Chemotherapy, which drugs and when

Surgery-induced tumor growth in (metastatic) colorectal cancer

Metastatic colorectal cancer (mCRC) is a devastating disease causing 700.000 deaths annually worldwide. Metastases most frequently develop in the liver. Partial hepatectomy has dramatically improved clinical outcome and is the only curative treatment option for eligible patients with mCRC. Pre-clinical studies have shown that surgical procedures can have tumor-promoting local 'side-effects' such as hypoxia and inflammation, thereby altering the behaviour of residual tumor cells. In addition, systemically released factors following (colon or liver) surgery can act as a wakeup-call for dormant tumor cells in distant organs and/or help establish a pre-metastatic niche. Tumor handling during resection may also increase the number of circulating tumor cells. Despite the overwhelming amount of pre-clinical data demonstrating the pro-tumorigenic side effects of surgery, clinical evidence is scarce. Indications for hepatic surgery are rapidly increasing due to a rise in the incidence of mCRC and a trend towards more aggressive surgical treatment. Therefore, it is increasingly important to understand the principles of surgery-induced tumor growth, in order to devise perioperative or adjuvant strategies to further enhance long-term tumor control. In the current study we review the evidence for surgery-stimulated tumor growth and suggest strategies to assess the clinical relevance of such findings.

Decoy receptor 1 (DCR1) promoter hypermethylation and response to irinotecan in metastatic colorectal cancer

Diversity in colorectal cancer biology is associated with variable responses to standard chemotherapy. We aimed to identify and validate DNA hypermethylated genes as predictive biomarkers for irinotecan treatment of metastatic CRC patients.

Candidate genes were selected from 389 genes involved in DNA Damage Repair by correlation analyses between gene methylation status and drug response in 32 cell lines. A large series of samples (n=818) from two phase III clinical trials was used to evaluate these candidate genes by correlating methylation status to progression-free survival after treatment with first-line single-agent fluorouracil (Capecitabine or 5-fluorouracil) or combination chemotherapy (Capecitabine or 5-fluorouracil plus irinotecan (CAPIRI/FOLFIRI)).

In the discovery (n=185) and initial validation set (n=166), patients with methylated Decoy Receptor 1 (DCR1) did not benefit from CAPIRI over Capecitabine treatment (discovery set: HR=1.2 (95%CI 0.7-1.9, p=0.6), validation set: HR=0.9 (95%CI 0.6-1.4, p=0.5)), whereas patients with unmethylated DCR1 did (discovery set: HR=0.4 (95%CI 0.3-0.6, p=0.00001), validation set: HR=0.5 (95%CI 0.3-0.7, p=0.0008)). These results could not be replicated in the external data set (n=467), where a similar effect size was found in patients with methylated and unmethylated DCR1 for FOLFIRI over 5FU treatment (methylated DCR1: HR=0.7 (95%CI 0.5-0.9, p=0.01), unmethylated DCR1: HR=0.8 (95%CI 0.6-1.2, p=0.4)).

In conclusion, DCR1 promoter hypermethylation status is a potential predictive biomarker for response to treatment with irinotecan, when combined with capecitabine. This finding could not be replicated in an external validation set, in which irinotecan was combined with 5FU. These results underline the challenge and importance of extensive clinical evaluation of candidate biomarkers in multiple trials.

WRN Promoter CpG Island Hypermethylation Does Not Predict More Favorable Outcomes for Patients with Metastatic Colorectal Cancer Treated with Irinotecan-Based Therapy

PURPOSE

WRN promoter CpG island hypermethylation in colorectal cancer has been reported to increase sensitivity to irinotecan-based therapies. We aimed to characterize methylation of the WRN promoter, determine the effect of WRN promoter hypermethylation upon expression, and validate a previous report that WRN promoter hypermethylation predicts improved outcomes for patients with metastatic colorectal cancer (mCRC) treated with irinotecan-based therapy.

EXPERIMENTAL DESIGN

WRN methylation status was assessed using methylation-specific PCR and bisulfite sequencing assays. WRN expression was determined using qRT-PCR and Western blotting. WRN methylation status was correlated with overall survival (OS) and progression-free survival (PFS) in 183 patients with mCRC. Among these patients, 90 received capecitabine monotherapy as first-line therapy, and 93 received capecitabine plus irinotecan (CAPIRI) therapy as part of the CAIRO phase III clinical trial.

