Does obesity modify the relationship between physical activity and breast cancer risk?

International Pooled Analysis of Leisure-Time Physical Activity and Premenopausal Breast Cancer in Women From 19 Cohorts

PURPOSE

There is strong evidence that leisure-time physical activity is protective against postmenopausal breast cancer risk but the association with premenopausal breast cancer is less clear. The purpose of this study was to examine the association of physical activity with the risk of developing premenopausal breast cancer.

METHODS

We pooled individual-level data on self-reported leisure-time physical activity across 19 cohort studies comprising 547,601 premenopausal women, with 10,231 incident cases of breast cancer. Multivariable Cox regression was used to estimate hazard ratios (HRs) and 95% CIs for associations of leisure-time physical activity with breast cancer incidence. HRs for high versus low levels of activity were based on a comparison of risk at the 90th versus 10th percentiles of activity. We assessed the linearity of the relationship and examined subtype-specific associations and effect modification across strata of breast cancer risk factors, including adiposity.

RESULTS

Over a median 11.5 years of follow-up (IQR, 8.0-16.1 years), high versus low levels of leisure-time physical activity were associated with a 6% (HR, 0.94 [95% CI, 0.89 to 0.99]) and a 10% (HR, 0.90 [95% CI, 0.85 to 0.95]) reduction in breast cancer risk, before and after adjustment for BMI, respectively. Tests of nonlinearity suggested an approximately linear relationship (Pnonlinearity = .94). The inverse association was particularly strong for human epidermal growth factor receptor 2-enriched breast cancer (HR, 0.57 [95% CI, 0.39 to 0.84]; Phet = .07). Associations did not vary significantly across strata of breast cancer risk factors, including subgroups of adiposity.

CONCLUSION

This large, pooled analysis of cohort studies adds to evidence that engagement in higher levels of leisure-time physical activity may lead to reduced premenopausal breast cancer risk.

Effect of Post-diagnosis Physical Activity on Breast Cancer Recurrence: a Systematic Review and Meta-analysis

PURPOSE OF REVIEW

Breast cancer (BC) recurrence dramatically decreases 5-year survival, which causes a fear of BC recurrence among a majority of BC survivors. Evidence is currently inconsistent on whether post-diagnosis recreational physical activity (rPA) can prevent BC recurrence due to the small number of included studies, as well as methodological heterogeneity among the studies. This systematic review aimed to clarify the association between post-diagnosis rPA and the risk of BC recurrence, by conducting a meta-analysis while controlling for the categories of rPA across the existing studies.

RECENT FINDINGS

Prospective cohort studies were searched, and five studies were eligible for the meta-analysis. Of 10,094 patients with BC, 1561 had recurrence during the follow-up period ranging from 12 to 156 months. The meta-analysis revealed that patients whose post-diagnosis rPA was ≥ 7.5 metabolic equivalents (MET-h/week) had a lower BC risk than patients whose rPA was 0-3 MET-h/week (hazard ratio [HR], 0.65; 95% CI, 0.58-0.73, p < 0.00001, I² = 0%). The review indicated that a post-diagnosis rPA of ≥ 7.5 MET-h/week could reduce the risk of BC recurrence by 35%. Although it is necessary to investigate randomized controlled studies in the future, this result will strengthen strategies for the care and/or treatment of patients after BC and can motivate BC survivors to participate in rPA programs after BC diagnosis.

Leisure-time physical activity is associated with reduced risks of breast cancer and triple negative breast cancer in Nigerian women

BACKGROUND

Leisure-time physical activity(LTPA) is associated with a reduced risk of breast cancer, but this has less been investigated by cancer subtypes in Africans living in Sub-Saharan Africa(SSA). We examined the associations between LTPA and breast cancer including its subtypes in Nigerian women and explored the effect modification of body size on such associations.

METHODS

The sample included 508 newly diagnosed primary invasive breast cancer cases and 892 controls from the Nigerian Integrative Epidemiology of Breast Cancer(NIBBLE) Study. Immunohistochemical(IHC) analysis was available for 294 cases. Total metabolic equivalents(METs) per hour/week of LTPA were calculated and divided by quartiles(Q1 <3.75, Q2:3.75-6.69, Q3:6.70-14.74, Q4:14.75 ≤). We applied logistic regressions to estimate the adjusted Odds Ratios(ORs) between LTPA and breast cancer and by its molecular subtypes and whether age-adjusted associations are modified by BMI.

