Intensity Modulated Radiation Therapy with Pulsed Reduced Dose Rate as a Re-irradiation Strategy for Recurrent Central Nervous System Tumors: An Institutional Series and Literature Review

Publication date: Available online 12 April 2017
Source:Practical Radiation Oncology
Author(s): Erin S. Murphy, Kevin Rogacki, Andrew Godley, Peng Qi, Chandana Reddy, Manmeet Ahluwalia, David Peereboom, Glen Stevens, Jennifer S. Yu, John H. Suh, Sam T. Chao
BackgroundPulsed reduced dose rate (PRDR) is a re-irradiation technique that potentially overcomes volume and dose limitations in the setting of previous radiotherapy for recurrent central nervous system tumors. Intensity modulated radiation therapy (IMRT) has not yet been reported as a PRDR delivery technique. We reviewed our IMRT PRDR outcomes and toxicity and reviewed the literature of available PRDR series for CNS re-irradiation.Material/MethodsA total of 24 patients with recurrent brain tumors received PRDR re-irradiation between 8/2012 and 12/2014. Twenty-two patients were planned with IMRT. Linear accelerators delivered an effective dose rate of 0.0667Gy/min. Data collected included number of prior interventions, diagnosis, tumor grade, radiotherapy dose and fractionation, normal tissue dose, radiotherapy planning parameters, time to progression, overall survival and adverse events.ResultsThe median time to PRDR from completion of initial radiotherapy was 47.8months (R: 11–389.1months). The median PRDR dose was 54Gy (R: 38–60Gy). The mean planning target volume was 369.1 +/− 177.9cm³. The median PFS and 6month PFS after PRDR treatment was 3.1months and 31%, respectively. The median OS and 6month OS after PRDR treatment was 8.7months and 71%, respectively. 50% of patients had ≥4 chemotherapy regimens prior to PRDR. Toxicity was similar to initial treatment including no cases of radiation necrosis.ConclusionIMRT PRDR re-irradiation is a feasible and appropriate treatment strategy for large volume recurrent CNS tumors resulting in acceptable overall survival with reasonable toxicity in our patients who were heavily pretreated. Prospective studies are necessary to determine the optimal timing of PRDR re-irradiation, the role of concurrent systemic agents, and the ideal patient population who would receive the maximal benefit from this treatment approach.SummaryIntensity modulated radiation therapy (IMRT) has not yet been reported as a pulsed reduced dose rate (PRDR) delivery technique for recurrent brain tumors and may allow for safe and comprehensive re-irradiation for large volume tumors. We reviewed our IMRT PRDR outcomes and toxicity and reviewed the literature of available PRDR series for recurrent central nervous system tumors. We conclude that IMRT PRDR re-irradiation is a feasible and appropriate treatment strategy for large volume recurrent brain tumors resulting in acceptable overall survival with reasonable toxicity in our patients who were heavily pretreated.



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