Targeting two radiation-induced immunosuppressive pathways to improve the efficacy of normofractionated radiation therapy in a preclinical colorectal cancer model.

PURPOSE: We have previously demonstrated in a murine colorectal cancer model that normofractionated RT (normoRT: 18 × 2 Gy) induced MDSC infiltration and PD-L1 expression, while hypofractionated RT (hypoRT: 3 × 8 Gy) induced Treg. Here, we wanted to assess whether the association of normoRT with treatments that target two radiation-induced immunosuppressive pathways (MDSC and PD-L1) could improve tumor control. MATERIALS AND METHODS: Subcutaneous tumors were induced using colon tumor cells (CT26) in immunocompetent mice (BALB/c) and were treated with RT alone (18 × 2 Gy or 3 × 8 Gy), or concomitantly with 5-Fluorouracil (5FU) (10 mg/kg) to deplete MDSC, and/or anti-PD-L1 (10 mg/kg). We assessed the impact of these combinations on tumor growth and immune cells infiltration by flow cytometry. In addition, we performed tumor rechallenge experiments and IFN-γ ELISpots to study the long-term memory response. RESULTS: Even though tumor growth was significantly delayed in the RT + 5FU compared to 5FU and untreated groups (p < .05), there was no significant difference between RT + 5FU (CRT) and RT alone. The rate of MDSC increased significantly 1 week after the end of normoRT (8.09% ± 1.03%, p < .05) and decreased with the addition of 5FU (3.39% ± 0.69%, p < .05). PD-L1 expressing tumor cells were increased after treatment. Adding anti-PD-L1 significantly delayed tumor growth, achieved the highest complete response rate, and induced a long-lasting protective specific anti-tumor immunity. CONCLUSIONS: These results tend to demonstrate the interest of inhibiting two radiation-induced immunosuppressive mechanisms. In patients, the combination of normoRT with 5FU is already the standard of care in locally advanced rectal cancer. Adding an anti-PD-L1 to this treatment could show promising results.

Definitive radio(chemo)therapy versus upfront surgery in the treatment of HPV-related localized or locally advanced oropharyngeal squamous cell carcinoma.

BACKGROUND: The treatment of stage I-III HPV+ oropharyngeal squamous cell carcinoma (HPV-OPSCC) is based on either surgery ± adjuvant therapy or exclusive radio±chemotherapy. We sought to compare these two therapeutic strategies in terms of efficacy, tolerance and quality of life (QoL). METHODS: Patients treated for stage I-III HPV-OPSCC from 2010 to 2021 in 3 academic centers were included and sorted according to the treatment strategy: surgery or exclusive radio±chemotherapy. Efficacy and tolerance were retrospectively assessed, and a transversal exploratory QoL assessment was performed using QoL instruments. RESULTS: A total of 83 patients were included, with 21 undergoing non-minimally invasive surgery and 62 receiving definitive radio-±chemotherapy. 2-year progression-free survival (PFS) and overall survival (OS) were respectively 80% and 86% in the surgical group and 92% and 95% in the non-surgical group, with no significant difference. At the end of treatment, 64.5% of patients presented with a grade III toxicity, without significant difference between the two groups. No patient had late grade III toxicity at 24 months. Forty-five patients (11 in the surgical group, 34 in the non-surgical group) participated in an exploratory quality-of-life analysis. Patients reported significantly more fatigue and loss of appetite after surgery, whereas patients in the radio±chemotherapy group described significantly more salivary and oral problems and difficulty swallowing, but the median time between treatment completion and the response to the questionnaires. CONCLUSION: There was no significant difference in efficacy, physician-reported toxicity and overall patient-reported quality of life was found between non-minimally invasive surgery and radio±chemotherapy in the treatment of stage I-III HPV-OPSCC.