Impact of surgical staging in evaluating the radiotherapeutic outcome in RTOG #77-06, a phase III study for T1BN0M0 (A2) and T2N0M0 (B) prostate carcinoma

Abstract

Purpose: To evaluate survival and time to metastatic disease in patients treated for localized prostatic carcinoma in a Phase III radiotherapy (RT) protocol, Radiation Therapy Oncology Group (RTOG) 77-06. Patients with T18N0M0 (A2) or T2N0M0 (B) disease after lymphangiogram (LAG) or staging laparotomy (SL) were randomized between prophylactic radiation to the pelvic lymph nodes and prostatic bed vs. prostatic bed alone. The outcome of both treatment arms, as well as a comparison of the LAG group, to that of the SL group, are updated.

Methods and materials: A total of 449 eligible males were entered into RTOG protocol 7706 between 1978 and 1983. Lymph node staging was mandatory but at the physician's discretion; 117 (26%) patients had SL, while 332 (74%) had LAG. Follow-up was a median of 12 years and a maximum of 16 years. For those randomized to receive prophylactic pelvic lymph nodal irradiation, 45 Gy of megavoltage RT was delivered via multiple portals in 4.5-5 weeks, while all patients received 65 Gy in 6.5-8 weeks to the prostatic bed.

Results: There was no significant difference in survival whether treatment was administered to the prostate or prostate and pelvic lymph nodes. The SL group had greater 12-year survival than the LAG group (48% vs. 38%, p = 0.02). Disease-free survival was statistically significant, with 38% for the SL group vs. 26% for the LAG group (p = 0.003). Bone metastasis was less common in the SL group (14%) than the LAG group (27%) (p = 0.003).

Conclusion: At 12-year median follow-up, there still was no survival difference in those patients treated prophylactically to the pelvic nodes and prostatic bed vs. the prostatic bed alone. Those patients not surgically staged with only LAG for lymph node evaluation were less accurately staged, as reflected by a statistically significant reduced survival and earlier metastases.