Precision Oncology in Gastrointestinal and Colorectal Cancer Surgery

Precision medicine is used to treat gastrointestinal malignancies including esophageal, gastric, small bowel, colorectal, and pancreatic cancers. Cutting-edge assays to detect and treat these cancers are active areas of research and will soon become standard of care. Colorectal cancer is a prime example of precision oncology as disease site is no longer the final determinate of treatment. Here, the authors describe how leveraging an understanding of tumor biology translates to individualized patient care using evidence-based practices.

Current advances in targeted therapy for metastatic colorectal cancer - Clinical translation and future directions

The last two decades have witnessed major breakthroughs in the development of targeted therapy for patients with metastatic colorectal cancer (mCRC), an achievement which stems largely from advances in translational research. Precision medicine is now widely practiced in routine oncological care, where systemic therapy is individualized based on clinical factors such as primary tumor sidedness, location and number of metastases, as well as molecular factors such as the RAS and BRAF mutation status, mismatch repair / microsatellite status and presence of other actionable genomic alterations in the tumor. The optimal selection of patients with RAS and BRAF-wild type (WT), left-sided primary tumor for treatment with epidermal growth factor receptor (EGFR) and chemotherapy (chemo) has markedly improved survival in the first-line setting. The pivotal trials of cetuximab in combination with BRAF/ MEK inhibitor for BRAF V600E mutant mCRC, and panitumumab with KRAS G12C inhibitor in KRAS(G12C)-mutant mCRC have been practice-changing. Anti-HER2 small molecular inhibitor, antibodies and antibody-drug conjugates have significantly improved the treatment outcome of patients with HER2 amplified mCRC. Anti-angiogenesis agents are now used across all lines of treatment and novel combinations with immune-checkpoint inhibitors are under active investigation in MSS mCRC. The non-invasive monitoring of molecular resistance to targeted therapies using Next Generation Sequencing analysis of circulating tumor-derived DNA (ctDNA) and captured sequencing of tumors have improved patient selection for targeted therapies. This review will focus on how latest advances, challenges and future directions in the development of targeted therapies in mCRC.

Efficacy of different maintenance strategies for RAS wild-type colorectal cancer: A network meta-analysis

INTRODUCTION

In metastatic RAS wild-type colorectal cancer (CRC), induction combination chemotherapy doublets (CT) with an anti-EGFR agent are considered the primary treatment. We performed a network meta-analysis (NMA) to compare the relative efficacy of different maintenance treatments for advanced RAS wild-type CRC.

MATERIALS AND METHODS

PubMed, EMBASE and Cochrane, from database inception until December 2021 were used. Randomized clinical trials enrolling adults with advanced RAS wild-type CRC and providing overall survival (OS) and/or progression-free survival (PFS) data PRISMA guidelines for NMA were followed. Between-group comparisons were estimated using hazard ratios (HRs) with 95% credible intervals (95% CrIs). Agents were ranked using surface under the cumulative ranking (SUCRA) probabilities.

RESULTS

A total of 7 randomized phase 2 trials were included (for a total of 1286 patients). Compared to depotentiation treatments, continuous CT + anti-EGFR was not significantly superior to other maintenance regimens for OS and was ranked as the best option for NMA (SUCRA p-score=0.69). Conversely, in the PFS analysis, single-agent fluoropyrimidines + anti-EGFR was ranked as the best treatment (SUCRA p-score=0.60).

CONCLUSIONS

Maintaining chemotherapy doublet + anti-EGFR until progression appears to be the best first-line strategy in terms of OS for advanced unresectable RAS wild-type mCRC treatment. However, fluoropyrimidines single-agent + cetuximab or panitumumab represent a reasonable choice regarding PFS.

Maintenance strategies after anti-EGFR-based induction in metastatic colorectal cancer: A systematic review and bayesian network meta-analysis

BACKGROUND

In RAS wild type (wt) metastatic colorectal cancer (mCRC) maintenance therapy after induction with fluoropyrimidine (FP)-based cytotoxic therapy (CT) plus anti-EGFR agents is controversial.

METHODS

Phase II-III randomized trials were included. Maintenance strategies considered were: observation, anti-EGFR or FP monotherapy, FP + anti-EGFR, doublet CT + anti-EGFR.

