Transformation to Small-cell Lung Cancer As a Mechanism of Acquired Resistance to Crizotinib and Alectinib

A 56-year-old woman, a never-smoker, had postoperative recurrence of anaplastic lymphoma kinase rearranged lung cancer. She achieved a partial response to treatment with an anaplastic lymphoma kinase tyrosine kinase inhibitor, crizotinib. After the tumor regrowth, crizotinib was switched to alectinib; once again a partial response was observed. At the second recurrence, transbronchial needle aspiration of the right paratracheal node was performed, which revealed cytological findings of small-cell carcinoma. While treatment with cisplatin-irinotecan chemotherapy made reduction of some tumor shadows, including the biopsied mediastinal lymph nodes, new, small, nodular shadows, highly suggestive of pulmonary metastases, were detected in both lung fields. This case may show proof of the transformation to small-cell lung cancer as a mechanism of resistance to anaplastic lymphoma kinase tyrosine kinase inhibitors in anaplastic lymphoma kinase rearranged tumor. However, this transformation may also be only one part of the resistance mechanism of the heterogeneous tumor.