The aim of this study is to recruit 50 rectal cancer patients planned to receive standard radiochemotherapy. A baseline ultrasonic elastography is performed prior to radiochemotherapy and followed by re-scans two and six weeks after initiation of treatment. The objective quantitative elastography findings are compared with the TRG score.

The purpose is to elucidate ultrasonic elastography's ability to predict treatment response at an early stage by comparing quantitative ultrasound parameters before, during and after treatment with MR scan results and histopathological Tumor Regression Grade (TRG score) after operation.

Inclusion Criteria:

1. Patients with biopsy verified adenocarcinoma in the rectum ≤ 10 cm from the anal verge.
2. T3/4 tumor assessed by transrectal ultrasound and MR, and CRMMR < 5 mm.
3. Life expectancy of more than 3 months.
4. Age ≥18 years.
5. Performance status ≤ 2 according to WHO.
6. Patient able to observe protocol guidelines.
7. Signed informed consent.

Exclusion Criteria:

1. Previous radiation treatment for the pelvis.
2. Known distant metastases.
3. Serious disease contraindicating treatment, including cardiovascular disease.
4. Other malignant disease apart from curativly treated non-melanotic skin cancer and previously treated carcinoma in situ cervicis uteri.
5. Pacemaker
6. other disease making the patient unfit for study participation as assessed by investigator

Rectal cancer patients planned for preoperative chemoradiation at the Dept. of Oncology, Vejle Hospital, Denmark.