Evaluation of the proliferative index as a prognostic factor in diffuse large cell lymphoma: Correlation with the International Index

The reasons for differences in outcome between groups of patients with diff use large cell lymphoma (DLCL) defined by clinical prognostic factors are l argely unknown. Measures of cell proliferation may offer a biological expla nation for these differences. This study tested the hypothesis that these s urvival differences between the groups defined by established prognostic fa ctors were due to the proliferative index. The bromodeoxyuridine labeling i ndex (LI), a measure of the S-phase fraction, was prospectively determined on fresh tumor specimens obtained at initial diagnosis in 80 patients with DLCL seen between 1986-1993 at a single institution. Patients were grouped using prognostic factors that were significant in a univariate analysis as well as the International Index (IPI). The LI in each of these groups was c ompared to determine whether the differences in outcome between the groups could be explained by differences in the LT. The median LI for ail patients was 5.1% (range: 0.1-25%). When the predicti ve effect of the LI on response and survival was analyzed, the LI did not c orrelate with complete response or disease-free survival (DFS). There was a trend, however, for patients with a lower LI to have a poorer overall surv ival (p=0.06). When the patients were analyzed using the International Inde x (LPI), the mean LI for patients in the low-risk, low-intermediate, high-i ntermediate and high risk groups was 7.1%, 10.0%, 6.4% and 6.6% respectivel y (p=0.41). When analyzed separately, there was no significant difference i n the LI for any of the patient groups defined by significant prognostic fa ctors. The only difference in the LI was that the median LI in patients wit h T-cell DLCL was significantly lower than the LI in patients with B-cell D LCL (p=0.001) and these patients had an inferior complete response rate (p= 0.001), dis ease-free survival (p=0.003) and overall survival (p=0.015). In this study, the LI, a measure of lymphoma cell proliferation, was not a si gnificant prognostic factor for response, disease-free survival or overall survival. Furthermore, the LI did not explain the differences in outcome be tween patient groups defined by the IPI. However, a lower LI seen in patien ts with T-cell DLCL may account for their poorer response to therapy and in ferior survival when compared to patients with B-cell DLCL.