Study Finds Adaptive Image-Guided Radiation Therapy for Bladder Preservation Clinically Feasible in Urinary Bladder Cancer
A prospective study examining a trimodality treatment approach in localized bladder cancer cases using adaptive image-guided, intensity-modulated radiation therapy found that the bladder preservation rate at 3 years was 83%. These findings were published by Murthy et al in the International Journal of Radiation Oncology • Biology • Physics.
Patients with moderately advanced bladder cancer typically undergo surgery with removal of the bladder resulting in the use of an external urine bag. The trimodality plan, which consists of the transurethral resection of the bladder tumor, image-guided, intensity-modulated radiation therapy, and chemotherapy, was developed as a bladder conservation protocol to preserve bladder function with good oncologic outcomes.
“Adaptive image-guided radiation therapy [with] plan-of-the-day approach for bladder preservation is clinically feasible, with good oncological 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 Oncologist at Tata Memorial Centre, Mumbai, India. “With adaptive image-guided radiation therapy, increasing the dose becomes possible, and serious side effects may be kept low, ensuring a good quality of life for our patients,” Dr. Murthy said.
Study Details
The study looked at 44 patients between August 2008 and August 2014. Thirty-nine (88%) patients were male, and five (11%) were female, ranging in ages from 55 to 72. Eighty-eight percent of patients 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 either three (n = 34) or six (n = 10) nonconcentrically grown planning target volumes. 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 planning target volume-encompassing bladder for the particular day with the plan-of-the-day approach.
Study Findings
At 6 to 10 weeks post-treatment, all patients had a complete response. The study had a median follow-up of 30 months. Overall survival at the last follow up was 77% (34 patients). Among those who died, three died from comorbidities and were disease-free at the time of death.
The 2-year locoregional control, disease-free survival, and overall survival rates were 78%, 66%, and 67%, respectively. Rates of locoregional control and overall survival were better in patients who received dose escalation. Acute and late Radiation Therapy Oncology Group (RTOG) grade 3 genitourinary toxicity was seen in five (11%) and two (4%) patients, respectively. No acute or late RTOG grade 3 or higher gastrointestinal toxicity occurred.
“Adaptive radiation therapy further helps in reduction of doses to normal tissues and improves accuracy of delivery,” Dr. 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 adaptive radiation therapy 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 image-guided, intensity-modulated radiation therapy–based adaptive therapy in clinical practice,” he said.
More follow-up with larger groups of patients is needed to establish the novel technique as the standard, Dr. Murthy said, but results from the study have shown the possibilities of adaptive radiation therapy in bladder cancer patients.
“These results provide proof of concept of using adaptive image-guided radiation therapy in the clinic,” Dr. Murthy said. “This will hopefully lead to more and more suitable patients undergoing bladder preservation around the world.”
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