Higher doses of radiotherapy control localized prostate cancer (PCa) more effectively than lower doses 10 years after treatment and reduced the need for follow-up androgen-deprivation therapy, according to investigators.
The phase 3, open-label, international, randomized controlled trial yielding these results involved 422 men who had been assigned to escalated-dose conformal radiotherapy and 421 men who had been assigned to control-dose conformal radiotherapy for the treatment of histologically confirmed localized PCa with PSA levels below 50 ng/mL. The men in the escalated-dose group received 74 Gy in 37 fractions, whereas the control group members received 64 Gy in 32 fractions—the standard dose at the time the study was designed.
The men joined the study between January 1998 and December 2001. The previously reported five-year outcomes pointed to the benefits of the dose-escalation radiotherapy regimen. Now, these results have been shown to be maintained over a median follow-up of 10 years.
As of August 2011, 118 patients in each group had died. Only 91 of these 236 deaths were due to prostate cancer.
Overall survival at 10 years was 71% in each group, but more men in the control group (221, or 57%) than in the escalated-dose group (170, or 43%) experienced biochemical progression or progressive disease. At the 10-year mark, biochemical progression-free survival was 55% in the escalated-dose group versus 43% in the control group.
The improvement in biochemical control of the cancer did not translate into an improvement in metastases-free survival, PCa-specific survival, or overall survival. At a median follow-up of 10 years, however, escalated-dose conformal radiotherapy with neoadjuvant androgen deprivation therapy (ADT) demonstrated an advantage in biochemical progression-free survival, concluded David P. Dearnaley, MD, uro-oncology professor at The Institute of Cancer Research, London, United Kingdom, and fellow investigators in The Lancet Oncology.
Having recorded a significant delay in the reported time to initiation of long-term, salvage ADT in the escalated-dose group, Dr. Dearnaley’s group noted that this advantage must be balanced against the known small increase in bowel side effects from the five extra treatments required by the escalated-dose treatment plan.
Although men receiving the higher-dose radiotherapy were more likely than the controls to experience treatment adverse effects (AEs), few men had severe AEs. Because the men in the higher-dose group were less likely to require follow-up hormone therapy, they were of course more likely to avoid the side effects from that treatment.