Researchers have identified subgroups of patients with node-positive prostate cancer (PCa) who might benefit from adjuvant radiotherapy in addition to androgen-deprivation therapy (ADT).1
Using the National Cancer Data Base, Firas Abdollah, MD, Deepansh Dalela, MD, and colleagues at the Vattikuti Urology Institute at Henry Ford Hospital in Detroit identified 5498 men with pathologic node-positive PCa who underwent radical prostatectomy, pelvic lymph node dissection, and ADT with or without adjuvant radiotherapy (aRT). Based on results of a prior study suggesting cancer specific mortality benefit of adjuvant radiotherapy in Italian men,2 the investigators stratified patients into 5 groups. Group 1 included patients with 1–2 positive nodes and a pathologic Gleason score of 6 or less; group 2 included patients with 1–2 positive nodes, a pathologic Gleason score of 7–10, pT2/pT3a disease, and negative surgical margins; group 3 had patients with 1–2 positive nodes, a pathologic Gleason score of 7–10, pT3b/pT4 disease, or positive surgical margins; and groups 4 and 5 included patients with 3–4 and more than 4 positive nodes (irrespective of other pathologic parameters), respectively.
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Results showed that only patients in groups 3 and 4 experienced a significant survival benefit with the addition of aRT to ADT. In group 3, the 8-year overall survival rate was 71.3% among men who received aRT plus ADT compared with 63.8% among those who received ADT alone. In group 4, the 8-year overall survival rates were 69.7% vs 49.4%, respectively. On multivariable analysis adjusting for all available covariates, aRT plus ADT was associated with a significant 22% and 43% decreased risk of death in groups 3 and 4, respectively, compared with ADT alone.
The authors concluded that patients at either end of the disease spectrum (i.e., locally limited disease despite positive nodes, and those with extensive lymph node involvement) are unlikely to benefit from aRT and can be spared the adverse effects and financial burden of aRT.
Compared with patients treated with ADT alone, men who received aRT plus ADT were younger (60.7 vs 62.4 years), had a lower mean PSA level (17.6 vs 20 ng/mL), were less likely to have Gleason 8–10 disease (62.3% vs 67.3%), and had fewer positive lymph nodes (mean 2.0 vs 2.5). The aRT plus ADT group, however, was more likely to have pT3b disease (63.4% vs 58.9%) and positive surgical margins (66.7% vs 54.2%). These differences, and the likelihood of selection bias towards healthier patients in adjuvant RT group, were accounted for in different sensitivity analyses. Results remained largely unchanged, suggesting a true biological interaction between adjuvant treatment and tumor burden on mortality outcomes.
Reference
1. Abdollah F, Dalela D, Sood A, et al. Testing the impact of adjuvant radiotherapy (aRT) after radical prostatectomy (RP) on overall mortality (OM) in prostate cancer patients with pathologically node positive disease: A nationwide analysis. Data presented at the 33rd European Association of Urology Congress in Copenhagen, Denmark. Abstract 1151.
2. Abdollah F, Karnes R, Suardi N et al. Impact of adjuvant radiotherapy on survival of patients with node-positive prostate cancer. J Clin Oncol. 2014;32:3939-3947.
