Mantle cell lymphoma (MCL) is a subtype of B-cell lymphoma and is one of the rarest forms of Non-Hodgkin's lymphoma, accounting for six percent of non-Hodgkin’s cases, for a total of around 15,000 patients in the US. It is one the more difficult to treat lymphomas, although, while not often “cured”, the average survival time has increased in recent years from three to six years.
The cause of MCL is unknown, although it has been traced to genetic transcription errors. Diagnosis requires microscopic examination of cells from the bone marrow, gastrointestinal tract, and occasionally the blood. Chest, abdominal, and pelvic CT scans may be performed, as may PET scans to determine spread/location of nodules.
The four means of treatment currently employed are chemotherapy, immunotherapy, radioimmunotherapy, and new biologic agents. The latter two are relatively new and less commonly prescribed.
Chemotherapy is the most widely used frontline treatment, with a number of different drugs used in various combinations, depending on the progression of the disease, the age and health of the patient, and whether the disease had been successfully treated before. Chemotherapy is sometimes used in conjunction with radiation therapy, resulting in the complete destruction of the patient’s immune system. This necessitates the transplantation of a new immune system based on stem cells previously harvested from the patient or a donor.
Immunotherapy seeks to boost the patient’s own immune response to cancer cells, enabling the body to heal itself. Some variations include cancer vaccines, adoptive cell transfer, and immunotransplant, though no immunotherapeutic protocol is considered an approved standard of care.
Prognosis for mantle cell lymphoma is problematic, in that prognostic criteria become less reliable at advanced stages of the disease. As a B-cell lymphoma, MCL tends to move throughout the lymphatic system, meaning most patients are initially diagnosed at Stage III or IV, rendering the standard staging system less helpful.
Using a set of 455 MCL patients in Germany, scientists have devised the Mantle Cell Lymphoma International Prognostic Index (MIPI) to classify patients into risk groups. Patients at low risk have a five-year survival rate of 60 percent, those at medium risk have a median survival time of 51 months, and those at high risk have a 29 month median survival expectation. Overall, the five-year survival rate is about 50 percent for advance stages of the disease, and 70 percent for more limited manifestations.
In addition to the prognostic indices put forth by the MIPI, other proposed indicators are the type of MCL cellular involvement and the Ki-67 cell proliferation index. For the former, when larger, blastic cells are involved, spread tends to be much faster, while diffuse and nodular involvements tend to spread more slowly. Approximately 25 percent of patients with blastic cell involvement live five years or more.
The Ki-67 index measures how fast cells mature and ranks them from roughly ten percent to 90 percent. The higher the percentage, the more quickly cells mature and therefore the more aggressive the spread of the cancer. Scores of 61-90 percent Ki-67 have a median survival time of one year, while 5-20 percent Ki-67 may have a median survival of as much as four years. Despite these additional prognostic criteria, an accurate prognosis for mantle cell lymphoma remains a troublesome and inexact science.