RESULTS

The mean age(Mean±SD) of cases vs. controls(45.5 ± 11.1vs.40.1 ± 9.0) was higher, and the mean total METs hour/week was higher in controls vs. cases(11.9 ± 14.9vs.8.3 ± 11.1,p-value<0.001). Overall, 43.2%(N = 127/294) were classified as HRP, and 41.8%(N = 123/294) as TNBC. Women in the higher LTPA quartiles(Q3-Q4) vs. Q1 had lower odds of having breast cancer(OR_Q4vs.Q1=0.51,95%CI:0.35-0.74) and TNBC(OR_Q4vs.Q1=0.51, 95%CI:0.27-0.96), but not HRP(OR_Q4vs.Q1=0.61,95%CI:0.34-1.09) after adjusting for age, age at first menarche, body size, breastfeeding, menopausal, parity, contraceptives, demographics, alcohol, smoking, and physical activity at home and work. Lastly, LTPA and its age-adjusted association with breast cancer was more pronounced in women with BMI< 30 vs. BMI 30 + .

CONCLUSIONS

LTPA may reduce the risk of breast cancer, especially TNBC, which is the more aggressive and prevalent molecular subtype of breast cancer in SSA.

Physical Activity and Long-Term Risk of Breast Cancer, Associations with Time in Life and Body Composition in the Prospective Malmö Diet and Cancer Study

Being physically active as part of everyday life reduces breast cancer risk. Less is known whether the benefits of an active lifestyle differ depending on the timing of physical activity in life or anthropometric characteristics. The aim of this study was to bring further insights to the association of physical activity in relation to menopausal status and body composition with breast cancer risk by making use of a prospective Swedish cohort (Malmö Diet and Cancer Study) with long-term follow-up. Physical activity information of 15,983 participants for the past 12 months prior to study entry was assessed according to metabolic equivalent task (MET)-hours/week to integrate duration and intensity of reported activities. During 23.2 years median follow-up, 1302 invasive breast cancers occurred. Women reporting a high physical activity at study baseline, corresponding to >1 h daily walking/week (≥28.5 MET-h/week), had a 23% lower long-term breast cancer risk (HRadj = 0.77, 95% CI 0.66−0.90) than those reporting low physical activity, being most pronounced among perimenopausal and postmenopausal women, and women with waist circumference, body fat percentage, or BMI in the upper-normal and overweight range. For premenopausal women or women having obesity or the largest body composition, high physical activity alone did not modify the breast cancer risk, suggesting additional preventive measures indicated in these groups to reduce the long-term risk of breast cancer.

Leisure-time physical activity, sedentary behavior, and risk of breast cancer: Results from the SUN ('Seguimiento Universidad De Navarra') project

Evidence is still limited on the influence of sedentary lifestyles on breast cancer (BC) risk. Also, prospective information on the combined effects of both sedentariness and leisure-time physical activity (LTPA) is scarce. We aimed to assess the association of higher sedentary behavior and LTPA (separately and in combination) with the risk of BC in a middle-aged cohort of university graduates. The SUN Project is a follow-up study initiated in 1999 with recruitment permanently open. Baseline assessments included a validated questionnaire on LTPA and sedentary habits. Subsequently, participants completed biennial follow-up questionnaires. Multivariable adjusted Cox models were used to estimate the hazard ratios (HR) for incident BC according to LTPA, TV-watching, the joint classification of both, and a combined 8-item multidimensional active lifestyle score. We included 10,812 women, with 11.8 years of median follow-up of. Among 115,802 women-years of follow-up, we confirmed 101 incident cases of BC. Women in the highest category of LTPA (>16.5 MET-h/week) showed a significantly lower risk of BC (HR = 0.55; 95% CI: 0.34-0.90) compared to women in the lowest category (≤6 MET/h-week). Women watching >2 h/d of TV sh owed a higher risk (HR = 1.67; 95% CI:1.03-2.72) than those who watched TV <1 h/d. Women in the highest category (6-8 points) of the multidimensional combined 8-item score showed a lower BC risk (HR = 0.35; 95% CI: 0.15-0.79) than those in the lowest category (<2 points) group. There was no significant supra-multiplicative interaction between TV-watching and LTPA. Both low LTPA and TV-watching >2 h/d may substantially increase BC risk, independently of each other.

