Objective
This study aims to compare late toxicity in patients undergoing salvage radiation therapy (SRT) for a detectable prostate-specific antigen level after radical prostatectomy between those who received low-dose three-dimensional-conformal radiation therapy (3D-CRT), high-dose 3D-CRT and intensity-modulated radiation therapy (IMRT).
Methods
We retrospectively identified 266 patients who underwent SRT at our institution. Patients were categorized into three groups: low-dose 3D-CRT (≤66.6 Gy, N = 142), high-dose 3D-CRT (>66.6 Gy, N = 49), and high-dose IMRT (>66.6 Gy, N = 75). Low-dose IMRT patients were not included due to their small number (N = 22). Late toxicity was defined as occurring 90 days or more after SRT completion.
Results
The cumulative incidence of any late complication at 5 years after SRT was 11.0 % for the low-dose 3D-CRT group, 18.8 % for the high-dose 3D-CRT group, and 14.7 % for the high-dose IMRT group, with no significant differences between groups (P ≥ 0.17). No significant difference between groups was found in the occurrence of any specific complication, although there were nonsignificant trends toward an increased incidence of diarrhea at 5 years in the high-dose 3D-CRT group (7.0 %) compared with the low-dose 3D-CRT (1.4 %, P = 0.061) and high-dose IMRT groups (0.0 %, P = 0.068), and more grade 2+ late complications in the high-dose 3D-CRT group (14.0 %) than the low-dose 3D-CRT group (6.0 %, P = 0.059).
Conclusion
Our results indicate that with the advancement in planning and delivery of SRT, it is possible to administer IMRT at higher doses without significantly increasing the risk of late complications. Future studies involving larger numbers of high-dose IMRT patients will further strengthen these findings.