ADT + dose-escalated IMRT improves survival outcomes in high-risk prostate cancer
Combining androgen-deprivation therapy (ADT) with dose-escalated intensity-modulated radiation therapy (IMRT) without elective pelvic nodal irradiation resulted in improved biochemical failure-free survival (BCFFS) and disease-free survival (DFS) in high-risk localized prostate cancer, according to a study.
Researchers evaluated 419 men with localized prostate adenocarcinoma (median age 74 years, 60.8 percent with high- or very high-risk disease) who underwent definitive dose-escalated IMRT (cumulative dose 78 Gy) on the prostate and seminal vesicles excluding the pelvis. Of these, 76 percent received ADT for a median duration of 10 months. Endorectal balloons were used in almost 70 percent of patients treated in the prone position (98 percent) to immobilize the prostate and rectum. [Asian J Androl 2017;19:596-601]
Compared with non-ADT recipients, those who received ADT had improved 5-year BCFFS (88 percent vs 83 percent; p=0.028) and DFS (88 percent vs 80 percent; p=0.009).
On multivariate analysis, BCFFS and DFS were independently predicted by ADT use (odds ratio [OR], 2.40; p=0.014 and OR, 2.90; p=0.002, respectively), as well as T stage (OR, 0.27; p<0.001 and OR, 0.24; p<0.001) and Gleason grade (OR, 0.29; p<0.001 and OR, 0.33; p<0.001).
“[Dose-escalated IMRT] … provides durable disease control with few pelvic nodal recurrences and distant metastases … ADT was notably an independent factor for BCFFS and DFS,” said the researchers, adding that the combined effects of the two approaches further decreased the cumulative incidence of biochemical failure and distant metastases.
Cumulative incidence of late ≥grade 2 gastrointestinal and genitourinary toxicities was 11 percent and 6.7 percent, respectively.
“[S]paring the pelvis in [dose-escalated IMRT] of the prostate lowers the rate of severe late GI toxicity,” said the researchers. Furthermore, the combined use of endorectal balloons and image guidance yielded acceptable GI toxicity rates and has shown benefit in prostate localization and immobilization. [Int J Radiat Oncol Biol Phys 2012;83:e257-264]
The exclusion of the pelvis and the use of similar radiation dosimetry and field configurations rendered uniform results, allowing for better risk-stratified assessment of hormone efficacy, said the researchers.
The findings were consistent with previous studies favouring the addition of ADT to dose-escalated IMRT in high-risk prostate cancer cases, [Int J Radiat Oncol Biol Phys 2013;86:64-71; Int J Radiat Oncol Biol Phys 2011;79:1323-1329; Lancet Oncol 2015;16:320-327] with similar or better disease control and toxicity profiles when compared with other trials. [Int J Radiat Oncol Biol Phys 2008;70:67-74; J Clin Oncol 2010;28:1106-1111]
Overall, the findings provide sufficient evidence to support the benefits of adding ADT to dose-escalated IMRT, according to the researchers. However, the results might not be applicable to the Western population as the study only represented an Asian setting, they added.