© 2015 Springer-Verlag Berlin Heidelberg. Purpose: The sequence bendamustine (B) + Irinotecan (I) followed by etoposide (E) + carboplatin (C) was hypothesized to increase progression-free survival (PFS) and overall survival (OS) in untreated extensive-disease small cell lung cancer (EDSCLC) patients compared to historical controls by exploiting mitotic catastrophe. Absent expression of ERCC-1 and expression of topoisomerases were hypothesized to be predictive for PFS and OS. Methods: This was a phase I/IIa trial in 30 patients to determine the maximum tolerated dose (MTD) of B + I and the PFS of B + I E + C with secondary end points including overall response rate (ORR) and OS. Biomarkers measured by immunohistochemistry (IHC) obtained from diagnostic specimens were correlated with outcome. Results: The MTD of B + I was not reached. During treatment with B + I, there were two grade 5 toxicities from neutropenic sepsis and metabolic encephalopathy. Other toxicities included fatigue, nausea/vomiting, diarrhea, and weight loss. For the sequence, the PFS and OS were 6.0 months and 10 months, respectively. The ORR for B + I and the sequence were 82% and 83%, respectively. Topoisomerase-2 expression was predictive for TTP and OS, but absent ERCC-1 expression was not, contrary to our hypothesis. Conclusions: B + I is an active regimen in EDSCLC. Toxicities included two grade 5 events but were otherwise manageable. The novel sequence B + I E + C increased PFS and OS compared to historical controls. Correlative studies are conflicting regarding the mechanism of action of this novel sequence.