Abstract
PurposeFlattening filter free (FFF) beams show the potential for a higher dose rate and lower peripheral dose. We investigated the planning study of FFF beams with their role for volumetric modulated arc therapy (VMAT) in squamous cell carcinoma of the scalp.Methods and MaterialsOne patient with squamous cell carcinoma which had involvement of entire scalp was subjected to VMAT using TrueBeam linear accelerator. As it was a rare skin malignancy, CT data of 7 patients with brain tumors were also included in this study, and their entire scalps were outlined as target volumes. Three VMAT plans were employed with RapidArc form: two half-field full-arcs VMAT using 6 MV standard beams (HFF-VMAT-FF), eight half-field quarter-arcs VMAT using 6 MV standard beams (HFQ-VMAT-FF), and HFQ-VMAT using FFF beams (HFQ-VMAT-FFF). Prescribed dose was 25×2 Gy (50 Gy). Plan quality and efficiency were assessed for all plans.ResultsThere were no statistically significant differences among the three VMAT plans in target volume coverage, conformity, and homogeneity. For HFQ-VMAT-FF plans, there was a significant decrease by 12.6% in the mean dose to the brain compared with HFF-VMAT-FF. By the use of FFF beams, the mean dose to brain in HFQ-VMAT-FFF plans was further decreased by 7.4% compared with HFQ-VMAT-FF. Beam delivery times were similar for each technique.ConclusionsThe HFQ-VMAT-FF plans showed the superiority in dose distributions compared with HFF-VMAT-FF. HFQ-VMAT-FFF plans might provide further normal tissue sparing, particularly in the brain, showing their potential for radiation therapy in squamous cell carcinoma of the scalp.
Highlights
Squamous cell carcinoma of the scalp (SCC) is a rare skin malignancy which may be associated with human papillomavirus type 16 [1]
By the use of 6 MV standard beams, in HFQ-volumetric modulated arc therapy (VMAT)-FF plan, there was a significant decrease by 12.6% (P,0.01) in the mean dose to the brain compared with HFF-VMAT-FF plan
When 6 MV flattening filter free (FFF) beams were used, compared with HFQ-VMAT-FF plans, mean dose to the brain was further decreased by 7.4% (P,0.01) for HFQ-VMAT-FFF
Summary
Squamous cell carcinoma of the scalp (SCC) is a rare skin malignancy which may be associated with human papillomavirus type 16 [1]. Volumetric modulated arc therapy (VMAT) had been widely used in the treatment of various tumors, such as nasopharyngeal carcinoma (NPC), pelvic malignancy, prostate cancer and so on [5,6,7]. Several investigators have studied the role of VMAT for stereotactic body radiotherapy (SBRT) which has been shown to shorten beam on times (BOT) if compared with static gantry IMRT [8]. Song JH et al [9] have compared lateral photon-electron (LPE), helical tomotherapy (HT), and VMAT plans for total scalp irradiation. Most of the studies focus on the high dose rates of FFF beams for the clinical application to SBRT, such as brain metastases, lung tumors, hepatic metastases and prostate cancer [14,15,16,17]. Dosimetric comparison was assessed for FFF beams compared with flattened beams for several authors, and the results showed that FFF beams resulted in dose distributions similar to flattened beams [18,19]
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