Intracranial response after extracranial radiation in a patient with rapidly progressing metastatic melanoma

Abstract

Growing literature supports the synergistic effect of radiation as a primer for renewed enhanced systemic immunological responses in patients receiving immunotherapy for metastatic melanoma. Radiographic regression of extracranial tumours after treatment of intracranial metastatic lesions has been reported and these observations point to an abscopal effect that traverses the blood-brain barrier. We describe a patient with rapidly progressing metastatic melanoma despite combined immune checkpoint blockade, who achieved a complete metabolic response of both his extracranial and intracranial disease after the commencement of palliative radiation to his axilla. This is the first published case, to our knowledge, of a sustained, complete intracranial abscopal response from extracranial radiation. We discuss potential mechanistic relations between radiation, the blood-brain barrier and the abscopal effect.

Keywords: immunology; radiotherapy; skin cancer.

Figure 1

Serial positron emission tomography imaging with time. November 2018: time of disease recurrence while on adjuvant nivolumab. February 2019: progressive disease post four cycles of combination ipilimumab and nivolumab. May 2019: partial response post completion of palliative radiotherapy to left axilla. July 2019: almost complete metabolic response. March 2020: complete metabolic response. June 2020: ongoing complete metabolic response.

Figure 2

Serial brain MRI T1 axial imaging with time. November 2018: no evidence of intracranial disease at time of extracranial recurrence. February 2019: development of left posterior parietal metastasis and left basal ganglia metastasis (white arrows) post four cycles of combination ipilimumab and nivolumab. May 2019: partial intracranial response post completion of palliative radiotherapy to left axilla; haemorrhagic transformation of left parietal metastasis (top image, white arrow) and resolution of left basal ganglia metastasis, replaced with gliosis (bottom image, white arrow). August 2019: complete intracranial response. June 2020: ongoing complete intracranial response.