Optimization strategies for pulsed low‐dose‐rate IMRT of recurrent lung and head and neck cancers

Abstract

Pulsed low‐dose‐rate radiotherapy (PLDR) has been proven to be a valid method of reirradiation. Previous studies of recurrent cancer radiotherapy were mainly based on conventional 3D CRT and VMAT delivery techniques. There are difficulties in IMRT planning using existing commercial treatment planning systems (TPS) to meet the PLDR protocol. This work focuses on PLDR using ten‐field IMRT and a commercial TPS for two specific sites: recurrent lung cancers and head and neck cancers. Our PLDR protocol requires that the maximum dose to the PTV be less than 0.4 Gy and the mean dose to be 0.2 Gy per field. We investigated various planning strategies to meet the PLDR requirements for 20 lung and head and neck patients. The PTV volume for lung cases ranged from 101.7 to 919.4 cm3 and the maximum dose to the PTV ranged from 0.22 to 0.39 Gy. The PTV volume for head and neck cases ranged from 66.2 to 282.1 cm3 and the maximum dose to the PTV ranged from 0.21 to 0.39 Gy. With special beam arrangements and dosimetry parameters, it is feasible to use a commercial TPS to generate quality PLDR IMRT plans for lung and head and neck reirradiation.PACS number: 87.55.D‐

Local Tumor Control and Normal Tissue Toxicity of Pulsed Low-Dose Rate Radiotherapy for Recurrent Lung Cancer

“…35 We have now developed treatment planning strategies for PLDR treatments of recurrent cancers utilizing advanced delivery techniques including intensity-modulated radiation therapy (IMRT) and volumetric-modulated radiation therapy (VMAT). [36][37][38][39][40] In comparison with 3-dimensional conformal radiation therapy (3DCRT), IMRT and VMAT exhibited significantly improved target dose conformity and organ at risk dose sparing, and clinical trials using PLDR with IMRT or VMAT techniques are ongoing for the management of recurrent cancers at FCCC.…”

Clinical Applications of Pulsed Low Dose-Rate Radiation Therapy

“…It was considered to be more definitive and descriptive to use PLDR than PRDR because "reduced dose rate" does not indicate the actual dose-rate range achievable by this special delivery technique. More studies focusing on the strategy for PLDR treatment planning and dose constraints for PLDR plan optimization following the same methodology were reported [15][16][17][18]. Many in vitro and in vivo experiments on PLDR were reported to investigate the therapeutic ratio and mechanisms of PLDR, and most of them used the same terminology [54][55][56][57][58][59][60][61][62][63][64][65].…”

“…The Fox Chase group was the first to investigate advanced delivery techniques systematically for PLDR treatment of recurrent cancers to further reduce normal tissue toxicities [10,[15][16][17]. These delivery techniques were used in their phase I dose escalation trial to investigate PLDR irradiation for palliation of recurrent tumors [74].…”

“…PLDR treatment was initiated with simple treatment techniques using single field electron beams or 3D conformal photon beams [6][7][8]. Advanced delivery systems and treatment planning optimization strategies were developed to support re-irradiation protocols [10,[14][15][16][17][18][19][20]. A number of clinical trials have been carried out to study the potential of PLDR treatments for recurrent cancers, bulky and/or radiation resistant cancers and the combination of PLDR with other treatment modalities, e.g.…”

TrueBeam Low Dose Rate Investigation for Pulsed Reduced Dose Rate IMRT

“…Researchers are actively investigating ways to apply PRDR to more advanced techniques, such as static field Intensity Modulated Radiation Therapy (IMRT) [6], Volumetric Modulated Arc Therapy (VMAT) [7] [8], and tomotherapy [9] [10]. The primary challenge with IMRT-based PRDR, however, is that IMRT fields are difficult to separate into 0.2 Gy pulses.…”