Lifestyle Patterns and Survival Following Breast Cancer in the Carolina Breast Cancer Study

Abstract

Background: Few studies have examined the impact of lifestyle patterns on survival following breast cancer. We aimed to identify distinct lifestyle patterns based on five behavior/dietary exposures among a population-based sample of women diagnosed with breast cancer and to examine their association with subsequent survival.

Methods: In the Carolina Breast Cancer Study Phases I/II, we interviewed 1,808 women 20-74 years of age following diagnosis of invasive breast cancer. We determined vital status using the National Death Index (717 deaths, 427 from breast cancer; median follow-up 13.56 years). We assessed lifestyle patterns using a latent class analysis based on five behavioral and dietary exposures: current versus never/former smokers; low versus high vegetable and fruit intake; high and low/moderate, versus no alcohol consumption; and no and low/moderate, versus high regular physical activity. We used Cox regression to estimate covariate-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause mortality, and cause-specific and subdistribution HRs for breast cancer-specific mortality within 5 years and 13 years postdiagnosis conditional on 5-year survival.

Results: We identified three distinct lifestyle patterns: healthy behavior and diet (n = 916); healthy behavior and unhealthy diet (n = 624); and unhealthy behavior and diet (n = 268). The unhealthy (vs. healthy) behavior and diet pattern was associated with a 13-year conditional all-cause mortality HR of 1.4 (95% CI = 1.1, 1.9) and with 13-year conditional breast cancer-specific and subdistribution HRs of 1.2 (95% CI = 0.79, 1.9) and 1.2 (95% CI = 0.77, 1.8), respectively.

Conclusions: Behavioral and dietary patterns can be used to identify lifestyle patterns that influence survival patterns following breast cancer diagnosis.

FIGURE 1.

Posterior probabilities of each of five behavior/dietary exposures, for each of three lifestyle patterns: Healthy behavior and diet (n = 916, 51%); healthy behavior and unhealthy diet (n = 624, 34%); unhealthy behavior and diet (n = 268, 15%).

FIGURE 2.

Kaplan-Meier survival curves for latent class assignment: healthy behavior and diet, dashed line (n = 916, 51%) versus healthy behavior and unhealthy diet (n = 624, 34%) and unhealthy behavior and diet (n = 268, 15%), solid line, for all-cause (top) and breast cancer–specific (bottom) survival. Carolina Breast Cancer Study participants were diagnosed with invasive breast cancer from 1993 to 1996 (Phase I) and 1996 to 2000 (Phase II) and followed-up for vital status through December 31, 2011 (n = 1,808). The x axes show time to death in years; the y axes show proportion of participants alive.