On your 6.
Top Line: Is ultra-hypofractionated whole bladder radiation an effective option for patients with muscle invasive bladder cancer who aren’t candidates for standard treatment?
The Study: Many patients with non-metastatic MIBC are not candidates for either radical surgery or chemoradiation. Yet, their localized disease may warrant more than strictly palliative treatment (or no treatment at all). The HYBRID Trial evaluated the efficacy of an ultra-hypofractionated regimen for treatment of 65 patients with node-negative MIBC who weren’t candidates for standard therapy. All patients were treated with 36 Gy in 6 once-weekly fractions to the whole bladder. The trial was a randomized, non-comparative phase 2 design that compared standard planning with adaptive planning. All patients were simulated with an empty bladder. The CTV consisted of the bladder (and tumor) and proximal urethra. In the standard arm, a single plan was generated using a 1.5 cm symmetric expansion. In the adaptive arm, three separate plans were generated using three (small, medium, and large) asymmetric PTV expansions. At 3 months, local control was >80% and at 1 year >80% were still free from invasive recurrence. Non-GU grade 3+ toxicity was favorable in both arms (13% standard tx, 6% adaptive tx). The utilization of adaptive plans (39%) exceeded a threshold (25%) that suggests such an approach may provide a clinically meaningful benefit.
Bottom Line: 36 Gy in 6 fractions (+/- adaptive planning) appears tolerable and effective for patients with localized MIBC who aren’t candidates for standard therapy. | Huddard, Int J Radiat Oncol Biol Phys 2020