Physical activity and premenopausal breast cancer: an examination of recall and selection bias

Recreational Physical Activity and Outcomes After Breast Cancer in Women at High Familial Risk

Background

Recreational physical activity (RPA) is associated with improved survival after breast cancer (BC) in average-risk women, but evidence is limited for women who are at increased familial risk because of a BC family history or BRCA1 and BRCA2 pathogenic variants (BRCA1/2 PVs).

Methods

We estimated associations of RPA (self-reported average hours per week within 3 years of BC diagnosis) with all-cause mortality and second BC events (recurrence or new primary) after first invasive BC in women in the Prospective Family Study Cohort (n = 4610, diagnosed 1993-2011, aged 22-79 years at diagnosis). We fitted Cox proportional hazards regression models adjusted for age at diagnosis, demographics, and lifestyle factors. We tested for multiplicative interactions (Wald test statistic for cross-product terms) and additive interactions (relative excess risk due to interaction) by age at diagnosis, body mass index, estrogen receptor status, stage at diagnosis, BRCA1/2 PVs, and familial risk score estimated from multigenerational pedigree data. Statistical tests were 2-sided.

Results

We observed 1212 deaths and 473 second BC events over a median follow-up from study enrollment of 11.0 and 10.5 years, respectively. After adjusting for covariates, RPA (any vs none) was associated with lower all-cause mortality of 16.1% (95% confidence interval [CI] = 2.4% to 27.9%) overall, 11.8% (95% CI = -3.6% to 24.9%) in women without BRCA1/2 PVs, and 47.5% (95% CI = 17.4% to 66.6%) in women with BRCA1/2 PVs (RPA*BRCA1/2 multiplicative interaction P = .005; relative excess risk due to interaction = 0.87, 95% CI = 0.01 to 1.74). RPA was not associated with risk of second BC events.

Conclusion

Findings support that RPA is associated with lower all-cause mortality in women with BC, particularly in women with BRCA1/2 PVs.

Recreational Physical Activity Is Associated with Reduced Breast Cancer Risk in Adult Women at High Risk for Breast Cancer: A Cohort Study of Women Selected for Familial and Genetic Risk

Although physical activity is associated with lower breast cancer risk for average-risk women, it is not known if this association applies to women at high familial/genetic risk. We examined the association of recreational physical activity (self-reported by questionnaire) with breast cancer risk using the Prospective Family Study Cohort, which is enriched with women who have a breast cancer family history (N = 15,550). We examined associations of adult and adolescent recreational physical activity (quintiles of age-adjusted total metabolic equivalents per week) with breast cancer risk using multivariable Cox proportional hazards regression, adjusted for demographics, lifestyle factors, and body mass index. We tested for multiplicative interactions of physical activity with predicted absolute breast cancer familial risk based on pedigree data and with BRCA1 and BRCA2 mutation status. Baseline recreational physical activity level in the highest four quintiles compared with the lowest quintile was associated with a 20% lower breast cancer risk (HR, 0.80; 95% confidence interval, 0.68-0.93). The association was not modified by familial risk or BRCA mutation status (P interactions >0.05). No overall association was found for adolescent recreational physical activity. Recreational physical activity in adulthood may lower breast cancer risk for women across the spectrum of familial risk. SIGNIFICANCE: These findings suggest that physical activity might reduce breast cancer risk by about 20% for women across the risk continuum, including women at higher-than-average risk due to their family history or genetic susceptibility.See related commentary by Niehoff et al., p. 23.

Comparison of Performance Between a Short Categorized Lifestyle Exposure-based Colon Cancer Risk Prediction Tool and a Model Using Continuous Measures

