Radical cystoprostatectomy (RC) is one standard treatment for muscle-invasive bladder cancer (MIBC) in male patients. Another therapeutic option is trimodal therapy (TMT). Including the prostate in the TMT radiotherapy volume is based on MIBC surgical series showing prostatic stromal (PS) involvement. Our aim is to establish the rate of pathological PS involvement by pre-operative T stage in men treated with RC for MIBC.

We conducted a retrospective review of men with MIBC treated with RC between 2006-2019. Electronic medical records were reviewed, and preoperative clinical staging data were collected. Chi-square test was done to test for a statistically significant difference in the rate of prostatic involvement between clinical tumor (cT) stages. Preoperatively identified CIS, lymph node involvement, tumor location, and urethral involvement were also analyzed to see if they conferred a higher risk of PS involvement. Multivariate analysis using Multiple Logistic Regression was performed.

We identified 283 men with bladder cancer treated with RC. Patients with non-MIBC, or incomplete medical data were excluded (n=72). We analyzed 211 patients, 46 (22%) had pathological PS involvement. PS involvement by preoperative T stage was cT2=18%, cT3=23%, and cT4=48%. 29 (12%) patients had clinical lymph node involvement, of whom 19 (76%) had PS involvement. 34 (16%) had urethral involvement, of whom 17 (50%) had PS involvement. 16% and 17% of percent of clinical T2 and T3 patients had bladder neck / trigone tumors, of whom 57% and 50% has prostatic involvement. Clinical T2 and T3 were not statistically different with regards to PS involvement (p =0.385). Pre-operative urethral involvement, lymph node involvement, cT4, and bladder neck/trigone location were statistically significant predictors of pathologic PS involvement (all p <0.05). On multivariate analysis, only clinical urethral involvement was significant (P<0.0001).

The high rate of pathological PS involvement seen in cT2 patients and the lack of ability of cT stage to predict PS involvement supports routinely treating the prostate in TMT. Patients with pre-operatively identified bladder neck/trigone tumors, urethral involvement, positive lymph nodes, or prostatic involvement are a subset at even higher risk of having pathologic PS involvement.