The Lymphatic System's Role in Cancer

Solid tumor cancers such as breast, melanoma, lung, colorectal and head-and-neck cancer frequently spread via the lymphatic system. Neoprobe believes it is the only company focused on better mapping of lymph nodes to improve the diagnosis of solid tumor cancers to enhance surgical outcomes and improve patient treatment.

The lymphatic system (also known as the immune system) is an important network of channels and filters that make up the body's main line of defense against disease. Lymph channels contain a clear, watery fluid that contains white blood cells, called lymphocytes, which fight infection and disease. Along the network are bean-shaped organs called lymph nodes or glands. These nodes are responsible for the manufacture and storage of the disease- or infection-fighting lymphocytes. Lymph nodes are clustered in the neck, under the arms, in the groin and abdomen and may swell and become tender when the body is fighting infection (such as in strep throat). The body has thousands of lymph nodes that are connected via the lymphatic system and collectively harness the body's defenses.

The lymphatic system provides a vital function in fighting disease; however, this intricate network also creates an ideal pathway for cancer cells to travel and spread.

When a person develops a malignant tumor, usually it is not the primary tumor itself that ultimately kills a person. Rather, death is caused by the spread of the cancer to vital organs such as the liver, brain or lungs. It is generally thought that the spread of cancer is caused by the migration (or draining) of tumor cells from the initial tumor to nearby lymph nodes and eventually to other vital sites via the lymphatic system. Cancer surgeons and medical oncologists believe the determination of whether a patient's primary tumor has spread to the lymph nodes is a major determinant of a patient's long-term prognosis. The spread of cancer to the patient's lymph nodes is established by the examination of the nodes by pathology to determine if tumor cells are present. If tumor cells are determined to be present in the lymph nodes, the patient's stage or severity of disease is increased. The staging of the cancer establishes the post-surgery treatment protocol for the patient.

In the case of breast cancer, standard therapy typically involves the surgical removal of the primary tumor followed by a determination whether the cancer has spread to a patient's lymphatic system. The determination of the spread of disease is accomplished by removing nearby lymph nodes for biopsy. Prior to intraoperative lymphatic mapping ("ILM") described below, it was not uncommon for a surgeon to remove virtually all (~20-30) of the lymph nodes in the surrounding area (a process known as auxiliary node dissection). This radical, and often unnecessary, procedure caused a large number of patients to experience significant complications following surgery while producing a high percentage of inconclusive pathology results.

In melanoma and colorectal cancers, the staging of solid tumors is even more complicated as it is often difficult to identify and then locate which of the nearby lymph nodes are potentially involved and draining from the tumor site. The surgeon may remove too many "clean"lymph nodes unnecessarily or fail to remove a cancerous lymph node that later leads to the spread of disease. Better solutions are clearly needed for identifying the pathway from the cancer to the lymphatic system and in isolating the initial spread of disease to the lymph nodes.

Intraoperative Lymphatic Mapping (ILM)

In an ILM procedure, a radioactive tracing agent is injected at the site of the primary tumor. Following injection, the tracing agent follows the drainage path of the tumor to the nearest lymph node or nodes, referred to as the "sentinel node(s)."A gamma detection device is used to detect the path of the tracing agent. Since the lymph nodes are connected, oncologists believe that if the sentinel nodes show no sign of malignancy, then the downstream nodes in the pathway are likely to be clear of disease. As such, the removal of other nearby lymph nodes would be clinically unnecessary. Therefore, the ability to rapidly locate and biopsy sentinel nodes provides vital information to the physician in determining if the cancer has spread or if it is localized to the site of the primary tumor.

Neoprobe is the leading provider of the gamma detection devices used in ILM with a significant market share worldwide. In addition, the Company is at the forefront of developing better tracing agents to improve the accurate staging of solid tumor cancers such as breast and melanoma.