Cytogenetic Abnormalities Predict Clinical Outcome In Patients Diagnosed With Relapsed Acute Myeloid Leukemia (rAML): Single Center Experience

Cytogenetic abnormalities have significant prognostic role in AML at the time of diagnosis. Several prognostic groupings have been recommended including the NCCN and European LeukemiaNet classification. It is still unknown whether cytogenetic abnormalities have any prognostic role at the time of relapse for predicting clinical outcome. In addition, clonal evolution (CE) has been seen in many AML cases, but its prognostic value remains to be identified.

To study cytogenetic abnormalities and clonal evolution impact on clinical outcome for patients diagnosed with rAML

A retrospective, single institution study through chart review of all cases diagnosed with rAML at Mayo Clinic Rochester between 2003 to 2011 was performed. Pts who achieved complete remission and relapsed at our institution were included. Pts with PML-RARA and BCR-ABL rearrangements were excluded from this study. Pts with available cytogenetics data, both at presentation and relapse, were included. Response to treatment was defined as per international working group (IWG) criteria (Cheson JCO 2003). Appropriate IRB approval was obtained in accordance with Helsinki declaration. Comparison between groups’ medians was done using Wilcoxon test, while survival estimates were calculated using Kaplan-Meier curves using JMP V9.

Out of 192 pts, 74 pts matched our inclusion criteria. The median age at diagnosis is 60 years (range 18-81), 53% were males. At relapse, median white blood cell (WBC) was 3.2 x10⁹, hemoglobin 10.4 g/dL, platelet 59 x10⁹, peripheral blood (PB) blast 2% (range, 0-96), bone marrow (BM) blasts 23% (range, 1-95) and cellularity 60%. Relapse site was mainly in the BM (95%). Flt3 mutation was found in 12/43 (28%), while NPM1 mutation in 2/7 (29%). Upon treatment with salvage therapy, 27 (36%) pts achieved complete remission (CR) and 16 (22%) pts partial remission (PR) for a total overall response (OR) of 58%. Twenty one (28%) pts were able to proceed to allogeneic stem cell transplant (SCT) after achieving remission. Median overall survival (mOS) was 198 days. Pts had a longer mOS if they proceeded to SCT (386 days vs 121 days, p =0.0003).

Cytogenetic analysis (CG) were diploid in 32 (43%) of 74 pts at relapse. Five pts had favorable cytogenetics (3 pts with t(8,21) and 2 pts with inv (16)). CG was divided into favorable, intermediate and poor prognosis as per NCCN classification in 5 (7%), 45 (61%), 24 (32%), respectively. As per European LeukemiaNet, there were 4 CG groups divided into: favorable, Intermediate-1, intermediate-2, and adverse in 5 (7%), 33 (45%), 12 (16%), 24 (32%), respectively. Upon comparison of CG at diagnosis and relapse; clonal evolution (a change in CG due to gain or loss of chromosomal abnormalities) was found in 42/74 (57%) of pts. CG reverted back to diploid in 8/42 (19%) or gained additional CG abnormalities at relapse in 32 (76%) pts.

CR2 was achieved in 80% of favorable CG (NCCN grouping), 40% (intermediate), and 21% in poor risk (p=0.01). Using NCCN CG grouping mOS was: 435 days (favorable), 266 (intermediate), and 104 (poor) (p value = 0.01). However, using European LeukemiaNet grouping mOS was: 435 days (favorable), 174 (intermeidtae-1), 363 (intermediate-2), and 104 (poor) (p=0.004). CE did not affect mOS (p =0.7). On multivariate analysis, response to salvage therapy (p<0.0001), NCCN CG grouping (p =0.03), wbc (p=0.045), and PB blasts (p=0.01) were significant but not age, BM blast, platelet and CE.

CG were diploid in 43% of relapsed pts. CE (gain or loss of cytogenetic abnormalities) was seen in 57% of CG at relapse compared to diagnosis but did not affect mOS. NCCN (and not European LeukemiaNet) cytogenetic grouping did affect clinical outcome through both achieving second CR and mOS (both on univariate and multivariate analysis). Our results confirm the prognostic value of CG on relapse, and need to be confirmed by larger studies. 

No relevant conflicts of interest to declare.