Hypofractionated proton beam scanning radiotherapy for prostate cancer
Reporter: J. Taylor Whaley, MD
The Abramson Cancer Center of the University of Pennsylvania
Last Modified: May 14, 2011
Presenter: Herbst M, Wilms M, Dohr D, Hillbrand M. Presenter's Affiliation: Renecker Proton Therapy Center, Munich, Germany
Prostate cancer is the most common non-skin cancer found in men, with approximately 200,000 cases occurring per year in the United States.
The optimal radiation dose fractionation schedule for localized prostate cancer is unclear.
Much interest has been given to hypofractionated radiation in recent years due to the potential advantages, including convenience for patients with shorter treatment duration, increased treatment capacity within a cancer center, and decreased costs to the healthcare system.
From the perspective of prostate cancer radiation biology, hypofractionation could offer an increased therapeutic benefit, which could improve tumor control.
However, despite the potential advantages, three randomized trials have failed to demonstrate these benefits, although each has its short-comings. Currently, several randomized trials are ongoing to evaluate hypofractioned radiation with photon and proton treatment.
With increasing availability of protons around the world, hypofractionated radiation with proton therapy has been an area of interest.
The purpose of this study was to validate dose escalation in prostate cancer treatment with proton beam scanning technique.
Materials and Methods
127 patients with prostate were treated with proton beam therapy from November 2009 to 2011 at the Rinecker Proton Therapy Center in Munich, Germany.
108 of the patients were treated in the definitive setting and 17 were treated in the post-operative setting. High risk patients composed 25% of the patient population and were treated with neoadjuvant and concurrent hormone ablation.
PSA prior to radiation ranged from 0.1 to 948 mg/ml. Mean was 21.6 mg/ml.
Treatment volumes included prostate and seminal vesicles in low risk patients. Regional lymphatics, up to the level of the common iliac nodes, were treated in high risk patients.
Median dose prescription was 63 Gy (RBE) (range- 54 to 70 Gy) with a fractionation schedule dictated by protocol. Protocol for fractionation called for 3 Gy per fraction to the prostate and 2.5 Gy to the regional lymphatics delivered daily.
Patients were treated with opposed lateral proton beams only.
Treatment set-up included a daily rectal balloon as well as gold fiducials.
Follow up was restricted to less than 1 year.
Toxicity was recorded in the acute setting, at 3 months, and at 6 months follow up.
Acute Side Effects
3 Months SE
6 Months SE
PSA evaluation occurred at 3 month follow up visit. Range was 0.01 to 130 ng/mL (mean of 6.56). No further follow up was available.
In patients with prostate cancer, hypofractionated proton beam scanning radiotherapy offers a viable option with dosimetric advantages of proton therapy and convenience advantages to patients.
The hypofractionated treatment was well tolerated despite dose elevation to 63 Gy. Acute toxicity in this cohort of patients was acceptable.
The acute side effects decreased within 4 to 5 weeks following treatment. At 3 and 6 months of follow up, no GI or GU side effects of grade 2 or greater were reported.
The acute decrease in PSA seen after 3 months was an impressive decline.
Further follow up is required to evaluate the local and biochemical control as well as any potential late side effects of hypofractionated proton therapy.
The authors present their experience with hypofractionated proton radiotherapy for prostate cancer, and the presentation is certainly a valuable contribution to the literature.
In this cohort of patients, the acute toxicity was acceptable and comparable to toxicity seen in previous trials for standard fractionation as well as photon treatment.
Although the acute decline in PSA is indeed striking, much longer follow up is required to evaluate the effectiveness of the treatment due to the indolent nature of prostate cancer.
Information on late effects and long term outcomes associated with this treatment remains unavailable and will certainly contribute to the literature when longer follow-up permits analysis of quality of life and disease control following hypofractionated proton beam radiotherapy.
Certainly, prospective randomized trials are preferred to further evaluate the role of proton therapy in prostate cancer.
Sep 30, 2011 - Hypofractionated intensity modulated radiotherapy (IMRT) and conventional IMRT therapy are equally effective in decreasing recurrence of intermediate- to high-risk prostate cancer at five years, according to a study presented at the anual meeting of the American Society for Radiation Oncology, held from Oct. 2 to 6 in Miami Beach.