Data from the CAPFISH-3 trial show that a high omega-3, low omega-6 diet supplemented with fish oil capsules significantly reduced proliferation of Ki-67, a biomarker for prostate cancer progression, metastasis, and death, in patients with prostate cancer who are on active surveillance (AS).1 No significant differences were seen in grade group, tumor length, Decipher genomic […]
Data from the CAPFISH-3 trial show that a high omega-3, low omega-6 diet supplemented with fish oil capsules significantly reduced proliferation of Ki-67, a biomarker for prostate cancer progression, metastasis, and death, in patients with prostate cancer who are on active surveillance (AS).1
No significant differences were seen in grade group, tumor length, Decipher genomic score, or prostate-specific antigen levels.
“This is an important step toward understanding how diet can potentially influence prostate cancer outcomes,” said lead author William J. Aronson, MD, professor of urology at the David Geffen School of Medicine at the University of California, Los Angeles, in a news release on the findings.2 “Many men are interested in lifestyle changes, including diet, to help manage their cancer and prevent the progression of their disease. Our findings suggest that something as simple as adjusting your diet could potentially slow cancer growth and extend the time before more aggressive interventions are needed.”
In total, the CAPFISH-3 trial included 100 men with low-risk or favorable intermediate-risk prostate cancer who were on AS. Patients were randomly assigned 1:1 to either continuation of their normal diet or to follow a high omega-3, low omega-6 diet supplemented with fish oil pills. Participants in the intervention arm received personalized dietary counseling by a registered dietician nutritionist.
All patients underwent same-site biopsies at baseline and 1 year. The primary end point was the change in Ki-67 index from baseline to 1 year.
In the intervention arm, patients demonstrated a decrease in omega-6 consumption and an increase in omega-3 consumption, as desired by the intervention. The primary end point was evaluable in 40 patients in each arm.
Overall, data showed a statistically significant difference between the 2 groups in the change of Ki-67 index from baseline to 1 year. Over the study period, the Ki-67 index decreased in the dietary intervention cohort by 15% and increased in the control cohort by 24% (95% CI, 2% to 52%; P = .043).
Specifically, the Ki-67 index in the intervention arm decreased from 1.34% at baseline to 1.14% at 1 year. In the control arm, the Ki-67 index increased from 1.23% at baseline to 1.52% at 1 year.
However, the investigators observed no significant difference between the 2 arms regarding the trial’s secondary outcome measures of grade group, tumor length, Decipher genomic score, or prostate-specific antigen levels.
Regarding safety, adverse-events due to the fish oil capsules resulted in 4 patients being withdrawn from the study. Further, 8% of patients discontinued the intervention due to grade 1 or 2 GI symptoms.
In an editorial responding to these findings, Nazli Dizman, MD, and Andrea Necchi, MD, explain that although the results are encouraging, interpretation of the findings requires an “in-depth examination of its methodology and results.”3
For example, they note that this was not a controlled dietary intervention. They write, “Instead, patients received monthly dietary counseling from a professional dietician which resulted in a notable shift in dietary habits, generally, in a positive direction.”
Additionally, they highlight that despite these significant changes in dietary habits, patients in the intervention arm maintained a stable weight.
“High body fat and low muscle mass have been associated with several prostate cancer outcomes, with specific fat depots such as visceral fat linked with increased risk of advanced prostate cancer, whereas many reports suggest that higher muscle mass is associated with a lower risk of biochemical recurrence, distant metastasis, and cancer-specific mortality,” they explain.
Thus, they caution that further research is necessary, in alignment with the authors from CAPFISH-3, who conclude, “These findings support future phase III trials incorporating this intervention in men on AS.”1
References
1. Aronson WJ, Grogan T, Liang P, et al. High omega-3, low omega-6 diet with fish oil for men with prostate cancer on active surveillance: The CAPFISH-3 randomized clinical trial. J Clin Oncol. 2024:JCO2400608. doi:10.1200/JCO.24.00608
2. A low omega-6, omega-3 rich diet and fish oil may slow prostate cancer growth, UCLA study finds. News release. University of California, Los Angeles (UCLA), Health Sciences. December 11, 2024. Accessed December 16, 2024. https://www.newswise.com/articles/a-low-omega-6-omega-3-rich-diet-and-fish-oil-may-slow-prostate-cancer-growth-ucla-study-finds
3. Dizman N, Necchi A. Promises and challenges of dietary intervention in patients with prostate cancer: Lessons learned from the CAPFISH-3 trial. J Clin Oncol. 2024:JCO2402444. doi:10.1200/JCO-24-02444
