Pharmacokinetics and pharmacodynamics of approved monoclonal antibody therapy for colorectal cancer

INTRODUCTION

The introduction of monoclonal antibodies to the chemotherapy backbone treatment has challenged the paradigm of metastatic colorectal cancer (mCRC) treatment. Their mechanism of action and pharmacokinetics are complex but important to understand in order to improve patient selection and treatment outcomes for mCRC population.

AREAS COVERED

This review examines the scientific data, pharmacodynamics, and pharmacokinetics of approved monoclonal antibodies used to treat mCRC patients, including agents targeting signaling via VEGFR (bevacizumab and ramucirumab), EGFR (cetuximab and panitumumab), HER2/3 target therapy, and immunotherapy agents such as pembrolizumab or nivolumab. Efficacy and mechanism of action of bispecific antibodies are also covered.

EXPERT OPINION

mCRC is a heterogeneous disease and the optimal selection and sequence of treatments is challenging. Monoclonal antibodies have complex pharmacokinetics and pharmacodynamics, with important interactions between them. The arrival of bioequivalent molecules to the market increases the need for the characterization of pharmacokinetics and pharmacodynamics of classic monoclonal antibodies to reach bioequivalent novel molecules.

Metastatic colorectal cancer in both sides of Aegean sea: practice patterns and outcome

OBJECTIVE

The successful results obtained in trials may not necessarily translate into prolonged survival of metastatic colorectal cancer (mCRC) patients in real life. This multinational registry study aimed to evaluate the real-life data effecting the survival of patients with mCRC.

METHODS

This is a multinational, retrospective registry study. Turkish and Greek mCRC patients diagnosed between 2005 and 2012, with at least 3 years of follow-up data or who died before 3 years of follow-up were included in the study.

RESULTS

A total of 364 were included in the study. RAS and BRAF mutation rates were found to be 36% and 39%, respectively. As first-line therapy, 196 (54%) patients received bevacizumab and Anti-EGFR treatments in combination with chemotherapy. The objective response rate was 42% (n = 152) and 32% (n = 78) for 1^st line and 2^nd line treatments, respectively. While the median progression-free survival (PFS) with the 1^st line treatment was 10 months, it was 7 months with the 2^nd line treatments. In the total study population median PFS and overall survival (OS) were 10 (95% CI, 8.3-11.6) and 35 (95% CI, 30.7-39.2) months, respectively. In Turkish and Greek patients, median OS (36 months versus 29 months, p = .81) and PFS (10.2 versus 9.2, p = .42) were not different. In multivariate analysis, ECOG PS of ≥2 and having metastases in more than one region decreased overall survival (p = .002 and p = .003), it was found that wild RAS and BRAF mutations and second metastasectomy contributed to overall survival (p = .047 and p < .001).

CONCLUSION

In conclusion, it seems that the patient's performance status, tumor location, number of metastatic lesions at the time of diagnosis affect the prognosis of mCRC. Although access to molecular tests and first-line treatments differ between Greece and Turkey, no significant difference was found in survival times.

OUP accepted manuscript

Background

Limited studies have suggested that mucinous histology is associated an attenuated response to anti-epidermal growth factor receptor (EGFR) therapy.

Methods

We conducted a single-institution, retrospective study to review the anti-EGFR response and the molecular profile of patients with left-sided microsatellite stable RAS/BRAF wild-type mucinous metastatic colorectal cancer.

