Observatory for Patients Treated for Relapsed or Refractory T-cell Acute Lymphoblastic Leukemia With Oncogenetic Features.

Depending on protocol and leukemia subtype, 5-10% of T-ALL patients are primary refractory, and 30-40% of patients will relapse. A new complete remission is attained in 20-40% of patients, but prolonged disease-free survival is observed in only 10-15% of cases. Nelarabine is approved for R/R T-ALL in second relapses, with a CR rate of 36% in the registration study, and an overall survival of 24% at 1 year and 12% at 3 years.

The biological landscape of T-ALL is well characterized, with the identification of at least 10 key recurrently mutated pathways including transcriptional regulation (91% of cases), cell cycle regulation and tumor suppression (84%), NOTCH1 signaling (79%), epigenetic regulation (68%), PI3K-AKT-mTOR signaling (29%), JAK/STAT signaling (25%), RAS signaling (14%), ribosomal function (13%), ubiquitination (9%) and RNA processing (9%). Furthermore, T-ALL cells are dependent upon BCL-XL and upon BCL-2, especially when the T-ALL blasts bear an ETP phenotype. However, genomic data cannot reliably predict the response of leukemic cells to a given treatment, due to interactions of the different cellular pathways affected in a living leukemic cell. Therefore, the combination of genotypic and phenotypic data may overcome this problem.

In France, patients with relapsed or refractory T-ALL (and also T-cell lymphoblastic lymphomas) are already proposed to undergo a genotypic (oncogenetic characterization) and a phenotypic (drug testing assay) characterization as a standard of care procedure. Based on the results obtained in fresh leukemic cells, a national scientific committee may recommend the used of targeted drugs alone or in combination, in the context of a "off-label" or a "compassionate" use (for example : Temsirolimus + Erwiniase + Venetoclax in PI3K-AKT-mTOR mutated ALL / Tofacitinib + Venetoclax in IL7R-JAK-STAT mutated ALL / 5-azacytidine + Venetocax in hypermethylated ALL / ...).

All patients who undergone this procedure will be proposed to be registered in the ALL-Target registry (ALL-target Observatory). After registration, data related to disease history, disease characterization and disease treatment as well as data describing the patient's condition will be collected.

Some patients may receive conventional chemotherapy as a salvage (conventional cohort), others may receive targeted therapy as a salvage (personalized medicine cohort). The aim of the registry is to evaluate the benefit of each treatment strategy in term of response as a primary end point. Comparison between the two cohorts will be performed after adjustment for confounding factors. Results of subgroups will also be reported using descriptive statistics. Secondary endpoints will include safety of the treatment strategy, survival, disease free survival and progression free survival.