High-dose prostate RT surpasses conventional dose in long-term outcome

MedWire News: Superior long-term cancer control can be achieved in men with early-stage prostate cancer by treating them with high-dose conformal radiation therapy (RT) rather than conventional-dose conformal treatment, researchers report.

Anthony Zietman (Massachusetts General Hospital, Boston, USA) and colleagues also report in the Journal of Clinical Oncology that this superior long-term cancer control is achieved without an increase in grade 3 or higher late urinary or rectal morbidity.

Zietman et al randomly assigned 393 men to receive either high-dose (79.2 GyE) or conventional-dose (70.2 GyE) RT, and followed-up the men over a median of 8.9 years. At baseline, the men had T1b–T2b prostate cancer and prostate-specific antigen (PSA) levels of no more than 15 ng/ml.

Men treated with 79.2 GyE were significantly less likely to have local failure (LF) than those who received 70.2 GyE, with a significant hazard ratio (HR) of 0.57. This result held when adjusted for other covariates.

High-dose RT also achieved a significantly better 10-year American Society for Radiation Oncology (ASTRO) biochemical failure (BF) rate than conventional-dose RT, at 16.7% versus 32.3%. This difference held when only those with low-risk disease were examined, with respective 10-year ASTRO BF rates of 7.1% and 28.2%.

There was no significant difference between the high-dose and convention-dose groups in the overall survival rates, at 83.4% versus 78.4%.

Acute genitourinary (GU) toxicity of Radiation Therapy Oncology Group (RTOG) grade ?3 was seen in just 3% of patients receiving conventional-dose RT and 2% of patients receiving high-dose RT. Just 2% of patients in both groups had developed late GU toxicity of RTOG grade 3 or above, and 1% had experienced late gastrointestinal toxicity of grade 3 or above at most recent follow-up.

Zietman et al conclude that “the choice of dose may therefore be made by the physician based on other patient characteristics, such as life expectancy and concern about normal tissue injury.”

They add: “Although this trial strongly validates the use of proton beam as effective therapy, it was not designed to test whether this modality is more or less efficacious than other conformal techniques or, for that matter, brachytherapy or surgery. Nor does it justify using doses above 79 Gy outside a clinical trial.”

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