ASSESSMENT OF RELATIVE RISK OF 2ND PRIMARY TUMORS AFTER OVARIAN-CANCER AND OF THE USEFULNESS OF DOUBLE PRIMARY CASES AS A SOURCE OF MATERIAL FOR GENETIC-STUDIES WITH A CANCER REGISTRY

Background. It now is accepted that a small proportion of people with certain forms of cancer have a dominantly inherited gene fault that pr edisposes them to it. This is more likely with an early age at onset o r when the person has had multiple primary tumors. Methods. Population -based data from the North West Regional Cancer Registry of England re garding 4157 ovarian cancer cases diagnosed between 1980 and 1989 were analyzed to determine the relative risks (RR) of second primary breas t and colorectal carcinomas. Results. Elevated risks approaching signi ficance were observed for breast and colorectal carcinoma subsequent t o ovarian cancer. After stratification into groups for ovarian histopa thologic characteristics and age at onset, significantly elevated risk s were obtained for both breast and colorectal tumors after ovarian ca rcinoma for women younger than 60 years of age at onset and with serou s histopathologic characteristics (breast RR, 2.68, P < 0.05; colorect al RR, 4.25, P < 0.05). Conclusions. These results emphasize the need for greater awareness of the possibility of development of additional cancer after ovarian carcinoma in high-risk groups. Overall, the study supports the theory that breast, colorectal, and ovarian tumors are r elated genetically.