Top Line: Moderate hypofractionation has become a popular regimen for organ-preserving bladder radiation.
The Study: Tata Memorial has now published its outcomes after switching from conventional fractionation (64 Gy to the bladder / 55 Gy to pelvic nodes all in 32 fractions) to moderate hypofractionation (55 Gy to bladder and 44 Gy to pelvic nodes all in 20 fractions) all while employing IMRT with a daily adaptive planning regimen of sorts. The low-tech adaptive planning is where things get interesting. All patients (n=221) were simulated with an empty bladder and the clinical target volume was the entire bladder including all gross disease. Then, three planning target volumes and three respective plans were generated for each patient: PTV_Small (0.5 cm radial expansion except 1 cm anteriorly and superiorly where there is more bladder filling variation), PTV_Medium (1 cm except 1.5 cm ant/sup), and PTV_Large (1.5 cm except 2 cm ant/sup). Daily cone beam CTs were used to select “the smallest PTV that fit the bladder comfortably in all directions on a given day,” a decision that could be made by well-trained radiation therapists. All patients received concurrent weekly cisplatin (or gem if cisplatin-ineligible). Acute grade 2 GI toxicity was higher with hypofractionation (27%, 20/75) than conventional (14%, 20/146), but there was little late grade 2 GI toxicity. Cancer control and survival outcomes were nearly identical. As expected, those getting concurrent gemcitabine had worse GI toxicity. Finally, the authors acknowledge elective nodal irradiation remains controversial in this setting but feel the use of IMRT and limiting the upper border to the bifurcation of the common iliacs provides a much better therapeutic ratio than that seen with older 3D-techniques.
TBL: In this study, hypofractionated daily adaptive IMRT for bladder preservation demonstrates excellent long term tolerability but slightly higher rates of acute grade 2 GI toxicity. | Krishnan, Int J Radiat Oncol Biol Phys 2025
The Study: Tata Memorial has now published its outcomes after switching from conventional fractionation (64 Gy to the bladder / 55 Gy to pelvic nodes all in 32 fractions) to moderate hypofractionation (55 Gy to bladder and 44 Gy to pelvic nodes all in 20 fractions) all while employing IMRT with a daily adaptive planning regimen of sorts. The low-tech adaptive planning is where things get interesting. All patients (n=221) were simulated with an empty bladder and the clinical target volume was the entire bladder including all gross disease. Then, three planning target volumes and three respective plans were generated for each patient: PTV_Small (0.5 cm radial expansion except 1 cm anteriorly and superiorly where there is more bladder filling variation), PTV_Medium (1 cm except 1.5 cm ant/sup), and PTV_Large (1.5 cm except 2 cm ant/sup). Daily cone beam CTs were used to select “the smallest PTV that fit the bladder comfortably in all directions on a given day,” a decision that could be made by well-trained radiation therapists. All patients received concurrent weekly cisplatin (or gem if cisplatin-ineligible). Acute grade 2 GI toxicity was higher with hypofractionation (27%, 20/75) than conventional (14%, 20/146), but there was little late grade 2 GI toxicity. Cancer control and survival outcomes were nearly identical. As expected, those getting concurrent gemcitabine had worse GI toxicity. Finally, the authors acknowledge elective nodal irradiation remains controversial in this setting but feel the use of IMRT and limiting the upper border to the bifurcation of the common iliacs provides a much better therapeutic ratio than that seen with older 3D-techniques.
TBL: In this study, hypofractionated daily adaptive IMRT for bladder preservation demonstrates excellent long term tolerability but slightly higher rates of acute grade 2 GI toxicity. | Krishnan, Int J Radiat Oncol Biol Phys 2025