Preoperative chemotherapy in clinically node positive muscle invasive bladder cancer: Radiologic variables can predict response.

Purpose: To evaluate pathologic downstaging after radical cystectomy and pelvic lymph node dissection for clinically lymph node positive urothelial bladder cancer and to determine optimal preoperative imaging variables in predicting pathologic nodal status.

Methods: We identified all patients with clinically lymph node positive urothelial bladder cancer who underwent radical cystectomy and extended pelvic lymph node dissection with intent to cure at our institution. Patients were stratified based on pathologic node status to determine clinical associations and survival outcomes. Pre and post-chemotherapy CT scans were reviewed to characterize lymph node size and morphology. We also sought to determine associations between post-chemotherapy radiology variables and pathologic response.

Results: We identified 130 patients with clinically node positive bladder cancer, out of which 76 (58.5%) received induction chemotherapy. Thirty three (43.4%) had pathologic T downstaging following chemotherapy, compared to 7 (12.9%) patients who had surgery alone (P< 0.0001). A complete nodal response (pN0) occurred in 31 (40.8%) patients post-chemotherapy, while 6 (11.1%) of those who received cystectomy alone ended up being pN0 (P< 0.0001). Median overall survival and recurrence-free survival were shorter in patients with pN+ versus pN0 disease (1.9 years vs. 12.8 years, P= 0.016 and 1.2 years vs. 4.3 years, P= 0.013, respectively). Review of 29 post chemotherapy CT scans showed that patients with pathologic nodal involvement had a greater median number of enlarged nodes (3.5 vs. 1, P= 0.038) and a greater median size of largest node (8.5 mm vs. 6.0 mm, P= 0.021) on imaging compared to those with complete pN0. Each 1 mm increase in size of the largest node on post-chemotherapy CT scan increased the chance of having pN+ disease by 1.57 (95% CI 1.02-2.44, P= 0.043). Using a median node size of 8 mm as a cut-off to predict pN+ disease provided a sensitivity and specificity of 72% and 80%, respectively (c-index = 0.761, P= 0.014). The positive predictive value for this cut-off was 87% (95% CI 58%-98%) and negative predictive value was 62% (32%-85%).

Conclusion: Patients with clinically node positive bladder cancer may have significant pN0 after induction chemotherapy. Our data suggest a post-chemotherapy CT scan with an 8 mm nodal size cut-off may be a better predictor of pathologic nodal status than more traditional measures.