Evaluating routinely available histopathological prognostic features from more than 500 MCL patients in prospective trials, researchers found that the Ki-67 index is a better prognostic factor than are cytology and growth pattern in mantle-cell lymphoma (MCL). In addition, the combination of the Ki-67 index with the Mantle Cell Lymphoma International Prognostic Index [MIPI] defined four prognostic groups with better discrimination than did MIPI or the two-category biologic MIPI (MIPI-b) alone.
Higher Ki-67 index was associated with poorer overall survival (OS) (hazard ratio [HR], 1.24 per 10% increase; P less than .001) and progression-free survival (PFS) (HR, 1.17; P less than .001). Consistent with an earlier, population-based study, results showed prognostic value for a 30% cutoff of the Ki-67 index. Quantitative levels below 30% provided no additional prognostic information.
“The Ki-67 index remains the only routinely available independent prognostic factor in addition to MIPI. In contrast to cytology and growth pattern, the Ki-67 evaluation has been standardized for routine application,” wrote Dr. Eva Hoster of University Hospital Munich, and colleagues. “The modified combination of Ki-67 index and MIPI integrates the most important clinical and biologic markers currently available in clinical routine and was shown to allow a simple and powerful risk stratification superior to MIPI and MIPI-b in our evaluation,” they added (J Clin Oncol. 2016 Feb. 29. doi: 10.1200/jco.63.8387).
Blastoid cytology was associated with inferior 5-year OS compared with nonblastoid cytology (35% vs. 68%; HR, 2.35; P less than .001) and PFS (29% vs. 44%; HR, 1.58; P = .007), but the effect was largely accounted for by a generally higher Ki-67 index in blastoid MCL. Diffuse growth pattern was associated slightly worse 5-year OS (61% vs. 72%; HR, 1.38; P = .048) and PFS (38% vs. 49%; HR, 1.25; P = .087), but the effect was largely explained by MIPI score.
Combining dichotomized Ki-67 (above or below 30%) with MIPI risk groups defined four prognostic groups by the sum of weights (total 0 to 3): Ki-67 of 30% or more (weight 1), intermediate-risk MIPI (weight 1), and high-risk MIPI (weight 2). The 5-year OS rates for the four groups ranged from 17% to 85%, with OS hazard ratios greater than 2 between adjacent risk groups.
The study analyzed pooled data from two randomized trials initiated in 2004 by the European Mantle Cell Lymphoma Network, MCL Younger and MCL Elderly. In total, 508 patients of median age 62 years were included. The proportion of low-risk, intermediate-risk, and high-risk MIPI were 41%, 35%, and 24%, respectively.
Research was supported in part by Roche. Dr. Hoster reported receiving funding from Roche Pharma AG and Celgene. Several of her coauthors reported ties to industry.