Impact of prior cancer history on the overall survival of younger patients with lung cancer

BACKGROUND: Patients with a history of prior cancer are frequently excluded from cancer trials. Previous studies indicated that prior cancer does not adversely impact clinical outcomes for patients with lung cancer older than 65 years. However, it remains unknown whether these results are applicable to patients with lung cancer aged younger than 65 years old. The study aimed to investigate the impact of prior cancer history on younger patients with lung cancer. METHODS: We identified younger patients with lung cancer (<65 years) diagnosed between 2004 and 2009 in the Surveillance, Epidemiology, and End Results database. Propensity score matching was performed to balance differences in baseline characteristics between groups. Kaplan-Meier method and the Cox proportional hazards model were used to evaluate the impact of prior cancer on overall survival (OS). RESULTS: Among 103 370 eligible patients with lung cancer, 15.18% had a history of prior cancer. Lung and bronchus (25.83%), breast (14.13%), prostate (8.85%) and cervix uteri (4.74%) were the most common prior cancer types. Of prior cancers, 61.56% are localised and regional stages. More than 67.98% of prior cancers were diagnosed within 5 years of the index lung cancer diagnosis. The median times of diagnosis for prior cancers were 38 months. Patients with prior cancer had the same/non-inferior OS as that of patients without a prior cancer diagnosis (propensity score-adjusted HR=1.01, 95% CI=0.99 to 1.04, p=0.324). Subgroup analyses stratified by timing of prior cancer displayed almost the same tendency (p>0.05). Interestingly, early-stage patients with a history of prior cancer had adverse survival curves (p<0.05). Advanced-stage patients with prior cancer had non-inferior survival (p>0.05). CONCLUSIONS: A prior cancer diagnosis has a heterogeneous effect on the survival of patients with lung cancer aged <65 years across different stages, but further prospective studies are still warranted.