Rectal cancer

How rectal cancer differs from cancer of other parts of the large intestine

The rectum is the last 12–15 cm of the large intestine. It lies in the narrow bony pelvis, and next to it are the bladder, the prostate or the vagina, the nerves that control urination and sexual function, and the anal sphincter, which controls continence. Around the bowel lies fatty tissue containing lymph nodes — the mesorectum — enclosed by its own fascia, the mesorectal fascia. It is into this tissue that the tumor spreads first.

For this reason rectal cancer is treated differently from colon cancer: the operation is technically more demanding and the risk of local recurrence is higher, so radiotherapy before surgery is used more often, and the question of preserving the sphincter is decided individually for each patient.

Tumors are conventionally classified by height: low rectal tumors — close to the anal canal, mid rectal and upper rectal tumors — closer to the sigmoid colon. The lower the tumor, the more important radiotherapy before surgery and the sphincter-preserving technique become; in terms of treatment strategy, upper rectal tumors are managed much like colon cancer.

What symptoms rectal cancer causes

At an early stage there are often no symptoms — the tumor is found during a colonoscopy done for another reason or for screening. As the tumor grows, the following appear:

• blood in the stool — often red, and easy to mistake for hemorrhoids;
• a change in bowel habits: constipation alternating with diarrhea;
• a feeling of incomplete emptying, frequent false urges to defecate;
• narrow, ribbon-like stools, mucus in the stool;
• pain in the sacrum or the perineum — a sign that needs urgent evaluation;
• anemia, weakness, unexplained weight loss.

None of these signs is specific: blood in the stool is indeed more often caused by hemorrhoids or an anal fissure. However, it is impossible to tell these conditions apart from a tumor without examining the bowel, so rectal bleeding is a reason to see a doctor and have the bowel examined, not to treat “hemorrhoids” blindly.

Which examinations are needed before a decision

Neither surgery nor radiotherapy is planned on a colonoscopy report alone. What is needed:

• Colonoscopy with biopsy — histological confirmation of the diagnosis and examination of the entire colon, because there may be more than one tumor.
• High-resolution pelvic MRI — the key study in rectal cancer. It shows the depth of tumor invasion, the approximate status of the lymph nodes, and the distance to the mesorectal fascia and to the sphincter. The MRI is what determines whether radiotherapy before surgery is needed and whether the sphincter can be preserved.
• Contrast-enhanced CT of the chest and abdomen — to rule out distant metastases, primarily in the liver and lungs.
• Digital rectal examination and, if needed, rigid proctoscopy — to clarify the distance from the tumor to the anal verge, which determines the choice of operation.
• Carcinoembryonic antigen (CEA) — a baseline level for monitoring over time, not for making the diagnosis.
• Testing the tumor for mismatch repair deficiency (dMMR/MSI) — on the biopsy sample; in some patients this result changes the treatment plan.

PET-CT and endorectal ultrasound are not ordered for everyone: the former when CT findings are equivocal, the latter for small tumors, when local (transanal) excision without bowel resection is being considered.

When surgery is possible

In rectal cancer without distant metastases, surgery is possible in most cases. The question is usually not whether to operate, but when and to what extent. Based on the MRI findings and the multidisciplinary team (MDT) review, three situations are distinguished:

• An early tumor (T1) that has not spread beyond the submucosa and has favorable features on histology: in some patients, local excision through the anal canal without bowel resection is possible — under strict criteria and with mandatory follow-up.
• A tumor confined to the bowel wall or extending only slightly beyond it, with no threat to the mesorectal fascia: in some of these patients, primarily with tumors of the mid and upper rectum, surgery is performed right away; for low rectal tumors that have grown beyond the bowel wall, radiotherapy usually comes first. The multidisciplinary team makes this choice based on the MRI.
• A locally advanced tumor — one that comes close to the mesorectal fascia, invades deep into the bowel wall, has multiple suspicious lymph nodes on MRI, or is located low and threatens the sphincter: the multidisciplinary team usually recommends radiotherapy or chemoradiotherapy first, in some patients together with chemotherapy, and only then surgery.

Whether the sphincter can be preserved is decided not by the diagnosis but by the distance from the lower edge of the tumor to the anal sphincter and by how the tumor has responded to preoperative treatment. A permanent colostomy is needed when the tumor invades the sphincter or lies so low that it cannot be removed with clear margins while preserving continence.

Liver metastases in themselves do not rule out surgery: if they can be removed, the bowel and the liver are operated on in one procedure or one after the other. Read more on the page liver metastases from colorectal cancer.

