Long-Term Follow-Up Results of Adults with T-Cell Acute Lymphoblastic Leukemia (T-ALL)-The Vancouver Experience.
Authors: Mourad Yasser R. Abou , Nantel Stephen H. , Toze Cynthia L. , Nevill Thomas J. , Barnett Michael J. , Forrest Donna L. , Hogge Donna E. , Lavoie Julye C. , Shepherd John D. , Sutherland Heather J. , Smith Clayton A. , Song Kevin W. 
Published: October 2019

T-cell acute lymphoblastic leukemia (T-ALL) is a rare disease accounting for approximately 20–25% of adult cases of ALL. The outcome of adult T-ALL has improved in the past decades, but relapse remains the major cause of treatment failure. Few studies have reported on the long-term outcome of adults with T-ALL. We retrospectively reviewed the charts of 39 adult patients (pts) diagnosed with T-ALL and treated at our center between August 1986 and April 2004.

Characteristics: Male/female ratio was 3.3/1. Median age was 28.4 years (16.8–73.2). ECOG PS: 0/1(n=27), ≥ 2 (n=12). Median WBC at diagnosis was 12.2 (0.9–445), Platelets 60.7 (6–270), LDH <2 x normal (n= 14), ≥ 2 x normal (n=23), unknown (n=2). CSF was involved in 7/39 pts, splenomegaly found in 13/39, mediastinal mass in 16/39 and lymphadenopathy in 16/39 pts. 36/39 pts received a consistent induction chemotherapy regimen consisting of prednisone, vincristine and daunorubicin ± L-asparaginase. A second phase of induction comprised of cyclophosphamide, cytarabine, methotrexate and mercaptopurine. Intensification was with dexamethasone, vincristine, daunorubicin, cyclophosphamide, cytarabine and thioguanine. Four cycles of consolidation with cytarabine and tenoposide were given. 30/39 pts (77%) achieved complete remission with induction chemotherapy. 1 patients died during induction chemotherapy secondary to disseminated aspergillosis, 2 patient during consolidation secondary to cerebral edema and aspergillosis. 8/30 pts proceeded to allogeneic BMT in CR1(4/8 due to high WBC>150, 3/8 MRD availability,1/8 in CR1 after salvage chemotherapy) of whom two pts died due to aGVHD and infection after transplantation. 8 pts had refractory disease; Only 1/8 achieved CR on salvage chemotherapy. 16/30 (53%) relapsed of whom 12/16 (75%) died of disease progression, 1 died of sepsis in CR2 and 3 pts alive in CR2. Median follow up of the 15 surviving patients is 59 months (1.5–183.4).

Results: Overall survival (OS) and event-free survival (EFS) at 3 years for all patients were 33.7% (95% CI 19–49%) and 28% (95% CI 13–43%) respectively. Using univariate analysis, significant factors for poor survival were CSF involvement: [3-year EFS was 14% vs 34% (p = 0.05)], LDH levels higher than 2 times normal [3-year EFS was 7% vs 43.5% (p = 0.005)] and ECOG PS ≥2: [3-year EFS was 16.6% vs 37% (p = 0.05)]. Non-significant factors included sex, age < 30 vs 30–55, presence of mediastinal mass, lymphadenopathy, splenomegaly, WBC > 50.

Conclusions: Adult T-ALL presents more commonly in young males with a third having a mediastinal mass. The outcome of treatment results in a 30% long term disease free survival. Patients refractory to induction as well as those who relapse have poor prognosis. As expected poor PS, high LDH and CSF involvement dictates worse outcome. Neither age, nor high WBC count contributed to worse prognosis.