Survival analyses from the Women's Intervention Nutrition Study (WINS) evaluating dietary fat reduction and breast cancer outcome

Abstract

522 Background: We previously reported five year results with follow up through October, 2003 of a phase III randomized trial where a dietary intervention targeting fat intake reduction, associated with significant weight loss, improved relapse-free survival compared to control in women with resected, early stage breast cancer receiving conventional cancer management (RR 0.79, P=0.034) (JNCI 2006;98:1767- 76). After initiating the dietary intervention with 16 visits over 8 weeks, ongoing adherence was addressed by q 3 month nutritionist contacts. Active dietary intervention and contacts with nutritionists ended in May, 2004. We now report a protocol-mandated survival analysis update. Methods: Updated survival information was obtained through October, 2007 largely through national death registries and randomization group survival differences were examined using Cox proportional hazards models in intention-to-treat analyses. Exploratory analyses examined survival by hormone receptor subgroups and active dietary intervention status. Results: Although fewer deaths were seen in the intervention group (9.1% vs. 11.1% cumulative mortality, RR 0.83) the difference was not statistically significant (P=0.146). In the 362 women with ER- and PR- disease, a significant overall survival benefit was seen for intervention group participants (7.5% vs. 18.1%, cumulative mortality, RR 0.41, P=0.003). The influence of ongoing active dietary intervention was examined by analyses censored six months after contact with nutritionists ended (for survival before and after 12/31/04). Conclusions: A dietary intervention targeting fat intake reduction did not significantly increase overall survival of women with resected breast cancer receiving conventional cancer management. Exploratory analyses suggest dietary intervention influence on survival may be greater in hormone receptor negative subgroups and during the period of active dietary intervention. Dietary Intervention Effect on Survival By Receptor Status and Active Dietary Intervention Interval Patient Group # entered Entire Period During Intervention After Intervention Ended # Deaths RR P value # Death RR P Value # Death RR P value All 2437 251 0.83 0.146 208 0.78 0.068 43 1.15 0.217 ER + 1959 183 0.88 0.146 147 0.85 0.459 36 1.08 0.221 ER − 478 68 0.68 0.059 61 0.60 0.049 7 1.57 0.599 No significant financial relationships to disclose.