RESULTS

WRN mRNA and WRN protein expression levels were low in colorectal cancer cell lines and in primary colorectal cancer and were largely independent of WRN methylation status. Patients with methylated WRN colorectal cancer had a shorter OS compared with patients who had unmethylated WRN colorectal cancer (HR = 1.6; 95% confidence interval [CI], 1.2-2.2; P = 0.003). Patients with unmethylated WRN showed a significantly longer PFS when treated with CAPIRI compared with capecitabine alone (HR = 0.48; 95% CI, 0.32-0.70; P = 0.0001). In contrast, patients did not benefit from adding irinotecan to capecitabine when WRN was methylated (HR = 1.1; 95% CI, 0.69-1.77; P = 0.7).

CONCLUSIONS

WRN expression is largely independent of WRN promoter hypermethylation in colorectal cancer. Moreover, we could not validate the previous finding that WRN promoter hypermethylation predicts improved clinical outcomes of mCRC treated with irinotecan-based therapy and found instead the opposite result. Clin Cancer Res; 22(18); 4612-22. ©2016 AACR.

ABC-Transporter Expression Does Not Correlate with Response to Irinotecan in Patients with Metastatic Colorectal Cancer

BACKGROUND

Active efflux of irinotecan by ATP-binding cassette (ABC)-transporters, in particular ABCB1 and ABCG2, is a well-established drug resistance mechanism in vitro and in pre-clinical mouse models, but its relevance in colorectal cancer (CRC) patients is unknown. Therefore, we assessed the association between ABC-transporter expression and tumour response to irinotecan in patients with metastatic CRC.

METHODS

Tissue microarrays of a large cohort of metastatic CRC patients treated with irinotecan in a prospective study (CAIRO study; n=566) were analysed for expression of ABCB1 and ABCG2 by immunohistochemistry. Kaplan-Meier and Cox proportional hazard regression analyses were performed to assess the association of ABC transporter expression with irinotecan response. Gene expression profiles of 17 paired tumours were used to assess the concordance of ABCB1/ABCG2 expression in primary CRC and corresponding metastases.

RESULTS

The response to irinotecan was not significantly different between primary tumours with positive versus negative expression of ABCB1 (5.8 vs 5.7 months, p=0.696) or ABCG2 (5.7 vs 6.1 months, p=0.811). Multivariate analysis showed neither ABCB1 nor ABCG2 were independent predictors for progression free survival. There was a mediocre to poor concordance between ABC-transporter expression in paired tumours.

CONCLUSION

In metastatic CRC, ABC-transporter expression in the primary tumour does not predict irinotecan response.

Treatment strategies in colorectal cancer patients with initially unresectable liver-only metastases, a study protocol of the randomised phase 3 CAIRO5 study of the Dutch Colorectal Cancer Group (DCCG)

Background

Colorectal cancer patients with unresectable liver-only metastases may be cured after downsizing of metastases by neoadjuvant systemic therapy. However, the optimal neoadjuvant induction regimen has not been defined, and the lack of consensus on criteria for (un)resectability complicates the interpretation of published results.

Methods/design

CAIRO5 is a multicentre, randomised, phase 3 clinical study. Colorectal cancer patients with initially unresectable liver-only metastases are eligible, and will not be selected for potential resectability. The (un)resectability status is prospectively assessed by a central panel consisting of at least one radiologist and three liver surgeons, according to predefined criteria. Tumours of included patients will be tested for RAS mutation status. Patients with RAS wild type tumours will be treated with doublet chemotherapy (FOLFOX or FOLFIRI) and randomised between the addition of either bevacizumab or panitumumab, and patients with RAS mutant tumours will be randomised between doublet chemotherapy (FOLFOX or FOLFIRI) plus bevacizumab or triple chemotherapy (FOLFOXIRI) plus bevacizumab. Radiological evaluation to assess conversion to resectability will be performed by the central panel, at an interval of two months.

The primary study endpoint is median progression-free survival. Secondary endpoints are the R0/1 resection rate, median overall survival, response rate, toxicity, pathological response of resected lesions, postoperative morbidity, and correlation of baseline and follow-up evaluation with respect to outcomes by the central panel.

Discussion

CAIRO5 is a prospective multicentre trial that investigates the optimal systemic induction therapy for patients with initially unresectable, liver-only colorectal cancer metastases.

Trial registration

CAIRO 5 is registered at European Clinical Trials Database (EudraCT) (2013-005435-24).

CAIRO 5 is registered at ClinicalTrials.gov: NCT02162563, June 10, 2014.

