A prospective study investigating the efficacy and toxicity of definitive ChemoRadiation and ImmunOtherapy (CRIO) in locally and/or regionally advanced unresectable cutaneous squamous cell carcinoma

Background Patients with unresectable advanced cutaneous squamous cell carcinoma (cSCC) are generally treated with palliative intent. Immune checkpoint blockade has significant activity in the palliative setting in patients with recurrent or metastatic cSCC. This single arm phase 2 prospective study aims to investigate the combination of curative intent chemoradiation and durvalumab (anti-PD-L1 checkpoint inhibitor) for this patient cohort. Methods Patients with unresectable locally and or regionally advanced pathologically confirmed cSCC (stage III-IVa) deemed fit for CRIO by consensus of the Multidisciplinary meeting will be eligible. In the first stage of a two-stage minimax design, we aim to recruit a total of 15 patients. If fewer than 7 patients achieved a complete response in the first stage, we will conclude the treatment is not more effective than standard treatment. The co-primary endpoints of CRIO are the safety of treatment (acute and late toxicities) and the rate of complete response. Secondary endpoints would include overall survival, progression free survival, and locoregional control. Translational research endpoints including biomarkers (CD73, CD39, PD-1, PD-L1) will also be explored utilising multiplex immunohistochemistry on tumour biopsy samples obtained prior to commencing treatment and during treatment (week 2). In addition, the utility of CXCR-4 PET/CT scan will be explored. Discussion CRIO is a novel trial evaluating the combination of curative intent chemoradiotherapy with concurrent and adjuvant durvalumab for patients with unresectable stage III-IVa cSCC. Trial registration: Trial registered with the Australian New Zealand Clinical Trial Registry (ACTRN12618001573246)