Reassessing the Chronic Lymphocytic Leukemia International Prognostic Index in the era of targeted therapies

We evaluated the prognostic value of the Chronic Lymphocytic Leukemia International Prognostic Index (CLL-IPI) using a pooled dataset of CLL-patients treated first-line with targeted drugs (N=991) or chemoimmunotherapy (N=1,256). With a median observation time of 40.5 months, the 3-year progression-free survival (PFS)-rates for targeted drug-treated patients varied by CLL-IPI risk group: 96.5% (low), 87.6% (intermediate), 82.4% (high), and 78.7% (very high). Differences between consecutive CLL-IPI risk groups were observed for intermediate vs. low (HR=3.296, 95%-CI 1.576-6.894, p=0.002), for high vs. intermediate (HR=1.365, 95%-CI 1.003-1.858, p=0.048), but not for very high vs. high. CLL-IPI factors β2-microglobulin, IGHV mutational status, and TP53 status each retained prognostic value for PFS. The 3-year overall survival (OS)-rates by CLL-IPI risk group were 100%, 96%, 93.9%, and 89.4% with no differences between consecutive risk groups. Age, Binet stage, β2-microglobulin, and TP53 status each retained prognostic value for OS. In chemoimmunotherapy patients (median observation time 66.9 months), 3-year PFS-rates for CLL-IPI risk groups were 78.1%, 51.4%, 40.1%, and 16.5%. Corresponding 3-year OS-rates were 97.4%, 93.1%, 81.8%, and 57.3%. In a matched-pair analysis, PFS-differences in targeted therapies (N=812) versus chemoimmunotherapy (N=812) across all risk groups, and OS-differences in all but low-risk patients were demonstrated. The CLL-IPI maintains its prognostic value in predicting PFS outcomes with targeted drugs. With the caveat of a short observation time its impact in predicting survival appears diminished. Targeted therapies showed enhanced outcomes over chemoimmunotherapy, highlighting their effectiveness across various risk groups. Our findings support ongoing assessment of prognostic tools in CLL treatment evolution. CLL2-BIG (NCT02345863), CLL2-BAG (NCT02401503), CLL2-BIO (NCT02689141), CLL2-BCG (NCT02445131), CLL2-GIVe (NCT02758665), CLL13 (NCT02950051), CLL14-trial (NCT02242942), CLL1 (NCT00262782), CLL8 (NCT00281918), and CLL11 (NCT01010061).