Optimal duration of systemic treatment in metastatic colorectal cancer

PURPOSE OF REVIEW

With the currently available cytotoxic and targeted drugs, metastatic colorectal cancer (mCRC) may be controlled by systemic treatment for a significant period of time. However, many questions remain about the optimal use of drugs and duration of treatment. We reviewed the data from clinical trials on the optimal duration of systemic treatment with chemotherapy and targeted therapy in mCRC patients.

RECENT FINDINGS

The feasibility of chemotherapy-free intervals has been studied in mCRC patients treated with chemotherapy alone, but the results are conflicting. Current data show that oxaliplatin may be safely interrupted, but do not allow a firm conclusion on the safety of a full treatment break of chemotherapy. For targeted therapy, continuous inhibition of intracellular signalling by prolonged administration would theoretically be beneficial for efficacy of treatment, and has been suggested by retrospectively collected data. Recent data from a prospective study show a clinical benefit for maintenance treatment with chemotherapy and bevacizumab with acceptable toxicity and preservation of quality of life. Survival benefits were seen in selected patient subgroups. No data on the optimal duration of treatment with anti-epidermal growth factor receptor agents are currently available.

SUMMARY

There are no definite data on the safety of chemotherapy-free intervals. Data on targeted therapy support the use of maintenance treatment of chemotherapy plus bevacizumab.

Systemic treatment: maintenance compared with holiday

With the currently available cytotoxic and targeted drugs, metastatic colorectal cancer (mCRC) may be controlled by systemic treatment for a substantial period of time. However, many questions remain about the optimal use of drugs and duration of treatment. The feasibility of chemotherapy-free intervals has been studied in patients with mCRC treated with chemotherapy alone, but the results are conflicting. Current data show that oxaliplatin may be safely interrupted, but they do not allow a firm conclusion on the safety of a full treatment break of chemotherapy. For targeted therapy, continuous inhibition of intracellular signaling by prolonged administration would theoretically be beneficial for efficacy of treatment. Recent data support the use of maintenance treatment with chemotherapy and bevacizumab. No data on the optimal duration of treatment with anti-epidermal growth factor receptor (EGFR) agents are currently available.

MTHFR polymorphisms and capecitabine-induced toxicity in patients with metastatic colorectal cancer

OBJECTIVE

The availability of current chemotherapeutic options for metastatic colorectal cancer (mCRC) has increased survival, but it is also accompanied by considerable morbidity. Fluoropyrimidines are the mainstay of systemic therapy. Germline pharmacogenetic markers involved in 5-fluorouracil pharmacodynamics could provide individualized pretreatment tools for predicting toxicity. Research on methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms and fluoropyrimidine treatment outcome has focused on intravenous 5-fluorouracil and has yielded inconclusive results. The literature on pharmacogenetics in capecitabine-based chemotherapy is scarce. Therefore, we analysed the association of MTHFR gene polymorphisms and the occurrence of serious toxicity of first-line capecitabine monotherapy and combination therapy.

METHODS

One hundred and twenty-seven patients treated with first-line monotherapy capecitabine and 141 patients on capecitabine-irinotecan combination therapy were recruited from the CAIRO trial, an open-label phase III randomized trial, comparing sequential versus combination chemotherapy with capecitabine, irinotecan and oxaliplatin in mCRC. All patients were genotyped for MTHFR 1298A>C and 677C>T polymorphisms and analysed in both cohorts separately for the association between the MTHFR genotype and incidence of grade 3-4 overall toxicity and specific adverse events, as well as efficacy parameters.

RESULTS

MTHFR 1298A>C and 677C>T genotypes were not associated with grade 3-4 overall toxicity, febrile neutropenia or hand-foot syndrome. MTHFR 1298CC homozygotes showed a borderline significantly higher incidence of grade 3-4 diarrhoea compared with MTHFR 1298AC or AA individuals (25 vs. 5%, P=0.041) in the monotherapy cohort. No significant association was found between the MTHFR genotypes and efficacy parameters in either treatment cohort.

CONCLUSION

MTHFR polymorphisms are not associated with toxicity or efficacy in mCRC patients treated with capecitabine-based chemotherapy.

Outcome of first line systemic treatment in elderly compared to younger patients with metastatic colorectal cancer: a retrospective analysis of the CAIRO and CAIRO2 studies of the Dutch Colorectal Cancer Group (DCCG)

BACKGROUND

Metastatic colorectal cancer (CRC) is predominantly a disease of the elderly, therefore the current standards should be evaluated in this population.

