Clinical impact of first response evaluation (FRE) in metastatic colorectal cancer (mCRC) patients (pts) treated with a cetuximab-based regimen (C-R): Results of a mono-institutional experience.

Abstract

e14717 Background: Some reports suggest positive impact from early tumor shrinkage in progression-free survival (PFS) and overall survival (OS) in mCRC pts receiving C-R. The aim was to evaluate the clinical impact of FRE in mCRC pts treated with a C-R in first-line (1st-L) or after 1st-L. Methods: Between May 2004 and Dec. 2012, 73 pts referred to our institution. The FRE was assessed 8-10 wks after the start of treatment by a CT-scan according to RECIST criteria 1.0. At the time of FRE, pts who achieved CR/PR were considered as responders (resp), and SD/PD as non-responders (non-resp). Were included KRAS wild-type (KRAS-wt) and KRAS undefined tumors (KRAS-ud). PFS and OS are reported in months. Results: Pt characteristics: 51M (70%) and 22F (30%); median age 62(27-80) yrs; 59 colon (80.8%) and 14 rectum (19.2%); median number of metastatic sites 2 (1-5); synchronous mts 47 (64.4%), metachronous mts 26 (35.6%); 46 (63%) KRAS-wt, 27 (37%) KRAS-ud. Twenty-nine (39.7%) pts were treated with C-R in 1st-L (all KRAS-wt), and 44 (60.3%) after 1st-L (17 KRAS-wt, 27 KRAS-ud). C was combined with FOLFIRI in 36 (49.3%) pts, irinotecan in 36 (49.3%), and was alone 1 (1.4%). At the time of FRE 26(35.6%) pts were resp: 13 1st-L and 13 after 1st-L; 47 (64.4%) were non-resp: 16 (34%) 1st-L and 31 (66%) in after 1st-L. In pts treated as 1st-L, the PFS in resp vs non-resp was: 13 (95% CI 6-20) vs 5 (95% CI 4-5) (p=0.03); the OS was: 23 (95% CI 11-34) vs 11 (95% CI 9-13) (p=0.11). In pts treated after 1st-L the PFS in resp vs non-resp was: 13 (95% CI 8-18) vs 5 (95% CI 0.4-9) (p< 0.0001); the OS was: 17 (95% CI 12-21) vs 12 (95% CI 6-19) (p 0.67). In the KRAS-wt pts the PFS in resp vs non-resp was: 13 (95% CI 11-15) vs 5 (95% CI 4-6) (p 0.00); the OS was 23 (95% CI 16-30) vs 11 (95% CI 8-14) (p 0.02). In the KRAS-ud pts the PFS, in resp vs non-resp was: 9 (95% CI 0-20) vs 3 (95% CI 0-8) (p 0.00), the OS was: 18 (95% CI 1-36) vs 13 (95% CI 10-15) (p 0.03). A Cox regression model, including: sex, age, KRAS, line of therapy, FRE, skin rash grade, shows that the FRE was the main predictor of PFS (p<0.0001) and OS (p=0.011). Conclusions: The FRE seems to predict the clinical outcome in pts receiving C-R as 1st-L or after 1st-L.