Breast Cancer Prevention : Dr. Nilesh D. Mehta

Breast Cancer Prevention : Dr. Nilesh D. Mehta

World wide, breast cancer is the most frequently diagnosed malignancy, accounting for over a million cases each year. This disease is the leading cause of cancer death in women worldwide.
According to statistics maintained by tumor registries in the United States, breast cancer is the most common female cancer (240,000 breast cancers yearly) and the second most common cause of cancer death in women. Several risk factors for breast cancer have been identified with primary risk factor being older age. The incidence of breast cancer rises sharply with age until the age of 45 to 50, at which point the rise is less steep. At age 75 to 80, the incidence rates flatten out and then start to decline.
The association between a higher BMI (body mass index) and postmenopausal breast cancer risk may be explained by higher estrogen levels resulting from the peripheral conversion of estrogen precursors (from adipose tissue) to estrogen. In addition, this may also explain the obesity-breast cancer relationship because a high BMI is associated with higher insulin levels.

When a physician does identify a woman with a high risk of developing breast cancer, then certain preventive strategies can be employed in some patients. Tamoxifen has been used for several years as a breast cancer prevention drug which incidentally also happens to be the same drug used by physicians to treat breast cancer. Role of tamoxifen in breast diseases has been established quite solidly, but newer drugs have been looked at for breast cancer prevention.

IBIS-II randomly assigned 3,864 postmenopausal women at high risk of breast cancer (either due to family history, atypia, lobular carcinoma in situ, or breast density) to treatment with anastrozole or placebo for 5 years.
At a median follow-up of 5 years, breast cancer occurred in 40 women in the anastrozole group (2%) and 85 (4%) in the placebo group. The predicted cumulative incidence of primary breast cancers (including ductal carcinoma in situ) occurring at 7 years of follow-up was 5.6% of women in the placebo group vs. 2.8% of the anastrozole group, representing a 53% decrease in risk. Estrogen receptor–positive invasive breast cancers developed in 3.3% of the placebo group vs. 1.4% of the anastrozole group, representing a 58% decrease in risk.
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Bone fractures occurred in 7.7% of those on placebo compared to 8.5% of women receiving anastrozole. Musculoskeletal aches and pains were the most common adverse events in the anastrozole group and were 10% higher than in the placebo patients. Other joint symptoms were also increased in the anastrozole group, including joint stiffness and carpal tunnel syndrome. It should be noted that women in the post-menopausal age group tend to have aches and pains to a certain degree and this particular side effect has to be carefully monitored.

A lower incidence of cancers other than breast cancer was noted in the anastrozole group compared to the placebo group (40 cases of other cancers in the anastrozole group vs. 70 cases in the placebo group). These were primarily skin cancers and colorectal cancers.
In summary, five years of treatment with anastrozole reduced the risk of primary breast cancer by 53% in postmenopausal women at high risk for developing the disease, according to an analysis of the IBIS II trial.

The study was funded by Cancer Research UK, the National Health and Medical Research Council of Australia, AstraZeneca, and Sanofi-Aventis.

Dr. Nilesh D. Mehta
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