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.