Women who survive breast cancer aren't completely out of the woods, according to a recent article in the International Journal of Cancer. The multicenter study included cancer data from 13 population-based registries in Europe, Australia, Canada and Singapore. More than 525,000 women diagnosed with a primary breast cancer between 1943 and 2000 were studied to see if, when, and what kind of second primary cancer they developed.

Their risk of a second primary breast cancer was also evaluated. The majority of women were postmenopausal at diagnosis. Thirty percent of the women had their breast cancers confirmed after 1990; 47 percent were diagnosed during 1975 to 1990 and 23 percent prior to 1975. In reviewing the results, the authors noted that because the participants were diagnosed and treated over a long period "when treatment has varied greatly," the observed pattern of second cancer may be different from women currently undergoing treatment. That's important to understand in that the study found a 25 percent increase in the risk of developing a new primary nonbreast cancer in women diagnosed with a first primary breast cancer compared with women who were cancer-free. They also noted that the elevated risk of cancers in the vicinity of the breast such as esophagus, lung, thyroid gland, stomach and soft tissue sarcomas of thorax and upper limb and leukemia may be due to radiation exposure, and that risk estimates decreased after 1975 possibly as a result of improved radiation techniques. Even so, the researchers observed that "the known effects of treatment and common risk factors do not seem to fully explain" the increase in subsequent second cancers. Women in the study had elevated risk for stomach, colorectal, lung, endometrial, ovarian, renal, and thyroid cancers, as well non-melanoma skin cancer, leukemia, and soft tissue sarcoma. Odds of developing a second cancer increased over time from diagnosis; women who were older when the disease was confirmed had a lesser risk of a new malignancy.