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Treatment Planning Evaluation of Various Modalities for the Tretment of Skin Cancer On Foot

J Park

J Park1*, K Kim2, J Kim3, C Choi4, S Ye5, (1) Seoul National University Hospital, Seoul, N/A, (2) Seoul National Univerisity Hospital, Seoul, ,(3) Seoul National University Hospital, Seoul, ,(4) Seoul National University College of Medicine, Seoul, ,(5) Seoul National University, Seoul,

SU-E-T-609 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To investigate the characteristics of various treatment modalities for skin cancer on foot.

Methods: Right foot was immersed in water reservoir and CT image was taken. Total 6 targets were virtually generated at the skin of foot. Targets are contoured at heel pad (PTV1), inner ankle (PTV2), inner arch (PTV3), dorsal surface (PTV4), inner big toe mound (PTV5) and outer little toe mound (PTV6). Four types of treatment plans using tangential-photon-beams (TPB), electron-beams (EB), high-dose-rate (HDR) brachytherapy technique with Freiburg flap applicator and volumetric-modulated arc therapy (VMAT) technique were generated for each 6 target (single-target plans) and the summed target of every 6 target (multi-target plans). TrueBeam STxâ„¢ and Microselectronâ„¢ were used for external beam and brachytherapy planning, respectively. Plan normalization was performed to cover 95% of target volume by 95% of prescribed dose. Conformity indices (CI) and homogeneity indices (HI) and the mean doses to the foot except targets were investigated.

Results: The averaged CI of single-target plans using TPB, EB, HDR and VMAT was 1.97, 2.39, 1.6 and 0.8, respectively. The averaged HI of single-target plans using aforementioned 4 techniques was 1.05, 1.1, 1.52 and 1.04, respectively. For the multi-target, CI was 3.99, 2.39, 1.6 and 0.8. The HI was 1.1, 1.36, 1.43 and 1.04. The averaged mean dose to the foot except target was 2.48 Gy, 2.66 Gy, 3.57Gy and 2.91 Gy for the single-target while it was 21.3 Gy, 14.6 Gy, 14.2 Gy and 13.1 Gy for the multi-target.

Conclusion: The VMAT technique showed better target conformity and homogeneity not only at the single-target plan but also at the multi-target plan than the other techniques to treat skin cancer on foot. In case of single-target treatment, the mean dose to normal tissue was lowest when using tangential-photon-beams while VMAT was best for multi-target treatment.

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