medwireNews: All-cause mortality is significantly reduced in men with prostate cancer receiving adjuvant versus early salvage radiotherapy (RT), particularly if they have four or more positive pelvic lymph nodes (LNs), research suggests.
This was observed after taking into account time-dependent use and duration of androgen deprivation therapy, which the team notes “are known to affect the time to death in this population,” and may not have been adjusted for in previous studies.
“Specifically, we observed an 8% reduction in the risk for of [all-cause mortality] for every additional positive pelvic LN found at [postradical prostatectomy],” report Anthony d’Amico (Brigham and Women’s Hospital and Dana Farber Cancer Institute, Boston, USA) and colleagues in the Journal of Clinical Oncology.
They say that “these findings provide evidence to support considering the use of adjuvant RT in men with pN1 [prostate cancer] and using a personalized approach on the basis of the number of positive pelvic LNs and other comorbidities.”
The study included 17,913 men (median age 64 years) with pT2–4, N1, M0 prostate cancer who received treatment at the University Hospital Hamburg-Eppendorf between 1995 and 2017. In total, 16.97% (n=3040) received early salvage RT and 4.75% (n=851) adjuvant RT.
In all, 9.01% (n=1614) of men had positive LNs; the majority (81.97%) had 1–3 while 18.03% had 4 or more. Among the men with positive LNs, approximately a quarter received adjuvant RT.
After a median follow-up of 7.02 years, 986 (5.50%) men had died, with 223 (22.62%) deaths attributed to prostate cancer.
Men given adjuvant RT had a lower risk for death than those given early salvage RT (all-cause mortality adjusted hazard ratio=0.92 per positive LN) and after adjusting for time-dependent use and duration of androgen deprivation therapy, both of which increased the risk for death significantly, the 7-year all-cause mortality rates continued to favor the use of adjuvant RT over early salvage RT. Among men with at least four positive LNs the rates were 7.74% versus 23.36%, respectively.
For men with fewer than four LNs, there was no difference in the risk for death between the treatment groups, at 14.27% with adjuvant RT and 13.89% with early salvage RT, but the study authors point out that their sample size was not large enough to detect a significant difference in all-cause-mortality among these men.
They say: “The clinical significance of this finding is two-fold.
“First, it is important to weigh the potential short- and long-term toxicity of pelvic RT against the possible but modest absolute reduction in the risk of [all-cause mortality] when considering its use in men with a single or a few positive LNs.
“Second, although on the basis of a previous report, one could conclude that men with four or more positive pelvic LNs would not benefit from [adjuvant] RT, the data in this study provide evidence to support that [adjuvant] RT in the setting of four or more positive LNs has the potential to translate into a reduced risk of [all-cause mortality].”
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J Clin Oncol 2021; doi:10.1200/JCO.21.02800