Are diet quality scores after breast cancer diagnosis associated with improved breast cancer survival?

Previous studies have found that diets rich in fruits and vegetables are associated with reduced breast cancer mortality. However, these eating patterns do not necessarily reflect overall diet quality. The association of breast cancer mortality with a priori defined dietary scores, which are based on recommended dietary guidelines and reflect diet quality, has not been evaluated. We hypothesized that diet quality indices based on recommended guidelines are associated with decreased risk of breast cancer and nonbreast cancer mortality in breast cancer survivors. We examined the association between the Dietary Approaches to Stop Hypertension (DASH) score, and the Alternative Healthy Eating Index (AHEI)-2010, and the risk of breast cancer mortality and total mortality among women from the Nurses' Health Study diagnosed with breast cancer. Adherence to DASH-style and AHEI-2010 diets were associated with reduced risk of nonbreast cancer mortality (comparing the fifth quintile with the first quintile, relative risk (RR) = 0.72, 95% confidence interval (CI): 0.53-0.99, P trend = 0.03 for DASH, and RR = 0.57, 95% CI: 0.42-0.77, P trend <0.0001 for AHEI-2010). Diet scores were not significantly associated with breast cancer mortality. Our findings suggest that adherence to a higher quality diet after breast cancer diagnosis does not considerably change the risk of breast cancer death and recurrence. However, healthy dietary choices after breast cancer were associated with reduced risk of nonbreast cancer mortality in women with breast cancer.