Preoperative Chemoradiation With Cetuximab, Irinotecan, and Capecitabine in Patients With Locally Advanced Resectable Rectal Cancer: A Multicenter Phase II Study

Locally advanced rectal cancer: a comparison of management strategies

Traditionally, there has been a high local recurrence rate in rectal cancer and 10-40% of patients require a permanent stoma. Both short-course preoperative radiotherapy (SCPRT) and long-course preoperative chemoradiation (CRT) are used to reduce the risk of local recurrence and enable a curative resection. Total mesorectal excision has reduced the rate of local recurrence (even without radiotherapy) to below 10%, but has highlighted a high risk of metastatic disease in 30-40% of patients. Current trials suggest that in resectable cancers, where the preoperative magnetic resonance imaging (MRI) suggests the circumferential resection margin (CRM) is not potentially involved, then SCPRT and CRT are equivalent in terms of outcomes such as local recurrence, disease-free survival (DFS) and overall survival (OS). For patients with more advanced disease, where the CRM is breached or threatened according to the MRI, the integration of more active chemotherapy and biological agents into chemoradiation is an attractive strategy because of the high risk of metastases. However, in none of the trials published in the last decade has chemoradiation impacted on DFS or OS. We examine the strategies of neoadjuvant, concurrent, consolidation (after chemoradiation and before surgery) and postoperative adjuvant chemotherapy with cytotoxic agents, and the integration of biological agents for future potential strategies of treatment. We also compare the trials and compare the different strategies of long-course preoperative radiotherapy and SCPRT; the intensification of preoperative radiation and chemoradiation with dose escalation of external beam radiotherapy, using brachytherapy, intra-operative radiotherapy, hyperfractionation, and various available techniques such as intensity-modulated radiotherapy. We recommend examining dose escalation of radiotherapy to the primary tumour where MRI predicts a threatened CRM. Of the potential treatment strategies involving cytotoxic agents, such as neoadjuvant, concurrent, consolidation and postoperative adjuvant chemotherapy, the most promising would appear to be consolidation chemotherapy following chemoradiation in locally advanced disease, and neoadjuvant chemotherapy in MRI-selected patients who do not require radiation. Improvement in the quality of surgery is also an important future goal.

Predictive factors of the response of rectal cancer to neoadjuvant radiochemotherapy

Locally advanced rectal cancer is currently treated with pre-operative radiochemotherapy (pRCT), but the response is not uniform. Identification of patients with higher likelihood of responding to pRCT is clinically relevant, as patients with resistant tumors could be spared exposure to radiation or DNA-damaging drugs that are associated with adverse side effects. To highlight predictive biomarkers of response to pRCT, a systematic search of PubMed was conducted with a combination of the following terms: "rectal", "predictive", "radiochemotherapy", "neoadjuvant", "response" and "biomarkers". Genetic polymorphisms in epithelial growth factor receptor (EGFR) and thymidylate synthase (TS) genes, the expression of several markers, such as EGFR, bcl-2/bax and cyclooxygenase (COX)-2, and circulating biomarkers, such as serum carcinoembryonic antigen (CEA) level, are promising as predictor markers, but need to be further evaluated. The majority of the studies did not support the predictive value of p53, while the values of Ki-67, TS and p21 is still controversial. Gene expression profiles of thousands of genes using microarrays, microRNA studies and the search for new circulating molecules, such as human telomerase reverse transcriptase mRNA and cell-free DNA, are providing interesting results that might lead to the identification of new useful biomarkers. Evaluation of biomarkers in larger, prospective trials are required to guide therapeutic strategies.