Tumor Sidedness and Enriched Gene Groups for Efficacy of First-line Cetuximab Treatment in Metastatic Colorectal Cancer

Longitudinal change of genetic variations in cetuximab-treated metastatic colorectal cancer

Recurrent gene mutations and copy number alterations in cancer patients are presumably associated with resistance to targeted therapy. In the present study, we assessed the gene mutations and copy number alterations that recurrently occurred in cetuximab-treated patients with metastatic colorectal cancer (mCRC). Targeted next-generation sequencing was performed in the tumor samples obtained pre- and postcetuximab treatment to assess the variations that occurred during cetuximab treatment. Moreover, we identified the emergent gene mutations (CDK6, EPHA3, ERCC2, MYC, PCMTD1, PIK3CA, PRIM2, RICTOR, and ZNRF3) and copy number alterations (ARAF, BCL2, BRCA2, EGFR, MYC, and SMAD4) that were recurrently observed only in postprogression samples and not in pretreatment or posttreatment samples from patients revealing clinical response. Furthermore, to identify the feasible candidate variations implicated in treatment resistance, we examined the variants with clonal expansion during treatment and discovered PCBP1 as a variant associated with posttreatment progression. Various recurrent mutations were enriched in the TGF-beta signaling pathway. Collectively, we identified recurrent variations in mCRC samples exhibiting post-cetuximab progression. Additionally, future studies are required to evaluate the therapeutic potential of these variations.

Clinical Impact of Primary Tumor Location in Metastatic Colorectal Cancer Patients Under Later-Line Regorafenib or Trifluridine/Tipiracil Treatment

Background

Primary tumor location (PTL) is an important prognostic and predictive factor in the first-line treatment of metastatic colorectal cancer (mCRC). Although regorafenib (REG) and trifluridine/tipiracil (FTD/TPI) have been introduced recently, the clinical impact of PTL in these treatments is not well understood.

Materials and Methods

We retrospectively evaluated patients with mCRC who were registered in a multicenter observational study (the REGOTAS study). The main inclusion criteria were Eastern Cooperative Oncology Group performance status (ECOG PS) of 0-2, refractory or intolerant to fluoropyrimidines, oxaliplatin, irinotecan, angiogenesis inhibitors, anti-epidermal growth factor receptor therapy (if RAS wild-type), and no prior use of REG and FTD/TPI. The impact of PTL on overall survival (OS) was evaluated using Cox proportional hazard models based on baseline characteristics.

Results

A total of 550 patients (223 patients in the REG group and 327 patients in the FTD/TPI group) were included in this study, with 122 patients with right-sided tumors and 428 patients with left-sided tumors. Although the right-sided patients had significantly shorter OS compared with the left-sided patients by univariate analysis (p = 0.041), a multivariate analysis revealed that PTL was not an independent prognostic factor (hazard ratio, 0.95; p = 0.64). In a subgroup analysis, the OS was comparable between the REG and FTD/TPI groups regardless of PTL (p for interactions = 0.60).

Conclusions

In the present study, PTL is not a prognostic and predictive factor in patients with mCRC under later-line REG or FTD/TPI therapy.