In the vast majority of cases, rectal cancer develops as a result of a change in the intestinal mucosa. Polyps - small outgrowths of the intestinal mucosa - develop into adenocarcinomas ("mucus-forming cells"), the actual cancerous tumors. In 95% of cases, polyps develop spontaneously in the course of a person's life, only 5% are due to a hereditary component.
Colorectal cancer is now one of the most common cancers in men and women worldwide, and the trend is rising. Poor diet and lack of exercise are the main causes of this development. The main risk factors are, for example, the consumption of large quantities of red meat, diabetes mellitus, overweight/obesity, smoking, increased alcohol consumption and older age.
Although the mortality rate from bowel cancer has been falling in Germany for 30 years now, the number of new cases continues to rise. In fact, bowel cancer is now the second most common cause of cancer-related deaths for both sexes.
Depending on the location of the tumor, rectal cancer forms metastases in different organs. Tumor foci located further inside the rectum spread mainly to the liver, similar to colon cancer. Closer to the exit of the rectum, rectal cancer mainly spreads lymphogenously, i.e. via the lymph vessels to the inguinal lymph nodes and via the blood to the lungs.

The localization of rectal cancer © bilderzwerg #247748992 | AdobeStock
As with many types of cancer, rectal cancer develops over a long period of time, which is usually completely symptom-free. However, colorectal cancer screening usually reveals the smallest residual bleeding, even at an early stage, which can indicate rectal cancer.
At an advanced stage, rectal cancer usually becomes symptomatic and manifests itself, for example, through blood and mucus discharge, changing stool consistency, i.e. a change between firm and soft stools, unwanted weight loss and possibly pain during bowel movements. These are the first signs that you should always consult a doctor for further clarification.
If rectal cancer is suspected, imaging is always carried out for clarification. As a rule, this is initially a rectoscopy together with a colonoscopy. The colonoscopy is intended to detect secondary tumors that may have formed further up in the intestinal tract. Around 7% of patients with rectal cancer have such secondary tumors in the colon.
If rectal cancer is diagnosed, an ultrasound examination is carried out using a special probe - a tissue sample (= biopsy) is usually taken for pathological fine diagnostics ("grading", classification according to TNM stages). In addition, the experts use ultrasound to clarify whether other organs are affected, e.g. by metastases. In the case of rectal cancer, the lungs and liver are the main organs considered.
Magnetic resonance imaging(MRI) is used to examine the lower abdomen and pelvis for existing lymph node metastases. MRI is preferred to computer tomography(CT), as the latter causes significantly higher radiation exposure.
The measurement of tumor spread and tumor markers also has an impact on the further treatment of rectal cancer.
There are three main methods available for the treatment of rectal cancer:
or a combination of these approaches.
Depending on the stage of the tumor, these treatment methods can be further adapted.
In the case of larger local tumors or a high risk of recurrence, experts will favor partial (partial mesorectal excision) or complete removal (total mesorectal excision) of the rectum. In these cases, an artificial anus must then be created, a so-called stoma or anus praeter.
If the rectal cancer has already spread to the surrounding tissue and lymph nodes, the rectum is partially or completely removed, as are the adjacent lymph vessels. An artificial anus must be created.
In the case of larger tumor foci, doctors often opt for radiotherapy prior to surgery in order to significantly reduce the tumor tissue before the operation. In the advanced stage of rectal cancer, surgery is usually followed by chemotherapy. This is primarily intended to prevent further spread (metastasis) of the rectal cancer.
In the final stage of the disease, surgical treatment of the rectum alone is no longer sufficient. If there are operable lung, lymph node or liver metastases, these are also removed and the patients are also treated with chemotherapy again after a stoma has been created.
In many cases, however, a cure can no longer be achieved at this stage of the disease due to the widespread metastasis, so that patients can usually only be given palliative and pain-relieving treatment.
The long-term prognosis for rectal cancer depends very much on the stage and possible distant metastases. Without distant metastases and with a localized tumour focus, 5-year survival rates of up to 75% are possible in the early stages of the disease. This means that at this stage, 75% of those affected are still alive after 5 years.
However, if there are limited distant metastases in the lungs and/or liver, which can still be surgically removed, up to 30% of patients can be cured of their rectal cancer. However, any metastasis generally worsens the prognosis considerably, as does a recurrence of the disease. Close follow-up care is therefore recommended in all cases.
Experts in the treatment of rectal cancer are specialists in internal medicine, proctology and oncology. For treatment, you should contact experienced, specialized colorectal cancer centers, which you can find here, among other places.