Primary tumor histology and location as predictive factors for clinical outcome in metastatic gastric cancer (GC) patients receiving first-line chemotherapy.

Abstract

e15081 Background: Recently, a new classification for GC has been proposed, based on Lauren’s histology and on anatomic tumour location, identifying three subtypes of disease: type 1 (proximal non diffuse GC), type 2 (diffuse GC) and type 3 (distal non diffuse GC). Aim of our analysis was to compare clinical outcome, in terms of response rate (RR), progression-free survival (PFS), and overall survival (OS), according to different GC subtypes (1, 2, 3) in metastatic GC patients (pts) receiving first-line chemotherapy. Methods: Advanced GC pts treated with a first-line combination chemotherapy were included in our analysis. Pts were divided in three subgroups (type 1, type 2, and type 3) as previously defined. Results: A total of 248 advanced GC pts were included: most of pts belonged to type 2 (45.15%) and type 3 (43.55%); type 1 included 28 pts (11.30%). The majority of pts (65.4%) received a fluoropyrimidine-based chemotherapy doublet while the remaining 88 pts received a three drugs regimen including a platinum derivate and a fluoropyrimidine with the addition of an anthracycline, a taxane or mytomicin C. Most of pts (55.5%) received a second-line treatment, with FOLFIRI o taxanes. The three subgroups resulted comparable for relevant clinical factors such as ECOG PS, tumour stage, number of metastatic sites, previous surgical resection, first-line combination and use of second-line treatments; as expected peritoneal carcinosis was more common in type 2 pts. RR was found to be higher in type 1 pts (RR= 46.1%) and type 3 (34,3%) compared to type 2 (20,4%), (p= 0.015). Type 2 pts presented a shorter PFS, median PFS 4.2 months, compared to type 1, mPFS= 7.5 months, and type 3, mPFS= 5.9 months (p= 0.007) and also a shorter OS with a median OS of 9,8 months vs 11.5 months for type 1 and 11.0 for type 3 (p= 0.024). Conclusions: Our analysis suggests that GC subtypes may be important predictors of benefit from chemotherapy in advanced GC patients. Future clinical trials should take in account these differences for a better stratification of patients. Biomarkers analysis on tumour samples are ongoing.