MATERIAL AND METHODS

We evaluated in different age groups the outcome in terms of median overall and progression-free survival, response rate, disease control rate, relative dose intensity (RDI), tolerability, and global quality of life (QoL) of first-line capecitabine monotherapy (CAP) versus capecitabine + irinotecan (CAPIRI) and capecitabine + oxaliplatin + bevacizumab (CAPOX + BEV) in the CAIRO and CAIRO2 study, respectively. Patients were categorized into three age groups: age > 75, 70-75 and < 70 years.

RESULTS

Clinical outcomes were not significantly different among age groups, with the exception of a higher response rate from CAP treatment in the elderly. Elderly patients treated with CAPOX + BEV showed a trend towards a worse median overall survival compared to younger patients. Only treatment with CAP resulted in a higher incidence of grade 3-4 toxicity and a lower RDI in elderly versus younger patients. Treatment with CAP and CAPOX + BEV in elderly patients was significantly more often discontinued due to toxicity instead of progression to disease compared to younger patients. The increase in global QoL was comparable for the three age groups for each treatment regimen.

CONCLUSION

We did not observe significant differences in survival outcomes between elderly and younger metastatic CRC patients with three different first-line systemic treatment regimens. Our data suggest that initial dose reduction of CAP monotherapy may be indicated in elderly patients.

TOP1 gene copy numbers in colorectal cancer samples and cell lines and their association to in vitro drug sensitivity

OBJECTIVE

A positive relationship between topoisomerase-1 (TOP1) protein and sensitivity toward the TOP1 inhibitor irinotecan has been reported in patients with metastatic colorectal cancer (mCRC). In this study, we analyzed TOP1 gene copy number variation in tumor tissue from CRC patients and CRC cell lines with different sensitivities to the TOP1 inhibitor SN-38 and oxaliplatin.

MATERIAL AND METHODS

A TOP1 gene probe with a chromosome 20 centromere (CEN-20) reference probe was applied on normal mucosa and on tumor tissue from 50 stage III CRC patients. Additionally, associations between TOP1/CEN-20 ratio and in vitro sensitivity to SN-38 (irinotecan) and oxaliplatin were tested on 10 CRC cell lines. Results. In the malignant epithelium, 84% of the samples demonstrated an increased TOP1 gene copy number and 64% had an increased TOP1/CEN-20 ratio compared with the non-affected mucosa. Sixteen (32%) of the tumors had a ratio of ≥ 1.5 and 9 (18%) of these had a ratio of ≥ 2.0. A positive association was observed between the TOP1 gene copy number and the TOP1/CEN-20 ratio and in vitro sensitivity toward SN-38, but not toward oxaliplatin.

CONCLUSIONS

A large fraction of the clinical samples demonstrated increased TOP1 gene copy number and increased TOP1/CEN-20 ratio. The cell line study suggested an association between TOP1 gene copy number or TOP1/CEN-20 ratio and sensitivity to irinotecan but not oxaliplatin.

Pyrosequencing-based methods reveal marked inter-individual differences in oncogene mutation burden in human colorectal tumours

BACKGROUND

The epidermal growth factor receptor-targeted monoclonal antibody cetuximab (Erbitux) was recently introduced for the treatment of metastatic colorectal cancer. Treatment response is dependent on Kirsten-Ras (K-Ras) mutation status, in which the majority of patients with tumour-specific K-Ras mutations fail to respond to treatment. Mutations in the oncogenes B-Raf and PIK3CA (phosphoinositide-3-kinase) may also influence cetuximab response, highlighting the need for a sensitive, accurate and quantitative assessment of tumour mutation burden.

METHODS

Mutations in K-Ras, B-Raf and PIK3CA were identified by both dideoxy and quantitative pyrosequencing-based methods in a cohort of unselected colorectal tumours (n=102), and pyrosequencing-based mutation calls correlated with various clinico-pathological parameters.

RESULTS

The use of quantitative pyrosequencing-based methods allowed us to report a 13.7% increase in mutation burden, and to identify low-frequency (<30% mutation burden) mutations not routinely detected by dideoxy sequencing. K-Ras and B-Raf mutations were mutually exclusive and independently associated with a more advanced tumour phenotype.

CONCLUSION

Pyrosequencing-based methods facilitate the identification of low-frequency tumour mutations and allow more accurate assessment of tumour mutation burden. Quantitative assessment of mutation burden may permit a more detailed evaluation of the role of specific tumour mutations in the pathogenesis and progression of colorectal cancer and may improve future patient selection for targeted drug therapies.

