Stage III melanoma includes cancers of any thickness that have spread to the regional lymph nodes. Optimal treatment of stage III melanoma consists of surgical removal of the cancer followed by systemic adjuvant treatment to reduce the risk of cancer recurrence and prolong survival.
Surgical Treatment of Stage III Melanoma
Standard surgical treatment for patients with stage III melanoma is removal of the primary cancer with up to 2-centimeter (over an inch) margins of the adjacent skin, depending on the thickness of the primary tumor, and removal of all of the regional lymph nodes. Outcomes of patients with stage III melanoma relate primarily to the extent of lymph node metastasis.
Lymphatic mapping and sentinel lymph node biopsy (SLNB) are used to assess the presence of melanoma cells in the regional lymph nodes in order to help determine which patients may require regional lymph node dissections (LNDs) and systemic adjuvant therapy.
SLNB should be performed prior to wide excision of the primary melanoma to ensure accurate lymphatic mapping. If metastatic melanoma is detected, a complete lymph node dissection (CLND) can be performed in a second procedure. Patients can be considered for a CLND if the sentinel node(s) is microscopically or macroscopically positive.
Systemic Adjuvant Treatment of Stage III Melanoma
Systemic therapy is any treatment directed at destroying cancer cells throughout the body. It is important to understand that many patients with stage III melanoma are at high risk for disease recurrence because undetectable cancer cells referred to as micrometastases may have already broken away from the primary cancer and traveled through the lymph and blood system to other locations in the body. The delivery of systemic cancer treatment following surgery is referred to as “adjuvant” therapy and improves survival.6,7,8
Adjuvant treatment of stage III melanoma with newer precision cancer medicines and immunotherapy drugs have rapidly become the standard of care because they delay the time to cancer recurrence and prolong survival. Patients should discuss the role of genomic testing for determining the best therapy to be used.
Systemic therapies commonly used in the treatment of stage III melanoma include:
Precision Cancer Medicine
Precision cancer medicines that target the genetic makeup of the cancer and immuno-oncology (drugs that use your immune system to help fight cancer) improve the outcomes of individuals with melanoma when compared with traditional chemotherapy. These therapies are designed to target the cancer cells while minimizing damage to normal, healthy cells. The ability to test a patient’s cancer for unique biomarkers that can identify differences at the genetic level, and to make treatment decisions based on those differences, is the hallmark of precision medicine.
BRAF & MEK Kinase Inhibitors
The BRAF and MEK genes are known to play a role in cell growth, and mutations of these genes are common in several types of cancer. Approximately half of all melanomas carry a specific BRAF mutation known as V600E. This mutation produces an abnormal version of the BRAF kinase that stimulates cancer growth. Some melanomas carry another mutation known as V600K. BRAF and MEK inhibitors block the activity of the V600E and V600K mutations respectively.8,9,10,11,12
- Zelboraf®(vemurafenib) BRAF V600E kinase inhibitor
- Tafinlar®(dabrafenib) BRAF V600E kinase inhibitor
- Braftovi® (enorafenib) BRAF inhibitor
- Mekinist®(trametinib) MEK V600 kinase inhibitor
- Cotellic® (cobimetinib) MEK V600 kinase inhibitor
- Mektovi® (binimetinib) MEK inhibitor
Combination of a BRAF and a MEK inhibitor appears to decrease the emergence of disease resistance that occurs in patients treated with BRAF inhibition alone. The combination of Taflinar plus Mekinist significantly improves survival compared to treatment with single agent Taflinar, when compared to no adjuvant therapy the combination reduced the risk of disease recurrence or death by 53%. The 3-year overall survival rate was 86% in the combination-therapy group compared to 77%.12
Immunotherapy treatment of melanoma has also progressed considerably and has also become a standard treatment. The immune system is a network of cells, tissues, and biologic substances that defend the body against viruses, bacteria, and cancer. The immune system recognizes cancer cells as foreign and can eliminate them or keep them in check—up to a point. Cancer cells are very good at finding ways to avoid immune destruction, however, so the goal of immunotherapy is to help the immune system eliminate cancer cells by either activating the immune system directly or inhibiting the mechanisms of suppression of the cancer.6,7
- Yervoy® (ipilimumab) is a monoclonal antibody that targets CTLA4, found on the surface of T cells. CTLA4 is thought to inhibit immune responses. By targeting this molecule, Yervoy enhances the immune system’s response against tumor cells. Yervoy has been demonstrated to improve survival in stage III melanoma patients who are at high risk of recurrence following complete surgical resection.7
PD-1 “Checkpoint Inhibitors”: PD-1 is a protein that inhibits certain types of immune responses, allowing cancer cells to evade an attack by immune cells. Drugs like Opdivo (nivolumab) and Keytuda (pembrolizumab) that block the PD-1 pathway can enhance the ability of the immune system to fight cancer and are referred to as checkpoint inhibitors for their ability to help the immune system recognize and attack cancer.6,13
- Both Keytruda and Opdivo are approved as adjuvant therapy for melanoma because they improve survival. Opdivo has also been shown to be superior to Yervoy for the management of stage IIIb/c melanoma following complete surgical resection.6,14
Imlygic® (talimogene laherparepvec), the first ever FDA-approved oncolytic virus therapy, has been approved for the treatment of melanoma sites in the skin and lymph nodes that cannot be surgically removed. Imlygic is given through a series of injections directly into the melanoma over the course of 6 months.
