In this comment on a study published in
British Journal of Cancer, it was shown that anemic colorectal cancer patients responded less well to chemo than those who were not anemic.
Anemia Associated with Fewer Responses to Chemotherapy in Advanced Colorectal Cancer
http://patient.cancerconsultants.com....aspx?id=37587
In the past I have seen some comments from the medical community advocating the treatment of even marginal anemia.
Some of their arguments relate to the low oxygen (hypoxia) associated with anemia as a factor of cancer progression or as a hinder in treatments which rely on oxygen to generate cancer cell killing oxidants.
One experiment with mice using a combination of omega-3 fish oil & iron supplementation showed increased response to radiotherapy.
However this has not been tested in humans.
In addition some other retrospective studies on humans have not shown a difference in outcomes between anemic & non anemic patients.
The colorectal cancer study nevertheless provides better data than retrospective ones.
So the question is still open.