11 years. 74 cases of SM developed in the cohort. To consider the exposure effect, rate ratio (RR), attributable risk (AR) and relative attributable risk (RAR) were computed for main sites of SM. The association between exposure and SM occurrence was tested by Fisher's test. Results: RR for the SM were as follows: breast cancer 5.39; lung cancer 0.77; colorectal cancer 10.3; stomach cancer 1.46; thyroid cancer 1.18; gynaecologic cancer 2.19. Rate ratio for NHL could not be established because of no case in the control group. Conclusion: The relative risk of solid tumors as second malignancies increased with the time of follow-up. Treatment by “risk RT” increases RR of breast cancer, colorectal cancer, gynecologic cancer and slightly thyroid cancer. Therefore this group of patient should be offered more intensive follow-up : yearly breast examination ( MG), yearly hemoccult ( colonoscopy every 3 years), yearly gynecologic examination according to the risk of SM. No significant financial relationships to disclose.