Higher Radiation Dose May Not Improve Prostate Cancer Outcomes

Escalating a patient’s radiotherapy dose for localized prostate cancer may not improve overall survival (OS), though it may reduce the likelihood of distant metastases, according to research published in JAMA Oncology.¹

While radiotherapy may be curative for patients with intermediate-risk, localized prostate cancer, it was previously unknown whether increasing radiation dosage would improve clinical outcomes. For the randomized phase 3 NRG Oncology RTOG 0126 study (ClinicalTrials.gov Identifier: NCT00033631), researchers evaluated whether 79.2 Gy in 44 fractions would improve clinical outcomes over 70.2 Gy in 39 fractions.

The primary endpoint was OS. Secondary outcomes included prostate-specific antigen (PSA) level change, prostate cancer–related mortality, local and distant disease progression, and grade 2 or worse gastrointestinal/genitourinary adverse events (AEs). Of 1499 included patients, the median age was 71 years, the median PSA level at baseline was 7.6 ng/mL, and 83.9% of patients had a Gleason score of 7 (all others had a Gleason score of 2-6).

Seven hundred and fifty-one patients were assigned to the 70.2 Gy group and 748 were assigned to the 79.2 Gy group. The median follow-up was 8.4 years.

No difference in OS was noted between the arms: the 5-year OS rates were 89% in the 70.2 Gy arm and 88% in the escalation arm; the 8-year OS rates were 75% and 76%, respectively (hazard ratio [HR], 1.0; P = .98). The rates of grade 2 or worse gastrointestinal/genitourinary AEs were, furthermore, higher in the 79.2 Gy arm.

The cumulative 8-year rates of distant metastases were, however, 6% and 4% in the 70.2 Gy and 79.2 Gy arms, respectively (HR, 0.65; P = .05). Biochemical (PSA) failure rates were also better in the 79.2 Gy arm.

The authors concluded that dose “escalation has several clinical advantages including improved rates of biochemical and clinical cancer control. These benefits do not translate into improved OS. The decision to deliver high radiation dose must be balanced against the risk of morbidity in the individual patient.”

Reference

1. Michalski JM, Moughan J, Purdy J, et al. Effect of standard vs dose-escalated radiation therapy for patients with intermediate-risk prostate cancer: the NRG Oncology RTOG 0126 randomized clinical trial. JAMA Oncol. 2018 Mar 15. doi: 10.1001/jamaoncol.2018.0039 [Epub ahead of print]