A comparison of analytic approaches for investigating the obesity paradox in kidney cancer.

PURPOSE: Body mass index (BMI) and kidney cancer mortality are inconsistently associated in the scientific literature. To understand how study design affects results, we contrasted associations between pre-diagnosis BMI and mortality under different analytic scenarios in a large, population-based prospective cohort study. METHODS: Using data from the NIH-AARP Diet and Health Study (1995-2011), we constructed two cohorts: a "full at-risk" cohort with no kidney cancer history at baseline (n = 252,845) and an "incident cancer" subset who developed kidney cancer during follow-up (n = 1,652). Cox Proportional Hazards models estimated hazard ratios (HR) and 95% confidence intervals (CI) between pre-diagnosis BMI and mortality for different outcomes (all-cause and cancer-specific mortality), in the different cohorts (full at-risk vs. incident cancer cohort), and with different covariates (minimally vs. fully adjusted). For the incident cancer cohort, we also examined time to mortality using different timescales: from enrollment or diagnosis. RESULTS: In the full at-risk study population, higher pre-diagnosis BMI was associated with greater cancer-specific mortality in fully adjusted multivariable models, particularly for obese participants [HR, (95% CI): 1.76, (1.38-2.25)]. This association was less pronounced in the incident cancer cohort [1.50, (1.09-2.07)]. BMI was not strongly associated with all-cause mortality in either cohort in fully adjusted models [full cohort: 1.03, (1.01, 1.06); incident cancer cohort: 1.20, (0.97, 1.48)]. CONCLUSIONS: Populations characterized by high adult BMI will likely experience greater population burdens of mortality from kidney cancer, partially because of higher rates of kidney cancer diagnosis. Questions regarding overall mortality burden and post-diagnosis cancer survivorship are distinct and require different study designs.

Hair dye and chemical straightener use and breast cancer risk in a large US population of black and white women.

Many hair products contain endocrine-disrupting compounds and carcinogens potentially relevant to breast cancer. Products used predominately by black women may contain more hormonally-active compounds. In a national prospective cohort study, we examined the association between hair dye and chemical relaxer/straightener use and breast cancer risk by ethnicity. Sister Study participants (n = 46,709), women ages 35-74, were enrolled between 2003 and 2009, and had a sister with breast cancer but were breast cancer-free themselves. Enrollment questionnaires included past 12-month hair product use. Cox proportional hazards models estimated adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association between hair products and breast cancer; effect measure modification by ethnicity was evaluated. During follow-up (mean = 8.3 years), 2,794 breast cancers were identified. Fifty-five percent of participants reported using permanent dye at enrollment. Permanent dye use was associated with 45% higher breast cancer risk in black women (HR = 1.45, 95% CI: 1.10-1.90), and 7% higher risk in white women (HR = 1.07, 95% CI: 0.99-1.16; heterogeneity p = 0.04). Among all participants, personal straightener use was associated with breast cancer risk (HR = 1.18, 95% CI 0.99-1.41); with higher risk associated with increased frequency (p for trend = 0.02). Nonprofessional application of semipermanent dye (HR = 1.28, 95% CI 1.05-1.56) and straighteners (HR = 1.27, 95% CI 0.99-1.62) to others was associated with breast cancer risk. We observed a higher breast cancer risk associated with any straightener use and personal use of permanent dye, especially among black women. These results suggest that chemicals in hair products may play a role in breast carcinogenesis.

Use of patient-reported controls for secular trends to study disparities in cancer-related job loss.

PURPOSE: Racial/ethnic minorities experience greater job loss than whites during periods of economic downturn and after a cancer diagnosis. Therefore, race/ethnicity-matched controls are needed to distinguish the impact of illness on job loss from secular trends METHODS: Surveys were administered during and 4-month post-completion of breast cancer treatment. Patients were pre-diagnosis employed women aged 18-64, undergoing treatment for stage I-III breast cancers, who spoke English, Chinese, Korean, or Spanish. Each patient was asked to: (1) nominate peers who were surveyed in a corresponding timeframe (active controls), (2) report a friend's work status at baseline and follow-up (passive controls). Both types of controls were healthy, employed at baseline, and shared the nominating patient's race/ethnicity, language, and age. The primary outcome was number of evaluable patient-control pairs by type of control. A patient-control pair was evaluable if work status at follow-up was reported for both individuals. RESULTS: Of the 180 patients, 25% had evaluable active controls (45 patient-control pairs); 84% had evaluable passive controls (151 patient-control pairs). Although patients with controls differed from those without controls under each strategy, there was no difference in the percentage of controls who were working at follow-up (96% of active controls; 91% of passive controls). However, only 65% of patients were working at follow-up. CONCLUSIONS: The majority of patients had evaluable passive controls. There was no significant difference in outcome between controls ascertained through either method IMPLICATIONS FOR CANCER SURVIVORS: Passive controls are a low-cost, higher-yield option to control for secular trends in racially/ethnically diverse samples.