Effect of Pelvic Lymph Node Irradiation in Salvage Therapy for Patients with Prostate Cancer with a Biochemical Relapse Following Radical Prostatectomy

Abstract

Radiation therapy (RT) as salvage treatment for a biochemical relapse following prostatectomy has been shown to be of benefit measured by serum prostate-specific antigen (PSA) control. However, identifying a target volume for RT has not been well established in this setting. In this study, the results of postoperative RT delivered to extended fields (EFs), prostatic fossa, and pelvic lymph nodes encompassing at least the obturator lymph nodes are compared with treatment of limited fields (LFs), prostatic fossa only, as salvage treatment for patients with a biochemical relapse. Between 1987 and 1999, 68 patients were referred for postprostatectomy RT. Of these patients, 46 were treated for salvage intent by RT alone without adjuvant hormones, 21 patients were treated to EFs and 25 treated to LFs. All patients were treated using 4-field plans. The mean field sizes measured 15 × 14 cm (AP/PA fields) and 12 × 14 cm LFs for the EFs and 10 × 10 cm (AP/PA fields) and 10 × 10 cm (lateral fields) for the LFs. The mean total doses for the EFs and LFs were 6300 and 6200 cGy, respectively, using 180-cGy daily increments. All patients treated to the EFs received boost doses to the prostatic fossa after 4500 cGy total dose to the pelvis. The 10-year actuarial biochemical diseasefree survival (DFS) rates for the EF and LF groups were 52% and 47%, respectively (P = 0.523). The distant metastasis-free survival (DMFS) rates were 77% and 78% (P = 0.925), and overall survival (OS) rates were 88% and 68% (P = 0.615) for the EF and LF group, respectively. A subset analysis of patients with adverse pathologic features (including tumor-involved surgical margins, lymph node involvement, seminal vesicle involvement, extracapsular extension, and/or perineural invasion) showed biochemical DFS rates of 57% and 44% (P = 0.217) for the EF and LF groups, respectively. The DMFS rates were 84% and 72% (P = 0.423), and OS rates 92% and 61% (P = 0.366) for the EF and LF groups, respectively. For patients with increasing PSA levels after a radical prostatectomy, salvage irradiation is a viable option for biochemical control. Our results suggest that EF radiation with coverage of pelvic lymph nodes shows a trend toward better PSA control in those with adverse pathologic features, although statistical significance was not achieved because of the limited number of patients who satisfied the restricted criteria excluding use of adjuvant hormones.