Rebiopsy in patients with or without prior TKIs revealed complicated histology of lung cancer.

Abstract

e20525 Background: The important of rebiopsy is well known in lung adenocarcinomas (ADs) after acquiring resistant to TKIs, for they may transform to SCLC. But histology transformation in non-ADs or ADs without TKIs seems infrequent. Methods: We performed a retrospective collection of cases with changed histology after rebiopsy in patients presenting from January 2015 to April 2018 in a single center. Results: Among 188 patients who conducted rebiopsy, there were 20 cases presenting changed histologic type, which can be divided into two groups based on if TKIs were used before histology change. Group1 (TKIs used, N = 14) including ADs changing to SCLC (N = 9), squamous cell carcinoma (SQ) (N = 2), carcinosarcoma combined with few AD component (N = 1), SCLC combined AD (N = 1), and adenosquamous carcinoma changing to SCLC (N = 1). Four cases in group 1 went through surgery, and one of them who never smoke was diagnosed as AD (pT2N0M1a, EGFR exon 19del), with no small cell carcinoma (SCC) component found, but rebiopsy of metastasis revealed SCC without any AD component after 3 months of gefitinib. The disease continued to progress during the following chemotherapy (CT), and biopsies with other two metastases also presented SCC without AD component. Group 2 were 6 cases without TKIs before the rebiopsy (Table). Case 2, 4, 6 were all heavy smokers. Rebiopsy of case 2 was ALK+, so the patient took 4 months crizotinib and then 2 months alectinib, the disease was still stable on January 6, 2019. Case 5 was a classic extensive-stage SCLC with fast response to EP therapy, but fast relapse and resistance to the following CT, and the primary lesion at right upper lobe showed AD-like imaging, so rebiopsy was performed and carcinoma favor AD was found. EGFR exon 19del was detected in the plasma, and the lesion gain PR after one month of icotinib. The third biopsy of the progress lesion came back to SCC after resistance to TKI. Conclusions: Rebiopsy of lung cancers with or without TKIs therapy revealed diversity histology changes. This reminded us the important of rebiopsy, not only for TKIs resistant lung ADs. [Table: see text]