Treating relapsed B cell-precursor ALL in children with a setting-adapted mitoxantrone-based intensive chemotherapy protocol (TMH rALL-18 PROTOCOL) — experience from Tata Memorial Hospital, India

The outlook of relapsed ALL in low- and middle-income countries (LMICs) is dismal due to high treatment-related toxicities and inadequate resources. We report our experience of using a locally adapted mitoxantrone-based protocol for non-high risk (HR) relapsed B-ALL (rALL). A retrospective cum prospective study of standard and intermediate risk (SR and IR) rALL patients treated on TMH rALL-18 protocol (adapted from COG/UKALLR3/Int-Re-ALL protocols) between November 2018 and January 2021 was analyzed. The protocol comprising of 7 blocks of multi-agent chemotherapy including mitoxantrone in induction followed by local irradiation and maintenance, underwent serial modifications based on our experience with initial patients. Eighty-two patients (SR rALL, 3; IR rALL, 79) were treated on TMH rALL-18 protocol. Of 321 grade 3/4 reported toxicities, around 43% (138 toxicities) were noted during induction. Induction chemotherapy was outpatient-based; however, 68 patients (82.9%) required supportive care admissions. Twelve out of 19 patients with gram negative bacilli sepsis (included 7 MDRO) died during reinduction. Five remission deaths were seen during block 3 after which cytarabine was dose reduced (3 g to 2 g/m 2 ). Post-reinduction minimal residual disease was negative in 54 (80.6%) out of 67 evaluable patients. At a median follow-up of 24 months (95% CI 22–27), the estimated 2-year event-free and overall survival of the entire cohort was 58% (95% CI 48.1–69.9) and 60.3% (95% CI 50.5–72). Until the time, targeted therapies are freely accessible in LMICs, strengthening supportive care as well as local adaptation of protocols that strike a fine balance between efficacy and tolerability are mandated.