Can tumor cells in the blood predict outcomes in metastatic melanoma?

The authors determined the benefit of measuring tumor cells in the blood for the treatment of advanced melanoma.  

Treatment options for advanced melanoma include targeted therapy (targeting specific genes or proteins) and immunotherapy (using the body’s own immune system to fight cancer). Targeted therapy is only effective in the short-term and immunotherapy is only effective for a small patient population. Factors that can predict the outcomes of the treatment could help patients decide on the appropriate treatment options.

Circulating tumor cells (CTC) are cells which have shed into the blood vessels from a tumor and circulate in the bloodstream. The presence of CTCs has been identified as an important factor in predicting the outcomes of several metastatic cancers (spreading from the original site to other parts of the body). However, only a few studies so far have evaluated the importance of CTCs in metastatic melanoma. 

Further evaluation of CTCs is needed to determine the value of CTCs in predicting survival and treatment outcomes in advanced melanoma.

The authors aimed to monitor the changes in CTC numbers in advanced melanoma patients to determine whether changes in CTCs could predict patient outcomes.

27 patients with metastatic melanoma were included in this study with an average follow-up of 53 weeks. All patients were enrolled in the study before treatments began. Treatments included surgery, chemotherapy or other targeted therapies (e.g. vemurafenib [Zelboraf]) as needed. CTCs were measured before the start of treatment (baseline), throughout treatment and after treatment.

The average progression-free survival (time from treatment until disease progressed) was 32 weeks. The average overall survival (patients who were still alive following treatment) was 53 weeks.

Patients who experienced a decrease in CTCs after treatment had a 12.7 times increased chance of experiencing a longer overall survival. This was compared to patients who did not experience a decrease in CTCs. Vemurafenib-treated patients, who experienced a decrease in CTCs, had a 12% faster response (how fast the tumors decreased in size) to treatment compared to patients who did not have decreased CTCs. There was no association between changes in CTCs after treatment and progression-free survival.

The authors concluded that measuring CTCs during the treatment of metastatic melanoma was useful in monitoring patient response to treatment. 

A large population of patients is needed to determine the utility of CTCs as a predictive factor in the treatment outcomes of metastatic melanoma. The patients in this study had variety of treatments which may have affected the treatment outcomes differently. As a result, the predictive value of baseline CTCs may have been biased..