Adaptive Radiotherapy for Carcinoma of the Urinary Bladder: Long-term Outcomes With Dose Escalation

Area of Science:

• Oncology
• Radiation Oncology
• Urology

Background:

• Muscle-invasive bladder cancer (MIBC) presents a significant clinical challenge.
• Bladder preservation strategies are crucial for maintaining quality of life in MIBC patients.
• Image-guided adaptive radiotherapy (ART) offers a potential approach for bladder preservation.

Purpose of the Study:

• To evaluate the long-term outcomes of dose-escalated, image-guided adaptive radiotherapy (ART) for bladder preservation in muscle-invasive bladder cancer (MIBC).
• To assess the safety, efficacy, and toxicity profile of ART in a cohort of MIBC patients.
• To determine the feasibility of implementing ART in routine clinical practice for bladder preservation.

Main Methods:

• A retrospective analysis of 106 MIBC patients treated with bladder-preserving ART between 2009 and 2018.
• ART involved daily plan selection ('plan-of-the-day') based on on-board imaging to adapt treatment delivery.
• Dose escalation included a total dose of 64 Gy to the whole bladder and a simultaneous integrated boost to 68 Gy for solitary tumors, with concurrent chemotherapy for eligible patients.

Main Results:

• 87% of patients completed the planned 64 Gy whole bladder dose, and 59% received the 68 Gy tumor bed boost.
• At a median follow-up of 26 months, 3-year locoregional control, disease-free survival, and overall survival rates were 74.3%, 62.9%, and 67.7%, respectively.
• 82% of patients maintained a disease-free bladder, with acceptable rates of acute (7.5% GU, 0% GI) and late (6.5% GU, 3.8% GI) toxicities (RTOG Grade III/IV).

Conclusions:

• 'Plan-of-the-day' ART is a safe and effective method for bladder preservation in MIBC patients.
• High rates of bladder preservation can be achieved with ART without compromising oncological outcomes or increasing toxicity.
• Dose escalation within this ART framework did not significantly impact survival or toxicity, suggesting its potential for routine clinical implementation.