Table 1.

Classification of Relapsed ALL – BFM versus COG

Berlin-Frankfurt-Munster Group (BFM), Germany		Treatment	5-year OS [6]
S1	Late IEM (>6 months from end of treatment)	Chemotherapy	60–70%
S2	Early and very early IEM (<6 months from end of treatment)	Chemotherapy Chemotherapy + HSCT	40% 60%
	B-ALL late BM (>6 months from end of treatment)
	B-ALL combined (early or late)
S3	B-ALL early BM (>18 months from diagnosis to < 6 months from end of treatment)	Chemotherapy Chemotherapy + HSCT	< 5% 30%
S4	Very early BM (<18 months from diagnosis)	Chemotherapy Chemotherapy + HSCT	< 5% 30%
	Very early combined (<18 months from diagnosis)
	T-ALL marrow (early or late)
Children’s Oncology Group (COG), USA		Treatment	5-year OS [11, 12]
Low	Late IEM (CR1 duration ≥ 18 months)	Chemotherapy	50–80%
Intermediate	B-ALL late BM (≥36 months from diagnosis)	Chemotherapy +/− HSCT	50–60% (late marrow) 30–50% (early IEM)
	B-ALL late combined (≥36 months from diagnosis)
	Early IEM (CR1 duration < 18 months)
High	B-ALL early BM or combined (<36 months from diagnosis)	Chemotherapy + HSCT	15%
	T-ALL marrow or combined marrow/extramedullary (early or late)

Definitions: OS: overall survival; IEM: isolated extramedullary; HSCT: hematopoietic stem cell transplantation; BM: bone marrow; combined: BM and extramedullary; CR1: first complete remission