Detection of BRAF V600E, KRAS G12D, KRAS G12V, and PIK3CA H1047R resistance-associated mutations in long-term cultured Erlotinib-resistant lung cancer PDOs revealed that tumor cells often harbor multiple associated mutations, which means that partial Erlotinib resistant patients require combination therapy to address tumor resistance [57]. The gene discussed is PIK3CA; the disease is neoplasm.