Successful cetuximab rechallenge in metastatic colorectal cancer: A case report

BACKGROUND

Metastatic colorectal cancer (mCRC) treatment has been evolving and increasingly driven by tumor biology and gene expression analysis. Rechallenge with epidermal growth factor receptor (EGFR) inhibitors (anti-EGFR) represents a promising strategy for patients with RAS wild-type (RAS-wt) mCRC and circulating tumor DNA has emerged as a potential selection strategy. Herein, we report the case of a RAS-wt mCRC patient who had a successful response to cetuximab rechallenge.

CASE SUMMARY

Our patient was diagnosed with stage IV RAS-wt, microsatellite-stable rectosigmoid junction adenocarcinoma. He was started on first-line treatment with FOLFIRI and cetuximab and achieved partial response, allowing for a left hepatectomy (R0), followed by post-operative chemotherapy and an anterior resection; progression-free survival (PFS) of 16 months was obtained. Due to hepatic and nodal relapse, second-line treatment with FOLFOX and bevacizumab was started with partial response; metastasectomy was performed (R0), achieving a PFS of 11 months. After a 15 months anti-EGFR-free interval, FOLFIRI and cetuximab were reintroduced upon disease progression, again with partial response and a PFS of 16 months. Following extensive hepatic relapse, cetuximab was reintroduced and a marked clinical and analytical improvement was seen, after only one cycle. RAS-wt status was confirmed on circulating tumor DNA. The patient’s overall survival exceeded 5 years.

CONCLUSION

Our case provides real-world data to support cetuximab rechallenge in later lines of RAS-wt mCRC treatment.

Emerging role of liquid biopsy in rat sarcoma virus mutated metastatic colorectal cancer: A case report

BACKGROUND

In patients with metastatic colorectal cancer (mCRC), the treatment options are limited and have been proved to be affected by rat sarcoma virus (RAS) mutational status. In RAS wild-type (wt) patients, the combination of anti-epidermal growth factor receptor (EGFR) monoclonal antibodies with chemotherapy (CT) is more effective than CT alone. On the other hand, RAS-mutated patients are not eligible for treatment with anti-EGFR antibodies.

CASE SUMMARY

Eleven patients with initially RAS-mutated mCRC were followed from diagnosis to May 2022. At the time of cell-free DNA determination, five patients had undergone one CT line, five patients had undergone two CT lines, and one patient had undergone three CT lines (all in combination with bevacizumab). At the second and third treatment lines [second line (2L), third line (3L)], patients with neo-RAS wt received a combination of CT and cetuximab. In neo-RAS wt patients treated with anti-EGFR, our findings indicated an increase in progression-free survival for both 2L and 3L (14.5 mo, P = 0.119 and 3.9 mo, P = 0.882, respectively). Regarding 2L overall survival, we registered a slight increase in neo-RAS wt patients treated with anti-EGFR (33.6 mo vs 32.4 mo, P = 0.385). At data cut-off, two patients were still alive: A RAS-mutated patient undergoing 3L treatment and a neo-RAS wt patient who received 2L treatment with anti-EGFR (ongoing).

CONCLUSION

Our case series demonstrated that monitoring RAS mutations in mCRC by liquid biopsy may provide an additional treatment line for neo-RAS wt patients.

Occurence of RAS reversion in metastatic colorectal cancer patients treated with bevacizumab

Background: A disappearance of RAS mutations in the plasma of about 50% of mCRCs (metastatic colorectal cancers) treated with bevacizumab-based chemotherapy has been reported. Our aim was to evaluate the same issue at tissue level.

Materials and Methods: Using next-generation sequencing and real-time PCR approaches, we characterized the primary tumor (PT) and paired liver metastases in 28 RAS mutant mCRCs. Patients were subdivided into 3 treatment groups: 1) bevacizumab plus chemotherapy; 2) chemotherapy alone; 3) any systemic therapy (control group). In groups 1 and 2, liver metastases were resected after removal of PT and subsequent neoadjuvant systemic therapy.

Results: RAS mutant alleles are at the same percentage in PT and liver metastases in the control group, while a significant reduction of the level of RAS mutations was detected in 57.1% of cases in group 1 and in 8.3% of cases in group 2. Differences among groups are statistically significant (p = 0.038).

