Ten-Year Follow-Up on 160 Patients Treated with Hypofractionated Prostate Salvage Radiation Therapy

Abstract

<h3>Purpose/Objective(s)</h3> Patients with biochemical failure after prostatectomy are commonly treated with standard fractionation radiotherapy requiring 6.5-8 weeks of treatment. GU003 recently reported favorable short-term efficacy and acceptable toxicity using hypofractionated salvage radiotherapy after prostatectomy. However, follow-up for the study is short and questions remain regarding whether late toxicities will remain acceptable. Here, we report on long term outcomes of patients treated with a similar regimen. <h3>Materials/Methods</h3> We evaluated a consecutive cohort of patients treated from 2003-2013 with salvage RT to 65-70 Gy in 25-28 fractions using image-guided IMRT. Freedom from biochemical recurrence (FFBR), prostate cancer specific survival (PCSS), and overall survival (OS) were assessed using Kaplan-Meier analysis. Factors associated with biochemical failure were assessed using Cox regression analysis (surgical margins, Gleason score ≥8, PSA nadir, time to detectable PSA, PSA doubling time, and presalvage PSA). Late GU toxicities were scored based on a modified LENT/RTOG grading system. <h3>Results</h3> A total of 160 patients were identified with a median follow-up of 155 months. Twenty-six patients (16.3%) received androgen deprivation therapy following surgery or concurrently with radiation and 20 patients (12.5%) had lymph nodes electively treated. FFBR was 63% at 5 years and 56% at 10 years; PCSS was 99% at 5 years and 93% at 10 years; OS was 97% at 5 years and 85% at 10 years. Factors associated with increased biochemical recurrence included negative surgical margin status and higher pre-salvage PSA (p =0.025, 0.050). Total incidence grade ≥3 late toxicities was 21.9% (n=35, 33 GU, 1 GI, 1 lymphovascular) which were observed a median of 101 months after the end of radiation. There were four late grade 4 toxicities and three observed deaths potentially associated with radiation (urothelial cancer, urosepsis related to a suprapubic catheter, and pelvic sarcoma). <h3>Conclusion</h3> Prostate cancer has a long natural history as do many late RT toxicities. This cohort of patients with >10 years follow-up treated with hypofractionated salvage RT shows long-term control comparable to that seen in other salvage RT series with long-term follow-up. Although we do not have a comparator group treated with standard fractionation, these data illustrate the importance of long-term follow-up when considering toxicity from salvage RT.