Over the past 40 years, the prevalence of obesity has increased epidemically worldwide, which raises significant concerns regarding public health and the associated economic burden. Obesity is a major risk factor for several conditions including cardiovascular disease and type 2 diabetes, and recent evidence suggests that obesity negatively affects cancer risk and outcome. The relationship between obesity and cancer is complex and involves multiple factors both at the systemic and cellular level. Indeed, disruptions in insulin metabolism, adipokines, inflammation, and sex hormones all contribute to the adverse effects of obesity in cancer development and progression. The focus of this review will be the impact of these systemic obesity-related factors on cancer biology, incidence, and outcome. Potential therapeutic interventions and current clinical trials targeting obesity and its associated factors will also be discussed.

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Sexual health and uro-genital symptom counseling should be provided to BCS, particularly pre/peri-menopausal patients, even at long-term follow-up.

Background Obesity at breast cancer (BC) diagnosis has been associated with poor outcome, although the magnitude of effect in different BC subtypes is uncertain. We report on the association of obesity/overweight at diagnosis of non-metastatic BC with disease-free (DFS) and overall survival (OS) in the following defined subtypes: hormone receptor positive/HER2 negative (HR+HER2-), HER2 positive (HER2+), and triple negative (TNBC). Methods We searched MEDLINE, EMBASE and COCHRANE databases until January 1, 2019. Study eligibility were performed independently by two authors. Studies reporting hazard ratios (HR) of OS and/or DFS for obesity/overweight in BC subtypes were included. Pooled HR were computed and weighted using generic inverse variance and random effects models. Results 27 studies were included. Obese, compared to non-obese, women, had worse DFS in all subtypes: the hazard ratios were 1.26 (95% confidence interval [CI] = 1.13 to 1.41, P < .001) for HR+HER2-BC, 1.16 (95%CI = 1.06 to 1.26, P < .001) for HER2+ BC, and 1.17 (95%CI = 1.06 to 1.29, P = .001) for TNBC. OS was also worse in obese vs non-obese women (HR+HER2-BC HR = 1.39, 95%CI = 1.20 to 1.62, P < .001; HER2+BC HR = 1.18, 95%CI = 1.05 to 1.33, P = .006 and TNBC HR = 1.32, 95%CI = 1.13 to 1.53, P < .001). As opposed to obesity, overweight was not associated with either DFS or OS in HER2+BC (HR = 1.02, 95%CI = 0.81 to 1.28, P = .85; and HR = 0.96, 95%CI = 0.76 to 1.21, P = .99, respectively) or TNBC (HR = 1.04, 95%CI = 0.93 to 1.18, P = .49; and HR = 1.08, 95%CI = 0.81 to 1.44, P = .17), respectively. In HR+HER2-BC, being overweight was associated with worse OS (HR = 1.14, 95%CI = 1.07 to 1.22, P < .001). Conclusions Obesity was associated with modestly worse DFS and OS in all BC subtypes.

Low vitamin D levels have been associated with poor breast cancer outcomes in observational studies. We examined the association of vitamin D blood levels with relapse-free survival (RFS), breast cancer-specific survival (BCSS), and overall survival (OS) in the MA.21 randomized clinical trial. Fasting blood was collected pre-chemotherapy in 934/2104 (44.4 %) of subjects; 25 hydroxy vitamin D was measured (radioimmunoassay, Diasorin) in one batch. Vitamin D was assessed as a transformed continuous factor, and categorically (quartiles and clinical classifications). Univariate and multivariate prognostic analyses (adjusted for treatment, stratification factors, and baseline imbalances) were performed using Cox models. Most patients were young (median 47.8 years), white (91.6 %) and premenopausal (69.4 %) with grade III (52 %), HER2 negative or missing (89.5 %), ER positive (61.9 %), T1-2 (89.4 %), N + (72.7 %) breast cancer. Compared to the full population, those with vitamin D levels were more likely to be white, PS 1 or 2, to have undergone mastectomy, and to have an ER + tumor. Mean vitamin D was 69.7 nmol/L (27.9 ng/ml) and did not vary by tumor subtype. The majority (80.5 %) had levels >50 nmol/L (20 ng/ml), considered adequate by Institute of Medicine. Continuous vitamin D was not multivariately associated with RFS, BCSS, or OS (p = 0.36, 0.26, 0.33, respectively); categorical vitamin D was also not associated with outcome. Vitamin D associations with RFS did not differ within ER/HER2 subgroups. There was no evidence that vitamin D blood level was associated with RFS, BCSS, and OS in MA.21; the majority of subjects had adequate vitamin D levels at study entry.

The prevalence of the metabolic syndrome and diabetes/pre-diabetes was significantly higher in BC survivors than in controls group, notably in those with lower levels of physical activity. Enhanced diabetes/metabolic syndrome screening and promotion of physical activity may be warranted in BC survivors.

Background Metformin has been associated with lower breast cancer risk and improved outcomes in observational studies. Multiple biologic mechanisms have been proposed, including a recent report of altered sex hormones (SHs). We evaluated the effect of metformin on SHs in MA.32, a phase III trial of nondiabetic BC subjects randomized to metformin or placebo. Methods We studied the subgroup of post-menopausal hormone receptor negative BC subjects not receiving endocrine treatment who provided fasting blood at baseline and at 6 months after randomization. Sex hormone binding globulin (SHBG), bioavailable testosterone (BT) and estradiol levels were assayed using ECLIA (electrochemiluminescense immunoassay). Change from baseline to 6 months between study arms was compared using Wilcoxon sum rank tests and regression models. Results 312 women were eligible (141 metformin vs 171 placebo); the majority of subjects in each arm had T1/2, N0, HER2 negative BC and had received (neo)adjuvant chemotherapy. Mean age ± SD was 58.1±6.9 vs 57.5±7.9 years, mean BMI was 27.3±5.2 vs 28.9±6.4 kg/m2 for metformin vs placebo respectively. Median estradiol decreased between baseline and 6 months on metformin vs placebo (-5.7 vs 0 pmol/L; p < 0.001) in univariable analysis and after controlling for baseline BMI and BMI change (p < 0.001). There was no change in SHBG or BT. Conclusion Metformin lowered estradiol levels, independent of BMI. This observation suggests a new metformin effect that has potential relevance to estrogen sensitive cancers.

Disease recurrence (locoregional, distant) exerts a significant clinical impact on the survival of estrogen receptor–positive breast cancer patients. Many of these recurrences occur late, more than 5 years after original diagnosis, and represent a major obstacle to the effective treatment of this disease. Indeed, methods to identify patients at risk of late recurrence and therapeutic strategies designed to avert or treat these recurrences are lacking. Therefore, an international workshop was convened in Toronto, Canada, in February 2018 to review the current understanding of late recurrence and to identify critical issues that require future study. In this article, the major issues surrounding late recurrence are defined and current approaches that may be applicable to this challenge are discussed. Specifically, diagnostic tests with potential utility in late-recurrence prediction are described as well as a variety of patient-related factors that may influence recurrence risk. Clinical and therapeutic approaches are also reviewed, with a focus on patient surveillance and the implementation of extended endocrine therapy in the context of late-recurrence prevention. Understanding and treating late recurrence in estrogen receptor–positive breast cancer is a major unmet clinical need. A concerted effort of basic and clinical research is required to confront late recurrence and improve disease management and patient survival.