Presenter: Punt C.J. Presenter's Affiliation: UMC St Radboud, Nijmegen, Netherlands Type of Session: Scientific
Prior studies have found an overall survival benefit in patients with advanced colorectal cancers (ACC) treated with fluoropyrimidine-based chemotherapy combined with bevacizumab (bev), as compared to fluoropyrimidine-based chemotherapy alone.
Cetuximab is a chimeric monoclonal antibody which binds to the epidermal growth factor receptor (EGFR) and has been shown to have efficacy in ACC.
Vascular endothelial growth factor (VEGF) and EGFR share several downstream pathways, and by inhibiting both receptors, there may be greater anti-tumor effect.
There are preclinical and clinical trials which suggest that the combined use of EGFR and VEGFR inhibitors may be of benefit in patients with ACC.
Materials and Methods
The present study is a phase III randomized trial comparing patients treated with capcitabine (cap), oxalliplatin (OX), and bev (arm A) versus those treated with cap, OX, bev and cetuximab (Arm B).
§Cap 1,000 mg/m2 orally bid day 1-14
§OX 130 mg/m2 day 1
§Bev 7.5 mg/kg IV day 1
§Same as arm A with the addition of cetuximab 400 mg/m2 iv in week one and 250 mg/m2 iv weekly thereafter
oAll cycles were given every three weeks
The primary endpoint of the present study was progression-free survival (PFS)
The secondary end points were overall survival (OS), response rate, and toxicity
Response was assessed every three weeks using the response evaluation criteria for solid tumors (RECIST) criteria
Toxicity was assessed with each cycle of chemotherapy
There was central review of all deaths within 30 days
The present study was powered to detect a change in median survival of three months (11 to 14 months) with a beta of 80% and p-value of 0.05 (two-tailed).
Inclusion and exclusion criteria included:
oHistologically confirmed ACC
o18 or older
oACC which was not surgically curable
oNo prior systemic therapy
oWHO 0-1 performance status
oNo use of anticoagulation
oNo prior coronary artery disease
A total of 79 hospitals enrolled 755 patients from June 2005 to December 2006.
731 patients had at least one cycle of chemotherapy
The median follow-up was 18.7 months
Demographics were well-balanced between the two arms aside from female gender representation, which was significantly higher in arm A
Median age was 62 yo (range 27-83)
Results are as follows:
Toxicity was as follows:
Grade 3-4 toxicity
Grade 3-4 toxicity excluding skin
All grade toxicity
Death within 30 days of treatment
Death within 60 days of treatment
PFS: in arm B patients with grade III skin toxicity had a better progression free survival compared with those who had grade 0-1 toxicity (p<0.01)
K-ras expression was assessed using real-time polymerase chain reaction (PCR). There was no significant difference in K-ras expression between the two arms. Patients with mutant K-ras had a worse PFS when treated with cetuximab than those without the mutation. There was no difference in OS in mutant versus wild type K-ras patients.
The addition of cetuximab to cap, OX and bev significantly worsened PFS but had no effect on OS.
There were higher rates of diarrhea and skin toxicity in arm B, but these toxicities were considered acceptable.
The grade of skin toxicity correlated with response to cetuximab.
Patients with K-ras mutations had a decrease in PFS when given cetuximab. Patients with wild type K-ras had the same outcome with and without cetuximab.
The present study illustrates a problem that may continue to develop as more biological agents are used and combined with more standard chemotherapy drugs. It appears that subsets of patients may benefit while others may have a detriment in outcome from certain biological agents. As we use more biological agents concurrently, this relationship may become even more complicated. We need better biomarkers which may then allow us to improve our ability to identify patients who will benefit from a given therapy. This study shows that the combination of biological agents can worsen prognosis overall, but there may be a subset within the patient cohort who do benefit, in this case, those with a grade 3 skin reaction. The authors suggest that these patients may do better when treated with cetuximab, cap, OX and bev than those treated with cap, OX and bev alone. If we could select out these patients prior to initiating therapy, we may be able to better custom-tailor therapy for individual patients.
Clearly, better systemic therapies are needed for the treatment of ACC. However, the simultaneous development of better molecular markers which are predictors of therapeutic effect are also needed. At this point, without a better ability to predict who will respond to combination therapy with cetuximab, along with the greater toxicity seen in arm B, and the worse PFS seen in arm B, combined therapy with cap, OX, bev and cetuximab can not be recommended in ACC.
Jun 6, 2012 - Continuing use of bevacizumab (Avastin) in combination with second-line chemotherapy improves overall survival and progression-free survival in patients with metastatic colorectal cancer who have progressed after discontinuation of first-line bevacizumab and chemotherapy, according to the results of a phase III study presented at the annual meeting of the American Society of Clinical Oncology, held from June 1 to 5 in Chicago.