954 - A pilot case-control study of second or third line treatment with cetuximab-containing chemotherapy (Cetux-chemo) in patients (pts) with metastatic colorectal cancer (mCRC) who were previously treated with Cetux-chemo

Background

This study hypothesized that: (1) pts who had prior exposure to Cetux-chemo in the treatment of mCRC followed by a chemo-break, would respond to re-treatment with Cetux at progression (PD), & that the overall response rate (ORR) would be better than those who are treated with chemo alone.

Methods

This study consisted of 2 cohorts. Cohort 1: Prospectively enrolled pts with KRAS-wild type mCRC who had prior Cetux-chemo in 1^st/ 2^nd line with a best ORR of SD/PR/CR followed by a chemo-break, were re-treated with Cetux-chemo at PD. Cohort 2: A retrospective cohort of KRAS-WT patients (matched by age, sex, no. of sites of metastases (mets), prior Cetux-chemo and prior surgery) who received chemo without any targeted therapy at PD following a chemo-break. The primary objective was to compare the overall response rate (ORR) of cohort 1 & 2, secondary objectives included disease control rate (DCR) & progression free survival (PFS).

Results

22 eligible pts were enrolled in cohort 1 across two centers in Hong Kong: median age 58yrs, M:F ratio= 1:1; site of metastases (mets) = solitary 36.3%, > 1 site 63.7%. None had prior bevacizumab; prior Cetux as 1^st line = 77.3% & as 2^nd line = 22.7%. In 21 evaluable pts, ORR = 52.4%, SD 33.3%, PD 14.3% & DCR 85.7%. The median OS for cohort 1 = 18.6 ms (95% CI: 11.1-27.1) & 1-yr PFS 36.4%. In cohort 2, 22 matching KRAS-WT patients were identified. The ORR for cohort 2 = 31.8%, DCR 50%, median OS 11ms (95% CI: 4.5-17.1) & 1-yr PFS 22.7%. In a regression analysis which included other prognostic variables (age, sex, prior no. of line of chemo, no. of sites of mets), DCR was the only significantly different factor (odd ratio, OR 6.0, 95% CI: 1.365-26.371, p = 0.018) favouring cohort 1. There was a non-significant trend favouring cohort 1 in ORR (52.4% vs 31.8 %, p = 0.171) and median PFS (8.1ms vs 5.3ms, p = 0.524).

Conclusions

The data suggests that in pts who had prior Cetux-chemo in the 1^st or 2^nd line treatment of mCRC, re-introduction of Cetux-chemo following a chemo-break was effective in most patients.

Editorial acknowledgement

Clinical trial identification

NCT01832467.

Legal entity responsible for the study

Brigette Ma.

Funding

Merck Serono.

Disclosure

B.B.Y. Ma: Speaker\'s honorarium: Merck Serono. All other authors have declared no conflicts of interest.