The effect of jaw tracking during radiotherapy for facial non-melanoma skin cancer
So Hyun Park,
Korea Republic of
PO-1551
Abstract
The effect of jaw tracking during radiotherapy for facial non-melanoma skin cancer
Authors: So Hyun Park1, Jinhyun Choi2, Dae-Hyun Kim3, So Hyun Ahn4
1Jeju National University, Radiation Oncology, Jeju, Korea Republic of; 2Jeju National Univerisy, Radiation Oncology, Jeju, Korea Republic of; 3Ulsan University Hospital, Radiation Oncology, Ulsan, Korea Republic of; 4Ewha Womans University, Ewha Medical Research Institute, Seoul, Korea Republic of
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Purpose or Objective
The higher extent of low dose radiation filed, the worse skin erythema result. In this study, we analyzed dosimetric effects of jaw tracking (VitalBeam, Varian) during the Volumetric Modulated Arc Therapy (VMAT) planning for facial non-melanoma skin cancer (NMSC).
Material and Methods
Twenty-two patients with facial NMSC underwent VMAT planning with or without jaw tracking. The target volume (TV) included the primary skin lesion with 1-cm margin around the surface and a 4 mm depth. A total of 55 Gy in 20 fractions was prescribed and the plans were considered acceptable if the TV was covered by 95%-105% of the isodose curve. Dosimetric comparison was performed with volumes of low dose regions which were defined as < 50% of prescription dose (V10-50%). The target coverage was evaluated by homogeneity index (HI) and conformity index (CI).
Results
The patients’ median TV was 4.07 cc (range: 1.03-10.27 cc). The use of jaw tracking provided mean volume reduction rates in 5.2% (0%-14.4%) for V30%, 10.2% (0.1%-21.0%)for V20%, and 14.7% (1.8%-30%) for V10% (all p < 0.001). Volume changes for V50% and V40% between two groups were 0.4% and 1.7%, respectively (p=0.408, 0.183). No significant differences were observed for HI (0.06) and CI (0.54).
Conclusion
The application of jaw tracking during VMAT for facial NMSC was associated with significant reduction in the volume of low dose delivered in the radiation field (V10-30%) while maintaining the target coverage. Future analyses should assess whether this volume difference affect treatment-related cosmetic outcome.