Radiation exposure and familial aggregation of cancers as risk factors for colorectal cancer after radioiodine treatment for thyroid carcinoma

Carole Rubino, Elisabeth Adjadj, Françoise Doyon, Akhtar Shamsaldin, Tahaa Moncef Abbas, Bernard Caillou, Marc Colonna, Claudia Cecarreli, Claire Schvartz, Stéphane Bardet, Christiane Langlois, Marcel Ricard, Martin Schlumberger, Florent De Vathaire

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    Abstract

    Purpose: In thyroid cancer patients, radioiodine treatment has been shown to be associated with an increased risk of colon carcinoma. The aim of this study in thyroid cancer patients was to evaluate the role of familial factors in the risk of colorectal cancer and their potential interaction with radioiodine exposure. Methods and Materials: We performed a case-control study on 15 colorectal cancer patients and 76 matched control subjects, nested in a cohort of 3708 thyroid cancer patients treated between 1933 and 1998. For each patient, the radiation dose delivered to the colon by radioiodine was estimated by use of standard tables. In those who received external radiation therapy, the average radiation doses delivered to the colon and rectum were estimated by use of DOS_Eg software. A complete familial history was obtained by face-to-face interviews, and a familial index was defined to evaluate the degree of familial aggregation. Results: The risk of colorectal cancer increased with familial aggregation of colorectal cancer (p = 0.02). After adjustment for the radiation dose delivered to the colon and rectum, the risk of colorectal cancer was 2.8-fold higher (95% CI, 1.0-8.0) for patients with at least one relative affected by colorectal cancer than for patients without such a family history (p = 0.05). The radiation dose delivered to the colon and rectum by 131I and external radiation therapy was associated with an increase of risk near the significance threshold (p = 0.1). No significant interaction was found between radiation dose and having an affected relative (p = 0.9). Conclusions: The role of familial background in the risk of colorectal cancer following a differentiated thyroid carcinoma appears to increase with the radiation dose delivered to the colon and rectum. However, the study population was small and no interaction was found between these two factors.

    Original languageEnglish
    Pages (from-to)1084-1089
    Number of pages6
    JournalInternational Journal of Radiation Oncology Biology Physics
    Volume62
    Issue number4
    DOIs
    Publication statusPublished - 15 Jul 2005

    Keywords

    • Case-control study
    • Colorectal cancer
    • Epidemiology
    • Familial aggregation
    • Radiation exposure
    • Radio-iodine
    • Second primary cancer
    • Thyroid cancer

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