The presence or absence of minimal residual disease predicted progression-free and, to a lesser degree, overall survival among chronic lymphocytic leukemia (CLL) patients who achieved complete or partial remission with six courses of chemoimmunotherapy, based on two randomized phase III trials.
These findings underscore the value of measuring minimal residual disease (MRD) in patients who respond to a defined period of CLL therapy, Dr. Gabor Kovacs of the University of Cologne (Germany) and his associates wrote Aug. 29 in the Journal of Clinical Oncology.
The investigators examined the predictive value of measuring MRD in peripheral blood by using four-color flow cytometry at a threshold of 10-4 by analyzing data from 554 adult CLL patients who achieved complete or partial remission during two phase III trials – one (CLL8) comparing fludarabine and cyclophosphamide with fludarabine, cyclophosphamide, and rituximab (FCR) and a second (CLL10) comparing FCR with bendamustine plus rituximab (J Clin Oncol. 2016 Aug 29. doi:10.1200/JCO.2016.67.1305).
The median progression-free survival (PFS) after the end of treatment was 61 months for the 34% (186 patients) who attained MRD-negative complete remission (CR), 54 months for the 29% of patients who attained MRD-negative partial remission (PR), 35 months for the 7% of patients who attained MRD-positive CR, and 21 months for the 30% of patients who attained MRD-positive PR. Progression-free survival did not differ significantly between MRD-negative CR and MRD-negative PR patients, but was significantly longer for MRD-negative PR patients than for MRD-positive CR patients (P = .048).
Progression-free survival was even more distinct for MRD-positive CR patients, compared with those who attained MRD-positive PR (P = .002). Overall survival was significantly shorter only when patients had MRD-positive PR rather than MRD-negative CR (72 months vs. not reached, P = .001).
Among the MRD-negative PR patients, 16% had only residual lymphadenopathy, 11% had only bone marrow involvement, 48% had only splenomegaly, and 25% had more than one organ system affected, the researchers noted. Importantly, PFS for MRD-negative PR with residual splenomegaly (63 months) was similar to that for MRD-negative CR (61 months, P = .354).
In contrast, patients with MRD-negative PR and residual lymphadenopathy had shorter PFS than did MRD-negative CR patients (31 months, P = .001). “We hypothesize that residual splenomegaly after chemoimmunotherapy often represents tissue that does not contribute to a subsequent clinical progression,” the researchers commented.
They also noted an important caveat – their findings are only valid for patients who received a defined period of CLL treatment followed by observation (without maintenance), not for patients who are treated indefinitely until progression.
The CLL8 and CLL10 trials were funded by Roche, Mundipharma, and the German Federal Ministry of Education and Research. Dr. Kavocs disclosed support for travel, accommodations, and expenses from Roche and Celgene.