Endometrial cancer forms in the tissues lining the uterus. The majority of women with early-stage endometrial cancer (meaning the cancer has not yet spread outside the uterus) will be cured simply by the surgical removal of the uterus. However, some women who are presumed to have early-stage disease will actually have higher-stage disease on final post-surgery pathological examination of the tumor.
To date, there has been no consensus on the optimal way to identify those women with presumed early-stage disease who will need further staging and treatment. For women with low-grade disease, there are surgeons who opt to remove no pelvic lymph nodes during surgery, while others choose to remove all nearby lymph nodes. Now, the results of a study by Memorial Sloan Kettering Cancer Center investigators, published in the May 2009 issue of Gynecologic Oncology [PubMed Abstract], demonstrate that a procedure known as sentinel lymph node (SLN) biopsy provides an accurate way to determine whether or not a tumor has spread. The use of SLN may help physicians avoid overtreating potentially low-risk patients and undertreating patients with more advanced cancer.
Endometrial Cancer Treatment
Endometrial cancer is initially diagnosed prior to surgery with either an endometrial biopsy or an outpatient surgical procedure called dilation and curettage (D&C). Doctors use the tissue obtained to determine the stage and grade of the tumor. There are four stages of endometrial cancer, with stage 1 representing no spread outside the uterus, and stage 4 representing spread to the bladder and/or bowel or beyond the pelvis. The grade describes how malignant the cells look under the microscope, escalating in severity from grade 1 to grade 3.
The most common surgical treatment for all stages of endometrial cancer is the removal of the uterus (total hysterectomy). In women who have a preoperative diagnosis of grade 1 endometrioid endometrial cancer — one of the most common forms of the disease — it is unlikely that the cancer will metastasize, or spread, to the pelvic lymph nodes. These women have a very high cure rate and consequently do not usually require further treatment after surgery.
But it has been shown that approximately 10 to 15 percent of women who receive a presurgery diagnosis of grade 1 endometrial cancer will actually have higher-grade lesions (grades 2 and 3) when the entire primary tumor is examined after being removed. Women with grade 2 and 3 lesions may have higher stage tumors that require additional therapies such as chemotherapy or radiation therapy to kill the tumor cells that have spread.
Pelvic Lymph Node Removal and Sentinel Lymph Node Mapping
The function of lymph nodes is to help to drain fluids and fight infection. Among women with grade 1 endometrial cancer who are treated by surgeons who routinely remove all the pelvic lymph nodes (total lymphadenectomy), a majority will have received unnecessary treatment, as they will be found to have disease that is confined to the uterus. For these women, the removal of the pelvic lymph nodes may result in lymphedema, a potentially lifelong condition characterized by swelling, in this case in the groin and legs. But of equal concern, for those women with a preoperative diagnosis of grade 1 endometrial cancer treated by surgeons who routinely remove no lymph nodes during surgery, some 10 to 15 percent will not have their metastatic cancer properly diagnosed and treated.
“If we use SLN mapping for patients with endometrial cancer, we can spare many patients the unnecessary removal of their pelvic lymph nodes.”
Nadeem Abu-Rustum, MD
The process of mapping lymph nodes — called intraoperative lymphatic mapping, or sentinel node mapping — allows doctors to look for tumor spread during surgery without having to remove a large number of lymph nodes. The procedure uses a radiolabeled medical substance or a blue dye (or in some cases a combination of the two) that is injected into the cervix near the tumor site. Lymph fluid carries the substance to the “sentinel” node, which is the first lymph node to which cancer cells are likely to spread from the primary tumor. The sentinel node is then removed and examined by a pathologist to determine the presence of cancer. If this node is free of cancer cells, usually no additional lymph nodes need to be removed. If the node does contain cancer cells, then doctors know that the patient has advanced stage IIIC disease, and she can receive appropriate postoperative chemotherapy or radiation therapy.
SLN Mapping Study
In the prospective, non-randomized Gynecologic Oncology study, researchers followed 42 women with a preoperative diagnosis of grade 1 endometrial cancer who were treated at Memorial Sloan Kettering between 2006 and 2008. Intraoperative sentinel lymph node mapping was possible in 36 of the patients. Of these 36 women, four — or 11 percent of all the patients — were found to have cancer present in the sentinel lymph nodes. Additionally, a post-surgery pathological examination confirmed that cancer was present in all lymph nodes testing positive for cancer during surgery, meaning there were no false positives.
“Endometrial cancer is a highly curable disease,” says Nadeem Abu-Rustum, a gynecologic surgeon at Memorial Sloan Kettering and the study's lead author. “But there are a small percentage of patients diagnosed with early-stage disease, in the neighborhood of 10 percent, for whom the standard treatment — removal of the uterus — may fail.”
Dr. Abu-Rustum explains that “intraoperative sentinel node mapping is a more refined method of staging these patients while they are in surgery. It offers us a better way to know which women need additional therapies and which women do not — rather than having to remove all the pelvic lymph nodes in a total lymphadenectomy.” He goes on to observe that sentinel lymph node mapping is already the standard of care for breast cancer and melanoma.
“If we use SLN mapping for patients with endometrial cancer, we can spare many patients the unnecessary removal of their pelvic lymph nodes, thereby preventing the development of lymphedema,” Dr. Abu-Rustum says. “And the other good news is that when we do find a positive lymph node, we can do something about it. Effective treatments are available.”