Radiographic patterns of progression in patients with EGFR-mutant NSCLC undergoing EGFR TKI therapy.

Background:  There is paucity of data about the radiographic patterns of progression in patients with EGFR mutant NSCLC undergoing EGFR TKI therapy. The progression may be linked to evolutional changes of the EGFR in the cancer cells (Tumor Darwinism). The evaluation of this pattern might provide additional insight into the tumor biology of the disease and also may serve as a guide for additional biopsies and therapeutic strategies.  Methods:  Twenty-one patients with advanced NSCLC undergoing EGFR TKI therapy at our institution were included in this study. An IRB-approved retrospective review of radiographic data was performed and assessed for progression at the primary and metastatic sites.  Results:  The patient population in this study was 47.6% male, with a median age 62 +/-10.1 years. The EGFR mutations were present on exons 18 (14.3%), 19 (47.6%), and 21 (38.1%). The initial sites of progression after initiation of EGFR TKI therapy were: primary site (4.7%), metastases (81.0%), and both primary and metastatic sites (14.3%). Of the progressed metastatic lesions, the most common sites were new pulmonary lesions (50.0%), osseous lesions (40.0%), and lymph nodes (30.0%).  Conclusions:  In our series, patients undergoing therapy with EGFR TKI tend to recur more at the metastatic sites than at the primary tumor site. This may be relevant for diagnostic and therapeutic strategies through the incorporation of additional biopsies to understand tumor biology and local therapies to treat distant sites of progression.