Unique clinico-biological, genetic and prognostic features of adult early T-cell precursor acute lymphoblastic leukemia

Funding: this project was supported by the Asociación Española Contra el Cáncer (project ref: GC16173697BIGA), PI14/01971 FIS, Instituto Carlos III, CERCA Program/Generalitat de Catalunya, 2014-SGR225 (GRE), Obra Social “La Caixa” . This work was also partially supported by FEDER funds from the ISCIII (PT13/0010/0026, CIBERONC (CB16/12/00284 and CB16/12/00400), Madrid, Spain). P. Barba was supported by the Instituto de Salud Carlos III FIS16/01433 and PERIS 2018-2020 from Generalitat de Catalunya (BDNS357800) grants

section_content: GRAALL 2003 and 2005 trials showed that treatment intensification with allogeneic hematopoietic stem cell transplantation (HSCT) in ETP-ALL with early treatment resistance could improve survival. 12 ere we retrospectively analyzed the frequency, clinico-biological and prognostic features of adult ETP-ALL vs. other T-ALL cases in a series of 185 adults with T-ALL treated within two consecutive minimal residual diseaseoriented trials by the Programa Español de Tratamientos en Hematología (PETHEMA): ALL-HR-2003 (NCT00853008) and ALL-HR-11 (NCT01540812), the latter still ongoing). 

All 185 patients were diagnosed with T-ALL using the WHO criteria. The treatment protocol schedules have been described previously elsewhere. 13, 14 The patients' characteristics at diagnosis and at follow-up are summarized in Table 1. The immunological T-ALL subtype was defined according to the European Group for the Immunological Characterization of Leukemias (EGIL) criteria after centralized review of immunophenotypic reports. In turn, the criteria proposed by Zuurbier et al. 2 were used to define ETP-ALL. The combination of markers used (<5% CD1a, CD8 and CD4; >25% CD34 and/or CD33/CD13), resembles that proposed by Coustan-Smith et al., while dim CD5 expression (<75% positive cells) was not considered. The inclusion of negativity for CD4 instead of dim CD5 expression as an immunophenotypic criterion, allows identification of most ETP-ALL cases identified by gene expression profiling (increased sensitivity of immunophenotyping to detect ETP-ALL cases). 2 Clinical data were obtained in accordance with the principles of the Declaration of Helsinki and Spanish legislation, after written informed consent had been provided by each patient. The study was approved by the Institutional Review Board of the Hospital Germans Trias i Pujol (Badalona, Spain). 

Comparisons between ETP-ALL and other T-ALL cases were performed with the χ 2 test, Fisher exact test, and the median test, as appropriate. Event-free survival and overall survival curves were plotted using the Kaplan-Meier method and compared by the log-rank test. A secondary haematologica 2020; 105:e294 Cumulative incidence of relapse and non-relapse-related mortality were analyzed as competing events with the Gray test. A Cox proportional hazard regression model was used to identify predictive factors for event-free and overall survival, whereas multivariate analysis for cumulative incidence of relapse was performed with the Fine and Gray model. Statistical significance was set at P-values <0. 05. Full immunophenotypic data according to the EGIL criteria were available for 167/185 T-ALL patients; 34/167 (20%) T-ALL cases met criteria for ETP-ALL as defined by both Zuurbier et al. and the WHO. 7 This frequency is similar to that observed in previously published cohorts of adults with T-ALL 11, 12 in which the phenotypic criteria applied in early pediatric studies to define ETP-ALL were used. 1 Significant differences were observed when comparing ETP-ALL and non-ETP-ALL cases at diagnosis (Table 1 ). Patients with ETP traits were older [mean ± standard deviation (SD): 39±12 years vs. 33±12 years, P=0. 01], more frequently had lymph node enlargement (79% vs. 56%, P=0. 02), had lower white blood cell counts (mean±SD: 72. 2±155. 1x10 9 /L vs. 96. 6±111. 7 x10 9 /L, P=0. 004), and showed a slightly different female to male ratio (13/21 vs. 30/103, P=0. 06), similarly to what has been shown for the GRAALL cohort. 12 In addition, our ETP-ALL cases frequently showed absence of CDKN2A/B (P<0. 001) and TCRG (P=0. 003) gene deletions. These results are in line with those previously reported in the literature 6, 14, 16 and support the use of both genetic markers for the diagnosis of ETP-ALL. However, some discordance between immunophenotypic and genetic results was observed, which might be due to the limited sensitivity of current immunophenotypic criteria, highlighting the need for more precise and robust criteria and standardized methods for the diagnosis of ETP-ALL.