Conclusions: Most of mCRC patients treated with bevacizumab-containing regimens experience a strong reduction of RAS mutant cells, suggesting bevacizumab as particularly active against RAS mutant cells. This finding might have potential therapeutic implications, as anti-EGFR could be reconsidered in primarily RAS mutant patients reverted to a wild-type status after bevacizumab exposure.

Rechallenge with Anti-EGFR Therapy in Metastatic Colorectal Cancer (mCRC): Results from South Australia mCRC Registry

BACKGROUND

Anti-epidermal growth factor receptor (EGFR) monoclonal antibodies (cetuximab or panitumumab) are today increasingly used in the first- or second-line setting for RAS wild-type metastatic colorectal cancer (CRC) patients. Following progression beyond third- or fourth-line therapy, some patients are unsuitable for further chemotherapy because of poor performance status or patient choice. However, a significant number of patients are still candidates for further therapy despite limited standard options being available. The role of rechallenge with anti-EGFR therapy, particularly in patients who had previously responded, is often considered, but there is limited evidence in the literature to support such a strategy.

OBJECTIVE

This retrospective study aims to review the outcome of metastatic CRC patients who had anti-EGFR rechallenge.

PATIENTS AND METHODS

Patients who had been rechallenged with anti-EGFR therapy were identified from the South Australian metastatic CRC database. Patient characteristics were recorded and tumor response was retrospectively assessed using Response Evaluation Criteria in Solid Tumors (RECIST). Kaplan-Meier analysis was used to assess progression free survival (PFS) for each rechallenge and overall survival (OS).

RESULTS

Twenty-two patients were eligible for inclusion in this analysis. Disease control rate (stable disease and partial response) was 45.4% (ten patients) for patients who received rechallenge anti-EGFR. Seven patients received a second rechallenge and disease control rate was 28.6% (two patients). The median interval time between initial anti-EGFR therapy and rechallenge was 13.5 months. The median PFS after rechallenge 1 was 4.1 months and after rechallenge 2 was 3.5 months. The median OS was 7.7 months from date of rechallenge.

CONCLUSIONS

Anti-EGFR rechallenge provides clinical benefit in patients with RAS wild-type metastatic CRC.

The Evolving Biomarker Landscape for Treatment Selection in Metastatic Colorectal Cancer

The approval of targeted therapies for metastatic colorectal cancer (mCRC) has led to important improvements in patient outcomes. However, it is still necessary to increase individualisation of treatments based on tumour genetic profiles to optimise efficacy, while minimising toxicity. As such, there is currently great focus on the discovery and validation of further biomarkers in mCRC, with many new potential prognostic and predictive markers being identified alongside developments in patient molecular profiling technologies. Here, we review data for validated and emerging biomarkers impacting treatment strategies in mCRC. We completed a structured literature search of the PubMed database to identify relevant publications, limiting for English-language publications published between 1 January 2014 and 11 July 2018. In addition, we performed a manual search of the key general oncology and CRC-focused congresses to identify abstracts reporting emerging mCRC biomarker data, and of ClinicalTrials.gov to identify ongoing clinical trials investigating emerging biomarkers in mCRC and/or molecular-guided clinical trials. There is solid evidence supporting the use of BRAF status as a prognostic biomarker and DYPD, UGT1A1, RAS, and microsatellite instability as predictive biomarkers in mCRC. There are a number of emerging biomarkers that may prove to be clinically relevant in the future to have prognostic (HPP1 methylation), predictive (HER3, microRNAs, anti-angiogenic markers, and CRC intrinsic subtypes), or both prognostic and predictive values (HER2, CpG island methylator phenotype, tumour mutational load, gene fusions, and consensus molecular subtypes). As such, new biomarker-led treatment strategies in addition to anti-epidermal growth factor receptor and anti-angiogenetic treatments are being explored. Biomarkers that are not recommended to be tested in clinical practice or are unlikely to be imminently clinically relevant for mCRC include thymidylate transferase, ERCC1, PIK3CA, and PTEN. We highlight the clinical utility of existing and emerging biomarkers in mCRC and provide recommended treatment strategies according to the biomarker status. An update on ongoing molecular-guided clinical trials is also provided.