Toward an individualizing therapy for colorectal cancer: the example of the anti-EGFR monoclonal antibodies

Anti-EGF receptor (EGFR) antibodies (cetuximab and panitumumab) have been demonstrated to be efficient in the treatment of metastatic colorectal cancer. However, these costly and potentially toxic treatments are active in a subset of patients, which renders necessary the identification of factors that are able to better define which patients will benefit from these treatments. Advances in the understanding of signaling pathways inhibited by these targeted therapies led to the identification of KRAS mutations as a strong predictor of resistance to anti-EGFR therapies. Other molecular markers, which are involved in the EGF signaling pathway or in the antibody dependent cell-mediated cytotoxicity-related anti-tumor effect of these anti-EGFR therapies, are also interesting and will have to be evaluated in future clinical trials.

Fluorouracil, leucovorin, and oxaliplatin with and without cetuximab in the first-line treatment of metastatic colorectal cancer

PURPOSE

This randomized study assessed whether the best overall response rate (ORR) of cetuximab combined with oxaliplatin, leucovorin, and fluorouracil (FOLFOX-4) was superior to that of FOLFOX-4 alone as first-line treatment for metastatic colorectal cancer. The influence of KRAS mutation status was investigated.

PATIENTS AND METHODS

Patients received cetuximab (400 mg/m(2) initial dose followed by 250 mg/m(2)/wk thereafter) plus FOLFOX-4 (oxaliplatin 85 mg/m(2) on day 1, plus leucovorin 200 mg/m(2) and fluorouracil as a 400 mg/m(2) bolus followed by a 600 mg/m(2) infusion during 22 hours on days 1 and 2; n = 169) or FOLFOX-4 alone (n = 168). Treatment was continued until disease progression or unacceptable toxicity. KRAS mutation status was assessed in the subset of patients with assessable tumor samples (n = 233).

RESULTS

The confirmed ORR for cetuximab plus FOLFOX-4 was higher than with FOLFOX-4 alone (46% v 36%). A statistically significant increase in the odds for a response with the addition of cetuximab to FOLFOX-4 could not be established (odds ratio = 1.52; P = .064). In patients with KRAS wild-type tumors, the addition of cetuximab to FOLFOX-4 was associated with a clinically significant increased chance of response (ORR = 61% v 37%; odds ratio = 2.54; P = .011) and a lower risk of disease progression (hazard ratio = 0.57; P = .0163) compared with FOLFOX-4 alone. Cetuximab plus FOLFOX-4 was generally well tolerated.

CONCLUSION

KRAS mutational status was shown to be a highly predictive selection criterion in relation to the treatment decision regarding the addition of cetuximab to FOLFOX-4 for previously untreated patients with metastatic colorectal cancer.

Markers involved in resistance to cytotoxics and targeted therapeutics in pancreatic cancer

Pancreatic cancer retains a poor prognosis among the gastrointestinal cancers and remains a challenge in oncology. In 1997, gemcitabine became the standard of care in metastatic setting. In the last decades, despite a number of clinical trials assessing novel cytotoxic agents and cell signaling inhibitors, overall survival has reached a plateau that remains difficult to improve. Development of mechanisms implicated in intrinsic and acquired resistance to chemotherapy are considered to play a key role that could explain the limited benefit of most treatment in pancreatic cancers. Key molecular factors implicated in this process include: deficiencies in drugs uptake, activations of DNA repair pathways, resistance to apoptosis, and tumor microenvironment. Moreover, for cell signaling inhibitors, mutations in kinase domains, activation of alternative pathways, mutations of genes downstream of the target, activation of autocrine/paracrine pathways and/or feed-back amplification of the target represent the most important mechanisms achieving resistance of pancreatic cancer cells.