PARITY, OBESITY AND BREAST CANCER SURVIVAL: DOES INTRINSIC SUBTYPE MODIFY OUTCOMES?

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  • March 19, 2019
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  • Sun, Xuezheng
    • Affiliation: Gillings School of Global Public Health, Department of Epidemiology
Abstract
  • Purpose: Parity and obesity have shown distinct associations with the breast cancer risk by intrinsic subtype. Little is known whether their influence on prognosis also varies by intrinsic subtype, although their general prognostic associations have been reported previously. Methods: Study subjects were 1,140 invasive breast cancer patients from the phases I and II of the population-based Carolina Breast Cancer Study (CBCS), with tissue blocks available for subtyping using immunohistochemical markers. Parity was measured by number of full-term birth and time since last birth. Obesity was measured by body mass index (BMI) and waist hip ratio (WHR). Vital status was determined using the National Death Index. The association of exposures with breast cancer (BC)-specific and overall survival was assessed using the Cox proportional hazards model. Results: During the follow-up (median =13.5 years), 450 patients died, with 61% due to breast cancer (n=276). For obesity, WHR, but not BMI, was associated with an increased risk of all-cause mortality (0.84+ vs. <0.77, adjusted hazard ratio (HR) = 1.50, 95% confidence interval (CI) =1.11-2.05), independent of age, race, adjusted lifestyle and socioeconomic factors. According to intrinsic subtypes, high BMI (30+ kg/m2) was an independent factor for all-cause mortality (adjusted HR=2.25, 95% CI=1.14-4.46, <0.25 kg/m2 as reference) among patients with basal-like tumors, while high WHR (0.84+) was associated with poor overall survival (adjusted HR=1.75, 95% CI=1.20-2.56, <0.77 as reference) among patients with luminal tumors. For parity, both high parity (3+ births) and recent birth (< 5 years before diagnosis) were associated with BC-specific mortality (parity: adjusted HR=1.76, 95% CI=1.13-2.73; birth recency: adjusted HR=1.90, 95% CI=1.10-3.34), with stronger effect observed in luminal tumors than basal-like tumors. The subtype-specific prognostic associations of parity and obesity were suggested to vary by follow-up period (greater HRs detected in patients surviving 5+ years), but not by race or menopause. Conclusions: Our study suggests the influence of obesity and parity on breast cancer prognosis may vary by intrinsic subtype. These results may contribute to a better understanding of how pregnancy and obesity influence the natural history of different breast cancer subtype, and help tailor treatment and optimize intervention strategies.
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  • In Copyright
Advisor
  • Olshan, Andrew
  • Nichols, Hazel
  • Robinson, Whitney
  • Troester, Melissa
  • Sherman, Mark
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2015
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  • Chapel Hill, NC
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  • There are no restrictions to this item.
Date uploaded
  • June 23, 2015

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