Diet quality indices and breast cancer survival in postmenopausal women.

A152

Background: Limited information exists on the role of diet in breast cancer survival. Most research has been restricted to investigating single nutrients or foods, with the focus on dietary fat, fruits and vegetables, fiber, and alcohol. Therefore we examined diet quality indices in relation to survival among women diagnosed with breast cancer. Methods: Using the Nurses' Health Study cohort, we calculated the cumulative average of diet quality scores from prospectively completed food frequency questionnaires from 1984, 1986, 1990, 1994, and 1998. We evaluated 4 dietary quality scores: Alternate Healthy Eating Index (AHEI), Diet Quality Index-Revised (DQIR), Recommended Food Score (RFS), and the alternate Mediterranean Diet Score (aMed). Cox proportional hazards models were used to evaluate the associations between diet quality scores and death from any cause, death from breast cancer, death from non-breast cancer causes, and breast cancer recurrences. We also stratified our analysis by estrogen receptor status of the primary tumor. Results: We documented 3058 invasive stage I-III breast cancer cases between 1984 and 2004 in postmenopausal women. In age and multivariate adjusted analyses, diet quality scores were not associated with breast cancer mortality, or with breast cancer recurrences. Furthermore, association between diet quality scores and breast cancer mortality or recurrences did not differ by estrogen receptor status of the primary/original tumor. However, higher AHEI score was associated with lower mortality from non breast cancer causes. In multivariate analysis, the RRs compared to the lowest quintile were 0.81, 0.84, 0.65, and 0.65 (95% CI, 0.41 - 1.02, P trend = 0.02). There was a similarly lowered risk of mortality from non breast cancer causes for the highest quintile of DQIR and aMed score compared with the lowest, although the linear trends were not significant. The RR comparing the highest to lowest quintiles for DQIR was 0.64 (95% CI, 0.40 - 1.02, P trend = 0.17), and for aMed was 0.68 (95% CI, 0.44, 1.07, P trend = 0.16), respectively. Women who did not die from breast cancer were most likely to die from heart, vascular, and lung disease. AHEI was also marginally associated with a lower total mortality. After multivariate adjustment; the RR comparing the highest to lowest quintiles was 0.84 (95% CI, 0.60 - 1.17, P trend = 0.04). Conclusion: Our results suggest that diet quality after breast cancer diagnosis does not change the risk of breast cancer recurrence or death. However, healthy dietary choices are important for women after breast cancer, because they are linked to risk of death from other causes.