ASCO GU 2018: Interim analysis of a prospective randomized trial of dietary carbohydrate restriction for men with a rising PSA after failed primary treatment: Carbohydrate and Prostate Study 2

San Francisco, CA (UroToday.com) As clinicians, we often get asked about dietary modifications or lifestyle modifications that may help prevent and improve prostate cancer. However, there has been very little data to support any dietary supplement / vitamins in reducing the risk of prostate cancer or improving outcomes.

Carbohydrates, an important staple in daily diet, which has been associated with various medical conditions when taken in excess. The authors note that in laboratory mice, an extreme low carbohydrate diet was shown to slow PCa growth. Hence, they went on to assess this in a population of men following definition local therapy for localized PCa.

Nearly one third of men treated with curative intent for localized prostate cancer (PCa), either with surgery or radiotherapy, will develop a rising PSA and biochemical recurrence (BCR). The rate of PSA rise (PSA doubling time aka PSADT) is a predictor of metastases development and eventually PCa death.

This abstract reports preliminary, interim results from a 6-month phase II multi-institutional randomized study of dietary carbohydrate restriction vs. no diet intervention control. Specifically, this is being done in men who received either RP or definitive local radiation for localized PCa in the past, have had a PSA between 0.4-20.0 ng/mL (RP) or 3-20 ng/mL (XRT) in the past 3 months, and a PSADT between 3-36 months.

Patients on the diet were instructed to eat < 20 grams/carbs/day with no other limits. However, it is unclear how well this is enforced or followed. The control arm was told to make no diet.

In this interim analysis, the primary outcome was weight loss. TThe primary outcome of the study as a whole is differences in PSADT between arms. Secondary outcomes include weight loss and dietary make-up. Total anticipated enrollment is 60 at completion.

As of right now, 28 patients (14 in each study arm) of the planned 60 patients have completed the study. Characteristics were well-balanced at baseline.

At the 6-month dietary assessment, calorie consumption was similar between the two study arms (p = 0.090) among the 16 patients (7 low-carb, 9 control) with diet information. Not all patients had diet information. Subjects in the low-carb arm ate fewer carbs (29 vs. 188 g, p = 0.008) and more protein (125 vs. 73 g, p = 0.044) but similar amounts of fat (75 vs. 67 g, p = 0.672) vs. subjects in the control arm. Six months on the low carb diet resulted in greater weight loss (median: 31.7 vs. 0.8 lbs, p < 0.001), lower BMI (24.4 vs. 29.6 kg/m2, p < 0.001), and smaller waist circumference (95.7 vs. 108.9 cm, p = 0.002).

Unfortunately, there is no data yet on whether this affects PSA progression and PCa outcomes. This dramatic weight loss, while obviously good for the patient’s overall health, does not yet translate to improved PCa outcomes. We look forward to these results to help better counsel our patients.

Presented by: Stephen Freedland, MD

Co-Author: Jennifer Allen, Andrew J. Armstrong, Judd W. Moul, Howard M. Sandler, Dana Levin, Lauren E. Howard, Pao-hwa Lin

Written by: Thenappan Chandrasekar, MD, Clinical Fellow, University of Toronto, Twitter: @tchandra_uromd at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA
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