Should positive phase III clinical trial data be required before proton beam therapy is more widely adopted? No.
ABSTRACT Evaluate the rationale for the proposals that prior to a wider use of proton radiation therapy there must be supporting data from phase III clinical trials. That is, would less dose to normal tissues be an advantage to the patient?
Assess the basis for the assertion that proton dose distributions are superior to those of photons for most situations. Consider the requirements for determining the risks of normal tissue injury, acute and remote, in the examination of the data from a trial. Analyze the probable cost differential between high technology photon and proton therapy. Evaluate the rationale for phase III clinical trials of proton vs photon radiation therapy when the only difference in dose delivered is a difference in distribution of low LET radiation.
The distributions of biological effective dose by protons are superior to those by X-rays for most clinical situations, viz. for a defined dose and dose distribution to the target by protons there is a lower dose to non-target tissues. This superiority is due to these physical properties of protons: (1) protons have a finite range and that range is exclusively dependent on the initial energy and the density distribution along the beam path; (2) the Bragg peak; (3) the proton energy distribution may be designed to provide a spread out Bragg peak that yields a uniform dose across the target volume and virtually zero dose deep to the target. Importantly, proton and photon treatment plans can employ beams in the same number and directions (coplanar, non-co-planar), utilize intensity modulation and employ 4D image guided techniques. Thus, the only difference between protons and photons is the distribution of biologically effective dose and this difference can be readily evaluated and quantified. Additionally, this dose distribution advantage should increase the tolerance of certain chemotherapeutic agents and thus permit higher drug doses. The cost of service (not developmental) proton therapy performed in 3-5 gantry centers operating 14-16 h/day and 6 days/week is likely to be equal to or less than twice that of high technology X-ray therapy.
Proton therapy provides superior distributions of low LET radiation dose relative to that by photon therapy for treatment of a large proportion of tumor/normal tissue situations. Our assessment is that there is no medical rationale for clinical trials of protons as they deliver lower biologically effective doses to non-target tissue than do photons for a specified dose and dose distribution to the target. Based on present knowledge, there will be some gain for patients treated by proton beam techniques. This is so even though quantitation of the clinical gain is less secure than the quantitation of reduction in physical dose. Were proton therapy less expensive than X-ray therapy, there would be no interest in conducting phase III trails. The talent, effort and funds required to conduct phase III clinical trials of protons vs photons would surely be more productive in the advancement of radiation oncology if employed to investigate real problems, e.g. the most effective total dose, dose fractionation, definition of CTV and GTV, means for reduction of PTV and the gains and risks of combined modality therapy.
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ABSTRACT: For cerebral arteriovenous malformations (AVMs) determined to be high risk for surgery or endovascular embolization, stereotactic radiosurgery (SRS) is considered the mainstay of treatment. To determine the outcomes of pediatric patients with AVMs treated with proton SRS. We reviewed the records of 44 consecutively treated pediatric patients (age < 18) who underwent proton SRS at our institution from 1998-2010. The median target volume was 4.5±5.9 mL (range= 0.3-29.0 mL) and the median maximal diameter was 3.6± 1.5 cm (range =1-6 cm). Radiation was administered with a median prescription dose of 15.50±1.87 CGE to the 90% isodose. At a median follow-up of 52±25 months, two patients (4.5%) had no response, 24 patients (59.1%) had a partial response, and 18 patients (40.9%) experienced obliteration of their AVM. The median time to obliteration was 49±26 months, inclusive of 17 patients who underwent repeat proton radiosurgery. Four patients (9%) experienced hemorrhage following treatment at a median time of 45±15 months. Univariate analysis identified modified AVM scale score (p=0.045), single fraction treatment (0.04), larger prescription dose (0.01), larger maximum dose (<0.001), and larger minimum dose (0.01) to be associated with AVM obliteration. High-risk AVMs can be safely treated with proton radiosurgery in the pediatric population. Since protons deposit energy more selectively than photons, there is the potential benefit of protons to lower the probability of damage to healthy tissue in the developing brain.Neurosurgery 01/2014; · 3.03 Impact Factor
Article: The proton problem.The Lancet Oncology 10/2013; 14(11):1046-1048. · 25.12 Impact Factor
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ABSTRACT: Compared with photon therapy, proton-beam therapy (pbt) offers compelling advantages in physical dose distribution. Worldwide, gantry-based proton facilities are increasing in number, but no such facilities exist in Canada. To access pbt, Canadian patients must travel abroad for treatment at high cost. In the face of limited access, this report seeks to provide recommendations for the selection of patients most likely to benefit from pbt and suggests an out-of-country referral process.Current oncology (Toronto, Ont.). 10/2014; 21(5):251-62.