Flare Responses in Small Cell Carcinoma of the Lung

Two cases of small cell carcinoma of the lung in which flare responses were demonstrated are discussed. Although the primary tumor and extraskeletal metastases responded to first-line chemotherapy, bone scintigraphs performed 3 months after the start of treatment suggested tumor progression. However, following repeat bone imaging and subsequent clinical evaluation, the interim scintigraphs appeared to represent an unusual flare response, in which the activity of pre-existing hot spots increased and new lesions developed.