Is Treatment Without Surgery Possible for Rectal Cancer (Large Bowel Cancer Near the Anus)?

What is the rectum? The colon, which follows the small intestine in the digestive system, and its final section, the rectum, together form the large bowel, a long muscular tube. The large bowel averages 1.5 m in length. The rectum is the final part of the digestive system, formed by a widening of the large bowel and averaging 15 cm long.

Rectal cancer , or rectal adenocarcinoma, begins in cells in the rectal region. As cell numbers increase, it spreads circularly around the rectum like a napkin ring. With early diagnosis, cancer cells may be found confined to the rectum. If diagnosis is delayed, however, cancer may spread to nearby organs, lymph nodes, and through the bloodstream to the liver, lungs, and other organs.

What are conventional rectal cancer treatments?

Although rectal cancer shares characteristics with colon cancer, unlike colon cancer treatment, it carries a risk of locoregional recurrence after surgery when the tumor involves all bowel layers and/or nearby lymph nodes. This is because it lacks an outer membrane called the serosa, as found in the large bowel, and its lymphatic flow is much richer than the colon's.

Surgery for a tumor in the middle or lower rectum may also expose the patient to losing the anus and requiring a lifelong colostomy. In these patients, preoperative rectal cancer treatment with radiotherapy and chemotherapy (neoadjuvant treatment) may increase anal preservation and reduce the likelihood of living with a bag (colostomy). Preoperative radiotherapy also avoids the increased side effects of postoperative radiotherapy.

Comprehensive assessment after a rectal cancer diagnosis and consideration of preoperative treatments are extremely important because they may reduce the likelihood of losing the anus. After adequate imaging, these patients should be evaluated jointly by a radiologist, surgeon, medical oncologist, and radiation oncologist working with a shared approach, and the final medical treatment plan should be made together.

Is treatment changing in locally advanced rectal cancer?

Rectal cancers account for approximately %30 of large bowel cancers. Their course and treatment also differ from other large bowel tumors. Rectal cancers are staged as early, local (regional), locally advanced, and metastatic (spread to distant sites).

Surgery and oncological treatments (chemotherapy and radiotherapy), vary according to disease stage and tumor location. Surgery is the cornerstone of early-stage treatment. The rectum consists roughly of three sections, considered the upper, middle, and lower rectum. Although surgery is a cornerstone in this cancer, it is not chosen first in some circumstances. If the tumor exceeds a certain size, reaching a locally advanced stage, or lies in the middle or lower rectum, surgery is not preferred initially because the anus would be lost.

Some rectal tumors extend beyond bowel layers into surrounding tissues and/or involve lymph nodes around the bowel. This is defined as locally advanced rectal cancer.

Particularly for tumors near the end of the middle rectum and/or in the lower rectum, surgery requires removal of both the rectum and the muscles enabling defecation, called the anal canal. This necessarily results in a colostomy (a bag attached to the abdomen for passing stool), an undesirable, distressing outcome for patients and their families.

When we encounter a rectal cancer patient, we first use PET-CT to determine whether it has spread to other organs such as the liver. In addition to PET-CT, if there is no distant metastasis , we also perform imaging of the rectal region using MRto assess, together with PET-CT, how far the tumor extends beyond bowel layers, whether lymph nodes are involved, and its location, and then decide.

In both situations described above, starting treatment with surgery is inappropriate. Operating directly without preliminary treatment (neoadjuvant chemotherapy / radiotherapy) will adversely affect treatment success. Based on knowledge acquired over the years, current rectal cancer treatment involves chemotherapy and radiotherapy before surgery, particularly for locally advanced tumors and those in the middle or lower rectum. In all patients, surgery is performed on the tumor area that has shrunk and/or disappeared after chemoradiotherapy, attempting to preserve the anus if possible; otherwise, a colostomy is created and the tumor removed with safe margins. In recent years, surgery for all patients after neoadjuvant chemoradiotherapy has been questioned, because %30 – 40 achieve a complete response and the tumor disappears. At this point, whether patients whose tumors disappear completely, with this complete response proven by biopsy, truly require surgery has become open to debate.

The starting point for this article was one of the important topics at last month's Gastrointestinal Cancers Symposium organized by the American Society of Clinical Oncology(ASCO): the safety and better quality of life offered by a "watch and wait" approach after chemoradiotherapy in some rectal cancer patients. The symposium emphasized that in suitable patients this approach did not increase recurrence risk, alongside the benefits listed above. Indeed, excellent results could be achieved because these patients avoided surgical risks and possible side effects entirely.

In summary, if the tumor disappears completely after chemoradiotherapy in locally advanced rectal cancer patients, which we call a "complete response to neoadjuvant treatment", these patients can be monitored without surgery using a "watch and wait" approach. Large studies on the subject are currently being conducted in America, Brazil, and the Netherlands, and nonsurgical rectal cancer treatment is becoming accepted worldwide as a standard option.