Watch and Wait as Treatment for Patients With Rectal Cancer

Inclusion Criteria: All patients in Sweden with a palpable rectal cancer staged as cT4bNX/anycTanycN and cMRF+/anycTanycN and lateral lymph nodes on MRI considered appropriate for 5x5 Gy and 6-8 weeks of wait prior to surgery according to Stockholm III (28) or a palpable rectal cancer staged as cT4bNX/anycTanycN and cMRF+/anycTanycN and lateral lymph nodes on MRI a planned schedule for CRT according to the Swedish National Program for rectal cancer scheduled for neoadjuvant therapy are possible to include. The study includes two parts, where part one is optional in including hospitals. The aim of the biopsy substudy to identify tumour and plasma markers for complete response, thus all patients that will receive (chemo)radiotherapy in the neoadjuvant setting are included to provide a control for the biopsies. For the WoW part of the study all patients that achieve complete response after neoadjuvant treatment according to the specified criteria above can be included in the Watch and Wait protocol. In detail this includes patients with: Midrectal or low rectal cancers that are palpable and considered with an indication of 5x5 Gy and long wait (6-8 weeks) (the indication for waiting may be logistics, co-morbidity, advanced age): * cT4bNX * anycTanycN and cMRF+ anycTanycN and lateral lymph nodes on MRI Exclusion Criteria: * No informed consent received for participation. * Patients with rectal cancer that is scheduled for (chemo) radiotherapy but is not palpable during rectal examination (10-15 cm) as this cannot be examined by digital examination and followed as scheduled. * Contraindication for MRI such as presence of non compatible metallic implants or claustrophobia.