The effect of bariatric surgery on breast cancer incidence and characteristics: A meta-analysis and systematic review

BACKGROUND

Obesity is a major risk factor for breast cancer. This study examines whether bariatric surgery affects breast cancer incidence in women with obesity compared to BMI-matched controls.

METHODS

EMBASE, MEDLINE, Web of Science, and CINAHL were searched. Primary studies on female breast cancer incidence after bariatric surgery were eligible.

RESULTS

11 studies were included (n = 1,106,939). The rate of cancer diagnosis was lower in the surgical group (0.54%) compared to control (0.84%; risk ratio (RR) 0.50, 95%CI 0.37-0.67, I² = 88%). The results were robust to sensitivity analyses for patient age and study size. Bariatric surgery was associated with increased risk of stage I cancer (RR 1.23, 95%CI 1.06-1.44) and reduced risk of stage III or IV cancer (RR 0.50, 95%CI 0.28-0.88). Hormone receptor characteristics were not affected.

CONCLUSIONS

Bariatric surgery is associated with reduced incidence and earlier stage at diagnosis of breast cancer in women with obesity compared to BMI-matched controls.

Joint associations of physical activity and body mass index with the risk of established excess body fatness-related cancers among postmenopausal women

PURPOSE

Excess body fatness and physical activity independently influence the risk of several types of cancer. However, few studies have examined whether physical activity mitigates the excess risk associated with higher body mass index (BMI).

METHODS

We examined the individual and joint associations between BMI (kg/m²) and leisure-time moderate-to-vigorous physical activity (MVPA, MET-hours/week) with the risk of three established excess body fatness-related cancers (breast, colon, and endometrial) among 43,795 postmenopausal women in the Cancer Prevention Study II (CPS-II) Nutrition Cohort (1992/1993-2015). Further exclusions for women without an intact uterus resulted in 31,805 women for endometrial cancer analyses. Multivariable Cox proportional hazards regression was used to calculate hazard ratio (HR) and 95% confidence intervals (CIs) with interaction terms to assess multiplicative interaction. The relative excess risk due to interaction (RERI) was calculated to assess additive interaction.

RESULTS

BMI and MVPA were individually associated with breast and endometrial cancer risk, but only BMI was associated with colon cancer risk. In joint analyses, increasing levels of MVPA did not lower the risk of these cancers among obese women. For example, compared to the common referent (BMI 18.5- < 25 kg/m², MVPA > 0- < 7.5 MET-hours/week), BMI ≥ 30 kg/m² was associated with a higher risk of breast cancer among women with low MVPA (> 0-< 7.5 MET-hours/week: HR = 1.42, 95% CI: 1.22 - 1.67) and high MVPA (≥ 15 MET-hours/week: HR = 1.53, 95% CI: 1.25 - 1.87; RERI = 0.20, 95% CI: -0.14, 0.54, multiplicative P_interaction = 0.64).

CONCLUSION

Our results do not support the hypothesis that leisure-time physical activity mitigates the excess risk associated with higher BMI for risk of breast, endometrial, or colon cancer among postmenopausal women.

Association of physical activity, body mass index and reproductive history with breast cancer by menopausal status in Iranian women

BACKGROUND

The incidence rate of breast cancer (BC) is increasing in low- and middle-income countries (LMICs), including Iran. We investigated the association between BC risk and physical activity (PA), body mass index (BMI), and reproductive history among Iranian women.

METHODS

We conducted a large hospital-based case-control study and compared 958 BC cases with 967 controls at the Cancer Institute of Iran during 2011-2016. We used multiple logistic regression models and adjusted for potential confounders to estimate odds ratios (ORs) and 95% confidence intervals (95%CIs) for the associations between BC and different risk factors, including low physical activity.

