Impact of Genetics on Neoadjuvant Therapy with Complete Pathological Response in Metastatic Colorectal Cancer: Case Report and Review of the Literature.

Treatment of colorectal metastatic cancer is still challenging, despite recent improvements in chemotherapy. A genetic cancer profile, such as the KRAS (Kirsten rat sarcoma) gene status, plays a key role in individualized tailored therapy. Molecular targeted therapy added to neo-adjuvant chemotherapy can achieve a better pathological response and prolong survival. Pathological complete response of colorectal cancer stage IV is rare. A 47-year-old female patient presented with rectal adenocarcinoma and three liver metastases (cT3d/4, N2, Ml). After seven cycles of Bevacizumab and CAPOX in neoadjuvant setting, we noted more than 70.0% regression of metastases and complete regression of the primary tumor. We performed low anterior resection of rectum and synchronous subsegmental resection of S3, because the other two lesions were not detectable. Pathology revealed complete response of the primary and also secondary tumors. After 8 months, diagnostic tests did not show any sign of recurrence and the remaining liver lesions disappeared. Colorectal cancer is a heterogeneous disease and it is necessary to identify patients who are at-risk of recurrence and suitable for neoadjuvant therapy. Genetic biomarkers play an important role in metastatic colorectal cancer treatment. Because of the mutated KRAS gene, Bevacizumab was added to cytotoxic therapy achieving a complete pathological response of primary tumor and metastasis. This case is unique because all reported cases with similar results, described staged surgery and one of reverse staged surgery, but with similar results. This neoadjuvant therapy has extraordinary results for colorectal cancer stage IV and can help disease-free and long-term survival.