High Omega-3, Low Omega-6 Diet with Fish Oil and Prostate Cancer
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Host Dr. Shannon Westin and guests Dr. Bill Aronson discuss the article "High Omega-3, Low Omega-6 Diet With Fish Oil for Men With Prostate Cancer on Active Surveillance: The CAPFISH-3 Randomized Clinical Trial" and how Omega-6 are predominant in the American diet while the study significantly lowered the intake of Omega- 6 fats.

TRANSCRIPT 

Dr. Shannon Westin: Hello everyone and welcome to another episode of JCO After Hours, the podcast where we get in depth on manuscripts published in the Journal of Clinical Oncology. I'm your host, Dr. Shannon Westin, GYN Oncologist by trade and one of the grateful Social Media Editors of the JCO. And I am very excited to welcome a special guest today, Dr. William Aronson. He is professor of Urology in the UCLA Department of Urology, the Chief of Urology at Olive View UCLA Medical Center, and Chief of Urologic Oncology at the Veterans Administration West Los Angeles.

Welcome, Dr. Aronson.

Dr. William Aronson: Thank you, Shannon, and delighted to be here.

Dr. Shannon Westin: We are so excited to have you discussing your manuscript, “High Omega-3, Low Omega-6 Diet With Fish Oil for Men With Prostate Cancer on Active Surveillance: The CAPFISH-3 Randomized Clinical Trial,” which was published in the Journal of Clinical Oncology on December 13, 2024.

So let's get right to it. First of all, you know we have a very mixed audience, so can you just level set for us and speak about the population you studied in this important trial - that low risk, favorable, intermediate risk prostate cancer. How common is that? How is it defined? That would really help.

Dr. William Aronson: I would say about 50% of the patients that we diagnose with prostate cancer either have low risk disease or what we call favorable intermediate risk disease. So when the pathologists look at the cancer under the microscope, they assign what's called a Gleason grade. Grade 3 is the slower growing type of prostate cancer, grade 5 is the fastest growing type, and grade 4 is somewhere in between. So a low risk group would be only the grade 3, the slower growing type. And the favorable intermediate risk group would actually be the grade 3+4, which means they mostly see the low risk type in there, but they also see the slightly faster growing type, grade 4. So this is what we typically see. We see these patients on a very regular basis when they're newly diagnosed with prostate cancer.

Dr. Shannon Westin: Okay, got it. And then can you walk us through just what the management options are typically for this patient population?

Dr. William Aronson: So typically for what we call the low risk group, the patients with a low PSA and only that grade 3 type, slower growing type of prostate cancer, the standard recommendations are active surveillance. So typically, we'll periodically monitor these patients with PSA blood testing and periodically do prostate biopsies depending upon the patient's other medical problems.

Dr. Shannon Westin: So I think it would also be really helpful just to understand what your typical management options are for this patient population.

Dr. William Aronson: So for patients with low risk prostate cancer, they only have the Gleason Grade 3+3 with a low PSA. The standard practice is observation. And so these men will periodically see them and measure their PSA values. And periodically, they'll undergo prostate biopsy to make sure they're not getting progression of their disease.

For men with favorable intermediate risk prostate cancer, that's a little different. In some practices, the patient and the urologist will decide to do active surveillance. In other scenarios, these patients will definitely elect treatment, either with radical prostatectomy or radiation therapy or other treatments that are available.

Dr. Shannon Westin: So your manuscript notes that there was a high level of interest in dietary supplements and approaches among patients with prostate cancer that do elect for active surveillance. Prior to the results of CAPFISH-3, did we have any data to support those types of recommendations?

Dr. William Aronson: We actually don't have any long term prospective randomized trials that support that recommendation. There have been a number of very interesting epidemiologic studies, for example, suggesting maybe a plant-based diet might be helpful. Or a number of other studies suggesting maybe more tomato-based products like tomato sauces or tomato paste may be helpful. But no prospective longer term randomized trials that were positive.

Dr. Shannon Westin: Okay, that makes sense. So what led you all to explore the high omega-3, low omega-6 fatty acid diet in this trial?

Dr. William Aronson: After our initial omega-6 studies, we subsequently did some studies where we raised the omega-3 from fish oil and lowered the 6, looking at a more favorable ratio of the omega-3 to omega-6. And once again, we found that in our animal models, there was a significant delay in progression of prostate cancer. That then led us to perform a clinical trial. It was a short term trial in men prior to undergoing radical prostatectomy. And in these men, they were randomly assigned to one of two groups, either a western high fat diet or a low fat diet with fish oil. And we found after just four to six weeks, a significant change in the Ki67 level in their radical prostatectomy tissue. And Ki67 is actually a strong indicator of prostate cancer progression, spread, or even death from prostate cancer.

