1437 LOW-CARBOHYDRATE DIETS AND PROSTATE CANCER GROWTH: HOW LOW IS “LOW ENOUGH”?
INTRODUCTION AND OBJECTIVES
Previous dietary studies indicate carbohydrate intake may influence prostate cancer biology, as LAPC-4 and LNCaP xenograft mice fed a no-carbohydrate ketogenic diet (NCKD; 84% fat-0% carbohydrate-16% protein kcal) had significantly smaller tumors and longer survival times compared to mice fed a Western diet (40% fat-44% carbohydrate-16% protein kcal). The NCKD mice were also found to have higher levels of circulating IGFBP-3 and the lowest levels of insulin, IGF-1, and IGF-1:IGFBP-3 ratio despite consuming more calories than the Western group. As it is nearly impossible for a human to consume and maintain a no-carbohydrate diet similar to that in the previous xenograft studies, we sought to determine whether diets containing 10% or 20% kcal from carbohydrates could slow tumor growth in a similar manner to the NCKD in a xenograft model.
A total of 150 male SCID mice were injected with LAPC-4 cells and placed on a Western diet (35% fat-49% carbohydrate-16% protein kcal) ad libitum. Two weeks post-injection, all mice were randomized to one of three arms: NCKD, 10% carbohydrate, or 20% carbohydrate. Ten mice not injected with tumor were fed an ad libitum low-fat diet (12% fat–72% carbohydrate–16% protein kcal) and served as the reference group in a modified-paired feeding protocol for the other three groups. Calorie intake and body weights were measured thrice weekly and tumor volumes twice per week. Mice were sacrificed when tumors reached 1,000mm3.
Despite consuming 5-10% extra calories on average, all mice receiving low-carbohydrate diets were significantly lighter than the mice consuming the low-fat diet (p<0.04). Overall, the mice fed a NCKD were significantly lighter than the other two arms at multiple time points (p<0.05). There were no significant differences in tumor volumes among groups at any time except at Day 52 and 59, where 10% carbohydrate mice had larger tumors (p<0.05). However, after adjusting for the fact that tumor volumes were compared at multiple time points (i.e. multiple comparisons), these were no longer significant. Dietary treatment did not impact overall survival (p=0.34). NCKD mice had significantly higher glucose levels at sacrifice compared to the mice fed 10% and 20% carbohydrates (p=0.001), but similar levels of urinary ketones (p=0.37).
LAPC-4 xenograft mice fed a low-carbohydrate diet (10-20% carbohydrate kcal) had similar survival to mice consuming a NCKD (0% carbohydrate kcal). Thus, the survival benefit of a NCKD may be achievable with less restrictive low-carbohydrate diets.