Endorectal brachytherapy boost after external beam radiotherapy in elderly or medically inoperable patients with rectal cancer: primary outcomes of the phase I HERBERT study

Publication date: Available online 20 January 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): E.C. Rijkmans, A. Cats, R.A. Nout, H.J.G.D. van den Bongard, M. Ketelaars, J. Buijsen, T. Rozema, J.H. Franssen, L.A. Velema, B. van Triest, C.A.M. Marijnen
PurposeThis study evaluated toxicity and efficacy of the combination of external beam radiotherapy (EBRT) followed by high dose rate endorectal brachytherapy (HDREBT) boost in elderly and medically inoperable patients with rectal cancer.Material and MethodsA phase I dose escalation study was performed. Treatment consisted of EBRT (13x3 Gy) followed by three weekly brachytherapy applications six weeks later. HDREBT dose started at 5 Gy per fraction, increasing with 1 Gy per fraction if dose limiting toxicity (DLT, defined as > grade 3 proctitis < 6 weeks after HDREBT) occurred in ≤ 2 patients per dose level. The primary endpoint was the maximum tolerated dose, defined as one dose-level below the dose were three patients experienced DLT. Secondary endpoints were severe treatment-related late toxicity, clinical tumor response, freedom from local progression (FFLP) and local progression free and overall survival (L-PFS and OS).ResultsThirty-eight patients with a median age of 83 years were included in the study. Thirty-two were evaluable for DLT and late toxicity and 33 for response evaluation. Maximum delivered dose was 8 Gy per fraction resulting in a recommended dose of 7 Gy per fraction. Response occurred in 29 of 33 patients (87.9%) with 60% complete response (CR). L-PFS and OS were 42% and 63% at two years. Patients with CR showed a significant improved L-PFS (60% at 2 yrs, p=0.006) and a trend in improved OS (80% at 2 yrs, p=0.11). Severe late toxicity occurred in 10/32 patients.ConclusionHDREBT after EBRT results in a high overall response rate, with improved local progression free survival for patients with a CR. The high observed rate of severe late toxicity requires further evaluation of the risks and benefits of a HDREBT boost.



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