Outcome evaluation of the 1997 American Joint Committee on Cancer staging system for prostate carcinoma treated by radiation therapy

BACKGROUND: The 1997 American Joint Committee on Cancer (AJCC) staging system condensed unilobular tumors into one entity and continues the use of both imaging and biopsy to alter classification status in T2 and T3 carcinomas. This study analyzes the biochemical freedom from disease recurrence (bNED) outcome in a large database to determine whether these changes reflect outcome differences. METHODS: Five hundred and thirty-seven patients with adenocarcinoma of the prostate were treated with radiation therapy to a median dose of 7180 centigrays (cGy) (range, 6316-8074 cGy) between November 1987 and November 1994. The median age of the patients was 70 years and the median follow-up was 51 months. The median pretreatment prostate specific antigen (PSA) was 11.0 ng/mL. Patients were analyzed using 1992 AJCC stage comparing bNED outcome after radiation therapy for T2a versus T2b versus T2c tumors using Kaplan-Meier estimation and the log rank test. Patients then were analyzed multivariately using Cox regression with the known prognostic variables of dose, pretreatment PSA, palpation stage, and grade in addition to palpation plus imaging stage and palpation plus biopsy stage. The prognostic endpoint was bNED with failure as defined by the 1997 American Society for Therapeutic Radiology and Oncology Consensus Panel. RESULTS: The 1992 AJCC palpation classifications T2a versus T2b versus T2c have a significantly different (P = 0.02) bNED outcome. Prognostic significance is lost by pooling these three classifications in the 1997 AJCC staging system. Adding imaging information to palpation did not improve the ability of palpation alone to assess bNED status (P = 0.33). However, the addition of biopsy information to palpation significantly (P = 0.02) increased the accuracy of palpation stage alone to predict for bNED outcome for T2 and T3 tumors. CONCLUSIONS: The subdivision of T2 tumors in the 1992 AJCC classification (T2a, T2b, and T2c) should be used in the next revision of the 1997 AJCC staging system. The addition of imaging data does not discriminate bNED outcome any better than palpation stage alone in T2 and T3 tumors and should not be used. The addition of biopsy information to palpation stage did significantly improve the predicted outcome compared with palpation alone and should continue to be used.