Comparison of the characteristics of uncommon epidermal growth factor receptor (EGFR) mutations and EGFR-tyrosine kinase inhibitor treatment in patients with non-small cell lung cancer from different ethnic groups

Patients with epidermal growth factor receptor (EGFR)-sensitive mutations generally have a significantly higher objective response rate (ORR) and longer progression-free survival (PFS) after EGFR-tyrosine kinase inhibitor (TKI) treatment. However, the efficacy of EGFR-TKIs in the case of uncommon EGFR mutations has remained elusive. In the present study, the characteristics of uncommon EGFR mutations and EGFR-TKI treatments were compared in patients with non-small cell lung cancer (NSCLC) from different ethnic groups. A total of 2,984 patients with pathologically confirmed NSCLC encountered between February 2012 to February 2017 at the Affiliated Tumor Hospital of Xinjiang Medical University (Urumqi, China) were enrolled in the present study. The Amplification Refractory Mutation System was adopted to determine EGFR gene expression, compare the ethnic differences in EGFR mutations between Xinjiang Uygur and Han people, analyze the distribution of uncommon mutation types and evaluate the link between clinicopathological features associated with uncommon mutations and the efficacy of EGFR-TKI treatment. There were significant differences in EGFR mutations in lung adenocarcinoma and lung squamous cell carcinoma between patients from the Xinjiang Uygur group and the Han group (P<0.001). The differences in the uncommon EGFR mutations were significant in patients with lung adenocarcinoma (P<0.05). The most common site of lymph node metastasis in patients with uncommon mutations was the hilar lymph node, supraclavicular/subclavian lymph node, cervical lymph node and mediastinal lymph node; the most common distant metastatic organs were the lung, bone, brain, liver and adrenal gland. Of the uncommon mutations, the most common single mutations were L861Q, G719X and 20ins mutations; the most common double mutation was the S768I and 20ins mutation. The incidence rate of EGFR gene mutations was significantly higher in Han people from Xinjiang than in Uygur people. There were marked differences between individuals regarding the efficacy of EGFR-TKI treatment and the survival time of patients with uncommon EGFR mutations, second-line EGFR-TKIs had a lower ORR and DCR while had a longer mPFS. All of these could provide a basis for the exploration of different regimens for patients with different types of uncommon mutations.