Molecular profiles of appendiceal adenocarcinoma: The UCSD experience.
397 Background: Appendix cancer is rare, which precludes its study in randomized trials. As such, no evidence-based guidelines currently exist regarding the optimum systemic therapy for this disease entity. Typically, these patients are treated with regimens for colorectal carcinoma. Previous studies have shown high intra-tumoral mRNA levels of EGFR were significantly associated with response to irinotecan based chemotherapy, and that mucinous colorectal cancer overexpresses markers of resistance to 5-FU and oxaliplatin. We examined pharmacogenomics markers for appendiceal cancer and colon cancer to understand underlying similarities and differences between these tumor types. Methods: Intratumoral gene expression levels were assessed from paraffin-embedded tissue samples, using laser capture microdissection and quantitative real-time PCR from 69 colorectal and 34 appendiceal adenocarcinomas. A retrospective chart review was performed to correlate gene expression with overall survival. KRAS and BRAF mutational analyses and gene expression levels of ERCC1, TS, and EGFR were correlated with overall survival. Results: Appendiceal tumors had significantly higher expression of EGFR, (2.66 vs 1.4, p<.0001). No BRAF V600E mutations were found in the appendiceal tumors, incidence was 8.97% of the colon patients. UPDATE: In appendix cancer, KRAS mutations were noted in 65.5% of patients, there were no BRAF mutations. Median ERCC1, TS, EGFR, and VEGFR2A expression was 1.4, 1.21, 1.57, 2.19 respectively. Patients with metastatic appendiceal cancer had a significantly longer median OS than metastatic colon patients, (113 mo vs 43.9 mo, p = .0154). For appendiceal cancer patients, there was no significant correlation between any of the biomarkers and OS, although the sample size was underpowered for such an analysis. Conclusions: Metastatic appendiceal cancer patients have significantly better outcomes than metastatic colon cancer patients. Molecular analyses reveal significant differences between these tumor types. Further molecular study of appendiceal cancer is needed, as this study and others suggest fundamental differences in biology from colon cancer.