Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2022

Checkpoint inhibitor immunotherapy-induced radiation recall pneumonitis: a case series (#222)

Andrew O Parsonson 1 2 , John J Park 2 3 , Deme Karikios 3 4 , Annette Tognela 1 5 , Howard Gurney 2 6 , Tim Wang 4 6 , Dhanusha Sabanathan 2 3
  1. Department of Medical Oncology, Macarthur Cancer Therapy Centre , Campbelltown, NSW, Australia
  2. Clinical Trials Unit, Macquarie University Hospital, Macquarie University, NSW, Australia
  3. Department of Medical Oncology, Nepean Cancer Care Centre, Penrith, NSW, Australia
  4. University of Sydney, Camperdown, NSW, Australia
  5. Western Sydney University, Campbelltown, NSW, Australia
  6. Crown Princess Mary Cancer Centre, Westmead, NSW , Australia

Introduction

Radiation Recall Pneumonitis (RRP) is a clinical syndrome that describes the development of focal pneumonitis in a previously irradiated field, triggered by systemic therapy months after completion of radiation therapy. We present three cases of checkpoint inhibitor immunotherapy-induced RRP.  

Case presentations

Our first patient, diagnosed with metastatic non-small cell carcinoma, received palliative radiation therapy to his lung and thoracic spine. He developed RRP after seven cycles of pembrolizumab, approximately six months after completing palliative radiation therapy.  Our second patient with metastatic triple negative breast cancer developed RRP following two cycles of treatment with pembrolizumab, nab-paclitaxel and a novel ILT3 inhibitor. She had received palliative radiotherapy to an axillary lymph node recurrence two months prior to commencing systemic therapy. Our third patient was diagnosed with metastatic Hurtle cell thyroid carcinoma and had received palliative radiotherapy to a left rib metastasis, two months prior to commencing a novel PD-L1 checkpoint inhibitor. All three patients were treated by temporarily withholding treatment and a course of oral corticosteroids, with clinical resolution of RRP and were able to be rechallenged with checkpoint inhibitor immunotherapy.   

Discussion

RRP is a distinct clinical phenomena that can occur with palliative doses of radiotherapy and small treated lung volumes, that are normally associated with a low risk of radiation induced lung injury.  Immunotherapy-induced RRP conforms to the prior radiation field and must be differentiated from diffuse checkpoint inhibitor immunotherapy induced pneumonitis, as well as local processes such as pneumonia. As indications for the use checkpoint inhibitor immunotherapy increase in cancer care, it is likely that immunotherapy-induced RRP will increase in incidence. Early diagnosis and management may allow for the continuation of systemic therapy. Further research is required to understand the mechanisms that lead to this rare form of RRP.