Dr. Shannon Westin: Well, and I think that leads us really nicely into the design of the current study. So why don't you walk us through how CAPFISH-3 was designed. And you've already spoken a little bit about your primary endpoint.

Dr. William Aronson: Based on the results of what we saw in the lab and what we saw in our short term clinical trial, we decided to perform a one year trial, a longer term trial in men on active surveillance. And these men were randomly assigned to either a diet with slight reduction in dietary fat, specifically reduction in the omega-6 intake as well as increase in foods with omega-3 and fish oil capsules. The other group, we asked the men to just not take fish oil capsules, but they could eat whatever else they wanted during the course of the study. Men in the diet where we lowered the omega-6 and raised the omega-3, they were seen by a dietitian once a month to really ensure that they were compliant with that intervention, which they were. The other intriguing part of our study, which I think is super important, is the precision that was used when these men underwent prostate biopsy. So, at baseline and at one year, when these men underwent prostate biopsy, they had the same site within the prostate biopsied. That's important because it's not so easy to find the same site within the prostate because of heterogeneity throughout the prostate. And so we were able to obtain that high level of precision as they were in an active surveillance program at UCLA with Dr. Leonard Marks.

Dr. Shannon Westin: So we spoke a little bit about what's important about the Ki67 index as your primary endpoint. Can you talk a little bit about what the study found with your intervention?

Dr. William Aronson: So we found that the Ki67 index increased by 24% in the control group and decreased by 15% in the low omega-6, high omega-3 group with fish oil capsules. So that ended up resulting in a statistically significant change between the groups favoring the low omega-6, high omega-3 group.

Dr. Shannon Westin: And then what were the secondary endpoints that CAPFISH-3 explored? Anything of note that you want to review for the listeners?

Dr. William Aronson: So a number of positive secondary endpoints from the trial. Firstly, we saw that the triglyceride levels were lower, which is what can typically be seen with omega-3 intake. We also saw reduced levels of a cytokine, a circulating factor in the bloodstream called ‘macrophage colony stimulating factor’. And that's particularly interesting because there's a certain type of macrophage which is well known to be involved in prostate cancer progression in men with more advanced prostate cancer, and we've been able to inhibit that in our animal models and in our tissue culture studies. And it was especially interesting to see that we did have an effect on this particular cytokine in this prospective randomized trial. We did not see changes in a number of other measures, including Gleason grade or PSA. These are measures that we use in clinical practice. To see an effect on those would have required a longer term and larger study to be performed.

Dr. Shannon Westin: That makes sense. I think it's always great to try to get as much of these types of translational data as we can. But sometimes you just have to do what is reasonable and you get what you get.

It looks to me like this regimen was fairly well tolerated. Did you obtain any patient reported outcomes or feedback on the trial?

Dr. William Aronson: So, there were four patients in the fish oil group that did have some side effects, and we withdrew them from the study. They did have some effects on their upset stomach, and a number of men also had some diarrhea as well. And so for those four patients, we did withdraw them from the study.

Dr. Shannon Westin: And then I guess the last question I have is really, what's next for this intervention? Are we ready to move this to the clinic or what do you see as next steps?

Dr. William Aronson: Well, this next step that we're working on right now is to better understand exactly what happened in these patients. So we have blood, we have tissue, we're doing genetic studies on these patients. So that's really the first step, in our mind, to better understand what happened before moving to the next step. I'm particularly intrigued about trying this intervention in men with more advanced prostate cancer, specifically because of what we see, this particular diet and how it's affecting the patient's immune system and how that may favorably affect their course of their prostate cancer.

Dr. Shannon Westin: Well, great. Well, thank you so much for taking the time to chat with us about such an important clinical trial, and I really appreciate all the work you're doing and hope to get to see you soon.

Dr. William Aronson: Well, thanks for having me, Shannon. It's really an exciting finding and I think it's something that clinicians and patients are going to be super interested in.

Dr. Shannon Westin: We love straightforward interventions that actually make a difference, so you guys are to be congratulated for that.

And I just want to thank all of you for listening. Thanks again, and I hope you enjoyed this episode of JCO After Hours. Be sure to check out our other podcast offerings wherever you get your podcasts. Have an awesome day.

The purpose of this podcast is to educate and to inform. This is not a substitute for professional medical care and is not intended for use in the diagnosis or treatment of individual conditions.

Guests on this podcast express their own opinions, experience, and conclusions. Guest statements on the podcast do not express the opinions of ASCO. The mention of any product, service, organization, activity, or therapy should not be construed as an ASCO endorsement.

Dr. Aronson Disclosures:

Stock and Other Ownership Interests Johnson and Johnson

Speakers' Bureau Company name: Janssen Oncology, Bayer, Blue Earth Diagnostics, AstraZeneca, Pfizer/Astellas

Research Funding: Lantheus Medical Imaging