Results

In comparison to nonmucinous population (n = 98), mucinous histology (n = 20) was associated with a younger age (48 vs 54, P = .02), wild-type APC (80% vs 15.3%, P < .0001), and wild-type TP53 (40% vs 8.2%, P = .001). Guanine nucleotide binding protein, alpha stimulating (GNAS) mutations were exclusively found in mucinous tumors (20% vs 0, P < .0001). Genomic alterations associated with resistance to anti-EGFR therapy, such as ERBB2 amplification, PIK3CA mutation, MAP2K1 mutation, and KRAS amplification, were identified in patients with left-sided RAS/BRAF wild-type mucinous metastatic colorectal cancer. Mucinous histology was not associated with a worse outcome than non-mucinous histology (34.3 vs 42.2 months, P = .85). However, patients with left-sided RAS/BARF wild-type mucinous colorectal cancer treated with first-line anti-EGFR therapy had significantly worse progression-free survival (4 vs 6.5 months, hazard ratio [HR] = 5.3, 95% confidence interval [CI] 1.3-21.7, P = .01) than patients treated with the first-line vascular endothelial growth factor A antibody, bevacizumab. Anti-EGFR therapy was associated with limited responses and a short PFS across all lines of therapy in 12 patients with left-sided RAS/BRAF wild-type mucinous colorectal cancer.

Conclusions

Mucinous histology is associated with diminished benefits from anti-EGFR therapy in patients with left-sided RAS/BRAF wild-type colorectal cancer. These patients should be considered for bevacizumab-based therapy in the first- and second-line settings.

Resolving the difference between left-sided and right-sided colorectal cancer by single-cell sequencing

Colorectal cancers (CRCs) exhibit differences in incidence, pathogenesis, molecular pathways, and outcome depending on the location of the tumor. The transcriptomes of 27,927 single human CRC cells from 3 left-sided and 3 right-sided CRC patients were profiled by single-cell RNA-Seq (scRNA-Seq). Right-sided CRC harbors a significant proportion of exhausted CD8⁺ T cells of a highly migratory nature. One cluster of cells from left-sided CRC exhibiting states preceding exhaustion and a high ratio of preexhausted/exhausted T cells were favorable prognostic markers. Notably, we identified a potentially novel RBP4⁺NTS⁺ subpopulation of cancer cells that exclusively expands in left-sided CRC. Tregs from left-sided CRC showed higher levels of immunotherapy-related genes than those from right-sided CRC, indicating that left-sided CRC may have increased responsiveness to immunotherapy. Antibody-dependent cellular phagocytosis (ADCP) and antibody-dependent cellular cytotoxicity (ADCC) induced by M2-like macrophages were more pronounced in left-sided CRC and correlated with a good prognosis in CRC.

Partnering bevacizumab with irinotecan as first line-therapy of metastatic colorectal cancer improves progression free survival-A retrospective analysis

Colorectal cancer remains one of the most frequent malignancies (third place at both genders) worldwide in the last decade, owing to significant changes in modern dietary habits. Approximately half of the patients develop metastases during the course of their disease. The available therapeutic armamentarium is constantly evolving, raising questions regarding the best approach for improving survival. Bevacizumab remains one of the most widely used therapies for treating metastatic colorectal cancer and can be used after progression. This study aimed to identify the best chemotherapy partner for bevacizumab after progression. We performed a retrospective analysis of patients with metastatic colorectal cancer who were treated with bevacizumab as first- and second-line chemotherapy. Data were collected for 151 patients, 40 of whom were treated with double-dose bevacizumab after the first progression. The two standard chemotherapy regimens combined with bevacizumab were FOLFIRI/CAPIRI and FOLFOX4/CAPEOX. The initiation of first-line treatment with irinotecan-based chemotherapy improved progression-free survival and time to treatment failure but not overall survival. After the first progression, retreatment with the same regimen as that used in the induction phase was the best approach for improving overall survival (median overall survival: 46.5 vs. 27.0 months for the same vs. switched strategy, respectively). No correlations were observed between the dose intensity of irinotecan, oxaliplatin, 5-fluorouracil, or bevacizumab and the overall survival, progression-free survival in the first-/second-line treatment, and time to treatment failure. Interaction between an irinotecan-based regimen as a second-line treatment and double-dose bevacizumab after progression was associated with an improved overall survival (p = 0.06). Initiating systemic treatment with an irinotecan-based regimen in combination with bevacizumab improved the progression-free survival in the first-line treatment and time to treatment failure. In terms of overall survival, bevacizumab treatment after the first progression is better partnered with the same regimen as that used in the induction phase.

