Dataset Information

Body Mass Index and Risk of Second Cancer Among Women With Breast Cancer.

ABSTRACT:

Background

Breast cancer survivors are at increased risk for developing second primary cancers compared with the general population. Little is known about whether body mass index (BMI) increases this risk. We examined the association between BMI and second cancers among women with incident invasive breast cancer.

Methods

This retrospective cohort included 6481 patients from Kaiser Permanente Colorado and Washington of whom 822 (12.7%) developed a second cancer (mean follow-up was 88.0 months). BMI at the first cancer was extracted from the medical record. Outcomes included: 1) all second cancers, 2) obesity-related second cancers, 3) any second breast cancer, and 4) estrogen receptor-positive second breast cancers. Multivariable Poisson regression models were used to estimate relative risks (RRs) and 95% confidence intervals (CIs) for second cancers associated with BMI adjusted for site, diagnosis year, treatment, demographic, and tumor characteristics.

Results

The mean age at initial breast cancer diagnosis was 61.2 (SD = 11.8) years. Most cases were overweight (33.4%) or obese (33.8%) and diagnosed at stage I (62.0%). In multivariable models, for every 5 kg/m2 increase in BMI, the risk of any second cancer diagnosis increased by 7% (RR = 1.07, 95% CI = 1.01 to 1.14); 13% (RR = 1.13, 95% CI = 1.05 to 1.21) for obesity-related cancers, 11% (RR = 1.11, 95% CI = 1.02 to 1.21) for a second breast cancer, and 15% (RR = 1.15, 95% CI = 1.04 to 1.27) for a second estrogen receptor-positive breast cancer.

Conclusions

We observed a statistically significant increased risk of second cancers associated with increasing BMI. These findings have important public health implications given the prevalence of overweight and obesity in breast cancer survivors and underscore the need for effective prevention strategies.

SUBMITTER: Feigelson HS

PROVIDER: S-EPMC8757319 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundObesity and elevated breast density are common risk factors for breast cancer, and their effects may vary by estrogen receptor (ER) subtype. However, their joint effects on ER subtype-specific risk are unknown. Understanding this relationship could enhance risk stratification for screening and prevention. Thus, we assessed the association between breast density and ER subtype according to body mass index (BMI) and menopausal status.MethodsWe conducted a case-control study nested within two mammography screening cohorts, the Mayo Mammography Health Study and the San Francisco Bay Area Breast Cancer SPORE/San Francisco Mammography Registry. Our pooled analysis contained 1538 ER-positive and 285 ER-negative invasive breast cancer cases and 4720 controls matched on age, menopausal status at time of mammogram, and year of mammogram. Percent density was measured on digitized film mammograms using computer-assisted techniques. We used polytomous logistic regression to evaluate the association between percent density and ER subtype by BMI subgroup (normal/underweight, < 25 kg/m2 versus overweight/obese, ≥ 25 kg/m2). We used Wald chi-squared tests to assess for interactions between percent density and BMI. Our analysis was stratified by menopausal status and hormone therapy usage at the time of index mammogram.ResultsPercent density was associated with increased risk of overall breast cancer regardless of menopausal status or BMI. However, when analyzing breast cancer across ER subtype, we found a statistically significant (p = 0.008) interaction between percent density and BMI in premenopausal women only. Specifically, elevated percent density was associated with a higher risk of ER-negative than ER-positive cancer in overweight/obese premenopausal women [OR per standard deviation increment 2.17 (95% CI 1.50-3.16) vs 1.33 (95% CI 1.11-1.61) respectively, Pheterogeneity = 0.01]. In postmenopausal women, elevated percent density was associated with similar risk of ER-positive and ER-negative cancers, and no substantive differences were seen after accounting for BMI or hormone therapy usage.ConclusionsThe combination of overweight/obesity and elevated breast density in premenopausal women is associated with a higher risk of ER-negative compared with ER-positive cancer. Eighteen percent of premenopausal women in the USA have elevated BMI and breast density and may benefit from lifestyle modifications involving weight loss and exercise.

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Project description:BackgroundWe investigated the association between body mass index (BMI) and breast cancer risk in women at increased risk of breast cancer receiving tamoxifen or anastrozole compared with placebo using data from the International Breast Cancer Intervention Studies [IBIS-I (tamoxifen) and IBIS-II (anastrozole)].MethodsBaseline BMI was calculated from nurse assessed height and weight measurements for premenopausal (n = 3138) and postmenopausal (n = 3731) women in IBIS-I and postmenopausal women in IBIS-II (n = 3787). The primary endpoint was any breast cancer event (invasive and ductal carcinoma in situ). We used Cox proportional hazards regression to calculate hazard ratios (HRs) for risk after adjustment for covariates.ResultsThere were 582 (IBIS-I) and 248 (IBIS-II) breast cancer events [median follow-up = 16.2 years (IQR 14.4-17.7) and 10.9 years (IQR 8.8-13.0), respectively]. In adjusted analysis, women with a higher BMI had an increased breast cancer risk in both IBIS-I [HR = 1.06 per 5 kg/m2 (0.99-1.15), p = 0.114] and in IBIS-II [HR per 5 kg/m2 = 1.21 (1.09-1.35), p < 0.001]. In IBIS-I, the association between BMI and breast cancer risk was positive in postmenopausal women [adjusted HR per 5 kg/m2 = 1.14 (1.03-1.26), p = 0.01] but not premenopausal women [adjusted HR per 5 kg/m2 = 0.97 (0.86-1.09), p = 0.628]. There was no interaction between BMI and treatment group for breast cancer risk in either IBIS-I (p = 0.62) or IBIS-II (p = 0.55).ConclusionsHigher BMI is associated with greater breast cancer risk in postmenopausal women at increased risk of the disease, but no effect was observed in premenopausal women. The lack of interaction between BMI and treatment group on breast cancer risk suggests women are likely to experience benefit from preventive therapy regardless of their BMI. Trial registration Both trials were registered [IBIS-I: ISRCTN91879928 on 24/02/2006, retrospectively registered ( http://www.isrctn.com/ISRCTN91879928 ); IBIS-II: ISRCTN31488319 on 07/01/2005, retrospectively registered ( http://www.isrctn.com/ISRCTN31488319 )].