Research on a technique for detecting the earliest spread of melanoma, the deadliest form of skin cancer, has confirmed that the procedure significantly prolongs patients’ survival rates compared with traditional watch-and-wait techniques.
The technique, which combines lymphatic mapping and sentinel-node biopsy, allows doctors to quickly determine whether the disease has metastasized to the lymph nodes, which occurs in approximately 20% of patients. Patients with cancer in their lymph nodes may benefit from having their other nearby lymph nodes removed. For the other approximately 80% of patients in whom the tumors have not spread to the lymph nodes, the technique spares the patient from unnecessary surgery and its associated complications and substantial costs.
The results of the decade-long study, which began at Jonsson Comprehensive Cancer Center of the University of California Los Angeles, were published in the New England Journal of Medicine (2014;370:599-609). Donald Morton, MD, who died in January 2014, and Alistair Cochran, MD, led the research team.
Researchers evaluated outcomes of 2,001 melanoma patients after 10 years. The results confirmed that lymphatic mapping and sentinel-node biopsy have been a significant advance in the treatment of melanoma, as the method improved patients’ long-term melanoma-specific survival and their survival without cancer spreading to other parts of the body.
One important finding was that the thickness of the initial melanoma tumor determined the effectiveness of the treatments in managing nodal and other metastases. Patients who had primary melanoma tumors of intermediate thickness (1.2 to 3.5 millimeters thick) and whose lymph nodes were completely removed after a positive biopsy had a disease-free survival rate of 71.3% after 10 years, compared with a 64.7% rate for those whose nodes were observed without sentinel biopsy.
The study confirmed that for patients with intermediate-thickness melanomas, early sentinel biopsy decreases the risk of cancer recurring in the lymph nodes and decreases their chances of dying from melanoma.
The research also demonstrated that sentinel-node biopsy prolonged patients’ survival without melanoma spreading to the brain, lungs, liver, or other organs; and that it improved the survival rate for patients with lymph node metastasis from primary melanomas of intermediate thickness without additional metastases.
Before cancer cells spread throughout the lymph nodes, they travel through the lymphatic vessels, first entering the sentinel lymph node, which is the lymph node most directly connected to the primary tumor. In the technique developed at UCLA, doctors inject the tissue near the primary tumor with a mixture of blue dye and radioactive tracer to find the lymphatic channels that lead directly to the tumor-draining sentinel lymph node. The dye–isotope mixture follows the same lymphatic path as the melanoma cells that spread to the sentinel node. Doctors can then remove the sentinel node and examine it in detail under a microscope using probes that are sensitive enough to detect even single melanoma cells.