Hyperthermia with Chemoradiotherapy in Rectal Cancer

The goal of this clinical trial is to evaluate the efficacy of deep regional hyperthermia in the context of radiochemotherapy followed by consolidation chemotherapy in locally advanced rectal cancer. Questions it aims to answer are: * Can surgery be avoided if the tumor completely regresses? * How high is the Local re-growth rate * Is the treatment safe? * Assessment of the Quality of life * Rate of sphincter-sparing surgery * Pathological staging, tumor downstaging * Assessment of continence during the course of therapy Participants will: Undergo radiochemotherapy with or without addition of hyperthermia (50:50 randomisation) followed by standard consolidation chemotherapy. After treatment response evaluation surgery or non-operative management takes place.