Risk prediction models that estimate an individual's risk of developing colon cancer could be used for a variety of clinical and public health interventions, including offering high-risk individuals enhanced screening or lifestyle interventions. However, if risk prediction models are to be translated into actual clinical and public health practice, they must not only be valid and reliable, but also be easy to use. One way of accomplishing this might be to simplify the information that users of risk prediction tools have to enter, but it is critical to ensure no resulting detrimental effects on model performance. We compared the performance of a simplified, largely categorized exposure-based colon cancer risk model against a more complex, largely continuous exposure-based risk model using two prospective cohorts. Using data from the Nurses' Health Study and the Health Professionals Follow-up Study we included 816 incident colon cancer cases in women and 412 in men. The discrimination of models was not significantly different comparing a categorized risk prediction model with a continuous prediction model in women (c-statistic 0.600 vs. 0.609, P _diff = 0.07) and men (c-statistic 0.622 vs. 0.618, P _diff = 0.60). Both models had good calibration in men [observed case count/expected case count (O/E) = 1.05, P > 0.05] but not in women (O/E = 1.19, P < 0.01). Risk reclassification was slightly improved using categorized predictors in men [net reclassification index (NRI) = 0.041] and slightly worsened in women (NRI = -0.065). Categorical assessment of predictor variables may facilitate use of risk assessment tools in the general population without significant loss of performance.

MEN1-Dependent Breast Cancer: Indication for Early Screening? Results From the Dutch MEN1 Study Group

OBJECTIVE

Multiple endocrine neoplasia type 1 (MEN1) is associated with an early-onset elevated breast cancer risk. This finding potentially has implications for breast cancer screening for women with MEN1, and therefore it is necessary to assess whether other risk factors are involved to identify those at greatest risk.

DESIGN

A cross-sectional case control study was performed using the Dutch MEN1 cohort, including >90% of the adult Dutch MEN1 population. All women with a confirmed MEN1 mutation received a questionnaire regarding cancer family history and breast cancer-related endocrine and general cancer risk factors.

RESULTS

A total of 138 of 165 (84%) eligible women with MEN1 completed the questionnaire. Eleven of the 138 women had breast cancer. Another 34 relatives with breast cancer were identified in the families of the included women, of whom 11 were obligate MEN1 carriers, 14 had no MEN1 mutation, and 9 had an unknown MEN1 status. The median age at breast cancer diagnosis of women with MEN1 (n = 22) was 45 years (range, 30 to 80 years), in comparison with 57.5 years (range, 40 to 85 years) in female relatives without MEN1 (n = 14; P = 0.03) and 61.2 years in the Dutch reference population. Known endocrine risk factors and general risk factors were not different for women with and without breast cancer.

CONCLUSION

The increased breast cancer risk in MEN1 carriers was not related to other known breast cancer risk factors or familial cancer history, and therefore breast cancer surveillance from the age of 40 years for all women with MEN1 is justifiable.

Physical activity from menarche to first pregnancy and risk of breast cancer

Breast tissue is particularly susceptible to exposures between menarche and first pregnancy, and a longer interval between these reproductive events is associated with elevated breast cancer risk. Physical activity during this time period may offset breast cancer risk, particularly for those at highest risk with longer menarche-to-first-pregnancy intervals. We used data from 65,576 parous women in the Nurses' Health Study II free of cancer in 1989 (baseline) and recalled their leisure-time physical activity at ages 12-34 in 1997. Current activity was collected at baseline and over follow-up. Relative risks (RRs) were estimated using multivariable Cox proportional hazards regression models. Between 1989 and 2011, 2,069 invasive breast cancer cases were identified. Total recreational activity between menarche and first pregnancy was not significantly associated with the risk of breast cancer. However, physical activity between menarche and first pregnancy was associated with significantly lower breast cancer risk among women in the highest category of a menarche-to first-pregnancy interval (≥20 years; RR for the highest versus the lowest quartile = 0.73, 95% confidence interval = 0.55-0.97; Ptrend  = 0.045; Pinteraction  = 0.048). This was not observed in women with a shorter interval. Physical activity between menarche and first pregnancy was associated with a lower risk of breast cancer among women with at least 20 years between these reproductive events. This may provide a modifiable factor that women can intervene on to mitigate their breast cancer risk associated with a longer interval.

Association between vegetable, fruit and carbohydrate intake and breast cancer risk in relation to physical activity

BACKGROUND

Although the nutritional may exert effect on the breast cancer risk, it is not clear whether the role diet is the same in sedentary and physically active women. The aim of this study was to evaluate the association between fruit, vegetable and carbohydrate intake and the risk of breast cancer among Polish women considering their physical activity level.

