Planning study for Merkel cell carcinoma based on the relapse pattern.

Hoeller, Ulrike; Schubert, Tina; Mueller, Thomas; Budach, Volker; Ghadjar, Pirus; Brenner, Winfried; Kuschke, Wolf · Radiother Oncol · 2017

case_series · Level IV

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Abstract

To develop a technique for radiation (RT) of in-transit path ways (IT) in Merkel cell carcinoma. In the planning study, IT were ink-marked on the skin during sentinel lymphscintigraphy and wire-marked in planning-CT. Pre- and post-operative planning-CTs were acquired. The clinical target volume (CTV) included tumor bed plus safety margin, IT and draining nodes, the planning volume (PTV) the CTV plus 0.5-1cm margin. VMAT plans with 2-3 arcs were analyzed. A planning study was performed for five pts. including two pts. with primary tumor (PT) in head and neck, 1 pt. each with PT of elbow, forearm and upper leg respectively. Plans showed satisfactory PTV coverage: D<sub>mean</sub> 100%±0%, D<sub>98%</sub> 92.4%±2.24%, homogeneity index (HI) 0.095±0.01, conformation number (CN) 0.84±0.01 and conformality index (CI) 0.95±0.01. The planning study confirms feasibility of highly conformal irradiation of IT pathways based on individualized target delineation. Currently, patients referred for non-metastatic MCC are encouraged to enroll in a prospective clinical study that evaluates the feasibility of radiation of IT pathways.

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