Circulating tumor cells (CTC) in small cell lung cancer (SCLC), a promising prognostic factor.

Abstract

7630 Background: Prognostic models for SCLC are using performance score (PS), laboratory tests or disease stage assessed by imaging tests. Even the recently introduced TNM system show that increasing from stage 1A (T1N0M0, 5 year survival 38%) to stage IV (metastasized, 5 year survival 1%) still provides us with a poor prognostic assessment. In this study we evaluated the use of CTC as a prognostic marker for Overall Survival (OS) in SCLC. Methods: In an ongoing study, patients (pts) with pathological proven SCLC were treated with firstline cisplatin /etoposide for a maximum of 4 cycles. Prior to the start, prior to the second cycle and at the end of chemotherapy 20 mL of whole blood was drawn and within 72 hours analyzed for circulating cells using CellTracks technology at a central laboratory (Veridex, Enschede, the Netherlands). Pts were staged as limited or extensive disease (IASLC 2009). Clinical data and CTC characteristics were analyzed in a blinded fashion. Pts were stratified into unfavorable and favorable prognostic groups based on CTC levels ≥ 2 or < 2 CTCs/7.5 mL, respectively. OS was analyzed in a Cox regression analysis using as covariates disease stage, PS and CTC before therapy or CTC decrease of at least 50% after the first cycle of chemotherapy. Results: A total of 41 pts with pathologically proven SCLC were included. Median (range) age was 66 yrs (47-84), male/female 26/15, PS 0/1/2/3 is 14/22/2/3, stage LD/ED 17/24, median (range) number of CTC is 9.5 (0-9909), 30 pts had ≥ 2 CTC at baseline. 33 pts were evaluable for CTC after one cycle of chemotherapy and 26 showed a decrease in CTCs of 50% or more. Median (range) OS was 240 days (219- 377). The predefined favorable prognostic group (baseline < 2 CTC count) was the most important prognostic factor (HR 3.3) after correction for age, sex, PS and stage. A decrease of at least 50% in CTC after one cycle of chemotherapy was the strongest prognostic factor (HR 0.015, 95%CI, 0.02-0.125, p < 0.0001) after correcting for baseline CTC, age, sex, PS and stage. Conclusions: Baseline CTCs and early decrease in CTCs in firstline chemotherapy are an independent predictive factor for OS in SCLC. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Veridex/Immunicon Veridex LLC Veridex LLC