SUO 2018: Diet in GU Cancers: Known Unknowns and Unknown Unknowns

Phoenix, Arizona ( Dr. Dorff gave an overview of the role of diet in genitourinary cancers. Many studies have been done trying to elucidate the role of different dietary factors in prostate cancer. These include studies assessing the role of fat, lycopene, vegetables, soy, dairy products, and vitamin E. It is also known that changing the diets results in the change of cancer risk. For example, Japanese men who live in Hawaii, and do not eat a typical Japanese diet, but rather a diet which resembles a North-American diet, have a much higher risk to develop cancer (1). Data has also shown that specific bacteria are associated with a healthier diet (green vegetables, fiber and nuts) and could lower risk of prostate cancer (2).

The general recommendations we as physicians should give patients about diet and reduction of cancer risk include avoidance of smoking, maintaining a healthy body weight, and eating a healthy diet. This includes plenty of whole grains and vegetables, limiting the amount of high fat and high sugary foods consumed, and avoiding processed meat, with a strict limit on the amount of red meat consumed. Lastly, alcohol consumption should be limited as well. What is still unknown, is whether these recommendations impact cancer patients during their treatment, and what are the associated mechanisms.

The Enhanced recovery after surgery (ERAS) protocol recommended for large procedures such as radical cystectomy, recommends a high protein, high carbohydrate supplement a day prior to surgery. No bowel preparation is recommended, and clear liquids should be given on postoperative day one. The length of hospital stay should be decreased to as low as possible. Implementation of this protocol has decreased gastrointestinal complications (16.6% vs. 29.6%) and wound infection rates (11.8% vs. 20.4%) (3). A metanalysis of trials of preoperative carbohydrate loading demonstrated that this leads to reduced length of stay and a lower rate of complications (4). The mechanism is not clear and might involve the microbiome and immune effects. It is also not clear whether increasing the calorie count would improve outcomes, and whether specific nutrients should be added.

In contrast, there are conflicting data showing an opposite approach with weight loss reduction (5) and calorie restriction (6) prior to prostatectomy, conferring improved outcomes. Calorie and protein restriction might even increase resilience (7).

In any case, we must understand that there are epidemiologic associations between diet and genitourinary cancers. Diet should be part of a comprehensive treatment plan and can be used to lower adverse effects of androgen deprivation therapy (ADT), reduce chemotherapy toxicity and improve outcome in general. Dietary supplements have shown minimal impact and are probably not the way to improve patient outcomes. There are several questions that are raised – whether different diets need to be prescribed to patients with different microbiomes? Different tumor types? And different comorbidities.

In conclusion, prospective randomized trials are needed to decipher the role of diet in cancer patients. It is known that dietary counselling is helpful and should be implemented during ADT, perioperatively in large procedures, and possibly before prostatectomy. Future directions include implementation of fasting or fasting-mimic diet with chemotherapy, and personalized and tumor/treatment specific diet for each patient.

Presented By: Tanya B. Dorff, City of Hope, Duarte, CA, USA


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