Planning study for Merkel cell carcinoma based on the relapse pattern

Radiother Oncol. 2017 Apr;123(1):154-157. doi: 10.1016/j.radonc.2017.01.021. Epub 2017 Mar 8.

Abstract

Purpose: To develop a technique for radiation (RT) of in-transit path ways (IT) in Merkel cell carcinoma.

Method: 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.

Results: 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: Dmean 100%±0%, D98% 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.

Conclusion: 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.

Keywords: In transit metastases; Merkel cell carcinoma; Planning study; Sentinel node scintigraphy.

MeSH terms

  • Carcinoma, Merkel Cell / diagnostic imaging
  • Carcinoma, Merkel Cell / radiotherapy*
  • Humans
  • Radiotherapy Planning, Computer-Assisted / methods*
  • Radiotherapy, Conformal / methods*
  • Recurrence
  • Skin Neoplasms / diagnostic imaging
  • Skin Neoplasms / radiotherapy*
  • Tomography, X-Ray Computed