C77-01 Unraveling the Heterogeneity and Challenges of Multiple Primary Lung Cancers: A Comprehensive Analysis of 71 Patients

Abstract Rationale Multiple primary lung cancer (MPLC) refers to the presence of synchronous and metachronous lung cancers. While in certain cases, multiple pulmonary nodules may be mistaken for metastases, knowledge about histological and genetic make-up of MPLCs remains limited. We sought to describe prevalence, characteristics, inclusive of genetic and histologic presentation, of MPLCs among lung cancer patients with the aim to improve understanding of this population. Methods The hospital database was retrospectively reviewed to identify surgically treated patients at a nationally certified lung cancer center from 2006-2023. Demographic and clinical information were collected. We classified patients with histologically and radiologically confirmed secondary lung nodules as synchronous if diagnosed within 12 months of the primary tumor and metachronous if after 12 months. Results A total of 978 surgically treated lung cancer patients with 1015 unique histologies were identified. The histologic analysis demonstrated 549 adenocarcinomas, 304 squamous cell carcinomas, 55 carcinoids, nine small cell lung cancer, 29 adenosquamous lung cancers, 26 large-cell-lung carcinomas, five carcinomas “not otherwise specified”, and one pleomorphic carcinoma. Of these, 71 (prevalence: 7%) primary lung cancers with concomitant MPLCs were identified. Amongst these, 43 were primary adenocarcinomas, 18 squamous cell carcinomas, one carcinoid, four small cell lung cancers, one adenosquamous lung cancer, three large-cell lung carcinomas, and one pleomorphic lung cancer. The most frequent sequence was Adenocarcinoma-Adenocarcinoma, which accounted for 23 cases. This is followed by Adenocarcinoma-Squamous cell carcinoma and Squamous cell carcinoma-Adenocarcinoma. Mean age was 75.3 years (± 8.5). Gender distribution revealed 33 (46%) females. Most MPLCs developed in a different lung lobe (n = 54, 76%). In addition, n = 21 (30%) patients had stable disease over a period of 3 ± 2 years. Mortality in patients with stable disease was 19% (n = 4). 38% (N = 27) patients experienced tumor progression with 2 ± 1 years until progression. The mortality of patients with progressive disease was 82% (n = 22). Patients with adenocarcinoma showed superior survival (p 0.001) compared to patients with squamous cell carcinoma as their primary lung cancer. Conclusions This analysis emphasizes the importance of comprehensive molecular and histologic analysis in multiple primary lung cancer, revealing a notable prevalence of 7%. Adenocarcinoma was the predominant subtype and sequence demonstrating significantly superior survival than squamous cell carcinoma. These findings underscore the need for refined staging and a paradigm shift in therapeutic decision making in multiple primary lung cancer. This abstract is funded by: None