Ontario's ombudsman has suspended an investigation into funding rules surrounding the drug Herceptin, after the province promised to expand a program that denied several patients financial support because their cancerous tumours were too small.

Andre Marin launched an investigation on March 18 after his office had discovered eight patients who had been denied funding because their breast cancer tumours were less than once centimetre in diameter.

The province's funding of Herceptin was previously limited to patients whose tumours are larger than one centimetre.

On Thursday, Marin suspended his investigation, after the Ministry of Health and Long-Term said it would fund the drug for patients with breast cancer tumours of one centimetre in diameter or less.

"I'm very pleased with the Ministry's ongoing efforts to make drug funding decisions more fair and evidence-based," Marin said in a statement.

"We received excellent co-operation from the Ministry from the start of this investigation and its officials were very receptive to our questions and advice. I'm glad we were able to resolve this quickly for the patients affected."

As part of the investigation, Marin's Special Ombudsman Response Team (SORT) also spoke with numerous officials in the Ministry of Health and at Cancer Care Ontario, as well as reviewing funding rules in other provinces.

Cancer Care Ontario said on Thursday that Herceptin will become the first drug to be funded through Ontario's Evidence Building Program – a new process for making drug funding decisions in Ontario.

While the investigation has been suspended, Marin is asking the province for regular updates to how its new evidence building program is implemented, and will continue to monitor for complaints.

This is the second time Ontario's ombudsman has investigated complaints into the limited funding of a cancer drug. In 2009, the Ministry of Health lifted a funding cap on Avastin, a treatment used to fight colorectal cancer.