Randomized phase 2 trial of high omega-3 and low omega-6 diet with fish oil for men with prostate cancer on active surveillance

The randomized phase 2 CAPFISH-3 trial at University of California Los Angeles evaluated a high omega-3 and low omega-6 diet with fish oil (D + FO) among men on active surveillance (AS) for prostate cancer. Men on AS for grade group 1 or 2 prostate cancer were randomized to D + FO or a control group for one year. Primary end point was change in Ki-67 index in same-site prostate biopsies. The average Ki67 index decreased from 1.34% at baseline to 1.14% at one year in the D + FO group (-15%) and increased from 1.23% at baseline to 1.52% at one year in the control group (+24%; p=0.043). There were no significant differences between the groups in the secondary outcomes grade group, tumor length, Decipher genomic score, or prostate-specific antigen. Eight percent of patients in the D + FO group were withdrawn from the trial because of adverse events related to the FO. The authors conclude that among men on AS for prostate cancer, the D + FO diet resulted in a significant decrease in Ki-67 index, a biomarker for prostate cancer progression, metastasis, and death.