Risk of Cancer in the Other Breast

QUESTION: What percentage of women develop a second cancer in the opposite breast, not a recurrence?

ANSWER: For most women who have had breast cancer (not women with an inherited gene abnormality), the risk of developing a new breast cancer in the opposite breast is about 1% a year (unrelated to the recurrence of the first breast cancer). Over 10 years, then, the risk would be approximately 10%. For some women, the risk may be a bit less. For women with an inherited gene abnormality, the risk can be 3-4% per year. You can read more on this subject in our section on Tamoxifen.

Close follow-up with high-quality mammography and breast examinations is essential to the early detection of a possible second cancer or a recurrence of the first.

—Marisa Weiss, M.D.