Relationship between single nucleotide polymorphisms and haplotypes in DPYD and toxicity and efficacy of capecitabine in advanced colorectal cancer

PURPOSE

To explore the effect of dihydropyrimidine dehydrogenase (DPD) single nucleotide polymorphisms (SNP) and haplotypes on outcome of capecitabine.

EXPERIMENTAL DESIGN

Germline DNA was available from 568 previously untreated patients with advanced colorectal cancer participating in the CAIRO2 trial, assigned to capecitabine, oxaliplatin, and bevacizumab ± cetuximab. The coding region of dihydropyrimidine dehydrogenase gene (DPYD) was sequenced in 45 cases with grade 3 or more capecitabine-related toxicity and in 100 randomly selected controls (cohort). Most discriminating (P < 0.1) or frequently occurring (>1%) nonsynonymous SNPs were analyzed in all 568 patients. SNPs and haplotypes were associated with toxicity, capecitabine dose modifications, and survival.

RESULTS

A total of 29 SNPs were detected in the case-cohort analysis, of which 8 were analyzed in all 568 patients. Of the patients polymorphic for DPYD IVS14+1G>A, 2846A>T, and 1236G>A, 71% (5 of 7), 63% (5 of 8), and 50% (14 of 28) developed grade 3 to 4 diarrhea, respectively, compared with 24% in the overall population. All patients polymorphic for IVS14+1G>A developed any grade 3 to 4 toxicity, including one possibly capecitabine-related death. Because of toxicity, a mean capecitabine dose reduction of 50% was applied in IVS14+1G>A and 25% in 2846A>T variant allele carriers. Patients were categorized into six haplotype groups: one predicted for reduced (10%), and two for increased risks (41% and 33%) for severe diarrhea. Individual SNPs were not associated with overall survival, whereas one haplotype was associated with overall survival [HR (95% CI) = 0.57 (0.35-0.95)].

CONCLUSIONS

DPYD IVS14+1G>A and 2846A>T predict for severe toxicity to capecitabine, for which patients require dose reductions. Haplotypes assist in selecting patients at risk for toxicity to capecitabine.

Randomized trial of two induction chemotherapy regimens in metastatic colorectal cancer: an updated analysis

BACKGROUND

In a randomized trial with a median follow-up of 18.4 months, 6 months of induction chemotherapy with a three-drug regimen comprising 5-fluorouracil (by continuous infusion)-leucovorin, irinotecan, and oxaliplatin (FOLFOXIRI) demonstrated statistically significant improvements in response rate, radical surgical resection of metastases, progression-free survival, and overall survival compared with 6 months of induction chemotherapy with fluorouracil-leucovorin and irinotecan (FOLFIRI).

METHODS

From November 14, 2001, to April 22, 2005, we enrolled 244 patients with metastatic colorectal cancer. To evaluate if the superiority of FOLFOXIRI is maintained in the long term, we updated the overall and progression-free survival data to include events that occurred up to February 12, 2009, with a median follow-up of 60.6 months. We performed a subgroup and a risk-stratified analysis to examine whether outcomes differed in specific patient subgroups, and we analyzed the results of treatment after progression. Survival curves were estimated by the Kaplan-Meier method. Multivariable Cox regression models were fit to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). All statistical tests were two-sided.

RESULTS

FOLFOXIRI demonstrated statistically significant improvements in median progression-free survival (9.8 vs 6.8 months, HR for progression = 0.59, 95% CI = 0.45 to 0.76, P < .001) and median overall survival (23.4 vs 16.7 months, HR for death = 0.74, 95% CI = 0.56 to 0.96, P = .026) with a 5-year survival rate of 15% (95% CI = 9% to 23%) vs 8% (95% CI = 4% to 14%). The improvements in progression-free survival and, to a lesser extent, in overall survival were evident even when the analysis excluded patients who received radical resection of metastases. With regard to the risk-stratified analysis, FOLFOXIRI results in longer progression-free survival and overall survival than FOLFIRI in all risk subgroups.

CONCLUSIONS

Six months of induction chemotherapy with FOLFOXIRI is associated with a clinically significant improvement in the long-term outcome compared with FOLFIRI with an absolute benefit in survival at 5 years of 7%.

