Assessment of circulating tumour cells (CTC) at patients’ first clinic visit for stage III melanoma could help identify those who might benefit from more aggressive treatment after primary treatment, US researchers have suggested. In their study*, published in Clinical Cancer Research, they found that the detection of CTCs – a type of "liquid biopsy" – was independently associated with an increased risk of relapse within six months.
The researchers, led from the University of Texas, said that until now there have been no available blood tests that could predict accurately which patients with melanoma are the most likely to relapse, and should be given therapy; and which patients are low risk, and could be observed. They pointed out that such a test could also help to prevent overtreatment. They pointed out that CTCs can be detected in melanoma patients, until now there had been limited data regarding their significance in stage III (node-positive) melanoma.
They noted that earlier research had already shown that the presence of CTCs in people with breast cancer was associated with an increased risk of relapse – independently of other existing methods of determining prognosis – so they conducted a prospective study to investigate the possible importance of CTCs in melanoma.
They recruited 243 patients during their first clinic visit for stage III melanoma, and found that 90 of these people had CTCs. They then compared relapse-free survival in patients found to have one or more CTCs, with survival in those without CTCs.
The study authors reported that CTC detection was not associated with sub-stage, or primary tumour characteristics. But multivariable analysis demonstrated that the detection of at least one CTC at baseline was significantly associated with decreased six-month relapse-free survival (hazard ratio, HR 3.62) and 54-month relapse-free survival (HR 1.69).
They concluded: “[Detecting] ≥1 CTC was independently associated with melanoma relapse, suggesting that CTC assessment may be useful to identify patients at risk for relapse who could derive benefit from adjuvant therapy… The data from this study provides support for the future pursuit of liquid biopsy techniques to help identify patients most likely to benefit from adjuvant systemic therapy.”
They added that at the moment there is no clear consensus on when to recommend immunotherapy for node-positive melanoma patients; although there are new targeted and immune therapies for melanoma, many people with melanoma either do not respond to these treatments, or they develop resistance to therapy within 6-8 months. Furthermore, these therapies can have adverse effects, and so avoiding treatment in those patients at low risk of relapse might prevent overtreatment.
They commented: “Our findings are significant, given that there is a need for blood-based biomarkers to guide clinical decision making for stage III melanoma patients. There currently are no blood tests available to help doctors accurately tell which patients are likely to relapse, and should be given therapy, and which are low risk, and could be observed.”
*Lucci A, Hall C, Patel SP, et al. Circulating tumor cells and early relapse in node-positive melanoma. Clin Cancer Res February 3 2020 DOI: 10.1158/1078-0432.CCR-19-2670