RESULTS

Women with high levels of physical activity had a lower risk of BC compared to those who were inactive (OR = 0.55, 95%CI: 0.41, 0.75). In premenopausal women, the association was observed only in normal-weight women (OR = 0.31, 95%CI: 0.13, 0.75), while it was limited to obese women in the postmenopausal group (OR = 0.29, 95%CI: 0.12, 0.66). We found a high risk of postmenopausal BC among overweight (OR = 1.69; 95%CI: 1.01, 2.81) and obese women (OR = 1.9; 95%CI: 1.14, 3.14) compared to women with a normal BMI. We observed an inverse association among postmenopausal women who had between three and five children (OR = 0.31, 95%CI 0.14, 0.64) and more than six children (OR = 0.21, 95%CI 0.12, 0.42) compared to nulliparous women.

CONCLUSIONS

Low levels of physical activity, low parity, and being overweight or obese were major risk factors for BC. For the first time, we report a strong association between physical activity and BC risk in Iranian women.

The effects of physical activity on physiological markers in breast cancer survivors: A meta-analysis

BACKGROUND

To systematically evaluate the effects of physical activity on physiological markers in breast cancer survivors.

METHODS

A systematic search of the PubMed, Wed of Science, Medline, CNKI and Wanfang Database was performed to identify eligible randomized controlled trials to explore physical activity on physiological markers in breast cancer survivors. STATA version 13.0 (Stata Corp LP, College Station, TX) was used for all statistical analyses.

RESULTS

A total of 11 articles with 941 cases were eligible in this meta-analysis. The results of the meta-analysis showed that physical activity could decrease the levels of insulin (SMD = -1.90, 95%CI: -3.2 to -0.60; I = 92.3%, P < .001), insulin-like growth factor 1 (IGF-I) (WMD = -4.67, 95%CI: -23.14 to 13.79; I = 96.2%, P < .001), insulin-like growth factor binding protein-3 (IGFBP-3) (WMD = -20.09, 95%CI: -47.15 to 6.97; I = 93.3%, P < .001). However, compared with the control group, there was not the significant change of insulin-like growth factor 2 (IGF-II), insulin-like growth factor binding protein-1 (IGFBP-1), leptin, adiponectin, glucose, C-reactive protein (CRP), Interleukin-6 (IL-6), Interleukin-10 (IL-10), and tumor necrosis factor alpha (TNF-ɑ) levels after the intervention.

CONCLUSIONS

Physical activity could improve the insulin function that might be associated with decreasing the levels of IGF-I, IGFBP-3 and insulin in breast cancer survivors.

Physical activity and breast cancer risk: results from the UK Biobank prospective cohort

BACKGROUND

Previous studies suggest a protective role of physical activity in breast cancer risk, largely based on self-reported activity. We aimed to clarify this association by examining breast cancer risk in relation to self-reported physical activity, informed by accelerometer-based measures in a large subset of participants.

METHODS

We analysed data from 47,456 premenopausal and 126,704 postmenopausal women in UK Biobank followed from 2006 to 2014. Physical activity was self-reported at baseline, and at resurvey in a subsample of 6443 participants. Accelerometer data, measured from 2013 to 2015, were available in 20,785 women. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated by using multivariable-adjusted Cox regression.

RESULTS

A total of 3189 cases were diagnosed during follow-up (mean = 5.7 years). Women in the top compared with the bottom quartile of self-reported physical activity had a reduced risk of both premenopausal (RR 0.75; 95% CI 0.60-0.93) and postmenopausal breast cancer (RR 0.87; 95% CI 0.78-0.98), after adjusting for adiposity. In analyses utilising physical activity values assigned from accelerometer measurements, an increase of 5 milli-gravity was associated with a 21% (RR 0.79; 95% CI 0.66-0.95) reduction in premenopausal and a 16% (RR 0.84; 95% CI 0.73-0.96) reduction in postmenopausal breast cancer risk.

CONCLUSIONS

Greater physical activity is associated with a reduction in breast cancer risk, which appears to be independent of any association it may have on risk through its effects on adiposity.