section_content: No significant differences in complete response, overall survival, event-free survival and cumulative incidence of relapse rates were observed between ETP-ALL patients enrolled in the two treatment protocols (data not shown). This allowed a combined evaluation of the data from both PETHEMA trials. ETP-ALL patients showed significantly poorer response to induction therapy compared to other T-ALL patients (Table 1 ). Thus, ETP-ALL patients had poorer bone marrow response (<10% blasts) on day +14 compared to other T-ALL cases (18% vs. 63%, P<0. 001); half of ETP-ALL cases required second induction treatment (vs. 10% of the remaining T-ALL cases, P<0. 001) and 23% of them did not attain a complete response (vs. only 6% of other T-ALL cases, P=0. 005). Minimal residual disease data were available for 132/167 patients who reached a complete resposne after one or two induction cycles. Two-thirds (65%) of ETP-ALL cases showed minimal residual disease levels ≥0. 1% (vs. 18% of non-ETP-ALL cases, P<0. 001), the percentage increasing to 85% (vs. 37%, P<0. 001) at a cut-off level of 0. 01%. Consequently, as indicated per protocol, more ETP-ALL patients underwent allogeneic HSCT (70% vs. 21%, P<0. 001). Despite treatment intensification with allogeneic HSCT, ETP-ALL patients did not attain a significant improvement in the probability of overall surhaematologica 2020; 105:e295 vival (Figure 1A, B ). In fact, differences in overall and event-free survival between ETP-ALL and other non-ETP T-ALL patients were mostly due to the greater rate of failure to induction therapy, with a minimal contribution of the higher (non-statistically significant) cumulative incidence of relapse observed among ETP-ALL patients vs. other T-ALL cases (Online Supplementary Figure S1 ). However, it should be noted that the overall survival rate of adult T-ALL patients from the PETHEMA cohort who underwent allogeneic HSCT was lower than that observed in other studies. 12, 13 Thus, the improvement of non-transplant-related mortality in transplanted patients might have a positive impact on survival of ETP-ALL patients. Multivariate analyses showed that ETP-ALL was an independent adverse predictor for both overall survival and event-free survival [hazard ratio of 2. 14 (95% confidence interval: 1. 29-3. 53), P=0. 003 and 1. 91 (1. 18-3. 11), P=0. 009, respectively] together with a high white blood cell count (Online Supplementary Table S1 ).
section_name: LETTERS TO THE EDITOR

section_content: In summary, here we confirmed the previously reported frequency and clinico-biological features of adult ETP-ALL and showed that adult ETP-ALL patients should be considered as a group with a worse prognosis. The poorer outcome of ETP-ALL patients in our study was due to a lower response to induction therapy and not to an increased relapse rate, which highlights the need to investigate the potential utility of alternative induction therapy for these patients. The use of acute myeloid leukemia-oriented chemotherapy, together with intensification of chemotherapy regimens, has been effective in clearing disease in pediatric ETP-ALL cases refractory to initial induction chemotherapy. 17 A similar strategy could be applied to adult ETP-ALL patients. Based on these findings, and given the poor response attained in adults with the conventional induction regimen, it makes sense to explore the potential benefit of the FLAG-IDA regimen (idarubicin; fludarabine; ARA-C and granulocyte colonystimulating factor), a more myeloid-oriented chemotherapy schedule, as front-line induction treatment together with allogeneic HSCT after standard consolidation. In addition, new therapies targeting specific genes altered in ETP-ALL patients, such as FLT3 inhibitors, have emerged as novel alternative treatment strategies. However, the potential benefit of this latter treatment is restricted to ETP-ALL patients carrying FLT3 mutations in the tyrosine kinase domain (1/9, ETP-ALL cases in our cohort; data not shown). Similarly, other potential targeted therapies (e. g. Jak2 inhibitors or Bcl-2 antagonists) may also provide a benefit, but require further investigation.
section_name: LETTERS TO THE EDITOR