Imlygic is a genetically modified live oncolytic herpes virus therapy. When Imlygic is injected into the site of the cancer the modified herpes virus replicates inside cancer cells and causes the cancer cells to rupture and die. Imlygic may also promote tumor shrinkage, trigger a systemic immune response and prolong survival in some patients with advanced melanoma. After acting locally within the tumor, it is intended to prompt an immune response against cancer cells elsewhere in the body.
Preliminary results showed that 64 percent of injected tumors shrank by half. The vaccine shrank tumors that were directly injected as well as those that were not injected—indicating that the vaccine was triggering the immune system to fight the distant tumors.15
Strategies to Improve Treatment
The progress that has been made in the treatment of melanoma has resulted from patient participation in clinical trials. Currently, there are several areas of active exploration aimed at improving the treatment of melanoma.
Precision Cancer Medicines & Immunotherapy: As promising as all of the new, medicines are they typically stop working at some point because melanoma cells find another pathway that lets them start growing again. In many cancers, combination therapy improves survival and leads to cures when compared to single agent treatment. In addition to developing new precision cancer medicines and immunotherapies, researchers are testing various combinations of two or more drugs with encouraging results.
BRAF & MEK: The combination of a novel BRAF inhibitor Braftovi (encorafenib) with a MEK Mektovi (binimetinib) significantly delayed cancer recurrence compared to treatment with Zelboraf (vemurafenib) alone. Zelboraf was the first BRAF inhibitor approved for treatment of advanced melanoma and represented a breakthrough by significantly improving survival compared with chemotherapy, replaced the latter as a treatment option.16
Vaccines: Currently, no vaccine has been approved for the treatment melanoma. Melanoma vaccines produce responses, often dramatic, in some patients, but effects are far from consistent.
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10 Chapman PB, Hauschild A, Robert C, et al. Improved survival with vemurafenib in melanoma with BRAF V600E mutation. New England Journal of Medicine. 2011;364(26):2507-16. doi: 10.1056/NEJMoa1103782.
11 Hauschild A, Grob JJ, Demidov LV, et al. Dabrafenib in BRAF-mutated metastatic melanoma: a multicentre, open-label, phase 3 randomised controlled trial. Lancet. 2012;380(9839):358-65. doi: 10.1016/S0140-6736(12)60868-X.
12 Flaherty KT, Infante JR, Daud A, et al. Combined BRAF and MEK inhibition in melanoma with BRAF V600 mutations. New England Journal of Medicine.2012;367(18):1694-703. doi: 10.1056/NEJMoa1210093.
13 Robert C, Long GV, Brady B, et al. Nivolumab in Previously Untreated Melanoma without BRAF Mutation. New England Journal of Medicine [early online publication]. November 16, 2014.
14 United States Food and Drug Administration. News Release. FDA approves first-of-its-kind product for the treatment of melanoma. Available at: http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm469571.htm. Accessed October 27, 2015.
16 Dummer R et al “Encorafenib plus binimetinib versus vemurafenib or encorafenib in patients with BRAF-mutant melanoma (COLUMBUS): A multicenter, open-label, randomized phase III trial” Lancet Oncol 2018; DOI:10.1016/S1470-2045(18)30161-X.