What is the Success Rate of Proton Therapy for Prostate Cancer?

Proton therapy has shown promising results in treating prostate cancer, with high rates of tumor control and low rates of side effects. So, what are the survival rates for prostate cancer treated with proton therapy? 

Measuring Treatment Success

After treatment for prostate cancer, the success of an individual’s treatment is measured with regular monitoring of PSA (prostate-specific antigen) levels. PSA tests are a simple blood test, the same that was used to help diagnose your prostate cancer and are recommended approximately every six months for the first five years after treatment, according to the American Cancer Society. After proton therapy radiation, PSA levels usually slowly decrease over the course of one to two years. Approximately two years after treatment, radiation oncologists expect that most PSA levels should reach its nadir – new PSA level after treatment. While it is normal for PSA levels to go up and down by a few decimal points over the years, a continuous increase in PSA may indicate a recurrence of prostate cancer.

The National Institute of Health indicates a 97 percent, five-year survival rate for men diagnosed with prostate cancer. Although this is encouraging data, it only addresses the survival rate, not the cure rate. In many studies, physicians and scientists monitor the biochemical recurrence rate. The biochemical recurrence is defined as increasing PSA after treatment. Comparing survival versus disease-free rates can be difficult, but it’s important for patients to understand the difference. Survival rates simply measure if people diagnosed with prostate cancer are alive after a certain period, while cure rates are monitoring the success of a particular treatment. 

Prostate Cancer Survival Rates After Proton Therapy Treatment:

The ability for proton therapy to target the prostate with a high, curative dose of radiation is one of the reasons that proton therapy can boast high survival rates for prostate cancer.

At UF Health Proton Therapy Institute, prostate cancer patients are monitored for years after treatment to provide excellent care and collect necessary data to demonstrate proton therapy’s efficacy. One of the initial studies to come out showing five-year results from the UF Health Proton Therapy Institute is highlighted in this article on the National Association of Proton Therapy website. In this study, UF physicians reported that five years after treatment, 99 percent of the patients were cancer-free if they had low- and intermediate-risk prostate cancer. Seventy-six percent of patients with high-risk prostate cancer were cancer-free at five years.

Two years later with an even larger study of more than 1,300 men, five-year survival rates continued to show high survival rates.¹ The table below shows prostate cancer survival rates of patients who received proton therapy at UF Health Proton Therapy Institute compared to patients treated with traditional X-ray radiation (IMRT) at Memorial Sloan Kettering Cancer Center in NY. While the survival rates are similar for men with low-risk prostate cancer, the percentage of men cancer-free at seven years following IMRT treatment is lower for those with intermediate- and high-risk prostate cancer.

Directly Comparing Success Rates of Prostate Cancer Treatments

Studies that directly compare two treatments, such as proton therapy vs. IMRT (traditional radiation therapy) are critical to understanding the success of treatments for cancer patients. The UF Health Proton Therapy Institute recently closed enrollment of more than 2,500 men on a large prostate cancer study called COMPPARE, which will do just that. This research will provide prostate cancer statistics that directly compare the potential benefits and harms of proton therapy to standard radiation therapy when treating prostate cancer. The goal is to help patients with prostate cancer (and ultimately, other cancers) have the information they need to decide which type of radiation treatment is best for them. Find out more about this groundbreaking study. 

Proton Therapy Success Rates in Fewer Treatments

One study further looked at the proton beam therapy success rates of patients treated for prostate cancer in a six-week course of treatment versus the more common eight-week course of treatment.³ At seven years after treatment, 98 percent of low-risk patients were cancer-free, and 91.9 percent of intermediate-risk patients were cancer-free (ranging from 88.8 percent to 95.2 percent, depending on whether they were identified as favorable intermediate-risk or unfavorable intermediate-risk). The continued high rates of patients with prostate cancer who were free from disease at seven years, still with low rates of patient-reported side effects to surrounding tissue, makes proton beam radiation therapy an exciting option for many men.

The Particle Therapy Co-Operative Group (PTCOG) Genitourinary Subcommittee published one of the most recent articles that summarize the advantages and disadvantages of proton therapy treatment for prostate cancer in the International Journal of Particle Therapy in 2021.⁴ Check out this comprehensive summary.

Prostate Cancer Survivor

A survivor of prostate cancer, Alon Genazia, completed proton therapy treatment in 2010 at UF Health Proton Therapy Institute in Jacksonville, Florida and shared that his PSA levels have usually remained between 0.3 and 0.6 since treatment. He continues to receive positive reports after each of his annual PSA tests, and the digital rectal exam every few years. Alon’s urologist in Virginia is very satisfied with his recovery from prostate cancer after proton therapy treatment. “My PSA levels have been low since I completed proton therapy treatment, and I am very happy with that. I researched a lot about the results and success rates of different treatments for prostate cancer, and comparing the options, I felt more comfortable going with proton therapy. I would absolutely consider the treatment with proton therapy to be successful for my prostate cancer.”  

The Most Important Outcome

The most important treatment outcome for men battling prostate cancer is different. Some men are extremely concerned about side effects while others about cure rates. Neither desire is wrong. A national survey conducted by Nancy P. Mendenhall, M.D., FACR, FASTRO, the medical director at the UF Health Proton Therapy Institute and faculty member at the University of Florida College of Medicine, and other radiation oncology researchers discovered that the long-term survival rate of treatment was the most important outcome in deciding which prostate cancer treatment to choose.⁵ While the survival rate and prostate cancer prognosis can depend on many factors, including a person’s medical history and the stage of the disease at the time of treatment, the promise of proton therapy survival rates, coupled with the low side effects reported by patients, makes proton therapy an appealing treatment option for many patients.  

Reviewed Aug. 28, 2023, by Romaine Charles Nichols, Jr., MD