RESULTS

Maintenance with FP + anti-EGFR (HR 0.56, 95% CrI 0.36-0.89) showed the greatest PFS benefit compared to observation, ranking first on SUCRA analysis (96.4%). Considering OS, doublet CT+ anti-EGFR, FP + anti-EGFR and anti-EGFR monotherapy yielded similar results. For PFS, FP + anti-EGFR confirmed to be valuable in BRAF wt patients and left sided tumors. In left sided tumors, the OS benefit of adding CT was limited. FP plus anti-EGFR showed a favourable safety profile compared to doublet CT + anti-EGFR.

CONCLUSIONS

FP + anti-EGFR can be considered a valuable maintenance option in RAS wt mCRC. EGFR monotherapy can be considered, especially in left-sided tumors.

Maintenance therapy with Fluoropyrimidine and cetuximab or bevacizumab after first line FOLFOX-chemotherapy in metastatic colorectal cancer according to RAS or BRAFV600E mutation status

PURPOSE

Fluoropyrimidine (FP) with oxaliplatin-based chemotherapy is the standard first-line treatment for metastatic colorectal cancer (mCRC); however, oxaliplatin-induced neuropathy critically affects the quality of life of patients. Maintenance strategies with FP plus bevacizumab have been well-established; nonetheless, the real-world outcomes of maintenance therapy with FP and cetuximab are unclear. We investigated the clinical outcomes of patients who underwent maintenance therapy with cetuximab.

METHODS

We retrospectively identified and analyzed patients with mCRC who were treated between 2012 and 2021 with first-line oxaliplatin-based induction chemotherapy (IC) plus biologic agents (either cetuximab or bevacizumab), and underwent maintenance therapy (IC regimen without oxaliplatin) after IC.

RESULTS

In total, 19 patients who were treated with mFOLFOX6 (FP/leucovorin/oxaliplatin) with cetuximab, and 26 patients who were treated with mFOLFOX6 with bevacizumab were included. In the cetuximab group, all patients were KRAS-, NRAS-, and BRAF-wild type, whereas most patients in the bevacizumab group harbored KRAS or BRAFV600E or NRAS mutants. During the maintenance treatment, seven patients (four [21%] in the cetuximab group and three [11%] in the bevacizumab group) achieved partial response after achieving nadir during induction chemotherapy. The disease control rates of maintenance therapy were 79% and 74% in the cetuximab and bevacizumab groups, respectively. The median progression-free survival of maintenance therapy and overall survival was 5.98 months and 32.4 months in the cetuximab group, and 4.83 months and 25.6 months in the bevacizumab group, respectively.

CONCLUSIONS

Maintenance therapy with FP plus biologic agents (either bevacizumab or cetuximab) is a feasible strategy for appropriate mCRC patients according to their RAS/BRAF status. Further large-scale randomized studies are needed to validate the efficacy of anti-epidermal growth factor receptor-based maintenance therapy.

New developments in targeted therapy for metastatic colorectal cancer

Colorectal cancer (CRC) is the second most lethal cancer worldwide and the prognosis of metastatic CRC (mCRC) remains poor. Recent advancements in translational research have led to the identification of several new therapeutic targets and improved the treatment outcome of patients with tumours harbouring BRAF V600E mutation, (HER2) ErBB2 alterations, NTRK gene fusions and KRAS(G12C) mutation. Improved understanding towards the mechanism of resistance to targeted therapy such as anti-epidermal growth factor receptor antibodies and the evolving role of therapeutic monitoring with circulating tumour DNA (ctDNA) has enabled the longitudinal tracking of clonal evolution during treatment and the individualization of subsequent treatments. To broaden the community-based implementation of precision oncology in directing targeted therapies for patients with gastrointestinal cancers including mCRC, the feasibility of 'Master Protocols' that utilizes ctDNA-based genotyping platforms is currently being evaluated. Such protocols encompass both observational and interventional clinical trials of novel targeted therapies conducted within a large clinical trial network. In this review, we will discuss the latest developments in targeted therapies, and therapeutic strategies for overcoming acquired drug resistance in patients with mCRC.

