There is growing evidence that inflammation is a central and reversible mechanism through which obesity promotes cancer risk and progression. MethodsWe review recent findings regarding obesity-associated alterations in the microenvironment and the local and systemic mechanisms through which these changes support tumor growth. ResultsLocally, hyperadiposity is associated with altered adipose tissue function, adipocyte death, and chronic low-grade inflammation. Most individuals who are obese harbor inflamed adipose tissue, which resembles chronically injured tissue, with immune cell infiltration and remodeling. Within this distinctly altered local environment, several pathophysiologic changes are found that may promote breast and other cancers. Consistently, adipose tissue inflammation is associated with a worse prognosis in patients with breast and tongue cancers. Systemically, the metabolic syndrome, including dyslipidemia and insulin resistance, occurs in the setting of adipose inflammation and operates in concert with local mechanisms to sustain the inflamed microenvironment and promote tumor growth. Importantly, adipose inflammation and its protumor consequences can be found in some individuals who are not considered to be obese or overweight by body mass index. ConclusionThe tumor-promoting effects of obesity occur at the local level via adipose inflammation and associated alterations in the microenvironment, as well as systemically via circulating metabolic and inflammatory mediators associated with adipose inflammation. Accurately characterizing the obese state and identifying patients at increased risk for cancer development and progression will likely require more precise assessments than body mass index alone. Biomarkers of adipose tissue inflammation would help to identify high-risk populations. Moreover, adipose inflammation is a reversible process and represents a novel therapeutic target that warrants further study to break the obesity-cancer link.

Purpose Obesity, insulin resistance, and elevated levels of circulating proinflammatory mediators are associated with poorer prognosis in early-stage breast cancer. To investigate whether white adipose tissue (WAT) inflammation represents a potential unifying mechanism, we examined the relationship between breast WAT inflammation and the metabolic syndrome and its prognostic importance. Experimental Design WAT inflammation was defined by the presence of dead/dying adipocytes surrounded by macrophages forming crown-like structures of the breast (CLS-B). Two independent groups were examined in cross-sectional (Cohort 1) and retrospective (Cohort 2) studies. Cohort 1 included 100 women undergoing mastectomy for breast cancer risk reduction (n=10) or treatment (n=90). Metabolic syndrome-associated circulating factors were compared by CLS-B status. The association between CLS-B and the metabolic syndrome was validated in Cohort 2 which included 127 women who developed metastatic breast cancer. Distant recurrence free survival (dRFS) was compared by CLS-B status. Results In Cohorts 1 and 2, breast WAT inflammation was detected in 52/100 (52%) and 52/127 (41%) patients, respectively. Patients with breast WAT inflammation had elevated insulin, glucose, leptin, triglycerides, C-reactive protein, and interleukin-6; and lower HDL cholesterol and adiponectin (P<0.05) in Cohort 1. In Cohort 2, breast WAT inflammation was associated with hyperlipidemia, hypertension, and diabetes (P<0.05). Compared to patients without breast WAT inflammation, the adjusted hazard ratio for dRFS was 1.83 (95% CI, 1.07 to 3.13) for patients with inflammation. Conclusions WAT inflammation, a clinically occult process, helps to explain the relationship between metabolic syndrome and worse breast cancer prognosis.

Purpose To evaluate the effects of exercise therapy on cardiorespiratory fitness (CRF) in randomized controlled trials (RCTs) among patients with adult-onset cancer. Secondary objectives were to evaluate treatment effect modifiers, safety, and fidelity. Methods A systematic search of PubMed, Embase, Cumulative Index to Nursing and Allied Health Literature, and the Cochrane Library was conducted to identify RCTs that compared exercise therapy to a nonexercise control group. The primary end point was change in CRF as evaluated by peak oxygen consumption (VO; in mL O × kg × min) from baseline to postintervention. Subgroup analyses evaluated whether treatment effects differed as a function of exercise prescription (ie, modality, schedule, length, supervision), study characteristics (ie, intervention timing, primary cancer site), and publication year. Safety was defined as report of any adverse event (AE); fidelity was evaluated by rates of attendance, adherence, and loss to follow-up. Results Forty-eight unique RCTs that represented 3,632 patients (mean standard deviation age, 55 ± 7.5 years; 68% women); 1,990 (55%) and 1,642 (45%) allocated to exercise therapy and control/usual care groups, respectively, were evaluated. Exercise therapy was associated with a significant increase in CRF (+2.80 mL O × kg × min) compared with no change (+0.02 mL O × kg × min) in the control group (weighted mean differences, +2.13 mL O × kg × min; 95% CI, 1.58 to 2.67; I, 20.6; P < .001). No statistical significant differences were observed on the basis of any treatment effect modifiers. Thirty trials (63%) monitored AEs; a total of 44 AEs were reported. The mean standard deviation loss to follow-up, attendance, and adherence rates were 11% ± 13%, 84% ± 12%, and 88% ± 32%, respectively. Conclusion Exercise therapy is an effective adjunctive therapy to improve CRF in patients with cancer. Our findings support the recommendation of exercise therapy for patients with adult-onset cancer.