Lymph node ratio in stage III melanoma

This article evaluated lymph node ratio (LNR) as a prognostic factor for stage III melanoma patients.

Melanoma often spreads beyond the original tumor site. Once cancer cells spread to nearby lymph nodes (these are referred to as cancer-positive lymph nodes) the disease is categorized as stage III melanoma, which suggests an increased risk for distant cancer spread and mortality. Therefore, determining whether the cancer has spread to the surrounding lymph nodes is a crucial step in the initial evaluation of melanoma patients. Lymph nodes surrounding the tumor are removed with the cancer during surgery, and examined under a microscope to determine whether they are cancer-positive.    

While the number of cancer-positive lymph nodes has long been known as a reliable prognostic factor, recent studies suggest that lymph node ratio (LNR) may predict survival and the risk of recurrence more accurately. LNR refers to the number of cancer-positive nodes, divided by the total number of lymph nodes removed during surgery (including both cancer-positive and cancer-negative nodes).

This study evaluated 411 patients with stage III melanoma. Patients were divided into two groups based on their LNR. 291 patients were found to have a low LNR (< 0.15), while only 120 patients were found to have a high LNR (≥ 0.15).

On average, patients with LNR < 0.15 registered longer survival times than patients with LNR ≥ 0.15. 3 year survival rates were 78% in the low LNR group compared to 69% in the high LNR group. 5 year survival rates were 67% in the low LNR group compared to 58% in the high LNR group. 10 year survival rates were 49% in the low LNR group compared to only 34% in the high LNR group. However, these differences in survival according to LNR were not more significant than differences in survival according to the current staging system (taking into account only the number of cancer-positive nodes).

In comparison, this study found that the risk of cancer recurrence was significantly reduced in patients who had a large number of lymph nodes removed (regardless of cancer status) during surgery. Among patients who had less than 8 inguinal, 15 axillary and 20 cervical lymph nodes removed and examined, 20% showed recurrence of the cancer during the study period. Among patients who had more than 8 inguinal, 15 axillary and 20 cervical lymph nodes removed and examined, only 8% experienced cancer recurrence.

This study concluded that LNR does not provide further prognostic information compared to current staging techniques. However, removal of at least 8 inguinal, 15 axillary and 20 cervical lymph nodes is associated with decreased recurrence rates regardless of the number of cancer-positive nodes.