Pulsed-Reduced Dose Rate (PRDR) Radiotherapy for Recurrent Primary Central Nervous System Malignancies: Dosimetric and Clinical Results

Abstract

Purpose: The objective was to describe PRDR outcomes and report EQD2 OAR toxicity thresholds. Methods: Eighteen patients with recurrent primary CNS tumors treated with PRDR at a single institution between April 2017 and September 2021 were evaluated. The radiotherapy details, cumulative OAR doses, progression-free survival (PFS), overall survival (OS), and toxicities were collected. Results: The median PRDR dose was 45 Gy (range: 36–59.4 Gy); the median cumulative EQD2 prescription dose was 102.7 Gy (range: 93.8–120.4 Gy). The median cumulative EQD2 D0.03cc for the brain was 111.4 Gy (range: 82.4–175.2 Gy). Symptomatic radiation necrosis occurred in three patients, for which the median EQD2 brain D0.03cc was 115.9 Gy (110.4–156.7 Gy). The median PFS and OS after PRDR were 6.3 months (95%CI: 0.9–11.6 months) and 8.6 months (95%CI: 4.9–12.3 months), respectively. The systematic review identified five peer-reviewed studies with a median cumulative EQD2 prescription dose of 110.3 Gy. At a median follow-up of 8.7 months, the median PFS and OS were 5.7 months (95%CI: 2.1–15.4 months) and 6.7 months (95%CI: 3.2–14.2 months), respectively. Conclusion: PRDR re-irradiation is a relatively safe and feasible treatment for recurrent primary CNS tumors. Despite high cumulative dose to OARs, the risk of high-grade, treatment-related toxicity within the first year of follow-up remains acceptable.

Pulsed low-dose rate radiotherapy for recurrent bone sarcomas: case reports and brief review

“…With a notable median follow-up of 64 months, the estimated 4-year OS and PFS were 60% and 35.7%, respectively. In a recent publication, Kutuk et al [ 13 ] reported on their experience with PLDR re-irradiation in 18 patients with recurrent primary CNS malignancies. At a median follow-up of 8.7 months, the median PFS and OS were 5.7 months and 6.7 months, respectively.…”

Re-irradiation of recurrent head and neck cancers using pulsed reduced dose rate radiotherapy: An institutional series

“…5,6 Previous research has shown encouraging results for Re-RT using PRDR-RT in multiple disease sites. [7][8][9] However, there are minimal reports on the use of PRDR-RT for HNSCC. The purpose of this study was to report preliminary efficacy and toxicity data from a single institution of a consecutive cohort of patients with HNSCC who received Re-RT via PRDR-RT.…”

Temporally modulated pulsed proton re-irradiation (TMPPR) for recurrent high-grade gliomas

“… 4 Photon PRDR is also associated with modest treatment-related toxicities and not widely available. 5 …”