Fresh Approaches for Treating Micro-Metastatic Melanoma Explored

Source: OncLive, September 2014

Approximately 85% of patients with newly diagnosed melanoma present with what appears to be clinically localized disease, making them candidates for standard treatment with surgery. But some of these patients may be harboring microscopic metastases in their lymph nodes.

How best to identify patients who may have microscopic metastatic disease, and should thus be tested via sentinel lymph node biopsy, was among the topics discussed during a recent OncLive Peer Exchange® roundtable discussion entitled “Practical Considerations in Metastatic Melanoma.” Mario Sznol, MD, served as moderator.

In patients found to have a positive node, a biopsy can help “optimize [the patient’s] chance for cure by treating lymph node disease early, and also optimize the chance for long-term regional control within the lymph node basin,” noted panel member Merrick I. Ross, MD.

The panel members also considered whether patients found to have a positive node should go on to receive completion lymph node dissection, and explored the prospect of biomarkers that might eventually be used to guide treatment decisions.

Determining When Biopsy is Appropriate

Determinations about when a patient should undergo sentinel node biopsy are based mainly on the thickness of the lesion, panel members said.

“It used to be 1 mm in Breslow thickness that we would perform this on,” said Robert H.I. Andtbacka, MD. “However, we have lately started looking at the risk of having micro-metastatic disease in those lymph nodes, and we have said that a risk of about 5% is the point at which we would offer the procedure to the patient. That risk of 5% falls at a Breslow thickness of about 0.75 mm, so at our institution, we would do it at 0.75 mm. At other institutions, they still do it at 1 mm.

“We also do look at other parameters of that primary melanoma, such as ulceration and increased mitotic count,” Andtbacka continued. “That’s a mitotic count of 1 per mm2 or greater. We do know that those factors increase the risk of having nodal involvement.”

According to Ross, the value in doing a sentinel node biopsy is that metastatic disease, if found, is at a very early stage. That makes early intervention possible, which is why such patients often have better outcomes than those who develop palpable disease after a wide excision, he said. Ross asserted that those whose metastasis is found while microscopic fare 20% better than those whose disease is found when macroscopic, but panelists debated that.

Jeffrey S. Weber, MD, PhD, pointed out that about 80% of patients with melanoma in the MSLT-1 [Multicenter Selective Lymphadenectomy Trial]1 who underwent sentinel node biopsy had negative results, thus diluting that 20% outcome advantage down to 5% for the overall group of melanoma patients with suspected microscopic metastases.

“Then, the question is, given the cost of doing the sentinel node biopsy, is it justified by the modest benefit?” Weber asked. “My personal feeling is probably yes, meaning I can sell it to patients, but I gather there are those who think it’s probably not worth it because there isn’t enough survival.”