Traditional Chinese Medicine Combined With Chemotherapy and Cetuximab or Bevacizumab for Metastatic Colorectal Cancer: A Randomized, Double-Blind, Placebo-Controlled Clinical Trial

Background

Huangci Granule is a traditional Chinese medicine for treating metastatic colorectal cancer (mCRC).

Objective

To evaluate the efficacy and safety of Huangci Granule combination with chemotherapy and cetuximab (CET) or bevacizumab (BV) for treating mCRC.

Methods

We performed a randomized, controlled, and double-blind trial and recruited patients with mCRC who were planned to undergo chemotherapy combined with CET or BV. The treatment group was treated with Huangci Granule, while the control group was treated with placebo. Continuous treatment until disease progression, death, intolerable toxicity or up to 6 months. The primary endpoint was progression-free survival (PFS), and the secondary endpoint was quality of life and safety.

Result

320 patients were randomly assigned to receive treatment, including 200 first-line patients and 120 second-line patients. In the first-line treatment, the median PFS was 9.59 months (95% CI, 6.94–13.25) vs 6.89 months (95% CI, 4.99–9.52) in treatment group and control group (HR, 0.69; 95% CI, 0.50–0.97; P = 0.027). Chinese medicine was an independent factor affecting the PFS. In the second-line treatment, the median PFS was 6.51 months (95% CI, 4.49–9.44) vs 4.53 months (95% CI, 3.12–6.57) in the treatment group and control group (HR, 0.65; 95% CI, 0.45–0.95; P = 0.020). Compared with the control group, “role function,” “social function,” “fatigue,” and “appetite loss” were significantly improved in the treatment (P < 0.05) and drug related grades 3 to 4 adverse events were less.

Conclusion

Huangci Granule combined with chemotherapy and CET or BV can prolong the PFS of mCRC, improve the quality of life, reduce adverse reactions, and have good safety.

Clinical Pharmacokinetics and Pharmacodynamics of the Epidermal Growth Factor Receptor Inhibitor Panitumumab in the Treatment of Colorectal Cancer

Despite progress in the treatment of metastatic colorectal cancer (mCRC) in the last 15 years, it is still a condition with a relatively low 5-year survival rate. Panitumumab, a fully human monoclonal antibody directed against the epidermal growth factor receptor (EGFR), is able to prolong survival in patients with mCRC. Panitumumab is used in different lines of therapy in combination with chemotherapy, and as monotherapy for the treatment of wild-type (WT) RAS mCRC. It is administered as an intravenous infusion of 6 mg/kg every 2 weeks and has a t_½ of approximately 7.5 days. Elimination takes place via two different mechanisms, and immunogenicity rates are low. Only RAS mutations have been confirmed as a negative predictor of efficacy with anti-EGFR antibodies. Panitumumab is generally well tolerated and has a manageable toxicity profile, despite a very high prevalence of dermatologic side effects. This article presents an overview of the clinical pharmacokinetics and pharmacodynamics of panitumumab, including a description of the studies that led to its approval in the different lines of therapy of mCRC.

Triple-drug chemotherapy regimens in combination with an anti-EGFR agent in metastatic colorectal cancer - prospects from phase II clinical trials

INTRODUCTION

The addition of monoclonal antibody (mAb) epidermal growth factor receptor (EGFR) inhibitors to classic chemotherapy doublet backbones has improved survival of metastatic colorectal cancer (mCRC). However, the role of triple-drug chemotherapy regimens in combination with an anti-EGFR mAb inhibitor is not yet clear.

AREAS COVERED

The activity of triple-drug chemotherapy regimens when combined with an anti-EGFR mAb in mCRC patients is examined. We describe the overall safety and tolerability profiles based on a literature review of all published phase I and II clinical trials in this setting. Drug exposure, tumor mutational status, and metastases resectability are discussed. A review of PubMed and abstracts of major oncology congresses from 2009 to 2018, with MeSH and full-text search terms for clinical trials of anti-EGFR for 'metastatic' or 'advanced' 'colorectal cancer/adenocarcinoma' was implemented. Only English language publications were included.