MATERIALS AND METHODS

A case-control study was conducted that included 858 women with histological confirmed breast cancer and 1,085 controls, free of any cancer diagnosis, aged 28-78 years. The study was based on a self-administered questionnaire to ascertain physical activity, dietary intake, sociodemographic characteristics, reproductive factors, family history of breast cancer, current weight and high, and other lifestyle factors. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated in unconditional logistic regression analyses including a broad range of potential confounders.

RESULTS

With comparison of the highest vs lowest quartile of intake, strong significant associations were observed for total vegetables (OR=0.37, 95%CI=0.20-0.69 P for trend <0.01 and OR=0.53, 95%CI=0.29-0.96, P for trend <0.02), and total fruits (OR=0.47, 95%CI=0.25-0.87, P for trend <0.05 and OR=0.47, 95%CI=0.24-0.90, P for trend <0.02) among women characterized by the lowest and the highest quartile of physical activity. No associations were observed for total carbohydrate intake. Additional analysis showed a positive association for sweets and desert intake among women in the lowest quartile of physical activity (OR=3.49, 95%CI=1.67-7.30, P for trend <0.009) for extreme quartiles of intake comparing to the referent group.

CONCLUSIONS

The results suggest that a higher consumption of vegetable and fruit may be associated with a decreased risk of breast cancer, especially among women who were low or most physically active throughout their lifetimes. These findings do not support an association between diet high in carbohydrate and breast cancer. However, a higher intake of sweets and deserts may by associated with an increased risk of breast cancer among women who were less physically active.

Self-reported psychological stress and the risk of breast cancer: a case-control study

The aim of this study was to examine the relationship between severe life events and breast cancer risk. This study was based on a case-control examination of 858 Polish invasive breast cancer cases and 1085 controls matched for age and place of residence. Data on life events, sociodemographic characteristic, reproductive factors, family history of breast cancer, current weight and height, and lifestyle habits were collected between January 2003 and May 2007 using a self-administered questionnaire. Odds ratios with 95% confidence intervals were estimated as the measure of the relationship between life event stress and breast cancer risk using unconditional logistic regression analyses. After adjustment for potential breast cancer risk factors, women with four to six individual major life events had 5.33 times higher risk for breast cancer, compared with those in the lowest quartile. Similarly, women with a lifetime life change score greater than 210 had about 5 times higher risk compared to women with corresponding scores in the range 0-70. Several life events (death of a close family member, personal injury or illness, imprisonment/trouble with the law, retirement) were significantly associated with breast cancer risk. These findings suggest that major life events can play an important role in the etiology of breast cancer.

Risk taking in avalanche terrain: a study of the human factor contribution

OBJECTIVE

To discover possible associations between the human factors and avalanche incidents.

DESIGN

Self-report, intercept, and Web-based, 1-year retrospective, cross-sectional study.

SETTING

Mountain Equipment Co-op stores in Calgary and Vancouver, Canada.

PARTICIPANTS

People shopping at the store and who had entered avalanche terrain in the past 12 months were invited to complete the survey (n = 447).

INDEPENDENT VARIABLES

Sex, age, sport activity, days of exposure, years of experience, socioeconomic status, level of training, risk propensity, and motivation.

MAIN OUTCOME MEASURES

Experiencing an avalanche incident.

RESULTS

Women and those traveling with women were less likely to experience an avalanche incident [odds ratio (OR) = 0.45; 95% confidence interval (CI), 0.21-0.96]. Those with the most training were more likely to report experiencing an avalanche incident (OR = 6.86; 95% CI, 2.37-19.83), but this difference was attenuated (OR = 2.25) and not statistically significant (95% CI, 0.57-8.81) after adjustment for exposure. Experience was not found to be a factor. Being motivated to seek intense experiences was found to be a factor (OR = 2.19; 95% CI, 1.03-4.66), whereas being motivated to create memorable experiences was protective (OR = 0.29; 95% CI, 0.10-0.86).

CONCLUSIONS

The results of this study suggest that people exposing themselves to avalanche risk do so to satisfy inherited and learned motivational needs and that some motivations are associated with higher or lower risk taking than others. Training appears to be exploited so as to increase access to these benefits rather than reduce risk. Within this risk/reward paradigm, risk taking among men is moderated by the presence of a woman in the group.

