Case-Based Review

Mantle Cell Lymphoma


 

References

For disease staging, bone marrow biopsy and aspiration are required. Radiographic staging using computed tomography (CT) scans and/or positron emission tomography (PET) scans had traditionally followed the Ann Arbor staging system, but recently the Lugano classification has emerged, which delineates only early or advanced stage.14 Gastrointestinal evaluation of MCL with endoscopy and colonoscopy with blind biopsies has been recommended to evaluate for the presence of lymphomatous polyps, but this is not an absolute requirement.15

RISK STRATIFICATION

At diagnosis, patients should undergo risk stratification in order to understand prognosis and possibly guide treatment. In MCL, the MCL international prognostic index (MIPI) is used. The MIPI is a prognostic tool developed exclusively for patients with MCL using data from 455 patients with advanced-stage MCL treated within 3 European clinical trials.16 The MIPI classified patients into risk groups based on age, ECOG performance status, LDH level, and WBC count. Patients were categorized into low-risk (44% of patients, median OS not reached), intermediate-risk (35%, median OS 51 months), and high-risk groups (21%, median OS 29 months). This is done through a logarithmic calculation, which can be accessed through online calculators (a prototype example can be found at www.qxmd.com/calculate-online/hematology/prognosis-mantle-cell-lymphoma-mipi). Cell proliferation using the Ki-67 index was evaluated in an exploratory analysis (the biologic [“B”] MIPI), and also demonstrated strong prognostic relevance.16 Currently, treatment of MCL patients is not stratified by MIPI outside of a clinical trial, but this useful tool assists in assessing patient prognosis and has been validated for use with both conventional chemoimmunotherapy and in the setting of autologous stem cell transplant (autoSCT).16,17 At this point in time, the MIPI score is not used to stratify treatment, although some clinical trials are incorporating the use of the MIPI score at diagnosis. Nonetheless, given its prognostic importance, the MIPI should be performed for all MCL patients undergoing staging and evaluation for treatment to establish disease risk.

As noted, the proliferative signature, represented by the Ki-67 protein, is also highly prognostic in MCL. Ki-67 is expressed in the late G1, S, G2, and M phases of the cell cycle. The Ki-67 index is defined by the hematopathologist as the percentage of lymphoma cells staining positive for Ki-67 protein, based on the number of cells per high-power field. There is significant interobserver variability in this process, which can be minimized by assessing Ki-67 quantitatively using computer software. The prognostic significance of Ki-67 at diagnosis was established in large studies of MCL patient cohorts, with survival differing by up to 3 years.18,19 Determann et al demonstrated the utility of the proliferative index in patients with MCL treated with standard chemoimmunotherapy.10 In this study, 249 patients with advanced-stage MCL treated within randomized trials conducted by the European MCL Network were analyzed. The Ki-67 index was found to be extremely prognostic of OS, independent of other clinical risk factors, including the MIPI score. As a continuous variable, Ki-67 indices of greater than 10% correlated with poor outcomes. The Ki-67 index has also been confirmed as prognostic in relapsed MCL.20 It is important to note that, as a unique feature, the Ki-67 index has remained an independent prognostic factor, even when incorporated into the “B” MIPI.

TREATMENT

CASE CONTINUED

The patient undergoes an excisional biopsy of a cervical lymph node, which demonstrates an abnormal proliferation of small-medium–sized lymphocytes with slightly irregular nuclear contours. Immunohistochemistry shows that the abnormal lymphocytes are positive for CD20 and CD5, negative for CD10 and CD23, and diffusely positive for cyclin D1, consistent with a diagnosis of MCL. The proliferative index, as measured by the Ki-67 immunostain, is 40%. A bone marrow aspirate and biopsy are then obtained, which show a clonal population of B lymphocytes expressing the same immunophenotype as the lymph node (positive for CD20 and CD5, negative for CD10 and CD23, cyclin D1 positive). A CT scan of the neck, chest, abdomen, and pelvis with contrast is obtained, along with a PET scan. These studies identify extensive hypermetabolic lymphadenopathy in the bilateral cervical chains, supraclavicular areas, mediastinum, and hilum. Mesenteric lymph nodes are also enlarged and hypermetabolic, as are retroperitoneal lymph nodes. The spleen is noted to be enlarged with multiple hypermetabolic lesions. Based on the presence of extensive lymphadenopathy as well as bone marrow involvement, the patient is diagnosed with stage IV MCL. He undergoes risk-stratification with the MIPI. His MIPI score is 6.3, high risk.

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