EXPERT OPINION

Efficacy data from phase II trials are promising, but the safety profiles are not as encouraging; the development of severe diarrhea and acneiform rash limit the drug exposure that is critical for improved outcomes. Phase II studies of these triplet chemotherapy/anti-EGFR mAb combinations have focused on conversion therapy in liver-limited disease or in the first-line setting in advanced disease. The identification of biomarkers of response and toxicity may support the use of personalized medicine and more precise design of phase III trials.

Circadian gene hCLOCK contributes to progression of colorectal carcinoma and is directly regulated by tumor‑suppressive microRNA‑124

An abundance of studies has demonstrated that disruption of circadian rhythms is one of the factors that may contribute to the initiation and development of human colorectal carcinomas (CRCs). Recently, microRNA‑124 has been demonstrated to suppress tumor growth or metastasis of CRCs. However, the mechanisms of cross‑talk between microRNA‑124 (miR‑124) and circadian rhythms in the regulation of CRCs are poorly understood. The present study demonstrated that the protein expression levels of human circadian locomoter output cycles protein kaput (hCLOCK) is significantly increased, while miR‑124 is attenuated in high‑grade human CRC tissues and in the more invasive colorectal cancer cell lines SW620 and LOVO. It was further demonstrated that hCLOCK is a direct target of miR‑124. Upregulation of miR‑124 significantly inhibited hCLOCK expression in LOVO cells, and consequently inhibited its promoting effects on the proliferation and migration of LOVO cells. In conclusion, these data revealed that hCLOCK serves an enhancing role, whereas mir‑124 serves a suppressive role, in human CRC. Attenuation of miR‑124, of which hCLOCK is a direct target, leads to increased hCLOCK expression and disruption of circadian rhythms in CRC.

Radioembolization as a Treatment Strategy for Metastatic Colorectal Cancer to the Liver: What Can We Learn from the SIRFLOX Trial?

OPINION STATEMENT

In the setting of liver metastases from colorectal cancer (CRC), radioembolization with yttrium-90 has been used to treat chemotherapy refractory disease with a growing interest to establish its efficacy in prospective trials combined with first- and second-line chemotherapy. SIRFLOX is an ongoing, multi-center, phase 3 randomized trial comparing first-line chemotherapy alone or in combination with yttrium-90 radioembolization in patients with CRC who have isolated liver metastases or liver-dominant metastases. Preliminary results from SIRFLOX demonstrate that radioembolization combined with first-line chemotherapy is safe and feasible. There was no significant difference in median overall progression-free survival (PFS) between the combined radioembolization-chemotherapy and chemotherapy-only arms (10.7 versus 10.2 months). Although the trial did not meet its primary endpoint of improved median PFS, there was a significant increase in the median hepatic PFS (20.5 versus 12.6 months; p = 0.02) favoring the combination arm. Thus, combining radioembolization with chemotherapy in the first-line setting may be most effective for liver-limited metastatic CRC. Since radioembolization targets liver disease, it is plausible that the trial failed to achieve an improvement in PFS given that 40 % of the SIRFLOX population had extra-hepatic disease. It is also possible that the overall median PFS may be a poor surrogate endpoint, and other endpoints like overall survival still needs to be delineated in this setting. In addition, it is crucial to document improvement or delay in time to deterioration in quality of life symptom endpoints in this population. SIRFLOX is the first of three prospective studies that assess the efficacy of adding radioembolization to first-line chemotherapy, and the combined data from these trials will provide the necessary power for an overall survival analysis. The final results of SIRFLOX will be eagerly awaited to determine if the increased hepatic PFS in preliminary data will translate to increased overall survival benefit.

