Risk assessment for cancer spread to lymph nodes in patients with intermediate thickness melanoma

The authors aimed to identify those melanoma patients having a low risk of cancer spreading to the lymph nodes. The authors found that most melanoma patients with intermediate tumor thickness (between 1.01 mm and 1.05 mm) had a similar risk of disease spread to the lymph nodes as found in patients with thin melanoma (tumor thickness of 1 mm or less). 

In skin melanoma, the sentinel lymph node (SLN) is the first lymph node (tiny, bean-shaped organs that help fight infection) to which the cancer cells are believed to spread. The presence of cancer in the SLN is determined by a procedure called sentinel lymph node biopsy (SLNB). It involves taking a tissue sample to determine whether cancer cells are present. Among patients with intermediate tumor thickness (between 1.01 mm and 4 mm), 15-20% have a chance of SLN positivity (cancer actually spreading to the lymph node). Currently, SLNB is recommended to all patients with a tumor thickness of more than 0.75 mm. 

It is thought that there may be some characteristics of intermediate thickness melanoma that may indicate a lower risk of cancer spread to the SLN. If these characteristics are well understood, some of the low-risk patients could be spared SLNB. 

The authors aimed to identify melanoma patients with intermediate thickness but with low risk of SLN positivity.

952 patients with melanoma thickness between 1.01 mm and 4 mm were included in this study. Among these 36% of patients had thickness of less than 1.5 mm. All underwent SLNB.

Overall, 157 patients (16.5%) had positive SLN. The odds of positive SLN were 71% lower in patients with tumor thickness less than 1.5 mm. The odds were 31% lower in patients aged 60 years or older. In patients who had a type of white blood cell in their tumors, the odds were 30% lower.

Only 6.6% of patients who had a tumor thickness less than 1.5 mm had SLN spread of cancer. In patients with a tumor thickness of less than 1.5 mm, 75% had more than one low-risk factor. Less than 5% of these patients had SLN positivity.

The authors concluded that melanoma patients with tumor thickness between 1 mm and 1.5 mm had a similar risk of SLN positivity as that observed in cases of thin melanoma.