The present invention provides a thermoplastic sheet for use in radiotherapy treatment, comprising a thermoplastic composition layer comprising a mixture of polycaprolactone and polyurethane, said layer is provided with an upper surface and a lower surface； and a support layer provided on at least one surface of the thermoplastic composition layer, said support layer comprises silicone, wherein the thickness of the thermoplastic composition layer is at most 2.2 mm.
