Conformal Proton Beam Therapy of Prostate cancer — Report of Long-term PSA Based Outcomes in Over Twelve Hundred Patients

James Metz, MD
OncoLink Associate Editor
Last Modified: October 25, 2000

Presenter: C. J. Rossi
Affiliation: Loma Linda University

Background:

Conformal proton beam therapy for prostate cancer has been performed for almost a decade at Loma Linda University Medical Center. This presentation is an update of the outcomes based on PSA.

Materials and Methods:

1257 patients with localized prostate cancer were treated with protons between 10/91-12/97.
The patients had T1c-T3 tumors, PSA < 50 ng/ml
Patients were treated with conformal protons to a dose of 74-75 Cobalt-Gray Equivalents (CGE) in fractions of 1.8-2 CGE.
PSA was obtained 4 months after completion of therapy and then every 6 months.
The median follow-up was 3 1/2 years.

Results:

The 7 year actuarial biochemical disease free survival for the entire group was 79%.
Failure based on pretreatment PSA was 95% (< 4 ng/ml), 86% (4-10 ng/ml), 67% (10-20 ng/ml), and 56% (20-50 ng/ml).
Failure based on PSA nadir was 91% (< 0.51 ng/ml), 77% (0.51-1 ng/ml), and 35% (if the PSA never fell below 1 ng/ml)
The rate of RTOG Grade 3 and 4 toxicity was only 0.3%.

Authors' Conclusions

The results of conformal proton beam therapy are comparable to the best radical prostatectomy results.
There is minimal toxicity associated with treatment of prostate cancer with protons.

Clinical/Scientific Implications:

Proton therapy is an effective option for the treatment of prostate cancer.
Both the biochemical DFS and toxicity profiles compare favorably to conventional photons and radical prostatectomy.
The optimal dose for treatment with protons is still not known, but a recently completed Phase III trial of dose escalation with proton therapy may help to answer this question.