Dose intensification of cytotoxic drugs is now being evaluated in seve
ral trials. Various methods are available to manage the hematopoietic
toxicity. Hematopoietic growth factors can be used alone and/or in com
bination with hematopoietic stem cell rescue. Patients undergoing auto
logous stem cell transplantation (AuSCT) have their own bone marrow an
d/or peripheral blood used for hematopoietic engraftment. In several m
alignancies, the bone barrow is involved with tumor, and in such situa
tions, the success of AuSCT may improve if hematopoietic elements are
enriched (positive selection) or if contaminating cancer cells are pur
ged by negative selection. In patients undergoing allogeneic bone marr
ow transplantation, T lymphocytes, from donor cells, contribute to the
development of graft-versus-host disease (GVHD), which can result in
major morbidity and mortality: The incidence of GVHD has decreased wit
h selective purging of T lymphocytes, but further modifications are ne
eded to improve hematopoietic engraftment. Methods for purging hematop
oietic stem cells are discussed, with emphasis on the therapeutic role
of purging. Growing stem cells from a small amount of bone marrow pre
sents a new possibility. Furthermore, genetic engineering can enhance
immune surveillance and decrease drug resistance. Analysis of the clin
ical trials utilizing various doses of cytotoxic therapy with proper m
ethods of hematopoietic rescue will help avoid unnecessary dose escala
tion and help decide the optimum use of cancer treatment modalities.