Efficacy of systemic treatments in patients with metastatic lung invasive mucinous adenocarcinoma.

e20609 Background: Invasive mucinous adenocarcinoma (IMA) is a relatively rare histological subtype of lung adenocarcinomas that differs in its clinical behavior, radiologic features, histopathological, and genomic characteristics than invasive non-mucinous adenocarcinomas (INMA). Methods: We retrospectively investigated medical records of patients diagnosed with lung IMA at four oncology centers in Turkey. Patients who were ≥18 years of age, pathologically diagnosed with lung IMA, and who received at least one course of treatment for metastatic or inoperable disease were included in the study. Results: Forty-one patients were included in the study. The median follow-up was 16.6 months. Among the included patients, 24 (58.5%) were male, 17 (38.5%) were female, and their average age was 62. Six (14.6%) patients had a targetable mutation. Three (7.3%) patients were epidermal growth factor receptor (EGFR), two (4.8%) anaplastic lymphoma kinase (ALK) mutation, and one (2.4%) neurotrophic tyrosine receptor kinase (NTRK2) fusion. Most patients (83.1%) had received platinum-based chemotherapy as a first-line treatment. Of the patients who received cytotoxic chemotherapy, 9 (25.7%) had a partial response, 14 (40%) had a stable response, and 12 (34.3%) had progression. The median PFS was 8.24 months (95% CI: 5.9-10.5 months), and the median OS was 20.4 months (95% CI: 14.4-26.3 months) in all study populations. In those receiving cytotoxic chemotherapy, median PFS and OS were 8.11 months (95% CI: 5.02-11.2) and 17.5 months (95% CI: 11.7-23.3 months), respectively. While the PFS of two EGFR-positive patients were similar at 18.9 months and 20.6 months, the third patient's PFS was quite prolonged (66.5 months). The ALK-positive patients receiving brigatinib and crizotinib PFS were 15.8 months and 2.73 months, respectively. The PFS of the patient receiving entrectinib was only two months. Among the entire patient population, only one patient used oxaliplatin and capecitabine combination (XELOX) as chemotherapy. In this patient, who progressed after four cycles of gemcitabine and platinum first-line treatment, a partial response and 7.23 months PFS were achieved with second line XELOX. Conclusions: Standard-of-care treatments have the same efficacy in IMA and INMA patients. Targetable mutation is less common in IMA patients compared to INMA. 5-FU-based chemotherapies also appear to be effective in lung IMA patients.