Blood-based detection of RAS mutations to guide anti-EGFR therapy in colorectal cancer patients: concordance of results from circulating tumor DNA and tissue-based RAS testing

An accurate blood‐based RAS mutation assay to determine eligibility of metastatic colorectal cancer (mCRC) patients for anti‐EGFR therapy would benefit clinical practice by better informing decisions to administer treatment independent of tissue availability. The objective of this study was to determine the level of concordance between plasma and tissue RAS mutation status in patients with mCRC to gauge whether blood‐based RAS mutation testing is a viable alternative to standard‐of‐care RAS tumor testing. RAS testing was performed on plasma samples from newly diagnosed metastatic patients, or from recurrent mCRC patients using the highly sensitive digital PCR technology, BEAMing (beads, emulsions, amplification, and magnetics), and compared with DNA sequencing data of respective FFPE (formalin‐fixed paraffin‐embedded) tumor samples. Discordant tissue RAS results were re‐examined by BEAMing, if possible. The prevalence of RAS mutations detected in plasma (51%) vs. tumor (53%) was similar, in accord with the known prevalence of RAS mutations observed in mCRC patient populations. The positive agreement between plasma and tumor RAS results was 90.4% (47/52), the negative agreement was 93.5% (43/46), and the overall agreement (concordance) was 91.8% (90/98). The high concordance of plasma and tissue results demonstrates that blood‐based RAS mutation testing is a viable alternative to tissue‐based RAS testing.

Targeted Therapy of Colorectal Cancer

Over the past decades, considerable progress has been made in the management of colorectal cancer (CRC), leading to a significant improvement in overall survival. Although part of this success has been rightly attributed to aggressive surgical management and advances in other adjunct treatments, our understanding of the pathogenesis of CRC and emergence of newer molecular targets for colon cancer has created a powerful impact. In this review article, we will discuss various targeted therapies in the management of metastatic CRC (mCRC). In particular, vascular endothelial growth factor (VEGF)- and epidermal growth factor receptor (EGFR)-targeting monoclonal antibodies have become integral components of the first-line treatment strategies for mCRC. Newer agents on the horizon soon to be incorporated in clinical practice will be briefly reviewed as well. Currently, the only predictive biomarker for treatment selection in patients with mCRC is tumor RAS mutational status.

Emerging tyrosine kinase inhibitors for the treatment of metastatic colorectal cancer

INTRODUCTION

Colorectal cancer (CRC) is a leading cause of cancer death worldwide. Over the last decade, the addition of antibodies that block the epidermal growth factor receptor (EGFR) or angiogenesis to the classic chemotherapy backbone has improved overall survival in metastatic colorectal cancer (mCRC). However, the role of the other major targeted therapy, the tyrosine kinase inhibitors (TKIs), is not yet fully clarified.

AREAS COVERED

This review discusses key published and ongoing studies with TKIs in mCRC, the mechanisms of resistance to standard treatments that are potentially targetable with these small molecules, along with the role of biomarkers in therapeutic decision-making process.

EXPERT OPINION

The current effectiveness of TKIs is limited by two principal reasons, firstly the use of combination chemotherapy necessitates lower dose-density to manage the toxicity profile and secondly, development of these drugs has mainly been performed in molecularly unselected populations. mCRC is a heterogeneous and dynamic disease, and clinical trials with TKIs must be designed on the basis of specific molecular alterations targeted by these drugs. Success with this approach relies on identifying mutations at the time of progression, raising the importance of minimally-invasive monitoring tools. Liquid biopsies are a promising option, although this technique remains to be validated. Overall, this approach contributes to the move towards personalized and precision therapeutic strategies.

BATON-CRC: A Phase II Randomized Trial Comparing Tivozanib Plus mFOLFOX6 with Bevacizumab Plus mFOLFOX6 in Stage IV Metastatic Colorectal Cancer

PURPOSE

Tivozanib, a selective inhibitor of VEGFR-1, -2, and -3, plus mFOLFOX6 in an advanced gastrointestinal cancer phase Ib study had encouraging antineoplastic activity and a tolerable safety profile. This randomized, open-label, phase II trial of tivozanib/mFOLFOX6 versus bevacizumab/mFOLFOX6 in patients with previously untreated metastatic colorectal cancer (mCRC) evaluated tivozanib activity versus bevacizumab.

