Second malignancy in non-small cell lung cancer (NSCLC): prevalence and overall survival (OS) in routine clinical practice

Patients with non-small cell lung cancer (NSCLC) and a prior or synchronous second malignancy are generally excluded from clinical trials. Therefore, little is known on prevalence and prognosis of these patients. 1252 patients diagnosed with NSCLC in our center from 2006 to 2017 were studied. Overall survival (OS) of patients with a prior or synchronous malignancy was compared to controls including case-control analysis. 158 patients (12.6%) had a prior malignancy. The most common sites were prostate (17%), breast (16%), gastrointestinal tract (12%), head and neck (11%), bladder (10%), and lung (8%). Compared to controls, patients with prior malignancy were older (71.3 vs. 67.5 years), but had otherwise better prognostic characteristics (stage I-III 63 vs. 53%). Survival was identical compared to controls [hazard ratio (HR) 1.017, CI 0.776-1.333]. A further 3.5% of patients had a synchronous malignancy including 34% prior lung cancer. Patients with a synchronous malignancy had an earlier stage (I-III 84%), and had longer median OS in unselected patients (38.6 vs. 16.2 months, p = 0.021). However, the case-control analysis showed similar OS [hazard ratio (HR) 0.899, CI 0.497-1.621]. Prior or synchronous second malignancies are common at diagnosis of NSCLC. The sites reflect the high proportion of smokers in the population. The earlier stage of NSCLC with a second malignancy might be attributed to chance finding of NSCLC during follow-up. The second malignancy does not affect OS of NSCLC. Therefore, the exclusion of patients with second malignancies from NSCLC trials should be reconsidered.