section_content: Eulàlia Genescà, 1* Mireia Morgades, 2 Pau Montesinos, 3 Pere Barba, 4 Cristina Gil, 5 Ramon Guàrdia, 6 María-José Moreno, 7 Daniel Martínez-Carballeira, 8 Irene García-Cadenas, 9 Susana Vives, 2 Jordi Ribera, 1 José González-Campos, 10 Celia González-Gil, 1 Lurdes Zamora, 2 José-Luís Ramírez, 2 Marina Díaz-Beya, 11 Santiago Mercadal, 12 María-Teresa Artola, 13 Antònia Cladera, 14 Mar Tormo, 15 Arancha Bermúdez, 16 Ferran Vall-Llovera, 17 Pilar Martínez, 18 María-Luz Amigo, 19 Silvia Monsalvo, 20 Andrés Novo, 21 Marta Cervera, 22 Antoni García-Guiñon, 23 Jordi Juncà, 2 Juana Ciudad, 24 Alberto Orfao 24 and Josep-Maria Ribera 1,2 1 Josep Carreras Leukaemia Research Institute, Campus ICO-Germans Trias i Pujol, Universitat Autònoma de Barcelona, Badalona; 2 Clinical Hematology Department, ICO-Hospital Germans Trias i Pujol, Universitat Autònoma de Barcelona, Badalona; 3 Hospital Universitari i Politècnic La Fe & CIBERONC, Instituto Carlos III, Madrid; 4 Clinical Hematology Service, Hospital Universitari de la Vall d'Hebron, Barcelona; 5 Clinical Hematology Service, Hospital General de Alicante, Alicante; 6 Clinical Hematology Service, Hospital Josep Trueta-ICO, Girona; 7 Clinical Hematology Service, Hospital Vírgen de la Victoria, Málaga; 8 Clinical Hematology Service, Hospital Universitario Central de Asturias, Oviedo; 9 Clinical Hematology Service, Hospital de la Santa Creu i Sant Pau, Barcelona; 10 Clinical Hematology Service, Hospital Vírgen del Rocío, Sevilla; 11 Clinical Hematology Service, Hospital Clínic de Barcelona, Barcelona; 12 Clinical Hematology Service, Hospital Duran i Reynals-ICO, Hospitalet del Llobregat ; 13 Clinical Hematology Service, Hospital Universitario de Donostia, Donostia; 14 Clinical Hematology Service, Hospital Son Llàtzer, Palma de Mallorca ; 15 Clinical Hematology Service, Hospital Clínico de Valencia, Valencia ; 16 Clinical Hematology Service, Hospital Marqués de Valdecilla, Santander; 17 Clinical Hematology Service, Hospital Mútua de Terrassa, Terrassa; 18 Clinical Hematology Service, Hospital 12 de Octubre, Madrid; 19 Clinical Hematology Service, Hospital Morales Meseguer, Murcia; 20 Clinical Hematology Service, Hospital Gregorio Marañón, Madrid; 21 Clinical Hematology Service, Hospital Son Espases, Palma de Mallorca ; 22 Clinical Hematology Service, Hospital Joan XXIII, Tarragona; 23 Clinical Hematology Service, Hospital Arnau de Vilanova, Lleida and 24 Centro de Investigación del Cáncer (IBMCC-CSIC/USAL), Hospital Clínico Universitario de Salamanca, Instituto Bio-Sanitario de Salamanca, CIBERONC Salamanca, Spain Acknowledgments: we would like to thank Rosa Coll, Rodrigo Martino, Raimundo García Boyero, Jesús Mª Hernández Rivas, Pilar Herrera, Juan Bergua, Mª Jesús Peñarrubia, Eloy del Potro, Magdalena Sánchez, Beatriz Soria, Aurelio López Martínez, Mª José Sánchez Sánchez, Pilar Bravo, Pilar Vivancos, Alfons Serrano, José Santiago Bermón, Maria Lourdes Amador Barciela and Matxalen Olivares Salaverri for providing retrospective clinical data for this study. Funding: this project was supported by the Asociación Española Contra el Cáncer (project ref: GC16173697BIGA ), PI14/01971 FIS, Instituto Carlos III, CERCA Program/Generalitat de Catalunya, 2014-SGR225 ( GRE), Obra Social "La Caixa ". This work was also partially supported by FEDER funds from the ISCIII ( PT13/0010/0026, CIBERONC ( CB16/12/00284 and CB16/12/00400 ), Madrid, Spain). P. Barba was supported by the Instituto de Salud Carlos III FIS16/01433 and PERIS 2018-2020 from Generalitat de Catalunya ( BDNS357800 ) grants. Correspondence: EULALIA GENESCA' -egenesca@carrerasresearch. org doi:10. 3324/haematol. 2019. 225078Information on authorship, contributions, and financial & other disclosures was provided by the authors and is available with the online version of this article at www. haematologica. org.