Post-surgery soy offers no prostate cancer advantage
medwireNews: A US randomized trial of the effects of soy consumption after prostatectomy has ended early after investigators found no benefit in terms of prostate cancer recurrence.
The study follows several epidemiologic reports of an inverse correlation between soy consumption and prostate cancer that was thought to underlie the lower rates of prostate cancer death seen in Asian men compared with those in the West.
But in the 2 years following radical prostatectomy, rates of biochemical recurrence did not differ between men at high risk for prostate cancer recurrence who took a daily supplement of soy protein 20g and those who took placebo.
The research team, led by Maarten Bosland (University of Illinois at Chicago), conclude that the approach may be a case of too little too late.
“It is conceivable that soy is protective against prostate cancer when consumption begins early in life but not later or when prostate cancer is already present,” they write in JAMA.
“If this is the case, chemoprevention of prostate cancer with soy is unlikely to be effective if started later in life, given the high prevalence of undetected prostate cancer in middle-aged men.”
Among 81 patients assigned to the intervention and 78 assigned to placebo, 22 (27.2%) and 23 (29.5%), respectively, developed confirmed biochemical recurrence (prostate specific antigen ≥ 0.07ng/mL) at interim analysis.
Regression analyses confirmed that there was no statistical difference between the groups, a finding that was repeated when the authors excluded definitively or potentially non-adherent patients.
“The findings of this study provide another example that associations in observational epidemiologic studies between purported preventive agents and clinical outcomes need confirmation in randomized clinical trials,” say Bosland and colleagues.
“Not only were these findings at variance with the epidemiologic evidence on soy consumption and prostate cancer risk, they were also not consistent with results from experiments with animal models of prostate carcinogenesis, which also suggest reduced risk.”
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Kirsty Oswald, medwireNews Reporter