The anti-PD-1 immune checkpoint inhibitor nivolumab is currently approved for the treatment of patients with metastatic renal cell carcinoma (mRCC); approximately 25% of patients respond. We hypothesized that we could identify a biomarker of response using radiomics to train a machine learning classifier to predict nivolumab response outcomes.
Patients with mRCC of different histologies treated with nivolumab in a single institution between 2013 and 2017 were retrospectively identified. Patients were labelled as responders (complete response [CR]/particle response [PR]/durable stable disease [SD]) or non-responders based on investigator tumor assessment using RECIST 1.1 criteria. For each patient, lesions were contoured from pre-treatment and first post-treatment computed tomography (CT) scans. This information was used to train a radial basis function support vector machine classifier to learn a prediction rule to distinguish responders from non-responders. The classifier was internally validated by a 10-fold nested cross-validation.
Thirty-seven patients were identified; 27 (73%) met the inclusion criteria. One hundred and four lesions were contoured from these 27 patients. The median patient age was 56 years, 78% were male, 89% had clear-cell histology, 89% had prior nephrectomy, and 89% had prior systemic therapy. There were 19 responders vs. eight non-responders. The lesions selected were lymph nodes (60%), lung metastases (23%), and renal/adrenal metastases (17%). For the classifier trained on the baseline CT scans, 69% accuracy was achieved. For the classifier trained on the first post-treatment CT scans, 66% accuracy was achieved.
The set of radiomic signatures was found to have limited ability to discriminate nivolumab responders from non-responders. The use of novel texture features (two-point correlation measure, two-point cluster measure, and minimum spanning tree measure) did not improve performance.
Canadian Urological Association journal = Journal de l'Association des urologues du Canada. 2021 Sep 24 [Epub ahead of print]
Eoghan R Malone, Hao-Wen Sim, Audrius Stundzia, Sacha Pierre, Ur Metser, Martin O'Malley, Adrian G Sacher, Srikala S Sridhar, Aaron R Hansen
Division of Medical Oncology and Hematology, Princess Margaret Cancer Centre, UHN, Toronto, ON, Canada., Tomographix IP Ltd., Toronto, ON, Canada., Division of Abdominal Imaging, Joint Department of Medical Imaging, University of Toronto, Toronto, ON, Canada., Division of Molecular Imaging, Joint Department of Medical Imaging, University of Toronto, Toronto, ON, Canada.