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Postoperative radiotherapy in 423 patients with pT3N0 prostate cancer
Zbigniew Petrovich1, Gary Lieskovsky, Bryan Langholz
1Department of Radiation Oncology, Keck School of Medicine, University of Southern California, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA. zpetrovi@hsc.usc.edu
Purpose:
To evaluate the treatment outcome in pT3N0 patients with adenocarcinoma of the prostate treated with an elective course of postoperative irradiation (RT).
Methods And Materials:
During a 22-year period, a total of 423 pT3N0 prostate cancer patients were treated at a single medical center with prostatic fossa RT, which was the only adjuvant therapy given. The patient characteristics were as follows: median age 66 years; Stage pT3aN0 in 296 (70%) and pT3bN0 in 127 (30%); Gleason score 2-4 in 12 (2.8%), 5-6 in 157 (37.1%), 7 in 151 (35.7%), and 8-10 in 100 (23.6%); and the median and mean preoperative prostate-specific antigen (PSA) level was 10 and 15.9 ng/mL, respectively. Radiotherapy consisted of a median dose of 48 Gy delivered to the prostatic fossa and its immediate vicinity. The median follow-up was 7 years.
Results:
The 5- and 10-year actuarial survival rate was 92% and 73%, respectively, and the 5- and 10-year disease-free survival rate (PSA <0.05 ng/mL) was 69% and 51%, respectively. In multivariate analysis, the Gleason score was the most important predictor for survival (p = 0.00005), and pathologic stage and Gleason score were independently predictive of disease-free survival (p = 0.00007 and 0.0003, respectively). The worst prognostic category was represented by pT3bN0, Gleason score 7-10 patients who had a 5.3 times greater risk of tumor recurrence than those with pT3aN0, Gleason score 2-6. A high (>25 ng/mL) preoperative PSA level was also a predictor of tumor recurrence (p = 0.03). A total of 43 patients (10.2%) developed clinical recurrence. This included 30 patients (7%) with distant metastases alone and 13 (3%) with local recurrence, which included 2 patients who also had distant disease. An additional 88 patients (20%) had PSA elevation (>0.05 ng/mL). This treatment program was well tolerated, with acute toxicity common (62%) but of no clinical significance. No late or severe toxicity was recorded.
Conclusion:
Adjuvant radiotherapy, as given in this study, appears to substantially reduce the expected incidence of local tumor recurrence in pT3N0 prostate cancer patients. The treatment outcome was poor in pT3bN0 and Gleason score 7-10 patients, with >80% showing evidence of clinical or PSA recurrence at 10 years after therapy. This group should be the target of a prospective trial of systemic therapy.