Abscopal Effect Demonstrated on [18F]FDG PET/CT in a Case of Renal Cell Carcinoma Postnephrectomy.

Renal cell carcinoma accounts for 3% of all malignancies with many of them presenting with metastasis at the time of presentation. The abscopal effect, a phenomenon characterized by systemic bystander effects on nontargeted lesions due to local therapy, has been extensively studied in the context of radiotherapy and immunotherapy. However, documentation of the abscopal effect following surgery remains limited. We present a case of a 67-year-old Indian male diagnosed with clear cell renal cell carcinoma (RCC), who underwent left radical nephrectomy. Baseline staging and postnephrectomy follow-up scans with fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET-CT) revealed an FDG-avid primary lesion in the left kidney with metastasis to the left lung. Surprisingly, the follow-up FDG PET-CT scan demonstrated the resolution of the left lung metastasis, indicating the occurrence of the abscopal effect resulting from the local nephrectomy. This rare clinical observation highlights the potential of surgery to induce immunogenic tumor neoantigens release and inflammatory factors, leading to systemic antitumor effects. While the abscopal effect has been extensively studied in the context of radiotherapy and immunotherapy, there is a scarcity of studies reporting nephrectomy promoting such systemic effects. The combination of radiotherapy and immunotherapy has shown promising results in enhancing tumor immunosuppression and facilitating the abscopal effect. We report a case of RCC with lung metastasis showing abscopal effect with resolution of lung nodule postnephrectomy on 18-F-FDG PET-CT.