If surgery is not possible right away

Often this is not a decision against surgery but a postponement for the duration of other treatment. Typical situations:

• a locally advanced tumor — a course of radiotherapy or chemoradiotherapy, followed by a repeat MRI; the timing of surgery is determined by the treatment regimen and the tumor’s response;
• bowel obstruction or bleeding at the time of diagnosis — the immediate threat is dealt with first: a diverting stoma is created or, for tumors of the upper rectum, a stent is placed, and treatment then continues according to the plan;
• distant metastases — the sequence of operations on the bowel and on the liver or lungs is determined by the MDT;
• mismatch repair deficiency (dMMR) in a locally advanced tumor — in such patients the MDT considers immunotherapy before surgery; this is a new option whose availability depends on the drug and the institution, and after it the question of surgery is reconsidered.

A separate situation is when, after radiotherapy, the tumor can no longer be detected on digital rectal examination, on MRI or at endoscopy (a clinical complete response). In that case the MDT discusses active surveillance (watch-and-wait) instead of immediate surgery: with frequent examinations, MRI and endoscopy on a strict schedule. This is not a decision against surgery but its postponement under surveillance: in some patients the tumor reappears, mostly within the first two years, and they are then operated on. This approach is not suitable for everyone and requires discipline on the patient’s part.

How the operation is performed

The standard operation for mid and low rectal tumors is total mesorectal excision (TME): the bowel with the tumor is removed en bloc together with the mesorectum within its own fascia. It is this technique, and not a “wide margin” along the bowel, that reduces the risk of local recurrence. For upper rectal tumors the mesorectum is removed partially — a partial mesorectal excision — with an adequate margin below the tumor.

During mobilization of the bowel, the pelvic autonomic nerves are preserved — this determines how well the bladder and sexual function work after the operation. This requires working under magnification and a clear view of the anatomical planes.

When the location of the tumor, the anatomy of the pelvis and the extent of resection allow it, the operation is performed laparoscopically — through several small incisions. The magnified image from the camera helps to see the nerves and the boundaries of the fascia deep in the narrow pelvis, and recovery after this approach is usually shorter. The approach is chosen according to the size of the tumor, the anatomy of the pelvis, previous operations and the patient’s condition; some patients need open surgery.

What follows depends on the height of the tumor:

• low anterior resection — the bowel is joined with a stapled anastomosis and the sphincter is preserved. With a low anastomosis, especially after radiotherapy, a diverting (temporary) ileostomy is created for several months: it diverts bowel contents away from the anastomosis while it heals and limits the consequences of a possible anastomotic leak; it is then closed in a separate small operation;
• abdominoperineal resection — when the tumor invades the sphincter or when continence cannot be preserved: the bowel is removed together with the anal sphincter and a permanent colostomy is formed.

With synchronous liver metastases, if the extent of both operations allows it, the bowel and the liver are operated on in one procedure, including laparoscopically; otherwise, sequentially.

Recovery after surgery

Postoperative care follows the enhanced recovery after surgery (ERAS) protocol: early mobilization, early return to oral nutrition, and controlled pain management. The length of the hospital stay depends on the extent of the operation and on the approach — after a laparoscopic operation it is usually shorter.

After a low anterior resection the bowel works differently for some time: urges are more frequent, bowel movements are fragmented, and it can be hard to tell gas from stool. This is expected after removal of the rectum, and in most patients it gradually improves over the first one to two years, and in some it persists longer; diet, pelvic floor muscle training and, if needed, medication help. This is something worth knowing in advance rather than finding out after the operation.

If a stoma has been created, the patient is taught to care for it while still in the hospital; a temporary ileostomy is closed after the anastomosis has been checked. Whether chemotherapy is needed after surgery is decided based on the stage, the histology report of the removed tumor and lymph nodes, and previous treatment; the regimen is determined by the medical oncologist together with the surgeon.

Follow-up after surgery

After surgery, regular monitoring is needed: CEA, CT of the chest, abdomen and pelvis, colonoscopy and, when indicated, pelvic MRI. The schedule is set by the doctor — it depends on the stage, previous treatment and the extent of the operation; check-ups are more frequent in the first years. For patients who have chosen active surveillance without surgery, examinations, MRI and endoscopy are performed much more often.

Recurrence may be local, in the pelvis, or distant — in the liver or lungs. In some cases it can also be treated surgically, and repeat operations after incomplete (R1/R2) resections are a separate area of my practice.

What to bring to the consultation

• the pelvic MRI and CT discs — the discs with the images themselves, not only the written reports;
• the colonoscopy report stating the distance of the tumor from the anal verge;
• the histology report and, if available, the paraffin blocks and slides and the MMR/MSI test result;
• discharge summaries of previous treatment: doses and dates of radiotherapy, chemotherapy regimens with the number of cycles, and operative reports from previous surgery;
• recent blood tests, in particular a complete blood count and CEA.

If some of the materials are missing, that is not a reason to postpone the consultation — some of the examinations 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”.