Abstract 6463: Persistence of smoking mutational signatures in the non-small cell lung cancer genome
Authors: Lindsay Colin R. , Nicola Pantelis , Gruber Andreas , Brown Kate , Carter Mathew , Adderley Helen , Rafee Shereen , Moss Anna , Wallace Andrew , Burghel George , Schlecht Helene , Baker Katie , Moghadam Sharzad , Rogan Jane , Weaver Jamie , Malliri Angeliki , Newman William , Blackhall Fiona , Wedge David , England Genomics 
Published: June 2023

Abstract
Mutational signatures offer insights into cancer etiology. Smoking tobacco is associated with three signatures involving single base substitutions (SBS4), double base substitutions (DBS2) and insertions/deletions (ID3). Combining mutational signatures with clinical data allows examination of temporal and quantitative aspects of carcinogenic exposures. We analyzed 132 non-small cell lung carcinoma (NSCLC) whole genomes, sequenced through the 100,000 Genomes Project (Genomics England), with paired clinical data available for 130/132 (98.5%). Clinical data included smoking status, duration, pack-years (py), and duration of smoking cessation. The majority were “ever-smokers” (ex-smokers: 90/130, 69.2%; current smokers: 32/130, 24.6%) and 120/122 (98.4%) had at least one smoking signature. DBS2 was the most sensitive signature for ever-smokers (118/122, 96.7%), although SBS4 was the optimal signature for diagnosing smoking-related NSCLCs (SBS4 positive likelihood ratio 7.15). An absence of ID3 best identified true never smoker NSCLCs (ID3 negative likelihood ratio 0.08). Ever-smokers had a higher tumor mutational burden (TMB) than never smokers (median 8.25 mutations/Mb vs 1.18 mutations/Mb, p = &lt;0.0001), while TMB positively correlated with smoking pack-years (p = 0.044). Following smoking cessation, the median length of discontinuation was 11 years before a smoking-related NSCLC was diagnosed and, in some cases, smoking signatures persisted for up to 50 years prior to NSCLC diagnosis. To complement existing epidemiological data, 40 pack years was estimated as a critical cut-off for minimizing ongoing NSCLC risk. Prolonged smoking cessation did not reduce TMB (p = 0.055) or SBS4 mutations (p = 0.11), although this did produce lower DBS2 counts (p = 0.0067). Further signatures observed included SBS92 (previously seen in the bladder urothelium of ever-smokers) and a novel signature hypothesized to be linked to DNA mismatch repair deficiencies. NSCLCs from two patients with prior platinum chemo-radiotherapy harbored signatures of both chemotherapy- and radiotherapy-induced damage in their recurrent biopsy sample. These results highlight the importance of paired sequencing and clinical data, revealing that smoking-induced DNA damage can have long-lived effects, and strengthening health guidance of abstinence from smoking at the earliest possibility.
Citation Format: Colin R. Lindsay, Pantelis Nicola, Andreas Gruber, Kate Brown, Mathew Carter, Helen Adderley, Shereen Rafee, Anna Moss, Andrew Wallace, George Burghel, Helene Schlecht, Katie Baker, Sharzad Moghadam, Jane Rogan, Jamie Weaver, Angeliki Malliri, William Newman, Fiona Blackhall, David Wedge, Genomics England. Persistence of smoking mutational signatures in the non-small cell lung cancer genome. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6463.