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Prostate Cancer May Raise Risk for Breast Cancer
Fri Mar 28, 1:49 PM ET Add Health - Reuters to My Yahoo!
NEW YORK (Reuters Health) - Men diagnosed with prostate cancer (news - web sites) are slightly more likely than other men to develop another type of cancer, including breast cancer (news - web sites), the results of a new study suggest.
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The increased risk may simply stem from greater surveillance in men diagnosed with prostate cancer. However, for at least one malignancy -- male breast cancer -- the risk does appear to be higher after prostate cancer, although the cancer remains uncommon.
The current findings run counter to previous reports showing that the overall risk of a second primary cancer is decreased after a diagnosis of prostate cancer. Still, a few reports have suggested that the risk of certain tumors, such as bladder and kidney cancer, is increased after a prostate cancer diagnosis, according to the report in the April issue of The Journal of Urology.
To further evaluate the link between prostate cancer and second primary cancers, Dr. Camilla Thellenberg and colleagues at Umea University in Sweden analyzed data from all prostate cancer cases that were entered in the Swedish Cancer Registry from 1958 to 1996. A total of 135,713 cases were included in the study.
In the study group, a total of 10,526 second primary cancers were identified. For a comparably sized group in the general population, 8,984 cancers would have been expected. This equates to an increased risk of 17 percent in men with prostate cancer.
Further analysis, however, revealed that the elevated overall risk was limited to the 6 months following prostate cancer diagnosis. Beyond that point, prostate cancer was actually associated with a decreased risk of other malignancies. Taken together, these findings suggest that much of the increased risk was due to surveillance bias, meaning that men with prostate cancer had their second cancer detected because they most likely saw doctors and had more tests than men who did not have cancer.
The researchers identified several tumor types that were more common after a prostate cancer diagnosis. Male breast cancer was 2 times more common and small intestine tumors were 1.39 times more common in prostate cancer patients than in the general population. Other tumors linked to prostate cancer included endocrine tumors and the skin cancer melanoma.
There are several possible explanations for the link between prostate cancer and male breast cancer, the authors note. First, the mammary tumor may not have actually been a primary breast cancer, but rather cancer that had spread from the prostate. Second, and a more likely explanation, is that the hormonal therapy used to treat prostate cancer induced the breast cancer.
"To our knowledge," the associations with male breast cancer and small intestine tumors "have not been reported previously, and they warrant more study," the investigators note.
SOURCE: The Journal of Urology 2003;169:1345-1348.
