Diet and breast cancer: evidence that extremes in diet are associated with poor survival.
OBJECTIVE
Diet has been postulated to influence breast cancer prognosis; however, existing evidence is weak and inconsistent. Previous studies have sought evidence of a linear relationship between diet and breast cancer outcomes. Because of a U-shaped association of body mass index (BMI) with survival in breast cancer, we hypothesized that a nonlinear association also existed for dietary variables.


METHODS
Four hundred seventy-seven women with surgically resected T1 to T3, N0/1, M0 breast cancer completed the Block Food Frequency Questionnaire 9.3 +/- 4.6 weeks (mean +/- standard deviation) after diagnosis, reporting intake over the preceding 12 months. Data on tumor-related factors, treatment, and outcomes were obtained prospectively from medical records. A series of Cox models was performed, modeling the association of dietary factors with breast cancer survival linearly and quadratically, adjusting for total energy intake, tumor- and treatment-related variables, and BMI.


RESULTS
Significant nonlinear survival associations were found for protein, oleic acid, cholesterol, polyunsaturated-saturated fat ratio, and for percentage of calories from fat and percentage of calories from carbohydrates in multivariate models. The shape of the survival associations varied across nutrients. Hazard ratios for highest risk quintiles ranged from 2.1 to 6.5. For total fat, adjustment for BMI reduced the multivariate P value obtained from nonlinear Cox models from.05 to.10. No significant linear associations were identified.


CONCLUSIONS
The association of key dietary variables with breast cancer survival may be U-shaped rather than linear. Our data suggest that midrange intake of most major energy sources is associated with the most favorable outcomes, and extremes are associated with less favorable outcomes.
Goodwin
Pamela J
PJ
Department of Medicine, Sam Lunenfeld Research Institute Mount Sinai Hospital, Toronto, Ontario, Canada. pgoodwin@mtsinai.on.ca
Ennis
Marguerite
M
Pritchard
Kathleen I
KI
Koo
Jarley
J
Trudeau
Maureen E
ME
Hood
Nicky
N
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000473:pathology* / Q000601:surgery; D015331:Cohort Studies; D004032:Diet; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D005260:Female; D006801:Humans; D008875:Middle Aged; D009367:Neoplasm Staging; D016017:Odds Ratio; D011379:Prognosis; D013534:Survival
D004040:Dietary Carbohydrates; D004041:Dietary Fats