Investigating the role of interim Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI) and blood markers to predict local and regional failure in patients with anal squamous cell carcinoma.

Interventions: FDG-PET, Biomarker testing with optional MRI will be administered to participants eligible and consenting to this study.
Patients will receive 5-6 weeks of CRT depending on their staging.
FDG- PET scans will be performed at 3 timepoints for all patients. PETpre is to be completed prior to commencement of CRT, PETinterim during the second week of CRT and PETpost at 3 months post CRT. If the PETpost at 3 months post-treatment FDG-PET reveals a partial response, and the patient does not have clinically progressive disease, a 4th FDG-PET (PETprogress) will be performed at 5 months after completion of CRT.
The scans will be performed in the Nuclear Medicine department at Liverpool Hospital on a digital PET scanner (GE Healthcare, Discovery MI) in 3D mode for a total acquisition time of 1.5 – 2.5 min per bed position, adjusted according to the patient weight, from mid brain to proximal femora at about 1 hour post injection of a radiotracer called fluorodeoxyglucose (3.4 MBq/Kg). PET images will be reconstructed using GE VUE Point FX (Time of Flight) algorithm into a 256 x 256 matrix size with a slice thickness of 3.75 to 4.0 mm, and GE Q.Clear iterative reconstruction and if required Q-static motion-corrected respiratory gated algorithm for measurement of SUV and other volumetric parameters. Transmission scans and attenuation corrections will be obtained by using a 128-slice CT, using helical mode without the use of a contrast medium. CT images are to be acquired at 3.75 to 5mm slice thickness and reconstructed to a transaxial matrix size of 512 x 512. The current (30-40 mAs) and voltage (120-140 kV) are varied according to the patient weight. All FDG PET images will be analysed by the consensus reading of a nuclear medicine physician and a radiation oncologist.
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Primary outcome(s): Locoregional failure will be assessed by using FDG PET, MRI imaging and HPV ctDNA biomarker testing.[ 6 months post chemoradiation treatment];MTV 2.5 will be assessed using FDG-PET imaging.[ 2 weeks during chemoradiation treatment, 3 and 6 months post chemoradiation treatment];Diffusion weighted images with B values 50, 400 and 800 will be assessed using MRI[ 2 weeks during Chemoradiation treatment]
Study Design: Purpose: Diagnosis; Allocation: Non-randomised trial; Masking: Open (masking not used);Assignment: Single group;Type of endpoint: Efficacy