The trial ended early, with 45 patients finishing the study, after interim results suggested it was unlikely to achieve statistical significance for differences in the rate of PSA rise between the two groups. However, when they re-examined the data, this time controlling for factors such as the type of prior cancer treatment, baseline PSA, the rate of PSA rise before the study started and the natural rise in PSA levels caused by weight loss, they noted significant differences.
"Our re-examination showed PSA levels in patients who followed the extremely low carbohydrate diet rose more slowly than did levels in patients who did not follow the diet," said Stephen J. Freedland, MD, director of the Center for Integrated Research in Cancer and Lifestyle and the Warschaw, Robertson, Law Families Chair in Prostate Cancer at Cedars-Sinai Cancer. "In addition, over six months, men on the low carbohydrate died lost an average of 26 pounds per person compared with one pound weight loss in the control group, without significant adverse effects on prostate cancer growth or overall health."
Freedland is professor of Surgery and the study's first and corresponding author. The senior author was Pao-Hwa Lin, PhD, associate professor of Medicine at Duke University School of Medicine in Durham, North Carolina.
The study's findings are preliminary, Freedland emphasized. "We need to conduct clinical trials with larger numbers of patients over longer periods of time to confirm the value of an extremely low carbohydrate diet in controlling recurrent prostate cancer," he said.
As one step toward that goal, the research team is examining prostate cancer tissues, collected after patients followed a low-carb diet for six months, to understand the effect on tumor biology. "Potentially, diet could be one tool to delay the time until a patient might need to start hormonal therapy," Freedland said.
Conflicts of interest: A.J. Armstrong reports receiving other commercial research support from Astellas, Janssen, and Pfizer and speakers bureau honoraria from Dendreon and Bayer. H. Sandler is an employee/paid consultant for Janssen and holds ownership interest (including patents) in Radiogel. No potential conflicts of interest were disclosed by the other authors.
Funding: Research reported in this publication was supported by the National Cancer Institute of the National Institutes of Health under award number NCI K24 CA160653 and by the Hartford Foundation.