LONDON, March 17 (Reuters) - Britain's cost-effectiveness medicines watchdog ruled on Friday that costly erythropoietin (EPO) drugs should not be used to treat anaemia caused by anti-cancer therapy, dealing a blow to drug firms and cancer campaigners.

Many cancer patients suffer anaemia as a result of their chemotherapy or radiotherapy treatment.

"Erythropoietin is recommended for use in the management of anaemia only as part of ongoing or new clinical trials," the National Institute for Health and Clinical Excellence (NICE) said in a statement on its Web site ( www.nice.org.uk ).

NICE's final appraisal determination follows a similar provisional recommendation last July, made after a lengthy assessment of EPO medicines made by Amgen Inc (AMGN.O: Quote, Profile, Research), Johnson & Johnson (JNJ.N: Quote, Profile, Research) and Roche Holding AG (ROG.VX: Quote, Profile, Research).

NICE -- whose job is to decide which therapies should be paid for by the state-run National Health Service -- said EPO drugs cost between 2,500 pounds ($4,388) and 5,000 pounds ($8,777) per course of treatment.

Patient groups said the alternative was increased use of blood transfusions, which would place a big burden on the National Blood Service.

They estimate that two out of three cancer patients suffer from anaemia, a debilitating condition that can making daily tasks very difficult