Impact and Dynamics of TP53 Mutated Clones in Shwachman Diamond Syndrome in a Series of 80 Patients

Introduction: Hematological complications (HC) as Aplastic anemia (AA) and myelodysplasia and acute leukemia (MDS/AL) are frequent and life threatening in patients with Shwachman Diamond Syndrome (SDS) with SBDS mutations. The therapy of such events is based on Hematopoetic stem cell transplantation (HSCT), which results remain quite poor, especially in case of malignancy. So far, it is difficult to anticipate to such HC and a lot is expected from the study of clonal evolution prior HC.

Methods: A Targeted panel of 43 genes involved in MDS/AL (sensibility 1%) has been evaluated in 80 patients with SBDS mutation, representative of a nation based cohort of 154 patients. This cross sectional study has been completed by a prospective study for 40 patients evaluated at several time points.

Results: The evaluation was performed in various situations: steady state i.e. no haematological complication, in MDS/AL and AA and lastly after HSCT. At the first evaluation, somatic mutation was found in 21 patients (30%) among the 70 in steady state and in 7 of the 8 cases with HC (6/6 cases with MDS/AL, in 1 among the 2 cases with AA) while the 1 of the 2 patients long term survivors after HSCT have no mutation and the other one kept a TP53 clone with a normal blood count and a low (1.5%) variant allele frequency (VAF). Among the 40 patients with several time points, 17 have a mutation at the first time points, but 10 others had additional mutation later. Globally, the most frequent gene involved was TP53 (82%) while mutations in other genes have been observed rarely. VAF in patients with vs without HC is lower (median VAF 0% vs 22.8% respectively p < 0.001) . Complex caryotype, monosomy 7, Iso7q were associated with P53 clone while in Del20q, 8 patients out 14 have a P53 mutations. The comparison between blood and bone marrow results allow the possibility to monitor such mutations in blood. Clonal evolution in one patient who presents a MDS in the course of the follow up had shown a competition between clones.

Conclusion: Acquired TP53 is extremely frequent in patients with SBDS mutations, even in the absence of HC, but the prevalence as well as the VAF increased in case of HC. When sequential evaluation could be performed, competition between clones is frequent and a clinical decision remains therefore difficult, just on the evaluation of a time point.

Acknowledgments: The French SCN registry is supported by grants from Amgen, Chugai, Prolong Pharma, X4 Pharma, Inserm, the Association 111 les Arts, the Association RMHE, the Association Sportive de Saint Quentin Fallavier. The authors thank the association IRIS and Mrs Grosjean and Mr Gonnot(ASSQF), the association Barth France for their support.