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TUESDAY, Dec. 13 (HealthDay News) -- Women with a history of breast cancer have a 25% increased risk of a new primary cancer, which may be related to breast cancer treatment, such as malignancies developing in the connective tissue of the thorax and arms, researchers report in the Dec. 8 online issue of the International Journal of Cancer.
Lene Mellemkjaer of the Institute of Cancer Epidemiology at the Danish Cancer Society in Copenhagen, and colleagues calculated risk of second primary cancers using a standardized incidence ratio (SIR). They looked at 13 cancer registries in Europe, Canada, Australia and Singapore, with a total of 525,527 women with primary breast cancer. The incidence of a second primary cancer, excluding contralateral breast cancer, was calculated for the years between 1943 to 2000.
A second primary cancer occurred in 31,399 women, for an overall SIR of 1.25. For specific cancer types, SIR was 2.25 for soft tissue sarcoma, 1.35 for stomach cancer, 1.22 for colorectal cancer, 1.24 for lung cancer, 1.29 for melanoma, 1.58 for non-melanoma skin malignancy, 1.27 for kidney, 1.62 for thyroid, 1.48 for ovarian cancer and 1.52 for leukemia and for endometrial cancer.
Many of the second cancers appear to be attributable to breast cancer treatment, the authors note. Shared genetic or environmental risk factors are likely involved. An increased cancer susceptibility and increased cancer surveillance may also play a role.
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