Lower-Dose Hypofractionated Radiotherapy Schedule Proves Effective for Patients With Locally Advanced Bladder Cancer

Using a hypofractionated schedule of 55 Gy in 20 fractions over 4 weeks to treat patients with locally advanced bladder cancer was noninferior to a schedule of 64 Gy in 32 fractions over 6.5 weeks with regard to both invasive locoregional control and toxicity, according to data published in The Lancet Oncology.

More, the schedule of 55 Gy in 20 fractions was superior with regard to invasive locoregional control compared with a schedule of 64 Gy in 32 fractions, further suggesting that the prior schedule should be adopted as the standard of care to treat this cohort of patients.

“Shorter treatment protocols have numerous socioeconomic advantages in any health care system,” wrote the investigators. “If evidence of superiority of treatment can be provided, with no difference in long-term side effects or detriment to the patient experience, the protocol should be adopted as standard of care. Therefore, we recommend 55 Gy in 20 fractions as a standard of care for bladder preservation in patients with locally advanced bladder cancer.”

The cohort of patients receiving 55 Gy in 20 fractions had a lower risk of invasive locoregional recurrence compared with patients receiving 64 Gy in 32 fractions (adjusted HR, 0.71; 95% CI, 0.52-0.96). Similar toxicity profiles were examined for both treatment schedules (adjusted risk difference, -3.37%; 95% CI, –11.85 to 5.10).

The population examined consisted of 782 patients with locally advanced bladder cancer across 2 studies (456 patients from the BC2001 trial and 326 patients from the BCON trial). The patients were on known fractionation schedules, with 376 patients (48%) receiving 64 Gy in 32 fractions and 406 (52%) receiving 55 Gy in 20 fractions in this meta-analysis. Median follow-up for the analysis was 120 months (IQR 99–159).

The 2 multicenter, randomized, controlled, phase 3 trials BC2001 (NCT00024349) which assessed the addition of chemotherapy to radiotherapy, and BCON (NCT00033436) which looked at hypoxia-modifying therapy combined with radiotherapy, recruited patients 18 years or older with locally advanced bladder cancer and utilized fractionation schedules in accordance with local practices.

“This study provides evidence that moderately hypofractionated radiotherapy was indeed noninferior with respect to invasive locoregional control and late bladder and rectum toxicity, and significantly improved invasive locoregional control,” wrote the investigators. “The observed benefit was robust regardless of radiosensitisation or radiosensitiser.”

The co-primary end points of the research were invasive locoregional control and late bladder or rectum toxicity measured via the Late Effects Normal Tissue Task Force-Subjective, Objective, Management, Analytic tool.

While the data showed compelling results, the research team admitted that the primary outcome in this analysis differs from the primary end points in both the BC2001 and BCON trials. More, the data collection methods for each trial differed, with toxicity outcomes being examined more frequently in the BCON trial when compared with the BC2001 trial.

“To our knowledge, this study is the first to compare the outcomes of conventional fractionation with moderately hypofractionated radiotherapy for locally advanced bladder cancer,” explained the investigators.

Reference:

Choudhury A, Porta N, Hall E, et al. Hypofractionated radiotherapy in locally advanced bladder cancer: an individual patient data meta-analysis of the BC2001 and BCON trials. Lancet Oncol 2021;22(2):246-255. doi:10.1016/S1470-2045(20)30607-0