Multicenter comparison of first salvage chemotherapy versus novel therapy regimens in adult relapsed/refractory acute lymphoblastic leukemia

Patients with relapsed/refractory (R/R) acute lymphoblastic leukemia (ALL) represent a heterogeneous population and therefore there is no standard of care first salvage regimen. We conducted a multicenter, retrospective analysis to compare chemotherapy (e.g. HyperCVAD, MOAD, Larson/CALGB-9511, etc.) to novel agents (blinatumomab or inotuzumab) in first salvage. The primary endpoint, overall survival (OS), was not significantly different among treatment arms, with a median OS of 10.6 months with chemotherapy and 10.1 months with novel therapy (p = .799). Similarly, there was no difference in the CR/CRi rate, with a CR/CRi in 18 patients (41.9%) versus 16 patients (47.1%) treated with salvage chemotherapy and novel therapy, respectively (p = .817). Age significantly impacted the probability of achieving CR/CRi with novel therapy versus chemotherapy. This analysis suggests the use of chemotherapy in first salvage still represents an appropriate treatment option, particularly for young fit patients, as the median OS was roughly 10 months regardless of whether patients received novel therapy or chemotherapy in first salvage. For the reported outcomes, 100% of patients in the novel therapy arm received a novel therapy (per design), whereas only 60.5% of patients in the chemotherapy arm required a novel therapy. Thus, 40% of patients did not require a novel therapy for similar OS. This analysis demonstrates that first-line chemotherapy can achieve similar results to novel therapies, especially now that novel therapies are available for subsequent relapses. However, this study has several limitations including younger age, increased CNS involvement, and higher blast percentage in the chemotherapy arm and potential confounders, including selection of treatment sequence as 43 patients (55.8%) ultimately received both chemotherapy and novel therapy. Therefore, a larger, prospective, randomized study with adequate chemotherapy comparators and availability of novel agents upon relapse is warranted to confirm these results.