Hyperthermia With Chemoradiotherapy in Rectal Cancer

Inclusion Criteria:

* Male and female patients with histologically confirmed diagnosis of rectal cancer localized 0-12 cm from the anocutaneous line (i.e. lower and middle third of the rectum)
* Indication for total neoadjuvant therapy irrespective of participation in the current study.
* Any MRI staged rectal cancer with one of the following high-risk features:

  * cT4
  * cN2 (see Appendix)
  * Distance to mesorectal fascia 1mm or less.
  * Involved Lateral pelvic lymph nodes
  * EMVI (extramural venous invasion) positivity
* Staging requirements: High-resolution, thin-sliced (i.e. 3mm) magnetic resonance imaging (MRI) of the pelvis is the mandatory local staging procedure.
* Cross-sectional imaging of the abdomen and chest to exclude distant metastases.
* Aged at least 18 years. No upper age limit.
* WHO/ECOG Performance Status ≤ 1
* Adequate hematological, hepatic, renal and metabolic function parameters
* Informed consent of the patient

Exclusion Criteria:

* Lower border of the tumor localised more than 12 cm from the anocutaneous line as measured by rigid rectoscopy
* Tumors with microsatellite instability ("MSI-High Tumors") and the possibility for treatment with immune checkpoint inhibition.
* Contraindication for hyperthermia such as metal implants or pacemakers
* Distant metastases (to be excluded by CT scan of the thorax and abdomen)
* Preexisting fecal incontinence for solid stool
* Prior antineoplastic therapy for rectal cancer
* Prior radiotherapy of the pelvic region
* Major surgery within the last 4 weeks prior to inclusion
* Subject pregnant or breastfeeding, or planning to become pregnant within 6 months after the end of treatment
* Subject (male or female) is not willing to use highly effective methods of contraception (per institutional standard) during treatment and for 6 months (male or female) after the end of treatment (adequate: oral contraceptives, intrauterine device or barrier method in conjunction with spermicidal jelly)
* Other concomitant antineoplastic therapy
* Serious concurrent diseases, including neurologic or psychiatric disorders (incl. dementia and uncontrolled seizures), active, uncontrolled infections, active, disseminated coagulation disorder
* Clinically significant cardiovascular disease (incl. myocardial infarction, unstable angina, symptomatic congestive heart failure, serious uncontrolled cardiac arrhythmia) ≤ 6 months before enrolment
* Prior or concurrent malignancy ≤ 3 years prior to enrolment in study (Exception: non-melanoma skin cancer or cervical carcinoma FIGO stage 0-1), if the patient is continuously disease-free
* Known allergic reactions on study medication
* Known dihydropyrimidine dehydrogenase deficiency
* Psychological, familial, sociological or geographical conditions potentially hampering compliance with the study protocol and follow-up schedule (these conditions should be discussed with the patient before registration in the trial)