Colon cancer: what it is, symptoms, diagnosis and treatment

Colon cancer is a malignant tumour that starts in the large intestine or in the rectum. It is the third most common cancer in Spain, with more than 40,000 new cases a year. Most develop from benign adenomatous polyps in a process that takes 10-15 years, which makes early detection possible.

Symptoms that call for a consultation include blood in the stool (visible or hidden), a persistent change in bowel habits, chronic abdominal pain, a feeling of incomplete evacuation, unexplained weight loss and iron-deficiency anaemia with no apparent cause. Having them does not always mean cancer, but they need medical evaluation.

Population screening with a faecal occult blood test is recommended every 2 years from the age of 50 in people with no family history and no symptoms. If you have first-degree relatives with colorectal cancer, screening starts earlier, at 40 or 10 years before the youngest case in the family.

Colonoscopy is the reference test: it shows the whole colon and allows biopsies to be taken and polyps to be removed, under sedation and without pain. It is complemented by chest and abdominal CT for staging, the tumour marker CEA for follow-up and, in rectal tumours, MRI to plan treatment.

Stage I has a 5-year survival above 90%. Stage III reaches 60-70%, compared with 30-40% twenty years ago. Stage IV with resectable metastases reaches 30-50% at 5 years. Overall survival is above 65%, compared with 50% three decades ago.

The main surgical treatment includes right or left hemicolectomy, sigmoidectomy, anterior resection of the rectum and abdominoperineal resection, depending on where the tumour is. These operations are performed with robotic or laparoscopic surgery, which allows faster recovery and fewer complications.

Adjuvant chemotherapy is given after surgery in stage III and in some high-risk stage II cases. The most common regimens are FOLFOX or CAPOX for 6 months. Its aim is to eliminate any remaining tumour cells and reduce the risk of recurrence.

Radiotherapy is used mainly in rectal cancer, either before surgery (neoadjuvant) to shrink the tumour, or after surgery in selected cases. In colon cancer itself it is used less often.

The main factors are age over 50, a first-degree family history of colorectal cancer (which doubles the risk), hereditary syndromes such as familial adenomatous polyposis or Lynch syndrome, long-standing inflammatory bowel disease, and lifestyle habits such as a diet high in red and processed meat, obesity, physical inactivity, tobacco and alcohol.

Yes. A second opinion from a team with specific experience in colorectal surgery can confirm the diagnosis, review the stage and propose treatment options, such as robotic surgery or other techniques, that are not always available at every centre. It can be requested with no commitment before starting any treatment.

Yes. With proper screening and lifestyle changes the risk can be reduced by up to 50%. Polypectomy during colonoscopy prevents 76-90% of cancers. A diet high in fibre (25-30 g/day), regular exercise and avoiding tobacco and excess alcohol are the measures best supported by the evidence.

Robotic surgery allows the operation to be performed through very small incisions, with more precision and control of movement than conventional laparoscopy. The advantages include less postoperative pain, less bleeding, shorter hospital stays and faster recovery, with the same oncological quality as open surgery.