Colorectal Cancer

What colorectal cancer is and where it comes from

The large bowel consists of the colon — the cecum, ascending, transverse, descending and sigmoid colon — and the rectum. The vast majority of tumors here are adenocarcinomas: they grow from the mucosa. Other types of bowel tumors, such as neuroendocrine or stromal tumors, are rare and are treated by different rules.

Most sporadic cancers develop from an adenomatous or serrated polyp, although not every cancer follows this path. The transformation usually takes years, which is why removing a polyp during colonoscopy is real prevention: a completely removed polyp will not turn malignant, although follow-up is still needed because new polyps can appear. More on the page precancerous conditions of the large bowel.

The risk rises with age. It is increased by bowel cancer in close relatives, hereditary syndromes (Lynch syndrome, familial adenomatous polyposis), long-standing inflammation of the colon, excess weight, smoking, alcohol, a diet high in red and processed meat, and low physical activity. Yet many patients have no obvious risk factor, so screening is recommended for everyone in the appropriate age group, not only for people at increased risk; with a strong family history it starts earlier.

Symptoms

At early stages bowel cancer often causes no complaints at all — it is found at screening. When symptoms appear, they depend on where the tumor lies:

• blood or mucus in the stool, dark stool;
• a change in usual bowel habits: constipation, diarrhea or both in turn;
• a feeling of incomplete emptying, false urges — more typical of rectal tumors;
• weakness, shortness of breath and pallor from iron deficiency anemia — typical of right-sided tumors;
• abdominal pain and bloating, weight loss with no obvious cause.

Blood in the stool is often put down to hemorrhoids. But bleeding should not be attributed to hemorrhoids without an examination: one does not rule out the other, and the extent of the examination is decided by the doctor based on age, symptoms and risk.

Tests needed before a decision

• Colonoscopy with biopsy — confirms the diagnosis and allows the whole large bowel to be examined: some patients have more than one tumor.
• Contrast-enhanced CT of the chest, abdomen and pelvis — the spread of the tumor, lymph nodes, metastases in the liver and lungs.
• Pelvic MRI — the main method of local staging in rectal cancer: together with the other findings it decides whether to start with surgery or with radiotherapy or chemoradiotherapy.
• Carcinoembryonic antigen (CEA) — a baseline level for later monitoring, not a way to make the diagnosis.
• Testing the tumor for deficient DNA mismatch repair (MMR/MSI) — done for everyone: the result affects the prognosis and the choice of treatment and can point to a hereditary syndrome.

Before treatment the stage is set from the examinations, and after surgery it is refined by the histology of the tumor and lymph nodes. That is why the treatment plan sometimes changes after the operation, and this is normal.

When surgery is possible

Surgery is the main treatment for colorectal cancer without distant metastases. But the approach depends heavily on the segment:

• Colon cancer — in most cases treatment starts with surgery: the affected segment is removed together with its mesentery and lymph nodes. Right- and left-sided tumors differ in symptoms and in the extent of the operation — in detail on the page colon cancer.
• Sigmoid colon cancer — one of the most common sites; the extent of resection depends on the spread of the tumor and the condition of the bowel. More — sigmoid colon cancer.
• Rectal cancer — the decision is made after pelvic MRI: some patients first need radiotherapy or chemoradiotherapy, others go straight to surgery; in selected cases, after a complete response to treatment, observation without surgery is discussed. More — rectal cancer.
• A tumor with liver metastases — surgery is possible if all lesions can be removed completely and enough functioning liver will remain; this is assessed by the multidisciplinary team, taking into account the number and location of the lesions and the course of the disease. More — colorectal liver metastases.

If the tumor has come back after previous treatment, repeat surgery may also be possible — there is a separate page on colorectal cancer recurrence.

If surgery is not possible right away

• locally advanced rectal cancer — radiotherapy or chemoradiotherapy first, in some patients combined with systemic chemotherapy (total neoadjuvant therapy), and further treatment is decided after a follow-up MRI;
• metastases that cannot be removed yet — treatment starts with systemic therapy, and the question of surgery is revisited after a follow-up examination;
• complications — obstruction, bleeding, perforation: the patient is stabilized first — with a stoma, a stent, a resection or otherwise depending on the situation — and the radical operation is done at once or as a second stage;
• poor general condition — anemia, malnutrition and other illnesses are corrected before surgery if the urgency allows.

An "inoperable" verdict given several months ago does not describe the situation today: after treatment some cases become operable, so the decision is reviewed on up-to-date images.

How the operation is performed

Whatever the segment, the principle is the same: the tumor is removed together with a section of bowel, its mesentery and the lymph nodes that drain that segment, within an intact anatomical plane. For the colon this is the mesocolic plane; for the rectum it is the embryological plane with an intact mesorectal fascia: for tumors of the upper third a partial mesorectal excision with an adequate margin is possible, for tumors of the middle and lower thirds a total mesorectal excision is performed. The quality of this step determines the risk of the disease coming back.

The removed lymph nodes are examined too: for reliable staging the aim is to assess at least 12 nodes, although after radiotherapy there may be fewer. The status of the nodes sets the final stage and is an important, though not the only, factor in deciding on chemotherapy after surgery.

After the tumor is removed, the ends of the bowel are joined — an anastomosis is created. In colon surgery a stoma is rarely needed; after low rectal resections a temporary stoma is often brought out to protect the join, and a permanent stoma is needed when the sphincter cannot be preserved in an oncologically and functionally safe way.

When the location and size of the tumor and previous operations allow, the operation is done laparoscopically — through a few small incisions. The choice of approach depends on the anatomy, the spread of the tumor and the safety of removing it en bloc; some patients, particularly those with large tumors or growth into adjacent organs, need open surgery.

Recovery after surgery

Care after surgery follows the enhanced recovery after surgery (ERAS) protocol: early mobilization, early return to eating, controlled pain relief. The length of hospital stay depends on the extent of the operation and the approach.

Bowel habits change in different ways after surgery: after right-sided resections stools are more frequent and looser for the first weeks, after low rectal resections frequent urges and fragmented bowel movements are possible. Function usually improves over time, but after low resections some patients have long-lasting problems (low anterior resection syndrome) that need treatment.

Whether chemotherapy is needed after surgery is decided from the final histology report: the stage, the lymph node status, adverse features of the tumor and the MMR/MSI result, taking the patient's condition into account. The regimen and timing are set by the medical oncologist together with the surgeon.

Follow-up after treatment

After radical treatment regular follow-up is needed: examination, CEA, CT of the chest, abdomen and pelvis and colonoscopy, and after treatment of rectal cancer also pelvic MRI when indicated. The schedule is set by the doctor; follow-up is more frequent in the first years.

The most common sites of recurrence are the liver and lungs, less often the area of the operation. A single lesion found in time can be treated surgically in some patients. If signs of a hereditary syndrome are found in the tumor, genetic counseling is needed: its result determines both the patient's follow-up and the testing of relatives.

What to bring to the consultation

• CT and MRI discs, and PET-CT if available — the discs with the images themselves, not only the written reports;
• the colonoscopy report describing where the tumor is;
• the histology report and, if available, the tissue blocks and slides and the MMR/MSI result;
• discharge summaries of previous operations, radiotherapy and chemotherapy regimens;
• recent blood tests, including a complete blood count and CEA.

If some documents are missing, that is no reason to postpone the consultation — some of the tests can be done on site.

The consultation is free of charge. How it goes and how long it takes is described on the page “Oncologist Consultation”.