Researchers have found that dietary changes may help reduce cancer cell growth in patients with prostate cancer undergoing active surveillance, according to a recent study published by Aronson et al in the Journal of Clinical Oncology. The findings demonstrated that a diet low in omega-6 and high in omega-3 fatty acids, combined with fish oil supplements, could reduce the growth rate of prostate cancer cells in men with early-stage disease.
Background
Many men with low-risk prostate cancer choose active surveillance—a treatment approach involving regular monitoring of cancer—over immediate intervention. However, within 5 years, about 50% of these men eventually need to undergo therapy with either surgery or radiation. Because of this, patients are eager to find strategies to delay the need for treatment, including through dietary changes or supplements. Nonetheless, specific dietary guidelines in this area have yet to be established. While other clinical trials have explored increasing vegetable intake and healthy diet patterns, none have found a significant impact on slowing cancer progression.
Study Methods and Results
In the prospective CAPFISH-3 trial, the researchers recruited 100 men with low-risk or favorable immediate-risk prostate cancer who selected active surveillance. The participants were then randomly assigned to continue their normal diet or follow a low omega-6, high omega-3 diet, supplemented with fish oil, for 1 year—with the goal of determining whether diet or supplements can play a role in managing prostate cancer.
The participants in the intervention group received personalized dietary counseling by a registered dietician nutritionist in-person, through telehealth, or by phone. The patients were guided on healthier, lower-fat alternatives for high-fat and high-calorie foods, including using olive oil or lemon and vinegar for salad dressing, and on reducing consumption of foods with higher omega-6 content like chips, cookies, mayonnaise, and other fried or processed foods. The goal was to create a favorable balance of their intake of omega-6 and omega-3 fatty acids and provide the participants with an opportunity to control how they change their behavior. They were also given fish oil capsules for extra omega-3 fatty acids. The control group did not receive any dietary counseling or take fish oil capsules.
The researchers tracked changes in a biomarker called the Ki-67 index, which indicates how fast cancer cells are multiplying—a key predictor of cancer progression, metastasis, and survival. Same site biopsies were obtained at the start of the study and again after the 1-year mark, using an image fusion device to help track and locate the cancer sites.
The researchers discovered that the low omega-6, high omega-3 diet and fish oil group had a 15% decrease in the Ki-67 index, whereas the control group saw a 24% increase.
“This significant difference suggests that the dietary changes may help slow cancer growth, potentially delaying or even preventing the need for more aggressive treatments,” explained lead study author William Aronson, MD, Professor of Urology at the David Geffen School of Medicine at the University of California, Los Angeles (UCLA) and a member of UCLA Health Jonsson Comprehensive Cancer Center as well as Chief of Urologic Oncology at the West Los Angeles Veterans Affairs Medical Center.
Despite the positive findings, the researchers did not identify any differences in other cancer growth markers, such as Gleason grade, which are commonly used to track prostate cancer progression.
Conclusions
“This is an important step toward understanding how diet can potentially influence prostate cancer outcomes,” highlighted Dr. Aronson. “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,” he indicated.
The researchers cautioned that further research may be necessary to confirm the long-term benefits of omega-3 fatty acids and lowering omega-6 fatty acids in the management of prostate cancer. The findings supported larger trials to assess the long-term impact of dietary changes on cancer progression, treatment outcomes, and survival rates in men on active surveillance.
Disclosure: The research in this study was funded in part by the National Cancer Institute, the UCLA Health Jonsson Comprehensive Cancer Center, Howard B. Klein, and the Seafood Industry Research Fund. For full disclosures of the study authors, visit ascopubs.org.
