Refining assessment of response to radiation-based therapy for muscle-invasive bladder cancer: Is post-treatment tumor bed biopsy always necessary?

Abstract

Introduction: Radiation-based therapy (RT) has emerged as a suitable alternative to radical cystectomy (RC) and pelvic lymph node dissection for muscle-invasive bladder cancer (MIBC) patients. Routine biopsy after RT to rule out residual disease remains inconsistent across guidelines. Our objective was to review the significance of a bladder biopsy in terms of assessment of response post-RT and its potential impact on survival.

Patients and methods: This was a single-center retrospective study on patients with MIBC (cT2-4aN0-2M0) treated with curative intent RT. A total of 169 patients with primary urothelial carcinoma were analyzed. Patients' demographic, clinical and pathological variables, imaging, cystoscopy, urine cytology, and biopsy reports after RT were collected and compiled. Whenever urine cytology was positive or cystoscopy showed any malignant-appearing lesion, the first assessment post-RT was considered suspicious for residual disease. A descriptive population analysis was reported. Cox regression multivariable analysis was performed to identify independent variables associated with survival outcomes.

Results: Median age was 75 years (interquartile range 66-82) and clinical staging was cT2 in 152 (90%) patients. Cytology and cystoscopy were normal in 140 (83%) after RT. Of patients with a control biopsy, residual MIBC was present in 3 (5%) and non-MIBC in another 6 (11%). On the contrary, a for-cause biopsy due to a suspicious assessment post-RT did not yield residual cancer in 45% of patients. Multivariable analysis showed that age (hazard ratio [HR] 1.04, P< 0.001), lymphovascular invasion (HR 1.68, P = 0.03) and a suspicious assessment after RT (HR 3.21; P< 0.001) were significantly associated with worse OS. This study was limited by its retrospective design.

Conclusions: A routine biopsy after RT may be warranted to assess treatment response. This might be particularly important for patients who may benefit from early surgical intervention for residual MIBC. Further prospective studies are needed to confirm our findings.

Keywords: Bladder biopsy; Bladder cancer; Chemotherapy; Muscle-invasive; Radiotherapy; Trimodal therapy.