The rectum is the 15 to 18 cm long straight end section of the large intestine that merges into the anus. Rectal cancer is a malignant tumour at this end of the large intestine

In contrast to the large intestine, the rectum is significantly shorter with a length of 15 to 18 cm. Its particular importance lies in the control of defecation, which is essentially coordinated by a complex sphincter apparatus. The incidence of rectal cancer in Germany is around 30 new cases per year and 100,000 inhabitants. This corresponds to around 25,000 new cases per year. The likelihood of developing the disease increases significantly from the age of 50. The average age of onset is in the 7th decade of life. While men and women are affected about equally often by colon carcinoma, men are more frequently affected by rectal carcinoma.

The following factors can favour the development of rectal carcinomas, but do not necessarily lead to the occurrence of a malignant tumour: High-calorie, high-fat, low-fibre diet, age over 50, chronic inflammatory bowel disease, hereditary cancer syndromes and a first-degree relative with colorectal carcinoma.

The first symptoms may be changes in bowel movements. Typical symptoms are bright red blood deposits and an increase in the frequency of bowel movements with a painful urge to defecate. If the tumour is located in the upper rectum, constipation and diarrhoea occur alternately. Pure mucus or blood discharge, very thin, so-called pencil stools and involuntary discharge of flatulence are already late symptoms and indicate an advanced stage of the disease. Sometimes sufferers also complain of pain in the sacrum area. Intestinal obstruction (ileus) only occurs at a very advanced stage of rectal cancer.

The medical history and a physical examination give the doctor initial indications of possible malignant tumours in the rectum.

Most rectal cancers can be felt with the finger (digitally). A digital rectal examination is therefore an essential part of cancer screening. Laboratory parameters such as the CEA (carcino-embryonic antigen) can be determined. Although this parameter is not tumour-specific, it is used to monitor progress. During a rectosigmoidoscopy (better known as a colonoscopy), the intestinal mucosa is examined with an endoscope. The endoscope is used to take tissue samples (biopsies) from suspicious changes in the mucous membrane, which are then analysed microscopically for possible cancer cells. The tissue layers can be examined for changes using an ultrasound probe that is inserted into the rectum. Possible cancerous growths in neighbouring organs such as the bladder, prostate or vagina can also be detected in this way.

Computed tomography (CT) or magnetic resonance imaging (MRI) can help to detect possible metastases and determine the local spread of the tumour. Tumour staging is necessary in order to select a suitable therapy. This involves dividing the tumour into different classes based on the examination findings. One common categorisation is the so-called TNM classification. This involves assessing tumour size, lymph node involvement and metastases.

T stands for the size and extent of the primary tumour, N stands for the number of affected regional lymph nodes and M stands for the occurrence and localisation of distant metastases (tumour metastases).

An exact assessment of the TNM stage is often only possible after tumour surgery.
Two further criteria are decisive for further therapy. Microscopic examination of the tumour tissue provides an indication of the malignancy of the tumour.
This involves comparing the similarity of the cancer cells with the organ cells (see table below).

On the other hand, it is of decisive importance whether the tumour could be completely removed.
The so-called R classification is used for this purpose (see table below).

The UICC classification is used for stage-appropriate therapy stratification of patients with colorectal cancer.

The particularly gentle and function-preserving surgical procedure of TME (total mesorectal excision) is performed at our clinic. The question of whether an artificial outlet needs to be created, either permanently or temporarily (as a "protective stoma"), depends on defined surgical rules, e.g. how advanced the tumour is and how close it is to the sphincter muscle. If an artificial bowel outlet cannot be avoided, we offer systematic counselling in advance (stoma therapy), which is continued after the operation.

Depending on the severity of the rectal cancer, additional chemotherapy or radiotherapy may be necessary in accordance with the recommendations of the German Cancer Society, the specifics of which are discussed in detail with our patients. This additional radiotherapy with simultaneous chemotherapy can be carried out before or after the operation. In principle, radiotherapy with concomitant chemotherapy is preferred before surgery. In the pre-operative situation, the radiation hits a tumour whose cells are more sensitive to radiation due to the lack of scarring. In comparison with post-operative radiotherapy, local tumour control can therefore be increased with the same or even lower dose. The use of preoperative radiotherapy remains indispensable for primarily non-resectable carcinomas. The aim of radiotherapy is to reduce tumour cells as far as possible in order to facilitate resection in the sense of microscopically complete tumour removal after tumour reduction ("downstaging"). In recent years, the introduction of special positioning techniques and radiotherapy planning techniques has reduced the rate of side effects. For example, positioning the patient in the prone position on the "perforated board", a table attachment with a hole at abdominal level, allows the small intestine to slide passively out of the small pelvis and thus out of the useful radiation beam by relaxing the abdominal wall. On the other hand, computer-assisted three-dimensional radiation planning can be used to achieve an individually configured target volume with minimal dose-volume exposure of the intestinal tract and bladder.

If the tumour has spread to several other organs, rectal cancer can often no longer be cured. Attempts are then made to provide the patient with so-called "palliative" measures to provide relief. For example, the tumour can be reduced in size using icing or laser therapy. However, isolated metastases in the lungs or liver can now be completely removed surgically if the tumour is limited. In recent years, the thermal destruction of metastases (laser, boiling, freezing) has also been further developed and may also be able to help patients with metastases that cannot be resected.

If there are no surgical options, the growth of the tumour is slowed down with palliative chemotherapy. Systemic chemotherapy should be initiated at an early stage. If successful, the therapy can also be interrupted and resumed if the tumour progresses. By introducing small molecule antibodies that block the effect of tumour-specific growth factors (e.g. epidermal growth factor (EGF)) or angiogenic cytokines (vascular growth factor (VEGF)), further improvements in therapy can be achieved in combination with chemotherapy. If chemotherapy reduces the size of a tumour/metastasis to such an extent that surgery is possible, this will of course be performed if tumour-free treatment can be achieved.

If a recurrence (reappearance of the tumour in the former tumour area) occurs, it should be surgically removed if possible. If metastases have also formed or the recurrent tumour is too large (has grown together with other organs), a decision must be made on a case-by-case basis as to whether surgery or another therapy (e.g. radiotherapy) is appropriate.

If the tumour is at an advanced stage, palliative (symptom-relieving) and supportive (supportive) treatment can also be carried out.

Aftercare following the completion of supportive therapy or after an operation follows a precisely defined plan and is intended to enable early treatment in the event of a recurrence of the cancer.

Rehabilitation measures are an integral part of reintegration into everyday life after completion of therapy.

Important parameters for the prognosis and for the decision on possible therapeutic measures are

• the presence or absence of distant metastases
• documentation of deep infiltration of the tumour into the intestinal wall
• the number and localisation of affected lymph nodes.