The impact of alcohol consumption and physical activity on breast cancer: The role of breast cancer risk

High alcohol consumption and physical inactivity are known breast cancer risk factors. However, whether the association between these lifestyle factors and breast cancer is modified by a woman's additional breast cancer risk factors has never been studied. Therefore, a population‐based prospective cohort study of 57,654 Swedish women aged 40–74 years, including 957 breast cancer cases, was performed. Alcohol consumption and physical activity were measured with validated web‐based self‐report questionnaires. The Tyrer–Cuzick risk prediction model was used to determine a woman's 10‐year risk of developing breast cancer. Logistic regression models were used to explore whether the effect of alcohol consumption and physical activity on breast cancer was modified by additional breast cancer risk factors. Findings showed that increased alcohol consumption was associated with a higher breast cancer risk (OR = 1.26, 95% CI 1.01, 1.59). However, the association between lifestyle factors (alcohol consumption and physical activity) and breast cancer was generally the same for women at below average, average and above average risk of developing breast cancer. Therefore, additional breast cancer risk factors do not appear to modify the association between lifestyle (alcohol consumption and physical activity) and breast cancer. Considering the general health benefits, preventative lifestyle recommendations can be formulated about alcohol consumption and physical activity for women at all levels of breast cancer risk.

What's new?

Alcohol consumption and physical inactivity are known breast cancer risk factors but it is currently unclear whether all women would benefit equally from drinking less alcohol and being more physically active. The authors found no difference in association between these lifestyle factors and breast cancer in women with below average, average or above average risk of developing breast cancer. They conclude that general preventative lifestyle recommendations about alcohol intake and physical activity apply to all women regardless of their breast cancer risk.

Prediagnostic BMI and thyroid cancer incidence in the PLCO trial

Aim: To assess the correlation between prediagnostic BMI and thyroid cancer risk within the prostate, lung, colorectal and ovary (PLCO) trial. Methods: PLCO trial participants without a history of thyroid cancer before study enrollment who have complete information about prediagnostic BMI were included. Multivariable Cox regression analyses were conducted to assess the impact of prediagnostic BMI on thyroid cancer risk. Results: Higher BMI at the time of the study enrollment was associated with a higher thyroid cancer risk (hazard ratio: 1.046; p < 0.01). Furthermore, compared with a normal to normal prediagnostic BMI trajectory, both normal to overweight as well as normal to obese trajectories were associated with a higher thyroid cancer risk (p = 0.04 and p = 0.03, respectively). Conclusion: Higher BMI at the time of study entry as well as an increasing prediagnostic BMI trajectory are associated with a higher thyroid cancer risk.

Physical Activity in Cancer Prevention and Survival: A Systematic Review

PURPOSE

This article reviews and updates the evidence on the associations between physical activity and risk for cancer, and for mortality in persons with cancer, as presented in the 2018 Physical Activity Guidelines Advisory Committee Scientific Report.

METHODS

Systematic reviews of meta-analyses, systematic reviews, and pooled analyses were conducted through December 2016. An updated systematic review of such reports plus original research through February 2018 was conducted. This article also identifies future research needs.

RESULTS

In reviewing 45 reports comprising hundreds of epidemiologic studies with several million study participants, the report found strong evidence for an association between highest versus lowest physical activity levels and reduced risks of bladder, breast, colon, endometrial, esophageal adenocarcinoma, renal, and gastric cancers. Relative risk reductions ranged from approximately 10% to 20%. Based on 18 systematic reviews and meta-analyses, the report also found moderate or limited associations between greater amounts of physical activity and decreased all-cause and cancer-specific mortality in individuals with a diagnosis of breast, colorectal, or prostate cancer, with relative risk reductions ranging almost up to 40% to 50%. The updated search, with five meta-analyses and 25 source articles reviewed, confirmed these findings.

CONCLUSIONS

Levels of physical activity recommended in the 2018 Guidelines are associated with reduced risk and improved survival for several cancers. More research is needed to determine the associations between physical activity and incidence for less common cancers and associations with survival for other cancers. Future studies of cancer incidence and mortality should consider these associations for population subgroups, to determine dose-response relationships between physical activity and cancer risk and prognosis, and to establish mechanisms to explain these associations.