Spontaneous Regression of Delayed Pulmonary and Mediastinal Metastases from Clear Cell Renal Cell Carcinoma

Renal cell carcinoma (RCC) is often metastatic at diagnosis. Conventional therapies such as chemotherapy, radiotherapy, and hormonal therapy have generally proven ineffective in the treatment of RCC. The abscopal effect, specifically, the ability of localized radiation to trigger systemic antitumor effects, has been reported to lead to regression of non-irradiated distant tumor lesions. Herein, we report 3 patients with non-metastatic clear cell RCC (CCRCC) who underwent a nephrectomy and experienced metachronous pulmonary/mediastinal metastases confirmed as CCRCC. No patients underwent radiation post-nephrectomy or pulmonary metastasectomy. The mean duration was 7.24 weeks from the last negative chest CT prior to the nephrectomy and 96.2 weeks post-nephrectomy. All patients achieved durable complete response by RECIST criteria, with a mean follow-up duration of 115 months. Our case series represents the largest in the literature of patients who underwent a nephrectomy for CCRCC with no pre-existing pulmonary/mediastinal metastatic disease confirmed by chest CT, did not undergo radiotherapy, and developed significantly delayed CCRCC pulmonary/mediastinal metastases. We highlight the spontaneous regression of delayed metastatic disease and the role of immune responses in curtailing the growth of pulmonary metastasis in CCRCC.