In-field and abscopal response after short-course radiation therapy in patients with metastatic Merkel cell carcinoma progressing on PD-1 checkpoint blockade: a case series

J Immunother Cancer. 2018 May 30;6(1):43. doi: 10.1186/s40425-018-0352-8.

Abstract

Background: Patients with metastatic Merkel cell carcinoma (mMCC) who experience disease progression on immunotherapy have limited additional standard options. Given evidence of synergism between radiation therapy (RT) and immunotherapy, two patients progressing on PD-1 inhibition were referred for short-course RT.

Case presentation: Two patients were found to have progressive mMCC on PD-1 inhibitor therapy and were treated with single-fraction palliative RT. Both patients were observed to have local control at irradiated regions, as well as durable abscopal response at unirradiated, out-of-field, sites of metastatic disease.

Conclusions: Short-course RT is a compelling strategy that could be a means to augment response in patients with mMCC who show progression on immune checkpoint blockade. Ongoing clinical trials are investigating the relationship between RT and immunotherapy in mMCC.

Keywords: Abscopal response; Metastatic Merkel cell carcinoma; PD-1 inhibition; Single-fraction radiation therapy; Stereotactic body radiation therapy.

Publication types

  • Case Reports
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Antibodies, Monoclonal, Humanized / therapeutic use*
  • Antineoplastic Agents, Immunological / therapeutic use*
  • Carcinoma, Merkel Cell / diagnostic imaging
  • Carcinoma, Merkel Cell / drug therapy*
  • Carcinoma, Merkel Cell / radiotherapy*
  • Combined Modality Therapy
  • Drug Resistance, Neoplasm
  • Humans
  • Male
  • Positron Emission Tomography Computed Tomography
  • Programmed Cell Death 1 Receptor / antagonists & inhibitors*
  • Skin Neoplasms / diagnostic imaging
  • Skin Neoplasms / drug therapy*
  • Skin Neoplasms / radiotherapy*
  • Treatment Outcome

Substances

  • Antibodies, Monoclonal, Humanized
  • Antineoplastic Agents, Immunological
  • PDCD1 protein, human
  • Programmed Cell Death 1 Receptor
  • pembrolizumab