The Predictive Value of TP53 FISH Analysis for Treatment Response and Survival in Cytogenetic Subgroups of AML Patients.

Abstract 2617

Poster Board II-593

In recent years, a number of studies emphasized AML with complex aberrant karyotype as a distinct biological entity which is characterized by a unique gene expression pattern, with very frequent alteration in TP53 and a median overall survival (OS) of less than 6 months. However, the definition of a complex karyotype (CK) or whether monosomal karyotype (MK) provides a better prognostic prediction than CK is not well established. In the present study, we examined whether a prompt and simple Fluorescence in situ hybridization (FISH) test for TP53 deletion (presence or absence of 17p13) at diagnosis, has a predictive value for response to therapy and overall survival in AML patients (pts) with CK or chromosomal deletions (either complete or partial of any other chromosome). Between 2000 and 2009 we analyzed 38 patients with newly diagnosed AML, with age ranged from 18 to 82 years (median 52 years). On cytogenetic analysis from bone marrow at diagnosis, 16 (42%) pts had a CK (≥3 chromosome abnormalities), 16 pts (42%) had a normal karyotype (NK) and 6 (16%) pts had other monosomy or deletion of any chromosomal region. Seven patients had a post myelodysplastic syndrome AML and 1 post therapy for a prior malignancy. For induction treatment patients received idarubicine, 12 mg/m²/d (age 18– 55y) or mitoxantron 10 mg/m²/d intravenous (IV) on days 1-3 (age 55–68y) and cytarabine, 100mg/m²/d by continuous IV infusion on days 1 through 7. Pts entering complete remission (CR) received three courses of consolidation with high dose cytarabine. Patients with a histocompatibale donor, which did not received CR or relapsed, were allografted. Elderly patients, 69–82 years old, were treated with one induction chemotherapy which included Mylotarg (3mg/m²/2h on day 1) plus cytarabine (100 mg/m²/24h on days 2-8). Patients at this group of age did not received consolidation therapy.

Of the16 pts with CK AML, 14 were treated with chemotherapy but only 3 pts (21%) achieved CR, 4 pts died during induction therapy. By comparison, of the 16 pts with NK AML, 15 pts were treated with chemotherapy, 11 pts achieved CR (73%), 3 pts died during induction therapy. Of the 6 AML pts with monosomy or deletion in cytogenetic analysis, 3 pts (50%) achieved CR (p =0.0067). In all NK AML patients examined the TP53 FISH was normal (mean 4% of cells examined), where as in patient with CK 75% of pts had TP53 deletion (mean 51%), and in the group with chromosomal deletion 50% of pts showed a loss of one TP53 (mean 18%) p=0.0016. Of note, in 13 pts (34%) with TP53 deletion by FISH analysis, cytogenetic analysis found no anomaly of 17p chromosome. In a stepwise logistic regression model FISH groups significantly entered the model in first step, and no other variable did (p=0.0056, C=0.833). In pts in which two copies of TP53 were found in FISH analysis ('10%) the median survival time is 440 days, whereas in pts with TP53 deletion was detected the median survival time was 189 days. The OS in pts with deletion of TP53 was significantly shorter as compared to pts that TP53 deletion was not found (p=0.025). However, a multivariate analysis including age, karyotype, deletion of TP53 and allogeneic transplantation showed that only CK and allogeneic transplantation are independent prognostic factors in this analysis.

In conclusion, TP53 status by FISH at diagnosis is important due to the following findings:

The test is sensitive, rapid and simple.

2. TP53 deletions are frequent in AML with CK and tend to segregate with additional chromosomal deletions.

TP53 status at diagnosis has a predictive value with respect to chemotherapy response and OS in AML pts with CK and chromosomal deletions.