Assessment of relative tumor burden in patients with clinical T1c prostatecancer treated with either external beam or radical prostatectomy

The choice between external beam radiation therapy (EBRT) or retropubic rad ical prostatectomy (RPX) as potentially curative treatment for localized ca rcinoma of the prostate gland (CaP) has not been delineated in randomized s tudies. Both treatments are more effective if tumor burden is low. We sough t to compare these two treatments in patients who had clinical stage Tlc (c Tlc) lesions and who were thought to have limited tumor burdens pretreatmen t. Sixty cTlc patients referred to the Department of Radiation Oncology rec eived 66 Gy in 33 sessions of EBRT to localized prostate ports and 59 cTlc patients had RPX. No neoadjuvant nor early adjuvant therapies were prescrib ed. Radiotherapy success was defined biochemically as a nonrising prostate- specific antigen (PSA) of less than or equal to 1.5 ng/ml. RPX success requ ired a postoperative PSA that was undetectable (PSA <0.2 ng/ml by the Hybri tech or Abbott IMx technics). Analysis for nonrising posttreatment PSA leve ls was performed using Kaplan-Meier and Cox regression methods. Mantel-Haen szel methods were used to determine odds ratios for treatment groups adjust ing for potential confounders. We ultimately assessed the relative tumor bu rden by histologic examination of the RPX specimens. The two treatment grou ps, although not randomized, were statistically similar in biopsy Gleason S cores, transrectal ultrasonography calculated gland volumes, number of posi tive biopsy cores, and estimated amount of cancer identified on initial bio psies. Pathologic stage T3 was identified in 25% of RPX patients. Fifty to 60% of RPX specimens histologically had substantial tumor burden and by inf erence also the EBRT patients. At a median follow-up (F/U) of 36 months, 76 % of RPX patients maintained an undetectable PSA, whereas 62% of EBRT patie nts had a PSA <1.5 ng/ml at a median F/U of 29 months. The pretreatment PSA values significantly affected EBRT patients' risk of a rising posttreatmen t PSA level. Twenty-four months after treatment, RPX patients were 3.7 time s more likely to maintain a nonrising PSA level (RPX patients posttreatment PSA < 0.2 ng/ml), than EBRT patients (posttreatment PSA less than or equal to 1.5 ng/ml) (p = 0.006). Sixty-six gray in 33 sessions to localized EBRT ports is not sufficiently aggressive therapy for one third or more of pati ents with cTlc CaP. RPX alone is insufficient therapy for one fourth of cTl c patients. Analysis of the RPX specimens showed that many cTle tumors have a significant tumor burden. Selection methodologies to separate out patien ts who require more than conventional dose or type of radiotherapy or more than RPX as monotherapy are needed. Pretreatment PSA and number of positive biopsies may assist this selection process.