Standard and reduced high-dose volume radiation therapy (RT) for muscle-invasive bladder cancer provides comparable tumor control and decreased late toxicity compared with surgery, according to a new study that was published in the International Journal of Radiation Oncology, Biology, Physics (2013;87[2]:261-269).

Cystectomy (removal of partial or whole bladder) is often the standard treatment for patients with muscle-invasive bladder cancer; however, advanced RT techniques that spare the bladder may be an effective alternative for patients who are unsuitable for or unwilling to undergo cystectomy. This research was conducted to determine if some of the drawbacks of RT of the bladder, such as local recurrence and late toxicity risks, could be reduced with a lower dose of RT delivered to the areas of the bladder outside of the tumor region, and to assess the tumor control and toxicity of RT.

The phase III randomized trial included 219 patients from 28 centers across the United Kingdom who received either standard radiation therapy or reduced high-volume radiation therapy. Patients were all 18 years and older and had stage T2 to T4a bladder cancer. The study participants were randomized, such that 108 received standard whole bladder radiation therapy (sRT) and the remaining 111 patients received reduced high-dose volume radiation therapy (RHDVRT), in which the full radiation dose was delivered to the tumor and 80% of the maximum dose was delivered to the uninvolved bladder.

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Study participants received RT doses based on their cancer center’s choice of either 55 Gy/20 fractions over 4 weeks or 64 Gy/32 fractions over 6.5 weeks. The median patient follow-up time was 72.7 months posttreatment. Late toxicity was defined in this study as radiation therapy-related side effects at least 1 to 2 years posttreatment.

Rates of late toxicity were lower than anticipated, and the number of patients reporting toxicities was not significantly different between the sRT and RHDVRT groups. The overall cumulative Grades 3/4 RTOG toxicity rate was 13% at 2 years posttreatment, and the percentage of patients with Grades 3/4 toxicity at any specific point was shown to be less than 8% throughout in both groups. The 2-year locoregional recurrence-free (LRRF) rate was 61% for the sRT group and 64% for the RHDVRT group.

“We have now demonstrated that delivering at least 75% of the dose [of RT] to the uninvolved bladder is deliverable across multiple sites without obvious detriment to local disease control or survival, although noninferiority could not be formally confirmed,” said lead author Robert A. Huddart, PhD, of The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust. “These results confirm, however, that RT is an effective alternative for patients unable to undergo cystectomy. Further study using image-guided treatment with or without dose escalation is now also warranted.”