Long‐term risk of cancer among the first‐degree relatives of epithelial ovarian cancer patients: A cohort study with 48 years of follow up

INTRODUCTION: The long‐term risk of cancer among first‐degree relatives of ovarian cancer patients, especially their offspring, is of apparent clinical importance. Risks caused by known inherited factors such as BRCA1 or BRCA2 pathogenic variants are well established, but these account for only about 15% of ovarian cancer cases. Less is known about the possible familial risks of sporadic ovarian cancers. MATERIAL AND METHODS: Using registry data, we conducted a retrospective cohort study with a total of 6501 first‐degree relatives of 559 epithelial ovarian cancer patients. We studied the occurrence of overall cancer and cancer in specific sites known or suspected to be associated with ovarian cancer (breast, cervix, colon, endometrium, lung and trachea, skin melanoma, ovary, pancreas, prostate, rectum, and stomach). RESULTS: The overall number of cancers was not increased among the first‐degree relatives of epithelial ovarian cancer patients during the up to 48 years of follow up. Among female relatives, the standardized incidence ratio for ovarian cancer was 1.92 (95% CI 1.27–2.79), mostly explained by a 2.30‐fold (95% CI 1.46–3.45) risk among the patients' sisters. There was a decreasing trend in the standardized incidence ratio for ovarian cancer among patients' sisters by increasing age of the index patient. CONCLUSIONS: In our study cohort, we did not observe an increase in the overall cancer risk among the first‐degree relatives of epithelial ovarian cancer patients in comparison with the general population. The risk for ovarian cancer, however, was increased. Current recommendations suggest prophylactic removal of the fallopian tubes and ovaries only with identified inherited risk factors. Our results emphasize the role of genetic counseling and testing, particularly in young ovarian cancer patients and their close female relatives.