Bladder cancer patterns of pelvic failure: implications for adjuvant radiation therapy

Abstract

Purpose: Local-regional failures (LFs) after cystectomy with or without chemotherapy are common in locally advanced disease. Adjuvant radiation therapy (RT) could reduce LFs, but toxicity has discouraged its use. Modern RT techniques with improved normal tissue sparing have rekindled interest but require knowledge of pelvic failure patterns to design treatment volumes.

Methods and materials: Five-year LF rates after radical cystectomy plus pelvic node dissection with or without chemotherapy were determined for 8 pelvic sites among 442 urothelial bladder carcinoma patients. The impact of pathologic stage, margin status, nodal involvement, and extent of node dissection on failure patterns was assessed using competing risk analysis. We calculated the percentage of patients whose sites of LF would have been completely encompassed within various hypothetical clinical target volumes (CTVs) for postoperative radiation.

Results: Compared with stage ≤pT2, stage ≥pT3 patients had higher 5-year LF rates in virtually all pelvic sites. Among stage ≥pT3 patients, margin status significantly altered the failure pattern whereas extent of node dissection and nodal positivity did not. In stage ≥pT3 patients with negative margins, failure occurred predominantly in the iliac/obturator nodes and uncommonly in the cystectomy bed and/or presacral nodes. Of these patients in whom failure subsequently occurred, 76% would have had all LF sites encompassed within CTVs covering only the iliac/obturator nodes. In stage ≥pT3 with positive margins, cystectomy bed and/or presacral nodal failures increased significantly. Only 57% of such patients had all LF sites within CTVs limited to the iliac/obturator nodes, but including the cystectomy bed and presacral nodes in the CTV when margins were positive increased the percentage of LFs encompassed to 91%.

Conclusions: Patterns of failure within the pelvis are summarized to facilitate design of adjuvant RT protocols. These data suggest that RT should target at least the iliac/obturator nodes in stage ≥pT3 with negative margins; coverage of the presacral nodes and cystectomy bed may be necessary for stage ≥pT3 with positive margins.