Overcoming Resistance to Osimertinib by T790M Loss and C797S Acquisition Using Gefitinib in a Patient With EGFR-Mutant NSCLC: A Case Report oleh Diego Enrico, MD, Florencia Tsou, MD, Greta Catani, MD, Carmen Pupareli, MD, María Romina Girotti, PhD, David Esteban Ulloa Alvarez, MD, Federico Waisberg, MD, Andrés Rodríguez, MD, Roxana Reyes, MD, Matías Chacón, MD, Noemí Reguart, MD, PhD, Claudio Martín, MD