The effect of prophylactic calcium and magnesium infusions on the incidence of neurotoxicity and clinical outcome of oxaliplatin-based systemic treatment in advanced colorectal cancer patients

BACKGROUND

Peripheral sensory neurotoxicity is a frequent and potentially debilitating side effect of oxaliplatin treatment. Calcium and magnesium (Ca/Mg) infusions are frequently used to prevent this toxicity. However, concerns about a negative impact of Ca/Mg infusions on outcome have been raised. We retrospectively assessed the effect of Ca/Mg infusions on the incidence of neurotoxicity and on clinical outcome in advanced colorectal cancer (ACC) patients treated in the phase III CAIRO2 study.

MATERIALS AND METHODS

Seven hundred and fifty five previously untreated ACC patients were randomised between treatment with capecitabine, oxaliplatin and bevacizumab or the same combination with the addition of cetuximab. Patients were retrospectively divided into two groups: patients in the Ca/Mg(+) group received Ca/Mg at least during their first treatment cycle, and patients in the Ca/Mg(-) group did not.

RESULTS

Seven hundred and thirty two patients were evaluable for this analysis. The Ca/Mg(+) group consisted of 551 patients, the Ca/Mg(-) group consisted of 181 patients. The incidence of all grade neurotoxicity in the Ca/Mg(+) group and the Ca/Mg(-) group was 85% and 92%, respectively (p = 0.02), and the incidence of grade ≥ 2 neurotoxicity was 40% and 45%, respectively (p = 0.22). The median PFS in the Ca/Mg(+) versus Ca/Mg(-) group was 10.1 versus 10.7 months (p = 0.92), the median OS was 19.8 versus 20.7 months (p = 0.10), and the response rate was 43.1% versus 50% (p = 0.11), respectively.

CONCLUSIONS

In this largest retrospective analysis to date we observed that Ca/Mg infusions significantly reduced all grade oxaliplatin-related neurotoxicity. Ca/Mg infusions did not affect the clinical efficacy of treatment.

Monoclonal antibodies in the treatment of metastatic colorectal cancer: a review

BACKGROUND

Two groups of agents targeting either the vascular endothelial growth factor (VEGF) receptor or the epidermal growth factor receptor (EGFR) have been added to the therapeutic arsenal against metastatic colorectal cancer (mCRC). Currently available agents in these groups are the anti-VEGF antibody bevacizumab and the anti-EGFR antibodies cetuximab and panitumumab.

OBJECTIVES

This article reviews the results of prospective randomized clinical trials of anti-VEGF and anti-EGFR antibodies in mCRC, either as monotherapy, combined with chemotherapy, or combined with each other. Also reviewed are retrospective subset analyses of the effect of a KRAS mutation on the response to anti-EGFR antibodies.

METHODS

MEDLINE (2004-2009) was searched for randomized Phase II-III clinical trials of monoclonal antibodies in mCRC published in English. The search terms were colorectal neoplasms, bevacizumab, cetuximab, panitumumab, and KRAS mutation, alone or in combination. Information on the effect of KRAS mutation status on the response to anti-EGFR antibodies was drawn from retrospective subset analyses within the selected trials.

RESULTS

The literature search identified 5 trials of bevacizumab in mCRC. Of these trials, 3 found a significant benefit on the primary end point (progression-free survival [PFS] or overall survival [OS]) when bevacizumab was added to chemotherapy, either as first-line (2 trials) or second-line (1 trial) treatment. The literature search identified 5 trials of cetuximab and 1 trial of panitumumab in mCRC. Of these trials, 4 found a significant benefit on the primary end point (response rate, PFS, or OS) with cetuximab or panitumumab as monotherapy or added to chemotherapy, either as first-line (1 trial) or later-line (3 trials) treatment. In all trials, the benefit of anti-EGFR therapy was limited to patients who had KRAS wild-type tumors. Of 3 identified trials of combined anti-EGFR and anti-VEGF therapy, 2 found that the combination of an anti-EGFR antibody and the anti-VEGF antibody bevacizumab had a significant negative effect on the primary end point (PFS) compared with no added anti-EGFR antibody.

CONCLUSIONS

In the studies reviewed, the anti-VEGF antibody bevacizumab added to chemotherapy and the anti-EGFR antibodies cetuximab and panitumumab as monotherapy or added to chemotherapy were associated with consistent efficacy in the treatment of mCRC, although the absolute benefit differed among trials. The efficacy of anti-EGFR antibodies was limited to patients with KRAS wild-type tumors. Given the lack of benefit when anti-VEGF and anti-EGFR antibodies were combined, such regimens should not be used in clinical practice.