EXPERIMENTAL DESIGN

Treatment-naïve patients received mFOLFOX6 every 2 weeks of each 28-day cycle plus either tivozanib orally 1.5 mg once daily for 21 days or bevacizumab intravenously 5 mg/kg every 2 weeks. Investigator-assessed progression-free survival (PFS) was the primary endpoint; some secondary endpoints included safety, overall survival, overall response rate (ORR), duration of response, time to treatment failure, and biomarker subgroup analyses.

RESULTS

A prespecified interim futility analysis demonstrated that the futility boundary for superiority of tivozanib/mFOLFOX6 over bevacizumab/mFOLFOX6 for PFS in the intent-to-treat population was crossed; median PFS was 9.4 versus 10.7 months [HR = 1.091; confidence interval (CI), 0.693-1.718; P = 0.706]. Tivozanib/mFOLFOX6 resulted in PFS and ORR comparable with bevacizumab/mFOLFOX6; interim analyses biomarker results revealed no significant PFS association. Post hoc final analyses demonstrated a potential difference in tivozanib-specific PFS in patients with low neuropilin-1 (NRP-1), but not in patients with high NRP-1. Tivozanib/mFOLFOX6 was tolerable and adverse events were comparable with both bevacizumab/mFOLFOX6 and previous tivozanib studies.

CONCLUSIONS

The efficacy of tivozanib/mFOLFOX6 was comparable with but not superior to bevacizumab/mFOLFOX6 in patients with previously untreated mCRC. Since data from the prespecified interim analysis did not demonstrate superiority, this resulted in discontinuation of the study. The safety and tolerability profile of tivozanib/mFOLFOX6 was consistent with other tivozanib trials. NRP-1 is a potential predictive biomarker for tivozanib activity, but these results require further validation. Clin Cancer Res; 22(20); 5058-67. ©2016 AACR.

The Best. First. Anti-EGFR before anti-VEGF, in the first-line treatment of RAS wild-type metastatic colorectal cancer: From bench to bedside. Cancer Chemother Pharmacol. 2016;78:233-244. [PMID: 27091467 DOI: 10.1007/s00280-016-3032-8]

BACKGROUND

Since 2013, informative trials exploring the optimal use of available biologic agents in the first-line setting of metastatic colorectal cancer (mCRC) have been presented. These trials have opened a stimulating debate on the biological effect that first-line therapies may have on subsequent lines of treatment even long after the first-line progression.

MATERIALS AND METHODS

We reviewed available preclinical and clinical data on the effect of different sequences of the biological drugs approved for use in mCRC patients. The importance of molecular selection of patients based on RAS mutational status and toxicity and quality-of-life issues were also analyzed.

RESULTS

Convincing evidence exists on the optimal therapeutic effect obtained by using anti-EGFR agents in first-line treatment before anti-VEGF agents. On the contrary, up-front anti-VEGF agents' use seems to determine biological changes that increase the risk of acquired resistance to subsequent EGFR inhibitors. This hypothesis is confirmed by the scarce evidence of EGFR inhibitor activity in second-line treatment. Such a therapeutic optimum is subject to a fine molecular selection based on RAS mutational status.

CONCLUSION

There is accumulating evidence suggesting that, after precise and well-established molecular selection, anti-EGFR agents deliver their maximum efficacy in mCRC patients when given early in the treatment strategy. Their toxicity profile seems manageable under the supervision of experienced physicians. Large randomized trials prospectively confirming the impact of different sequencing strategies are eagerly awaited.

90Y Radioembolization of Colorectal Hepatic Metastases Using Glass Microspheres: Safety and Survival Outcomes from a 531-Patient Multicenter Study

Hepatic metastases of colorectal carcinoma are a leading cause of cancer-related mortality. Most colorectal liver metastases become refractory to chemotherapy and biologic agents, at which point the median overall survival declines to 4-5 mo. Radioembolization with (90)Y has been used in the salvage setting with favorable outcomes. This study reports the survival and safety outcomes of 531 patients treated with glass-based (90)Y microspheres at 8 institutions, making it the largest (90)Y study for patients with colorectal liver metastases.

