Optimal Radiation Delivery Methods and Dosing Strategies Under Study

Ben Leach
Published: Monday, Jun 17, 2013
Dr. Howard M. Sandler

Howard M. Sandler, MD, MS

The quest to deliver optimal radiation therapy for patients with prostate cancer has led to a variety of advances in technologies and techniques, yet key questions remain unanswered. Clinical trials now under way are expected to help clarify unsettled issues in several areas, particularly in proton beam therapy and hypofractionation, according to Howard M. Sandler, MD, MS.

Sandler, who is chair of Cancer Therapeutics and chair of Radiation Oncology at Cedars-Sinai Medical Center in Los Angeles, provided an overview of treatment options for radiation therapy in prostate cancer during the 6th Annual Interdisciplinary Prostate Cancer Congress™.

Although therapy trends have varied during the past two decades, radiation therapy remains an important modality. The percentage of patients treated with external-beam radiation therapy or brachytherapy ranged from 20.9% to 23.5% depending on risk level, according to the most recent Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) database analysis, which Sandler cited (Figure 1).1

Figure 1. Primary Treatment
of Localized Prostate Cancer1

Graph describing the Primary Treatment
of Localized Prostate Cancer

Data from 11,892 men in the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) registry are analyzed.

CAPRA indicates Cancer of the Prostate Risk Assessment scores.

 When it comes to delivering radiation therapy to a patient, Sandler said that determining the best dose of a particular form of radiation therapy is at the heart of the specialty. It also is important to keep that dose of radiation concentrated on the tumor and spare the surrounding tissue as much as possible, he stressed.

Proton Beam Therapy Growing

To achieve those goals, proton beam therapy theoretically would be more beneficial than several other methods of external radiation therapy because the technology allows for greater doses to be delivered to the tumor while reducing the incidence of treatment-related tissue damage, Sandler said.

Indeed, he noted that cancer centers throughout the country are increasingly investing in proton technology, which can cost as much as $150 million or $200 million for large systems. At least 10 centers have established proton sites, and approximately a dozen additional centers are planning to do so.

However, Sandler said there is scant evidence that proton beam therapy delivers superior outcomes, citing a review of 36 studies in various tumor types.2 In a 2007 paper, Brada et al found no studies demonstrating that proton beam therapy was superior to best available photon therapies such as intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiotherapy (3-D CRT).

In April, Gray et al3 reported that results of seven trials indicate patients treated with proton therapy experienced a low rate of acute and late grade 3 gastrointestinal and genitourinary toxicity, and that the method appears to keep disease under control. The paper also noted that smaller systems costing $15 million to $25 million are now hitting the market, which would make the technology more cost-effective.

Currently, the American Society for Radiation Oncology (ASTRO) believes that the role of proton therapy in prostate cancer is unclear and that more research is needed, including data comparing its efficacy to such other modalities as IMRT and brachytherapy.4 Indeed, the first head-to-head clinical trial is under way. A phase III trial being conducted at Massachusetts General Hospital and the University of Pennsylvania is currently enrolling 461 patients with low- or low-intermediate risk prostate cancer and randomizing them either to proton beam therapy or IMRT (Figure 2). The results of the study are expected in 2016, at which point Sandler hopes the role of proton beam therapy in prostate cancer will be decided.

“If proton therapy doesn’t reduce toxicity for prostate cancer, then there’s no reason to be doing it,” Sandler said.

 

Figure 2. Proton Beam Versus IMRT in Low- or Low-Intermediate Risk Prostate Cancer

Clinical trial coparing radiation delivery route in Low- or Low-Intermediate
Risk Prostate Cancer

EPIC, indicates Expanded Prostate Cancer Index Composite; IMRT, intensity-modulated radiation therapy; QoL, quality of life.

Source: www.ClinicalTrials.gov, NCT01617161




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