Effect of metformin in the prognosis of patients with small-cell lung cancer combined with diabetes mellitus

Background. The prognosis for small-cell lung cancer (SCLC) is very poor, so a new therapeutic strategy and new drugs are imperative. Objectives. The aim of this study was to examine the effect of metformin on the prognosis of patients with SCLC combined with diabetes mellitus (DM). Material and methods. From 2005 to 2013, 32 patients (4 female and 28 male) with SCLC combined with DM were included in this retrospective study at the Zhejiang Cancer Hospital, China. All patients were diagnosed with SCLC by pathological analysis and had received more than 4 cycles of chemotherapy. Metformin was used in 12 patients. Seventeen patients had limited-stage disease (LD) and 15 patients had extensive-stage disease (ED). Patients with LD SCLC were administered thoracic radiotherapy. The follow-up deadline was January 27, 2016. At that point, 4 patients were alive, 21 patients had died, and 7 patients did not participate in follow-up examinations. Results. In patients with SCLC combined with DM using metformin, a complete response (CR) was observed in 4 patients, a partial response (PR) in 6 patients, a stable disease (SD) in 1 patient, and a progressive disease (PD) in 1 patient, whereas in patients who did not use metformin, CR was observed in 2 patients, PR in 15 patients, SD in 2 patients, and PD in 1 patient (p = 0.384). There was no difference in the median survival time (MST) between patients using metformin and those who did not (12 vs 13 months; p = 0.784). There was a trend toward prolonged MST in patients with LD SCLC using metformin compared with those who did not use metformin (58 vs 29 months; p = 0.084). There was no difference due to the use of metformin observed in MST of patients with ED SCLC (12 vs 13 months; p = 0.396). Conclusions. Metformin use may have a prognostic benefit in patients with SCLC combined with DM. This combination is promising and further clinical trials are required.