Drugs that help boost production of red blood cells in people with cancer and anemia increase the risk of death and serious side-effects such as blood clots, researchers said.

Anemia, a frequent side-effect of cancer as well as cancer treatments such as chemotherapy, can leave already frail patients more debilitated.

'These agents shouldn't be routinely used in cancer patients as an alternative to blood transfusion.'— Dr. Tony Reiman

In Thursday's online issue of the Canadian Medical Association Journal, Dr. Marcello Tonelli of the University of Alberta and his co-authors reviewed 52 clinical trials involving 12,006 participants to assess the safety and benefits of the drugs, which are called erythropoiesis-stimulating agents.

"Most patients with advanced cancer encounter this problem at some point," said study author Dr. Tony Reiman, a medical oncologist in Saint John, N.B.

The meta-analysis showed a relative increased risk of death of 15 per cent to 16 per cent, but because of the high mortality rates in cancer patients, that could translate into a significant number of people.

"Overall, I think there's an international consensus emerging here that these agents need to be used with caution in cancer patients," Reiman said.

"Our position … is that these agents shouldn't be routinely used in cancer patients as an alternative to blood transfusion."

Before evidence started to mount about the risks of erythropoiesis-stimulating agents in cancer patients with anemia, the drugs were widely used, he said.

Some studies suggested potential benefits from the drugs, such as reducing the need for blood transfusions to limit demand on blood supplies, as well as improvements in quality of life for cancer patients with anemia.

The findings are important for doctors treating cancer patients and — given the high cost of the drugs —for Canadian policy makers who decide on drug coverage.

A related study by European researchers appearing in this week's edition of the medial journal The Lancet came to similar conclusions, based on a review of 53 of the same clinical trials involving almost 14,000 patents.

The erythropoiesis-stimulating agents were associated with a relative increase in mortality of 17 per cent for the period the drugs were given plus four weeks afterwards.

When compared with cancer patients received chemotherapy, the relative increase in mortality attributed to the drugs was 10 per cent.

More data is needed on the effects of quality of life and tumour progression, Dr. Julia Bohlius, of the University of Bern, Switzerland, and her colleagues said.