Neoadjuvant chemoradiotherapy for patients with unresectable radically locally advanced colon cancer: a potential improvement to overall survival and decrease to multivisceral resection.

BACKGROUND: The management of unresectable locally advanced colon cancer (LACC) remains controversial, as resection is not feasible. The goal of this study was to evaluate the treatment outcomes and toxicity of neoadjuvant chemoradiotherapy (NACRT) followed with surgery and adjuvant chemotherapy in patients with unresectable radically LACC. METHODS: We included patients who were diagnosed at our institution, 2010-2018. The neoadjuvant regimen consisted of radiotherapy and capecitabine/ 5-fluorouracil-based chemotherapy. RESULTS: One hundred patients were identified. The median follow-up time was 32 months. The R0 resection rate, adjusted nonmultivisceral resection rate and bladder preservation rate were 83.0, 43.0 and 83.3%, respectively. The pCR and clinical-downstaging rates were 18, and 81.0%%, respectively. The 3-year PFS and OS rates for all patients were 68.6 and 82.1%, respectively. Seventeen patients developed grade 3-4 myelosuppression, which was the most common adverse event observed after NACRT. Tumor perforation occurred in 3 patients during NACRT. The incidence of grade 3-4 surgery-related complications was 7.0%. Postoperative anastomotic leakage was observed in 3 patients. CONCLUSIONS: NACRT followed by surgery was feasible and safe for selected patients with LACC, and can be used as a conversion treatment to achieve satisfactory downstaging, long-term survival and quality of life, with acceptable toxicities.

Targeting Myeloid-derived Suppressor Cells and Programmed Death Ligand 1 Confers Therapeutic Advantage of Ablative Hypofractionated Radiation Therapy Compared With Conventional Fractionated Radiation Therapy.

PURPOSE: Ablative hypofractionated radiation therapy (AHFRT) presents a therapeutic advantage compared with conventional fractionated radiation therapy (CFRT) for primary and oligometastatic cancers. However, the underlying mechanisms remain largely unknown. In the present study, we compared the immune alterations in response to AHFRT versus CFRT and examined the significance of immune regulations contributing to the efficacy of AHFRT. METHODS AND MATERIALS: We established subcutaneous tumors using syngeneic lung cancer and melanoma cells in both immunocompetent and immunocompromised mice and treated them with AHFRT and CFRT under the same biologically equivalent dose. RESULTS: Compared with CFRT, AHFRT significantly inhibited tumor growth in immunocompetent, but not immunocompromised, mice. On the cellular level, AHFRT reduced the recruitment of myeloid-derived suppressor cells (MDSCs) into tumors and decreased the expression of programmed death-ligand 1 (PD-L1) on those cells, which unlashed the cytotoxicity of CD8+ T cells. Through the downregulation of vascular endothelial growth factor (VEGF), AHFRT inhibited VEGF/VEGF receptor signaling, which was essential for MDSC recruitment. When combined with anti-PD-L1 antibody, AHFRT presented with greater efficacy in controlling tumor growth and improving mouse survival. By altering immune regulation, AHFRT, but not CFRT, significantly delayed the growth of secondary tumors implanted outside the irradiation field. CONCLUSIONS: Targeting MDSC recruitment and enhancing antitumor immunity are crucial for the therapeutic efficacy of AHFRT. When combined with anti-PD-L1 immunotherapy, AHFRT was more potent for cancer treatment.