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

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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.