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

Tugce Kutuk; Ranjini Tolakanahalli; Nicole C McAllister; Matthew D Hall; Martin C Tom; Muni Rubens; Haley Appel; Alonso N Gutierrez; Yazmin Odia; Alexander Mohler; Manmeet S Ahluwalia; Minesh P Mehta; Rupesh Kotecha

doi:10.3390/cancers14122946

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

Cancers (Basel). 2022 Jun 15;14(12):2946. doi: 10.3390/cancers14122946.

Authors

Tugce Kutuk¹, Ranjini Tolakanahalli^{1

2}, Nicole C McAllister¹, Matthew D Hall^{1

2}, Martin C Tom^{1

2}, Muni Rubens³, Haley Appel¹, Alonso N Gutierrez^{1

2}, Yazmin Odia⁴, Alexander Mohler⁴, Manmeet S Ahluwalia⁵, Minesh P Mehta^{1

2}, Rupesh Kotecha^{1

2

6}

Affiliations

¹ Department of Radiation Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA.
² Department of Radiation Oncology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA.
³ Department of Clinical Informatics, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA.
⁴ Department of Neuro-Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA.
⁵ Department of Medical Oncology, Miami Cancer Institute, Baptist Health South Florida, Miami, FL 33176, USA.
⁶ Department of Translational Oncology, Herbert Wertheim College of Medicine, Florida International University, Miami, FL 33199, USA.

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 D_0.03cc 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 D_0.03cc 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.

Keywords: CNS malignancies; PRDR; glioma; pulsed reduced dose rate radiotherapy; re-irradiation; recurrence.

Grants and funding

This research received no external funding.