Current concepts of anti-EGFR targeting in metastatic colorectal cancer

Anti-EGFR targeting is one of the key strategies in the treatment of metastatic colorectal cancer (mCRC). For almost two decades oncologists have struggled to implement EGFR antibodies in the mCRC continuum of care. Both sidedness and RAS mutational status rank high among the predictive factors for the clinical efficacy of EGFR inhibitors. A prospective phase III trial has recently confirmed that anti-EGFR targeting confers an overall survival benefit only in left sided RAS-wildtype tumors when given in first line. It is a matter of discussion if more clinical benefit can be reached by considering putative primary resistance mechanisms (e.g., HER2, BRAF, PIK3CA, etc.) at this early stage of treatment. The value of this procedure in daily routine clinical utility has not yet been clearly delineated. Re-exposure to EGFR antibodies becomes increasingly crucial in the disease journey of mCRC. Yet re- induction or re-challenge strategies have been problematic as they relied on mathematical models that described the timely decay of EGFR antibody resistant clones. The advent of liquid biopsy and the implementation of more accurate next-generation sequencing (NGS) based high throughput methods allows for tracing of EGFR resistant clones in real time. These displays the spatiotemporal heterogeneity of metastatic disease compared to the former standard radiographic assessment and re-biopsy. These techniques may move EGFR inhibition in mCRC into the area of precision medicine in order to apply EGFR antibodies with the increase or decrease of EGFR resistant clones. This review critically discusses established concepts of tackling the EGFR pathway in mCRC and provides insight into the growing field of liquid biopsy guided personalized approaches of EGFR inhibition in mCRC.

Panitumumab Plus Fluorouracil and Folinic Acid Versus Fluorouracil and Folinic Acid Alone as Maintenance Therapy in RAS Wild-Type Metastatic Colorectal Cancer: The Randomized PANAMA Trial (AIO KRK 0212)

PURPOSE

The randomized PANAMA trial investigated the efficacy of panitumumab (Pmab) when added to maintenance therapy with fluorouracil and folinic acid (FU/FA) in patients with RAS wild-type metastatic colorectal cancer.

METHODS

Following first-line induction therapy with six cycles of FU/FA and oxaliplatin plus Pmab, responding patients (stable disease or partial or complete remission) were randomly assigned (1:1, open-label) to maintenance treatment with either FU/FA plus Pmab or FU/FA alone. The primary objective was to demonstrate superiority of progression-free survival (PFS, time from random assignment until progression or death) in favor of FU/FA plus Pmab with a hazard ratio (HR) of 0.75, a power of 80%, and a significance level of 10%. Secondary end points included overall survival, objective response rate of maintenance therapy, and toxicity. Survival end points were analyzed by the Kaplan-Meier method and compared by log-rank test and Cox regressions. Dichotomous variables were compared by Fisher's exact test; odds ratios were indicated when appropriate. The trial is registered with ClinicalTrials.gov (NCT01991873).

RESULTS

Overall, 248 patients were randomly assigned and received maintenance therapy with either FU/FA plus Pmab (125 patients) or FU/FA alone (123 patients). At data cutoff, with 218 events (of 218 needed), PFS of maintenance therapy was significantly improved with FU/FA plus Pmab (8.8 months v 5.7 months; HR, 0.72; 80% CI, 0.60 to 0.85; P = .014). Overall survival (event rate 54%) numerically favored the FU/FA plus Pmab arm (28.7 months v 25.7 months; HR, 0.84; 95% CI, 0.60 to 1.18; P = .32). Objective response rates were 40.8% in patients receiving FU/FA plus Pmab versus 26.0% in patients receiving FU/FA alone (odds ratio, 1.96; 95% CI, 1.14 to 3.36; P = .02). The most frequent Common Terminology Criteria for Adverse Event grade ≥ 3 event during maintenance therapy was skin rash (7.2%).

CONCLUSION

In RAS wild-type metastatic colorectal cancer, maintenance therapy with FU/FA plus Pmab induced a significantly superior PFS compared with FU/FA alone. If active maintenance therapy is aspired following induction therapy with FU/FA and oxaliplatin plus Pmab, FU/FA plus Pmab appears to be the most favorable option.