What Kinds of Gastrointestinal Stromal Tumors (GISTs) Can Be Treated With Surgery?

If you’ve been diagnosed with a GIST and are discussing treatment options with your cancer care team, your doctors may recommend surgery as a part of your treatment plan. Understanding what happens during this surgical procedure is very important. Not only will it help you stay on top of medical discussions, but it can make the whole experience a little less unnerving and allow you to better prepare yourself for this major operation.

GISTs are a rare type of soft tissue sarcoma — a general term for cancers beginning in connective tissues surrounding and protecting organs of the body. While these tumors can occur anywhere along the gastrointestinal (GI) tract, most begin in the stomach and small intestine. GISTs originate from specialized cells called the interstitial cells of Cajal (ICCs), which are found in the muscularis propria layer of the GI wall. Known as the ‘pacemaker’ cells of the gut, ICCs are responsible for sending signals to trigger muscular contractions that move stomach food and liquid along the digestive tract (peristalsis).

GISTs are mostly indolent (slow-growing), and usually smaller than 2 cm. In these cases, they are quite unlikely to spread to other parts of the body and are typically not life-threatening. On the other hand, fast-growing and larger GISTs, especially those above 5 cm, are at a higher risk of growing into nearby tissues and spreading to other organs.

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Surgery is the main treatment for resectable GISTs of more than 2 cm in size. The aim of surgery is to remove all of the tumor intact to avoid rupturing the tissue surrounding it, which can cause cancer cells to break off into nearby areas and grow uncontrolled.

Surgery can be performed to treat both smaller, more localized GISTs and larger, more regional GISTs.

Smaller, more localized tumors

If the tumor is small (more than 2 cm but less than 5 cm), located in a place where it can be safely removed and has not spread (localized), surgery is often the first and only treatment that needs to be done. This is because smaller GISTs can be cured with surgery.

During the procedure, be it with the open or laparoscopic approach, the GIST is removed along with some nearby healthy tissue. The removal of the section of the stomach containing a small GIST is called a wedge resection.

Unlike many other cancers, GISTs rarely spread to the lymph nodes. As such, removing lymph nodes, which are small bean-shaped structures belonging to the immune system, is typically not necessary.

Larger tumors that have spread to other sites but only to a limited extent

Some tumors may be larger, located in an area that makes it difficult to remove completely or have grown into other organs such as the liver. In such cases of metastatic GISTs, curing the cancer with surgery alone will not be possible, and other options would have to be considered.

Here, targeted therapy with imatinib is typically given as a first-line treatment to shrink the tumor so that it is easier to remove during surgery. This is known as neoadjuvant therapy. But before starting on imatinib, your doctors will conduct a biopsy to confirm that the tumor is a GIST and to test for certain mutations (changes or abnormalities) in either of two genes: c-KIT and platelet-derived growth factor receptor alpha (PDGFRA). This is done to determine if your tumor will respond to imatinib, which specifically targets the proteins produced from these two genes and therefore will only be helpful for GISTs whose cells have these gene mutations.

If the metastatic GIST appears stable or responsive to imatinib treatment, surgical removal of the tumor may then be considered afterwards. However, careful case selection is still necessary, and the main treatment approach still remains to be systemic treatment with imatinib.

Generally, there are two surgical approaches used by surgeons in the treatment of GISTs: open surgery and laparoscopic (or keyhole) surgery. Which method your surgeon chooses will depend on the size and location of the GIST.

Open surgery

A single, large incision (cut) is made in the upper part of your abdomen, just below the breastbone down to the belly button. The incision is closed with staples or sutures after the GIST and a small area of healthy tissue around it are removed. It is important to remove this border of healthy tissue as it reduces the risk of the cancer returning.

Open surgery is typically used for tumors larger than 5 cm.

Laparoscopic (or keyhole) surgery

This surgical approach is typically offered in specialist cancer centers with specially trained surgeons. During this minimally-invasive procedure, several small incisions are first made in the abdomen. Through one of the incisions, your surgeon will insert a thin, lighted tube with a tiny video camera at its tip. This is known as a laparoscope. The use of this instrument allows images of the inside of your abdomen to be projected onto a screen, which your surgeon uses for guidance as he performs the operation. Through the other incisions, long surgical tools are inserted and used to remove the GIST and a small margin of healthy tissue. Laparoscopic surgery is generally used for small GISTs that are more than 2 cm but less than 5 cm in size.

During surgery, be it open or laparoscopic, your surgeons will remove as much of the tumor as possible, together with a small margin of healthy tissue surrounding the GIST, in what is known as a wedge resection. If parts of nearby organs are affected or if there are tumors that have spread elsewhere in the abdomen, such as the liver, these may be removed as well. The removal of the tumor and surrounding areas as one piece is known as an en bloc resection. If the tumor is located near the pylorus of the stomach, your surgeons may perform a distal gastrectomy. Similar to surgery for smaller tumors, removing lymph nodes is typically unnecessary.

It is likely that you will continue to receive imatinib after surgery as part of adjuvant therapy. The goal of this is to lower the chances of the cancer coming back and spreading to other organs. Imatinib is usually given for at least a year after a GIST has been completely removed by surgery. However, some GISTs have a higher risk of returning than others. If there is an increased risk of your tumor coming back, your doctors may recommend taking imatinib for at least three years post-surgery. Factors determining the risk of the GIST recurring include the location of the tumor, its size and how fast it was growing (known as its mitotic rate).