Rapid subcutaneous progression after immunotherapy in pretreated patients with metastatic carcinoma: two case reports.

There is heterogeneity in cancer patients' responses to immune checkpoint inhibitors (ICIs), including hyperprogression, which is very rapid tumor progression following immunotherapy, and pseudoprogression, which is an initial increase followed by a decrease in tumor burden or in the number of tumor lesions. This heterogeneity complicates clinical decisions because either premature withdrawal of the treatment or prolonged ineffective treatment harms patients. We presented two patients treated with ICIs with heterogeneous responses. One patient had Merkel cell carcinoma in the right thigh, and the other had nasopharyngeal squamous carcinoma. The first patient was treated with sintilimab and the second with sintilimab combined with abraxane. In the first patient, subcutaneous lesions grew substantially after the first cycle of treatment with sintilimab. In the second patient, subcutaneous lesions grew gradually after the second cycle of treatment with sintilimab combined with abraxane. In both cases, biopsy examination confirmed that newly emerged lesions were metastases of the primary tumor. These two cases remind clinicians that when subcutaneous nodules appear after treatment with ICIs, pathological biopsy is needed to determine the nature-pseudoprogression or rapid progression-of the disease course.