Relapse is common after hematopoietic cell transplantation for acute lymphoblastic leukemia (ALL). While 1200 cGy total body irradiation (TBI) and cyclophosphamide (Cy) is standard, attempts to lower relapse have led to the addition of a second chemotherapeutic agent and/or higher dose TBI. We examined transplantation outcomes in patients aged <18 years with ALL, in second or subsequent remission or in relapse at transplantation. Most transplants occurred in remission. Patients received grafts from an HLA-matched sibling or unrelated donor. Four treatment groups were created: 1) Cy + TBI≤1200 cGy (n=304), 2) Cy + etoposide + TBI≤1200 cGy (n=108), 3) Cy + TBI≥1300 cGy (n=327), and 4) Cy + etoposide + TBI≥1300 cGy (n=26). Neither TBI in excess of 1200 cGy nor the addition of etoposide resulted in fewer relapses. The 5-year probabilities of relapse were 30%, 28%, 35% and 31% for groups 1, 2, 3 and 4, respectively. However, transplant-related mortality was higher (35% vs. 25%, p=0.02) and overall survival lower (36% vs. 48%, p=0.03) after Cy + etoposide + TBI ≥1300 cGy compared to Cy + TBI ≥1300 cGy. Compared to the standard regimen neither TBI in excess of 1200cGy nor the addition of etoposide improves survival after HCT for ALL.
3506 Recurrent disease is the most important cause of treatment failure after HCT. Total body irradiation (TBI)-containing conditioning regimens are associated with fewer relapses and longer leukemia-free survival (LFS) in children and adolescents with ALL. While TBI <13 Gy + cyclophosphamide (Cy) is considered standard, attempts to lower relapse rates have led to addition of a second chemotherapeutic agent (etoposide) or higher dose TBI (≥13 Gy) with or without addition of etoposide. TBI dosing (<13 Gy vs. ≥13 Gy) or the addition of etoposide to TBI + Cy regimen has not been examined in children. We report on 765 patients aged <18 years, who received either an HLA-matched sibling (n=160) or an unrelated donor (URD, n=605) HCT between 1998 and 2007. Seventy percent of patients were in 2nd complete remission (CR), 20% were in 3rd CR, and the remaining 10%, in relapse at HCT. The median age of the study population is 9 years and the median follow-up of surviving patients is 4 years. Transplant outcomes were examined in four treatment groups: 1) TBI <13 Gy + Cy (n=304), 2) TBI <13 Gy + Cy + etoposide (n=108), 3) TBI ≥13 Gy + Cy (n=327), and 4) TBI ≥13 Gy + Cy + etoposide (n=26). Ninety-six percent of patients in the TBI <13 Gy group received 12 Gy and 4%, 10 Gy. Irradiation doses in the TBI ≥13 Gy group were 13.2 Gy (24%), 13.5 Gy (41%) and 14 Gy (35%). Patient and disease characteristics (performance score, disease status, NCI-risk score, duration of first remission and cytogenetic risk) were similar among the treatment groups. The 3-year probabilities (95% confidence interval) of treatment-related mortality (TRM), relapse, and LFS in the four treatment groups are shown in the Table below. Neither higher dose TBI (≥13 Gy) nor the addition of etoposide regardless of TBI dose was associated with lower risks of leukemia recurrence or longer LFS after HCT. In the absence of an advantage for leukemia control, further intensification of the conditioning regimen TBI <13 Gy + Cy is not recommended. TRM Relapse LFS 1) TBI dose <13 Gy + Cy 25 (21–31)% 30 (24–35)% 45 (39–51)% 2) TBI dose <13 Gy + Cy + etoposide 29 (21–38)% 26 (18–34)% 45 (35–54)% 3) TBI dose ≥13 Gy + Cy 23 (19–28)% 33 (28–39)% 43 (38–49)% 4) TBI dose ≥13 Gy + Cy + etoposide 35 (17–52)% 31 (15–69)% 35 (17–52)% Disclosures: No relevant conflicts of interest to declare.
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