Proton therapy is effective and safe for prostate cancer treatment, according to new research from the University of Florida Proton Therapy Institute. The findings from seven studies were presented Oct. 28-31 in Boston during the American Society for Radiation Oncology (ASTRO) 54th Annual Meeting, the premier scientific conference on radiation oncology.

Among the most significant results reported are:
– Five-year cancer progression-free survival rate of 99% in low- and intermediate-risk prostate cancer patients[1]
– Five-year cancer progression-free survival rate of 74% in high-risk prostate cancer patients [2]
– Minimal bowel and urinary side effects that return to pre-treatment levels or improve upon pre-treatment levels within 2 years of treatment.[1, 2, 3, 4]
– Minimal impact on sexual function with decrease in erectile function in the first year that stabilizes in years 2 and 3.4
– The studies, which followed UF Proton Therapy Institute patients over time, evaluated both patient-reported and provider-reported data.

Notably, patient-reported data mirrors provider-reported data and concurs with study results from other institutions.

Effectiveness of a therapy
To assess the effectiveness of a therapy, radiation oncologists balance the probability of cure with the probability of side effects ? called therapeutic ratio. The UF prostate cancer studies found relatively high therapeutic ratios ? which are desirable ? for radiation.

“These data confirm what we already knew about the excellent outcomes with proton therapy and I think represent as high a therapeutic ratio for early and intermediate stage prostate cancer as has been achieved with any other modality? perhaps the best,” said Nancy P. Mendenhall, M.D. medical director of UF Proton Therapy Institute and principal investigator on two of the seven studies.

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Benchmarks for evaluating
Other studies established benchmarks for evaluating the effects of proton therapy on testosterone production5 as well as for comparing outcomes between African-American and white men6 and comparing outcomes for use of prostate-only versus whole-pelvis irradiation.[7]

“All of these studies are based on actual clinical outcomes. They are not surrogate data, this is actually what happened to the patient as the patient expresses it or as the providers have interpreted it following the patients closely in a prospective fashion,” said Mendenhall. “This quality data adds to the body of evidence that exists in the literature showing the benefits of proton therapy for prostate cancer treatment.”


[1]Mendenhall NP, Li Z, Hoppe BS, Marcus RB, Mendenhall WM, Nichols RC, Morris CG, Williams CR, Costa J, Henderson R. The Value of Dose Constraints in Minimizing Rectal Toxicity in Patients Receiving Radiation Therapy for Prostate Cancer: Three-Year Analysis of Toxicity Outcomes in 2 Prospective Trials of Image-Guided Proton Therapy for Early- And Intermediate-Risk Prostate Cancer; ASTRO 54: Poster Presentation 2441

[2] Mendenhall NP, Hoppe BS, Nichols RC, Mendenhall WM, Marcus RB, Morris CG, Li Z, Williams CR, Costa J, Henderson R. Early Patterns of Failure in a Prospective Trial of Concomitant Docetaxel and Proton Therapy for High-Risk Prostate Cancer; ASTRO 54: Oral Presentation 226

[3]Henderson RH, Li Z, Hoppe BS, Marcus RB, Mendenhall WM, Nichols RC, Morris CG, Williams CR, Costa J, Mendenhall NP. Three-year Analysis of Urinary Toxicity in Two Prospective Trials of Image-guided Proton Therapy for Early- and Intermediate-Risk Prostate Cancer: Outcomes in Men with Moderate to Severe Pretreatment Urinary Obstructive Symptoms; ASTRO 54: Poster Presentation 2514

[4]Hoppe BS, Nichols RC, Henderson R, Mendenhall WM, Williams C, Costa J, Morris CG, Su Z, Li Z, Mendenhall NP. Patient-Reported Quality of Life Following Treatment of Prostate Cancer with Proton Therapy. ; ASTRO 54: Poster Presentation 1119

[5]Kil W, Nichols RC, Hoppe BS, Marcus RB, Mendenhall WM, Mendenhall NP, Li Z, Costa JA, Williams CR, Henderson RH. Hypofractionated Proton Radiotherapy for Low and Intermediate Risk Prostate Cancer Is Not Associated with Post-Treatment Testosterone Suppression; ASTRO 54: Poster Presentation 2416

[6]Bryant C, Hoppe B, Mendenhall NP. Does Race Influence Quality of Life, Toxicity or Early Relapse Following Proton Therapy in Men with Prostate Cancer?; ASTRO 54: Poster Presentation 3150

[7]McGee L, Hoppe BS, Henderson RH, Morris CG, Nichols RC, Su Z, Li Z, Mendenhall WM, Williams CR, Mendenhall NP. Impact of Proton Therapy to the Prostate Alone Versus the Whole Pelvis on Patient-Reported Outcomes and Toxicities in High-Risk Prostate Cancer Patients; ASTRO 54: Poster Presentation 2443

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