Ensuring long-term sustainability of existing cohorts remains the highest priority to inform cancer prevention and control

The case for continued follow-up of existing cohorts arises from the key attributes of cohorts that are already meeting the goals proposed by Potter for the creation of a new cohort. These attributes include the basic nature of ongoing cohorts in that they are, by design, hypothesis-driven and must adapt to emerging technologies over time. Importantly, cohort investigators must identify and address gaps in knowledge that will inform public health strategies and clinical practices. Above all, cohorts must capitalize on their unique features to address public health priorities and inform our prevention strategies. Continued follow-up adds substantial return on investment to guide cancer prevention.

Intensity and timing of physical activity in relation to postmenopausal breast cancer risk: the prospective NIH-AARP diet and health study

BACKGROUND

Despite strong evidence of an inverse association of physical activity with postmenopausal breast cancer risk, whether a certain intensity or time of life of physical activity is most effective for lowering breast cancer risk is not known.

METHODS

In 118,899 postmenopausal women in the prospective NIH-AARP Diet and Health Study, we examined the relations of light and moderate-to-vigorous intensity physical activity during four periods of life ("historical": ages 15-18, 19-29, 35-39 years; "recent": past 10 years) to postmenopausal breast cancer risk. Physical activity was assessed by self-report at baseline, and 4287 incident breast cancers were identified over 6.6 years of follow-up.

RESULTS

In age-adjusted and multivariate Cox regression models, >7 hours/week of moderate-to-vigorous activity during the past 10 years was associated with 16% reduced risk of postmenopausal breast cancer (RR:0.84; 95%CI:0.76,0.93) compared with inactivity. The association remained statistically significant after adjustment for BMI (RR:0.87; 95%CI:0.78,0.96). Neither moderate-to-vigorous activity during other periods of life nor light intensity activity during any period of life was related to breast cancer risk, and associations did not vary by tumor characteristics.

CONCLUSION

A high level of recent, but not historical, physical activity of moderate-to-vigorous intensity is associated with reduced postmenopausal breast cancer risk. More precise recall of recent physical activity than activity in the distant past is one possible explanation for our findings.

Physical activity and the risk of breast cancer in BRCA1/2 mutation carriers

BRCA1/2 mutation carriers have a high lifetime risk of developing breast cancer. Differences in penetrance indicate that this risk may be influenced by lifestyle factors. Because physical activity is one of the few modifiable risk factors, it may provide a target to add to breast cancer prevention in this high-risk population. We examined the association between self-reported lifetime sports activity and breast cancer risk in a nationwide retrospective cohort study, including 725 carriers, of whom 218 had been diagnosed with breast cancer within 10 years prior to questionnaire completion. We found a nonsignificantly decreased risk for ever engaging in sports activity (HR = 0.84, 95%CI = 0.57-1.24). Among women who had participated in sports, a medium versus low level of intensity and duration (i.e., between 11.0 and 22.7 mean MET hours/week averaged over a lifetime) reduced the risk of breast cancer (HR = 0.59, 95%CI = 0.36-0.95); no dose-response trend was observed. For mean hours/week of sports activity, a nonsignificant trend was observed (HR(low versus never) = 0.93, 95%CI = 0.60-1.43; HR(medium versus never) = 0.81, 95%CI = 0.51-1.29; HR(high versus never) = 0.78, 95%CI = 0.48-1.29; p (trend overall) = 0.272; p (trend active women) = 0.487). For number of years of sports activity no significant associations were found. Among women active in sports before age 30, mean MET hours/week showed the strongest inverse association of all activity measures (HR(medium versus low) = 0.60, 95%CI = 0.38-0.96; HR(high versus low) = 0.58, 95%CI = 0.35-0.94; p (trend) = 0.053). Engaging in sports activity after age 30 was also inversely associated with breast cancer risk (HR = 0.63, 95%CI = 0.44-0.91). Our results indicate that sports activity may reduce the risk of breast cancer in BRCA1/2 mutation carriers.