Adaptive IGRT for Urinary Bladder Cancer Is Clinically Feasible With Good Outcomes
A bladder preservation rate of 83% occurred at 3 years after a trimodality treatment approach for localized bladder cancer that used adaptive image-guided, intensity-modulated radiation therapy (IG-IMRT).1
Urinary bladder cancer is the cause of approximately 150 000 cancer deaths worldwide each year. For patients with moderately advanced bladder cancer, the typical treatment is resection of the urinary bladder, which results in the use of an external urine bag.
The trimodal plan examined in this study was developed to conserve the bladder and to have good oncologic outcomes. The plan consists of transurethral resection of the bladder tumor (TURBT), IG-IMRT, and chemotherapy.
“Adaptive IGRT [with] plan-of-the-day approach for bladder preservation is clinically feasible, with good oncologic outcomes and low rates of acute and late toxicities. Dose escalation is safe and possibly improves outcomes in bladder preservation,” said Vedang Murthy, MD, radiation oncology, Tata Memorial Centre, Mumbai, India, and lead author of the study.
“With adaptive IGRT, increasing the dose becomes possible, and serious side effects may be kept low, ensuring a good quality of life for our patients.”
The study included 44 patients between August 2008 and August 2014. The participants included 39 males and 5 females, age 55 to 72 years. Most participants (88%) had stage II disease. Patients underwent maximal safe resection of bladder tumor and concurrent platinum-based chemotherapy, and those with large tumors were offered induction chemotherapy.
Radiation therapy planning was done using 3 (n = 34) or 6 (n = 10) nonconcentrically grown planning target volumes (PTV). Patients received 64 Gy in 32 fractions to the whole bladder and 55 Gy to the pelvic nodes. If appropriate, they received a simultaneous integrated boost to the tumor bed to 68 Gy. Daily megavoltage imaging was used to find the most appropriate PTV encompassing bladder for the particular day with the plan-of-the-day approach.
When evaluated 6 to 10 weeks after treatment, all patients had a complete response. The median follow-up time was 30 months, and overall survival was 77% (34 patients) at last follow-up. Among those who died, 3 deaths were due to comorbidities and were disease-free at the time of death.
The 3-year locoregional control (LRC) was 78%, disease-free survival was 66%, and overall survival (OS) was 67%.
“Adaptive radiation therapy further helps in reduction of doses to normal tissues and improves accuracy of delivery,” Murthy said. “These procedures, in theory, should result in less acute and late toxicity, while allowing for dose escalation to gross tumor to improve outcomes.”
“Although a number of investigators have conceived and developed a variety of ART techniques, there are few clinical outcome data to validate this dosimetric concept. The present proof-of-concept prospective study was conducted with the aim of establishing the safety, efficacy, and feasibility of IG-IMRT–based adaptive radiation therapy in clinical practice,” he said.
Murthy stated that more follow-up with larger groups of patients is needed to establish this novel technique as the standard, but this study's results show the possibilities of adaptive radiation therapy in bladder cancer patients.
“These results provide proof of concept of using adaptive IGRT in the clinic,” Murthy said. “This will hopefully lead to more and more suitable patients undergoing bladder preservation around the world.”
1. Murthy V, Masodkar R, Kalyani N, et al. Clinical outcomes with dose-escalated adaptive radiation therapy for urinary bladder cancer: a prospective study. Int J Radiat Oncol Biol Phys. 2016;94(1):60-66.