MA27.01 Establishment of PDX From Tumors Characterized by EGFR Mutations or ALK Fusion Genes from Resections, Biopsies and Pleural Fluids

Abstract

Patient-derived xenograft (PDX) models allow for cancer tissue expansion, providing an effective method to evaluate tumor biology and mechanisms of response or resistance. Our study aims to establish models in patients enriched for lung adenocarcinoma (LUAD) with EGFR mutations or ALK fusion genes which respond initially to oral targeted therapy, but typically develop resistance and disease relapse within 2 years. The PDXs will be evaluated for their potential to model therapy outcomes, to determine resistance mechanisms and to evaluate novel therapy strategies to overcome resistance. From August 2015 to January 2018, we collected 109 samples from patients with EGFR- or ALK-driven LUAD and from never-smoker LUAD patients with unknown mutation status. Five samples with low tissue viability (i.e. necrotic) or very low tumor content (<100 malignant cells) were excluded. Adequate samples were implanted into the subcutaneous tissue of NOD-SCID mice. At this time, 16 samples have reached the study endpoint (tumor growth ≥1.5cm3) and 60 showed no tumor-growth following implantation (median follow-up: 8m). Results are currently pending for 18 models. Samples were collected from surgical resections (31, 36%), CT-guided biopsies (12, 14%), EBUS (19, 22%) and pleural fluid effusions (24, 28%). Most patients were female (51/86, 59%), never smokers (62/85, 73%), and had stage III or IV cancer (55/79, 70%). Mutations in EGFR and ALK were found in 55/81 (68%) and 12/84 (14%) primary cancers, respectively. Early-passage xenograft engraftment (XG) was observed in only 16 (19%) PDXs, including 9/55 (16%) EGFR- and 1/12 (8%) ALK-mutant cancers. The phenotype and molecular changes (EGFR and ALK) were consistent within the PDX model and its corresponding patient sample. Samples collected from surgical-resection specimens showed a trend towards higher engraftment rates (p=0.084). Conversely, the presence of EGFR or ALK mutations showed a trend towards non-engraftment (noXG, p=0.075). Patient smoking status and tumor stage did not influence engraftment rate. To identify reasons for no tumor-growth, we conducted histological analysis in the subcutaneous fat-pads (nodes in the implant sites) of 28 noXG mice. Interestingly, we identified small non-palpable foci of carcinoma in 8 animals (4 EGFR+ and 2 ALK+). Environmental or molecular factors may impair engraftment rates of EGFR+ and ALK+ LUAD samples in PDX models. Nevertheless, these models recapitulate the primary disease and could be useful for population-based drug-screening studies.