Update of the Results of the Dutch Multicenter Dose Escalation Trial of Radiotherapy for Localized Prostate Cancer

Article Outline

• Background
• Purpose
• Materials/Methods
• Results
• Conclusions
• Copyright

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Background 

The Dutch Multicenter Dose Escalation Trial has shown, after a median follow-up of 51 months, that an increase in the dose of radiotherapy by 10 Gy (68 v 78 Gy) is beneficial for patients with localized prostate cancer in terms of Freedom From Failure (FFF), without statistically significant differences in Freedom From Clinical Failure (FFCF) and Overall survival (OS).

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Purpose 

We report on an updated analysis of this trial after a median follow-up of 69 months.

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Materials/Methods 

This study entered 669 patients with stage T1a-4 prostate cancer between June 1997 and February 2003. Patients were randomly assigned to receive 68 or 78 Gy with external beam radiotherapy. Follow-up data were available until June 2006. The median follow-up time was 69 months (range 9–115 months). Patients were stratified by age, institution, use of (neo)adjuvant hormonal therapy, and treatment groups. The primary end point was FFF, which was defined as clinical or biochemical failure, according to the American Society of Therapeutic Radiation Oncology definition. Secondary end points were FFCF, OS, Genitourinary (GU) and Gastrointestinal (GI) toxicities.

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Results 

FFF is still significantly better in the 78-Gy arm compared with the 68-Gy arm (at 7-year follow-up, FFF rate is 57% v 45%, respectively), with an adjusted hazard ratio of 0.75 (p = 0.015). However, no differences in OS (75% v 74% at 7 years, HR = 0.93, p = 0.66) and FFCF (70% v 69% at 7 years, HR = 0.99, p = 0.96) were observed. The cumulative incidence of late GU toxicity of RTOG/EORTC grade 2 or higher was the same in both arms (36% at 5 years and 40% at 7 years), while the cumulative incidence of late GI toxicity of RTOG/EORTC grade 2 or higher was increased in the 78-Gy arm (36% v 25% at 7 years, p = 0.04).

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Conclusions 

This Multicenter Randomized Trial still shows a statistically significant improvement in FFF in prostate cancer patients treated with 78 Gy of external beam radiotherapy without statistically significant differences in FFCF and OS. Late GU toxicity was similar in both treatment arms, but there is a higher rate of late GI toxicity in the 78-Gy arm.