The Impact of Histologic Subtypes on Clinical Outcomes After Radiation-Based Therapy for Muscle-Invasive Bladder...

Area of Science:

• Uro-oncology
• Radiation oncology
• Cancer research

Background:

• Muscle-invasive bladder cancer (MIBC) treatment outcomes vary by histologic subtype.
• Limited data exists on radiation therapy (RT) efficacy for MIBC with diverse histologic subtypes (HS-UC) compared to pure urothelial carcinoma (PUC).

Purpose of the Study:

• To compare survival outcomes between patients with PUC and HS-UC treated with curative-intent RT for MIBC.
• To determine if HS-UC confers resistance to RT in MIBC.

Main Methods:

• Multicenter retrospective study of 864 MIBC patients treated with curative RT (2001-2018).
• Compared complete response (CR) and survival outcomes between PUC and HS-UC groups.
• Used multivariable Cox regression to analyze the association between HS-UC and outcomes.

Main Results:

• 122 patients (14%) had HS-UC, with 75% showing squamous and/or glandular differentiation.
• Complete response rates were similar: 69% for PUC and 63% for HS-UC.
• No statistically significant differences in overall survival or cancer-specific survival were observed between PUC and HS-UC groups.

Conclusions:

• Histologic subtypes of urothelial cancer (HS-UC) respond to RT similarly to pure urothelial carcinoma (PUC) in MIBC.
• HS-UC does not appear to confer resistance to RT, supporting bladder preservation strategies.
• Further research is needed for definitive conclusions on specific HS-UC subtypes due to limited patient numbers.