EPIC: Proton therapy appears highly effective for men with prostate cancer
Proton therapy achieved excellent outcomes and quality side effect profiles for men with prostate cancer, according to results of three studies presented at the American Society for Radiation Oncology’s 54th Annual Meeting.
“This body of data reconfirms what we thought we saw on the clinical end in terms of excellent outcomes associated with proton therapy, only we are now hearing it from patients who have actually gone through the treatment,” Andrew K. Lee, MD, MPH, associate professor in the department of radiation oncology at The University of Texas MD Anderson Cancer Center, said during a press conference.
The three studies used the validated survey instrument known as the Expanded Prostate Cancer Index Composite (EPIC) survey. The comprehensive validated survey measured the quality of life of men treated for prostate cancer. It included patients who underwent radical prostatectomy, external beam radiation therapy — including proton therapy — brachytherapy and hormone therapy.
The EPIC survey assessed the urinary, bowel, sexual and hormonal/vitality outcomes of men with prostate cancer and converted their responses into a linear scale, from 0 to 100, with 100 equaling perfect quality of life.
Similar quality of life
Lee and colleagues used the EPIC survey to evaluate the quality of life of 1,090 men with prostate cancer who underwent proton therapy at one of five centers.
Most of the men (88.3%) underwent proton therapy alone, while 11.7% underwent proton therapy plus hormone therapy.
The median patient age was 65 years. All patients completed treatment at least 1 year prior, and more than half were more than 4 years post-treatment.
“[The study] is a snapshot of how patients are doing down the road, away from proton treatment,” Lee said.
Lee and colleagues compared the proton therapy cohort with a control group of men who did not have prostate cancer (n=112).
The researchers compared the EPIC survey quality-of-life scores from urinary, bowel and sexual domains.
Study results showed no significant differences between quality-of-life scores among treated patients and control patients in the urinary (89.8 vs. 89.5) or bowel (92.7 vs. 92.4) domains, Lee said.
The results showed a significant difference in sexual quality of life between patients treated with proton therapy and the control group (53.6 vs. 61.4; P=.004). That difference primarily was driven by older men who received hormone therapy, had higher Gleason scores and were farther from completion of therapy, Lee said.
Outcomes tracking protocol
The outcomes tracking protocol study represents the earliest data from any community center treating men with prostate cancer with proton therapy, according to Sameer Keole, MD, radiation oncologist in the department of radiation oncology at ProCure Proton Therapy Center.
Keole and colleagues evaluated 76 patients with prostate cancer treated with proton therapy; of them, 65 also received androgen deprivation therapy. The median patient age was 65 years, and minimum follow-up was 1 year.
The patients received proton therapy with a target dose of 79.2 Gy in 44 daily fractions, unless dose constraints to critical structures such as the rectum, bladder or femoral heads were violated.
Patients completed EPIC surveys pre-treatment, as well as at 3, 6, 12, 18 and 24 months post-treatment.
Based on survey results, genitourinary and gastrointestinal function appeared to be stable in patients starting as early as 3 months after treatment. Keole and colleagues observed no decline in function up to 2 years after radiation therapy.
Researchers noted a slight decline in sexual score in men who did not receive ADT. After testosterone recovery, patients did not experience a decline in sexual function at 1-year post-treatment and beyond, according to study results.
“These patients did remarkably well,” Keole said. “Their urinary and bowel function scores were identical going out to 18 months as they were prior to treatment. Sexual function scores were quite similar, although there was a slight decline.”
It is important to assess the outcomes from the perspectives of patients and providers, according to Nancy Mendenhall, MD, associate chairwoman for the department of radiation oncology at the University of Florida.
Mendenhall and colleagues conducted a study to assess whether dose-volume constraints minimized the risk for rectal toxicity with image-guided proton therapy in men with early- and intermediate-risk prostate cancer. The researchers evaluated 171 patients, and minimum potential follow-up was 5 years.
Low-risk patients (n=89) received high doses of radiation — 78 cobalt gray equivalent (CGE) delivered in 39 fractions — while patients with intermediate-risk disease (n=82) received 78 CGE to 82 CGE.
Researchers correlated toxicity rates with clinical factors and prospectively calculated dose volume relationships to organs at risk. One patient with low-risk disease and one patient with intermediate-risk disease experienced disease progression. Two patients developed grade 3 or higher gastrointestinal toxicities. Both events resolved post-intervention and did not recur.
The prevalence of all grade 2 or higher gastrointestinal toxicities at 3 years and 5 years was 7.1%, Mendenhall said.
“What we wanted to do in this study was try to correlate these GI toxicities with dose distribution that we were able to achieve with proton therapy,” Mendenhall said. “Those dose distributions were all prospectively calculated and recorded.”
Mendenhall and colleagues found a significant correlation between grade 2 or higher rectal bleeding and/or proctitis and the percent of rectum-receiving dose levels ranging from as low as 30 CGE (P=.0475) to 75 CGE (P=.0152).
“There was an extremely low toxicity rate,” Mendenhall said. “We were also able to document an extremely high disease control rate, so the therapeutic ratio for this approach is extremely high, both in high disease control and very low toxicity.”
All three studies are valuable because they are based on clinical outcomes, Mendenhall said.
“This is what actually happened to the patient as the patient expresses it or as the providers have interpreted it by following the patients closely in a prospective fashion,” she said. “[Proton therapy] represents as high a therapeutic ratio for early- to intermediate-stage prostate cancer as has been achieved with any other modality — perhaps the best.” – by Anthony Calabro
Keole S. Abstract #2516.
Lee AK. Abstract #3139.
Mendenhall NP. Abstract #2441.
All presented at: ASTRO Annual Meeting; Oct. 28-31, 2012; Boston.
Keole reports receiving stock options from ProCure. Lee and Mendenhall report no relevant financial disclosures.