Roche U.S. cancer drug trial enrollment suspended

* Chemo combination trial for early-stage breast cancer

* Six patients suffer congestive heart failure, no deaths

* Trial participants can still take drug once informed

ZURICH/BOSTON, Sept 25 (Reuters) - Swiss drugmaker Roche Holding AG ROG.VX said enrollment into a late-stage U.S. trial of Avastin in breast cancer patients had been suspended after six patients suffered congestive heart failure (CHF).

Roche, the world’s largest maker of cancer drugs, said on Friday current participants in the trial with early stage breast cancer could continue taking the drug, in combination with chemotherapy, once informed of the cases of CHF.

This is a condition in which the heart does not pump blood efficiently, leading to shortness of breath, fluid accumulation, fatigue and other symptoms.

There had been no deaths due to cardiac toxicity and the rate of CHF in the trial was consistent with that previously reported for Avastin, Roche said, adding 3,439 of the planned 4,950 patients had already entered the study.

Avastin, which cuts off blood supply to tumours, is already a blockbuster and a key drug for Roche, with global sales of 5.2 billion Swiss francs ($5.02 billion) in 2008 as a treatment for colon, lung and breast cancers.

Ed Lang, a spokesman for Genentech, which developed Avastin and was later acquired by Roche, said that on a scale of one to five, with five representing death, the patients had grade three and four CHF.

The hearts of five patients returned to their previous condition once the patients had stopped taking the drug, Lang said. No further information was available for the sixth case.

Reporting by Jason Rhodes and Toni Clarke