Emergence of KRAS-mutation in liver metastases after an anti-EGFR treatment in patient with colorectal cancer: Are we aware of the therapeutic impact of intratumor heterogeneity?

Tumors represent a dynamic system where the genomic plasticity permits to adapt to the perturbation induced by environmental pressures, supporting the importance of longitudinal tumor sampling strategies to deciphering the temporal acquisition of driver event that could impact treatment outcome. We describe the case of a metastatic colorectal cancer (mCRC) patient, RAS wild-type, who responded to anti-EGFR therapy and underwent liver surgery, revealing a KRAS mutations in the metastatic lesion, not detectable prior to initiation of therapy in the colonic biopsy. After liver surgery, the patient received chemotherapy alone, then underwent left colectomy and the final pathological report confirmed the KRAS wild-type status. We can speculate the existence of two distinct populations of KRAS wild-type and mutant CRC cells sharing the same genetic origin. The anti-EGFR treatment represented a selective pressure which allowed the selection of KRAS mutant subclones. The prognostic and /or predictive role of intratumor heterogeneity has not been assessed prospectively. Our case report is of clinical relevance because patients with mCRC who respond to anti-EGFR antibodies often develop resistance within several months of initiating therapy, thus outlining the importance to better ascertain the molecular landscape of tumors to design better therapeutic strategies.

Estimating 12-week death probability in patients with refractory metastatic colorectal cancer: the Colon Life nomogram.

Background: Regorafenib and TAS-102 have recently demonstrated statistically significant survival gains in patients with refractory metastatic colorectal cancer (mCRC). Life expectancy ≥12 weeks was an inclusion criterion in registrative trials, and the identification of proper clinical selection tools for the daily use of these drugs in heavily pre-treated patients is needed to improve the cost-benefit ratio. We aimed at building a nomogram able to predict death probability within 12 weeks from the date of assessment of refractory mCRC. Patients and methods: Four hundred eleven refractory mCRC patients with ECOG performance status (PS) ≤2 receiving regorafenib, TAS-102 or other treatments were used as developing set. Putative prognostic variables were selected using a random forest model and included in a binary logistic model from which the nomogram was developed. The nomogram was externally validated and its performance was evaluated by examining calibration (how close predictions were to the actual outcome) and discriminative ability (Harrell C index) both on developing (internal validation) and validating (external validation) sets. Results: Four variables were selected and included in the nomogram: PS (P < 0.0001), primary tumor resection (P = 0.027), LDH value (P = 0.0001) and peritoneal involvement (P = 0.081). In the developing set, the nomogram discriminative ability was high (C = 0.778), and was confirmed in the validating set (C = 0.778), where the overall outcome was better as a consequence of the enrichment in patients receiving regorafenib or TAS-102 (46% versus 34%; P < 0.0001). Conclusions: Our nomogram may be a useful tool to predict the probability of death within 12 weeks in patients with refractory mCRC. Based on four easy-to-collect variables, the 'Colon Life' nomogram and free app for smartphones may improve mCRC patients' selection for later-line therapies and assist researchers for the enrollment in clinical trials in this setting.