Exceptional Regression of Malignant Pleural Mesothelioma with Pembrolizumab Monotherapy

Our plain-English summary of Exceptional Regression of Malignant Pleural Mesothelioma with Pembrolizumab Monotherapy, by B.F. Hearon, K.N. Redelman, G.C. Elhomsy, et al (Case Reports in Oncology, 2020).

The study

• Authors: B.F. Hearon, K.N. Redelman, G.C. Elhomsy, D.F. Moore
• Journal: Case Reports in Oncology
• Published: 2020;13(3):1483-1489
• Type of article: Case report
• Cited by: 1 article, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The lead author with clinical stage I malignant pleural mesothelioma, epithelioid type, highly programmed cell death ligand 1 (PD-L1) positive, and BAP1 negative, experienced a prompt and exceptionally favorable response to pembrolizumab monotherapy. After cessation of treatment due to immune-related endocrinopathies, complete metabolic response on interim PET/CT scan was achieved. Two years after initial diagnosis, unifocal tumor reactivation was addressed with successful pembrolizumab monotherapy rechallenge. Immunotherapy, typically not used as frontline treatment for malignant pleural mesothelioma, may provide an effective and durable response for some patients. Based on this single case study, epithelioid type tumors with strongly positive PD-L1 and BAP1-negative immunohistochemical markers may be well suited for treatment with immune checkpoint inhibitors such as pembrolizumab.

Copyright © 2020 by S. Karger AG, Basel.

In plain English

This article is a case report of one patient: the lead author, a 66-year-old male orthopaedist who had been exposed to asbestos nearly 50 years earlier while working as a pipe fitter during college summers. The article does not name a fiber type. A needle biopsy showed malignant pleural mesothelioma, epithelioid type, judged to be clinical stage I. The tumor showed strong PD-L1 labeling in 80% of cells and had lost BAP1 labeling. The patient declined standard surgery, chemotherapy and radiation, and instead received the immunotherapy drug pembrolizumab off-label. After 3 cycles, symptoms improved and all tumor masses shrank on imaging. After 8 cycles, treatment was stopped because of new hypothyroidism and type 1 diabetes. A scan 8 months later showed a complete metabolic response. About 2 years after diagnosis, one pleural-based nodule by the heart grew modestly, and pembrolizumab was restarted. At 33 months after diagnosis, scans showed no evidence of active disease. No surgery, chemotherapy or radiation was used. The authors concluded that patients with similar early-stage tumors may be good candidates for pembrolizumab alone. They noted that no randomized trials support immunotherapy for this disease.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: case report (single patient)
• Who was studied: One patient, a 66-year-old male orthopaedist (the lead author), with clinical stage I malignant pleural mesothelioma, epithelioid type, that was strongly PD-L1 positive (80% of cells) and BAP1 negative.
• Exposure: Asbestos exposure nearly 50 years earlier while working as a pipe fitter during college summer breaks. No fiber type is given. The treatment studied was pembrolizumab 200 mg every 3 weeks, used off-label as first-line therapy.
• Main results:
  • After 3 treatment cycles, chest pain and sense of well-being improved. Imaging showed reduced size and FDG uptake of all tumor masses. In the largest mass, maximum standardized uptake value fell from 10.3 at baseline to 2.6, described as a 75% reduction.
  • After 5 more infusions, the patient developed new-onset primary hypothyroidism and type 1 diabetes mellitus. Treatment was suspended because of these immune-related side effects.
  • A PET/CT scan 8 months after stopping treatment showed no FDG uptake, which the authors call a complete metabolic response.
  • Elevated lymphocyte and eosinophil counts persisted for months after pembrolizumab was stopped.
  • Two years after diagnosis, one pleural-based pericardial nodule had modestly increased in size and FDG uptake. Pembrolizumab was resumed, and after 4 infusions the nodule had decreased with no significant metabolic activity.
  • At 33 months after diagnosis, PET/CT showed no evidence of active disease. No surgery, chemotherapy or radiation therapy had been used.
• The authors' conclusion: The authors concluded that patients with early clinical stage, epithelioid, strongly PD-L1 positive, BAP1 negative malignant pleural mesothelioma may be good candidates for pembrolizumab monotherapy.
• Limitations the authors state:
  • The findings come from a single case.
  • No randomized clinical trials support the use of immunotherapy for malignant pleural mesothelioma.
  • The effect of changing the drug dose or frequency on response and side effects is not yet known.

Topics

Medical terms in this study, explained in our Lexicon: Pleural Mesothelioma, Pembrolizumab (Keytruda), Epithelioid, PD-L1, BAP1, CT Scan, Immunotherapy, checkpoint inhibitors.

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