Early Allogeneic Stem Cell Transplantation and Use of Asparaginase during Induction Chemotherapy Appear to Improve Otherwise Poor Outcomes in Adult T-Cell Acute Lymphoblastic Leukemia/Lymphoma (T-ALL/T-LBL) Patients: A Multi-Institutional Review

Background: AdultT-cell acute lymphoblastic leukemia/lymphoma (T-ALL/T-LBL) is a rare, aggressive bone marrow malignancy with a historically poor prognosis despite use of various chemotherapies.

Methods: After institutional review board approval, we compiled a database of all adult T-ALL/T-LBL cases at three large cancer centers between the years 2005-2015, treated at the physician's discretion. Data collected included patient demographics, tumor characteristics (white cell count at diagnosis, blast phenotype, FISH, cytogenetics, bone marrow involvement), treatment regimens and patient outcomes. Relapse-free survival (RFS) and overall survival (OS) were examined looking at medians and interquartile ranges of times to events. Kaplan Meier curves provided a graphical representation of the survival probability. Moreover, we provided estimates of the 50^th percentile along with corresponding 95% confidence intervals (CIs). We also used Univariate and Multivariable Cox Regression to estimate unadjusted and adjusted Hazard Ratios (HRs) and their 95% CIs. Stratified analysis was also performed using the Mann-Whitney U-test to compare median survival times, and the Log-rank to compare survival curses for RFS and OS.

Results: The final analysis included 95 adult patients. Median age at diagnosis was 32 (range 17-75). 71.6% of patients were male. 49.5% of patients were white, 14.7% were black, 6.3% were Hispanic, 7.4% were Asian and in 22.1% of patients the race was unknown. Multiple frontline treatment regimens were used with 60% of patients treated with Hyper-CVAD, an additional 5.3% of patients received Hyper-CVAD with asparaginase, 24.2% of patients were treated on a pediatric-based protocol, 4.2% on a clinical trial, and 6.3% received other regimens. In total, 40 patients (42.1%) received asparaginase at some point during treatment regimen with 27 patients (28.4%) receiving it in the initial treatment regimen. After induction therapy, 65 patients (68.4%) achieved remission. Twenty-eight patients (29.5%) underwent transplant (8 matched-related donors, 10 matched unrelated donors, 5 mismatched unrelated donor, 2 cord transplants, 2 autologous, and 1 haplo-identical transplant). Ten patients (10.5%) underwent transplant in first complete remission (CR1) while two patients (2.1%) proceeded to transplant with minimal residual disease following induction. Despite therapy, 59 patients (62.1%) had known disease relapse or progressive disease. 16 patients (16.8%) underwent transplant after disease relapse. At time of analysis, 57 patients (60.6%) died. In the entire cohort, median RFS was 12.9 months and median OS was 19 months. In patients with a very high white count (>100 x 10³/cmm at presentation) there was a trend toward earlier relapse when compared to patients presenting with white counts in the normal range (HR 2.27, p-value 0.085). Patients who received asparaginase in their initial treatment regimen have statistically improved RFS (HR 2.65, p-value = 0.014) and OS (HR 2.3, p-value=0.017). When adjusting for the presence of the covariates of age, sex, and WBC, patients who received initial asparaginase still had significant improvement in RFS (HR 3.18, p-value 0.033). In overall survival, significant benefit was seen in the addition of asparaginase in patients under 40 (HR 3.4, CI 1.22-9.5), however in patients greater than 40, asparaginase use seemed to decrease survival (HR 0.24, CI 0.03-1), although this did not reach statistical significance. All patients who underwent transplant had an improvement in OS, with median survival in the transplant group of 27 months compared to 18.2 months in the non-transplanted patients (log-rank test p-value = 0.048). Patients who received a transplant in CR1 had a trend towards improvement in RFS of 6.3 months (17.8 months versus 11.5 months in non-transplanted patients; log-rank test p-value = 0.03).

Conclusion: Overall, adult T-ALL/T-LBL has a poor prognosis. Our multi-institutional retrospective review showed that OS and RFS may be improved by incorporating asparaginase use in front line therapy and by transplanting patients in first CR. Our data is limited in that actual dosing of asparaginase was not examined and that relatively few patients > 40 yrs old received asparaginase (4 pts) or SCT (5 pts). More prospective studies are needed in older adult T-ALL/LBL patients using these approaches to possibly improve their outcomes.