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Description of Evidence


    The question arises whether breast cancer patients treated with lumpectomy and radiation therapy (L-RT) are at increased risk for second breast malignancies or other malignancies compared with those treated by mastectomy. Outcomes of 1,029 L-RT patients were compared with 1,387 patients who underwent mastectomies. After a median follow-up of 15 years, there was no difference in the risk of second malignancies.[62] Further evidence from three RCTs is also reassuring. One report of 1,851 women randomly assigned to undergo total mastectomy, lumpectomy alone, or L-RT showed rates of contralateral breast cancer to be 8.5%, 8.8%, and 9.4%, respectively.[63] Another study of 701 women randomly assigned to undergo radical mastectomy or breast-conserving surgery followed by radiation therapy demonstrated the rate of contralateral breast carcinomas per 100 woman-years to be 10.2 versus 8.7, respectively.[64] The third study compared 25-year outcomes of 1,665 women randomly assigned to undergo radical mastectomy, total mastectomy, or total mastectomy with radiation. There was no significant difference in the rate of contralateral breast cancer according to the treatment group, and the overall rate was 6%.[65]


    Obesity is associated with increased breast cancer risk, especially among postmenopausal women who do not use HT. The WHI observational study observed 85,917 women aged 50 to 79 years and collected information on weight history as well as known risk factors for breast cancer.[66] Height, weight, and waist and hip circumferences were measured. With a median follow-up of 34.8 months, 1,030 of the women developed invasive breast cancer. Among the women who never used HT, increased breast cancer risk was associated with weight at entry, body mass index (BMI) at entry, BMI at age 50 years, maximum BMI, adult and postmenopausal weight change, and waist and hip circumferences. Weight was the strongest predictor, with a RR of 2.85 (95% CI, 1.81–4.49) for women weighing more than 82.2 kg, compared with those weighing less than 58.7 kg.


    Many epidemiologic studies have shown an increased risk of breast cancer associated with alcohol consumption. Individual data from 53 case-control and cohort studies were included in a British meta-analysis.[67] Compared with women who reported no alcohol consumption, the RR of breast cancer was 1.32 (95% CI, 1.19–1.45; P < .001) for women consuming 35 g to 44 g of alcohol per day and 1.46 (95% CI, 1.33–1.61; P < .001) for those consuming at least 45 g of alcohol per day. The RR of breast cancer increases by about 7% (95% CI, 5.5%–8.7%; P < .001) for each 10 g of alcohol (i.e., one drink) consumed per day. The same result was obtained, even after additional stratification for race, education, family history, age at menarche, height, weight, BMI, breast-feeding, oral contraceptive use, menopausal hormone use and type, and age at menopause.


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