Long-Term Benefits of Elective Radiotherapy After Prostatectomy for Patients With Positive Surgical Margins

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Abstract
The benefit of adjuvant radiotherapy after prostatectomy for patients with pathological risk factors but with an undetectable postoperative PSA remains controversial. In this retrospective study we define the benefits of elective postoperative radiotherapy in this setting. A total of 44 patients received elective postoperative radiotherapy at a single institution in the PSA era (1989 to 1995) for positive surgical margins and undetectable postoperative PSA. Radiotherapy was delivered to a median dose of 60 Gy. Clinical target volume included the prostate bed. Pelvic nodes were not treated. The four-field box technique with customized blocking of bladder, rectum and small bowels was used and defined the planning target volume. The patients were then compared to a contemporaneous group of 189 patients with positive surgical margins who underwent radical prostatectomy without any adjuvant therapy. Failure was defined as biochemical (PSA) recurrence and was timed from first detectable PSA. The 5 and 10-year biochemical no evidence of disease was 90.9% and 90.9% for the elective postoperative radiotherapy group, and 66.4% and 54.5% for the observation group, respectively (p = 0.0012). Median time to biochemical failure was also longer in the elective postoperative radiotherapy group (88.6 months) compared to the observation group (43.5 months) (p <0.001). Risk factors for biochemical recurrence on multivariate analysis were Gleason score greater than 7 (p = 0.017), established extracapsular extension (p = 0.002) and lack of elective postoperative radiation (p = 0.001). This is one of the longest followup studies showing that elective postoperative radiation therapy is associated with improved bNED and prolonged time to recurrence. Combined radical prostatectomy and elective postoperative radiotherapy should be considered in the management of high risk prostate cancer, especially in the presence of positive surgical margins despite undetectable PSA.

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