Prognostic impact of elevated C-reactive protein and procalcitonin in patients with extensive-stage small cell lung cancer

Small cell lung cancer (SCLC) constitutes around 15% of lung cancer cases and stands as the primary cause of cancer-related fatalities in men and the second leading cause in women globally. In this study, our objective was to evaluate the levels of C-reactive protein (CRP) and procalcitonin (PCT) in newly diagnosed extensive-stage SCLC patients without evidence of infection. We aimed to demonstrate that elevated CRP and PCT levels may not solely indicate infection but could also be elevated in malignancies. Furthermore, we sought to correlate these marker levels with patient and disease characteristics to elucidate the relationship between these inflammation markers and disease progression. A total of 115 patients who were pathologically and radiologically diagnosed with extensive-stage SCLC between January 2020 and December 2022 and who had received no prior treatment were included in the study. The Kaplan–Meier analysis revealed a median progression-free survival (PFS) of 7.46 months [95% confidence interval (CI), 6.85–8.07] and a median overall survival (OS) of 10.50 months (95% CI, 8.69–12.30) for all patients. In the group with elevated PCT, the median PFS was 6.73 months (95% CI, 3.92–9.54), whereas it was 7.86 months (95% CI, 7.13–8.59) in the group with normal PCT ( P = 0.002). Similarly, the median OS was 9.10 months (95% CI, 5.61–12.58) in the elevated PCT group and 11.66 months (95% CI, 9.59–13.74) in the normal PCT group ( P = 0.006). Patients with elevated procalcitonin (PRC) levels at the time of diagnosis exhibited shorter PFS and OS durations compared to patients with normal PRC levels. Furthermore, elevated CRP has also been demonstrated to correlate with poorer prognosis in extensive-stage SCLC.