METHODS

Data were retrospectively compiled from 8 institutions for all (90)Y glass microsphere treatments for colorectal liver metastases. Exposure to chemotherapeutic or biologic agents, prior liver therapies, biochemical parameters before and after treatment, radiation dosimetry, and complications were recorded. Uni- and multivariate analyses for predictors of survival were performed. Survival outcomes and clinical or biochemical adverse events were recorded.

RESULTS

In total, 531 patients received (90)Y radioembolization for colorectal liver metastases. The most common clinical adverse events were fatigue (55%), abdominal pain (34%), and nausea (19%). Grade 3 or 4 hyperbilirubinemia occurred in 13% of patients at any time. The median overall survival from the first (90)Y treatment was 10.6 mo (95% confidence interval, 8.8-12.4). Performance status, no more than 25% tumor burden, no extrahepatic metastases, albumin greater than 3 g/dL, and receipt of no more than 2 chemotherapeutic agents independently predicted better survival outcomes.

CONCLUSION

This multiinstitutional review of a large cohort of patients with colorectal liver metastases treated with (90)Y radioembolization using glass microspheres has demonstrated promising survival outcomes with low toxicity and low side effects. The outcomes were reproducible and consistent with prior reports of radioembolization.

Maintenance strategy in metastatic colorectal cancer: A systematic review

PURPOSE

Colorectal cancer is the third most common cancer in men and second in women, estimated to cause 694,000 deaths worldwide in 2012. Although 5-year survival rate of CRC has increased, inoperable metastatic colorectal cancer (mCRC) is almost always fatal. The aim of this systematic review is to outline the maintenance strategies that increase the chance and duration of survival with less toxicity and sustained quality of life.

DESIGN

Literature search in PubMed, in American Society of Clinical Oncology (ASCO) Annual Meetings and in ASCO Gastrointestinal Symposia and European Society for Medical Oncology (ESMO) Congresses was performed. Studies conducted in adult patients were written in English language and were published in peer-reviewed journals as phase II or III randomized controlled trials (RCTs) comparing continuous chemotherapy to intermittent chemotherapy, each with or without maintenance therapy was included along with at least one of the outcomes of interest.

RESULTS

Twenty randomized controlled trials and systematic reviews were included from Medline search, together with 4 abstracts from ASCO meetings and 2 abstracts from ESMO meetings.

CONCLUSION

Existing evidence-based data show that prolonged progression free survival (PFS) can be achieved with less toxic regimens compared to complete drug holidays or continued treatment. However, the impact of maintenance on overall survival is less clear. The specific data for maintenance with biological agents are evolving, while in general fluoropyrimidine based maintenance with bevacizumab is better than Bev alone or observation for PFS. Data regarding Cetuximab maintenance are less pronounced than that of Bev maintenance. Preliminary data show that erlotinib-Bev combination may be of benefit as maintenance. Although maintenance may provide significant clinical benefit in clinical studies, the optimal strategy should still be individualized.

Recent Therapeutic Advances in the Treatment of Colorectal Cancer

Metastatic colorectal cancer is a prevalent disease for which novel targeted therapies and biologically based combinations are under development. Cytotoxic chemotherapy doublets (FOLFOX, FOLFIRI) and triplets (FOLFOXIRI) in combination with biologics are standard regimens, and efforts are ongoing to delineate the optimal sequence for each patient based on unique underlying tumor biology. Molecular profiling of metastatic colorectal cancer (including mutational analysis for KRAS, NRAS, BRAF, PIK3CA, and others) has become increasingly important for identification of prognostic and predictive biomarkers, as well as for insights into the biology that drives the tumor. Large comprehensive analyses such as that of The Cancer Genome Atlas have provided important clues into carcinogenesis and discerned potentially druggable targets for metastatic colorectal cancer. Novel therapeutic agents currently under investigation for subtypes of this disease include immunotherapies such as anti–programmed cell death receptor antibody, cancer stem cell inhibitors, targeted combinations such as BRAF and PI3K inhibitors, and the anti-RAS reovirus Reolysin®.