Superior Outcomes in Hispanic Patients Compared to Non-Hispanic Patients with Ph-Negative Acute Lymphoblastic Leukemia Using the Modified Pediatric-Based University of Southern California Acute Lymphoblastic Leukemia (USC ALL) Regimen for Newly Diagnosed ALL Patients in the Era of Novel Agents; A Retrospective Study

INTRODUCTION:

Hispanic patients with acute lymphoblastic leukemia (ALL) are historically known to have poor outcomes compared to non-Hispanic patients. Our institution, LAC-USC (LA County Hospital/University of Southern California) has shown a complete remission rate of 96% with use of pegasparagase at 2000 IU/m2 using the USC ALL regimen (based on CCG-1882) for patients aged 17-55 years with a 7-year OS of 51% reported in 2014. The modified USC ALL regimen now uses a single dose of cytarabine rather than fractionated doses and uses a single dose 3g/m ² methotrexate compared to 1g/m ² (2.5g/m ² if T-cell) D1, 15 in original USC ALL regimen to improve compliance, while consolidation was increased to six cycles allowing for PEG holidays to improve toxicity (Table 1). Since our institution takes care of a large population of Hispanic patients with ALL, we now report outcomes in Hispanic and Non-Hispanic patients using the modified USC ALL regimen in the era of novel agents like blinatumomab and inotuzumab.

METHODS:

This retrospective, single institution chart review included adults >18 years old with newly diagnosed Ph-negative ALL (2016-2020). Primary objectives were 3-year over-all survival (OS), event-free survival (EFS), disease-free survival (DFS). Secondary objectives were complete remission/complete remission with incomplete recovery (CR/CRi), minimal residual disease (MRD) by flow cytometry, descriptive statistics of patients who were stratified into Hispanic and non-Hispanic cohorts and evaluated using Fisher's exact test. OS, DFS, EFS were reported through Kaplan Meier curves and Log-rank tests. Two-sided p-value ≤0.05 was significant.

RESULTS: 121 Ph-negative patients were reviewed. 87 were Hispanic patients (HP) and 34 non Hispanic patients (NHP). Median ages were 39 and 35 years (p=0.51) and median BMI were 29 and 26.9 kg/m ² (p=0.42), respectively. There were about equal males and females in HP while NHP had 70.6% males compared to 29.4% females (p=0.076). Both HP and NHP were mainly of the Ph-negative ALL subtype, 50.6% vs 47.1%, followed by Ph-like, 25.4% vs 20.6%, respectively (p=0.884).

Majority of the population were unfavorable risk by NCCN karyotypic risk stratification, 55.9% in HP compared to 56.0% in NHP (p=0.99). Over-all, no significant difference between baseline characteristics in both cohorts.

After induction 1: CR/CRi was 85.9% in HP and 73.4% in NHP (p=0.09). MRD negativity by flow cytometry in HP was 41.4% compared to 26.4% in NHP (p=0.13).

After induction 2: 83% of HP were in CR/CRi compared to 80% in NHP (p=0.99) and MRD negativity by flow was 35.6% in HP compared to 32.4% in NHP (p=0.73).

Blinatumomab was given in 33.3% of HP and 32.3% of NHP (p=0.92) while only 5.7% of HP and 2.9% of NHP received inotuzumab (p=0.99). 34.5% of HP underwent allogenic hematopoietic stem cell transplant (allo-HSCT) versus 26.5% in NHP (p=0.40).

3-year OS was 92.2% in HP versus 67.4% in NHP (p=0.004). 3-year DFS was 92.8% in HP versus 60.7% in NHP (p=0.003). 3-year EFS was 54.1% in HP versus 32.3% in NHP (p=0.02) (Table 2).

Rate of relapse for HP and NHP were 23.4% vs 29.4% (p=0.74) while rate of mortality for HP and NHP were 7.5% vs 28% (p=0.015), respectively.

No clear difference in grade 3/4 PEG toxicities were found in HP and NHP except more hypertriglyceridemia in HP (p=0.019).

CONCLUSIONS:

We present comparison of outcomes in Hispanic and non-Hispanic patients using our modified USC ALL pediatric-based regimen in an era of novel agents. Our data shows significantly better outcomes in Hispanic patients compared to non-Hispanic patients [OS (92.2% vs 67.4%, p=0.004), DFS (92.8% vs 60.7%, p=0.003) and EFS (54.1% vs 32.3%, p=0.02)].

This study demonstrates that given equal access to care (eg. receiving blinatumomab, allo-HSCT), outcomes in HP with Ph-negative ALL are not worse, but rather superior to those in NHP. Utilization of novel immunotherapy like blinatumomab in the salvage setting to achieve deeper molecular response and increased utilization of haploidentical allo-HSCT have likely contributed to reducing ethnic disparities in Hispanic ALL patients. Future studies are needed to validate these findings with larger patient populations.

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