ATLANTA -- Researchers at the University of California San Francisco report that melanoma patients whose cancer has spread to their sentinel lymph nodes (SLNs) have a greater chance of experiencing disease recurrence and mortality compared to those whose cancer has not advanced to their SLNs.
The sentinel lymph node (SLN) earned its name because it is the first region in a person's body that receives cancer cells from the place where the disease originated. After cancer cells drain to the SLN, the disease may spread, or metastasize, to other regions of the body. Lymph nodes are the body's first line of defense against infections and cancers. They produce infection-fighting lymphocytes that are distributed via the lymphatic system that functions as a channel of freeways throughout the body.
"Sentinel lymph nodes are a strong marker for predicting a patient's outcomes in regards to disease recurrence and death due to advanced melanoma," says Stanley P.L. Leong, MD, FACS, UCSF professor of surgery and director of the Sentinel Lymph Node program in the UCSF Cancer Center. "We found that patients who have a positive SLN biopsy are more likely to experience a disease recurrence and die from melanoma than those with a negative SLN biopsy."
Leong will present data on the role of SLNs in melanoma today at the American Society for Clinical Oncology (ASCO) meeting.
During the UCSF study, a total of 358 advanced melanoma patients underwent a selective SLN dissection and were followed for a median period of 546 days.
Leong reports that for patients whose cancer spread to their SLNs and therefore had a positive SLN biopsy (63), 78 percent had no evidence of disease and 22 percent experienced recurrent melanoma. Eighty-six percent of these patients remained alive and 14 percent (9) died from melanoma by the end of the study.
For patients with negative SLNs (295), 93 percent showed no evidence of disease and 7 percent developed a recurrence of the disease. Ninety-seven percent of these patients remained alive and 3 percent (9) died by the end of the study.
Of the nine deceased patients, 44 percent died of melanoma and 56 percent died of causes unrelated to the disease.
Study participants underwent a SLN dissection using selective techniques called preoperative lymphoscintigraphy and intraoperative lymphatic mapping.
These procedures allow surgeons to pinpoint the SLN where cancer potentially could have spread (only 18 percent of all melanoma spreads to a person's lymph nodes) by injecting a blue dye and/or radiocolloid substance that enters lymphatic capillaries and concentrates in the SLNs. A hand-held gamma probe can be used to further identify a radiolabeled SLN.
Overall, the success rate of harvesting the SLN using blue dye alone is 82 percent, by radioactive mapping is approximately 94 percent, and by combination method is 98 percent. After the SLN is identified, a surgeon removes the lymph node and a pathologist analyzes the area for evidence of cancer.
Before these SLN identifying techniques were developed, some patients with melanoma underwent elective lymph node dissection (ELND) to determine whether or not their cancer had spread to their lymph nodes. During an ELND, all of a patient's lymph nodes were removed and tested for cancer cells. Leong says that numerous retrospective studies suggest that patients with melanoma who underwent an ELND had an improved survival rate compared to those who chose to wait and have a therapeutic lymph node dissection only after it became clinically evident that their cancer had spread.
However, he notes that because only 18 percent of melanoma patients' cancers spread to their lymph nodes, roughly 80 percent of patients underwent unnecessary invasive surgery. Some of the post-operative side effects of an ELND include extensive swelling, numbness, pain, and an increased susceptibility to infections.
"Selective sentinel lymph node dissection helped to solve a clinical dilemma by providing us with the necessary information regarding the status of a patient's cancer without having to remove all of a person's lymph nodes," Leong says. "A selective SLN dissection functions like a staging procedure for melanoma because the results tell us what a patient's next treatment steps should be to manage their disease."
He adds that a patient who has negative SLN biopsy can be assured that the likelihood of their disease recurring or spreading to other parts of the body is very low; therefore, experiencing great psychological relief.
"We now know the relationship between positive SLN biopsies and disease recurrence and mortality rates," Leong says. "In future clinical trials, we aim to determine if SLN biopsies will also enhance survival rates in patients."
Leong and his colleagues have performed selective SLN dissection on over 600 melanoma patients and are currently initiating a SLN program with breast cancer patients. UCSF also is participating in a National Cancer Institute-sponsored multicenter trial that will study the role of SLNs in breast cancer.