Avastin treatments cost about $35,000 a year per patient. (CBC)

The Nova Scotia government has started paying for a costly drug used in the treatment of advanced colorectal cancer.

The government announced in April that Avastin would be publicly funded but only released details Friday, saying it needed time to determine how the program would work.

Avastin extends the lives of some patients in the late stages of colorectal cancer by stopping the blood supply to cancerous tumours. A year-long round of treatment costs about $35,000 per patient.

Starting this week, the province is paying the bill for patients currently getting the drug, provided they meet eligibility requirements. People who paid for Avastin after April 1 can apply for a reimbursement.

Patients will have to be assessed by their oncologist to determine whether they qualify.

Health Minister Chris d'Entremont said Friday's announcement will be a "great relief" to people who want Avastin.

The government had previously refused to cover Avastin, based on the recommendation of a provincial drug therapy committee that looked at its cost and the potential of other drugs in early cancer stages.

Last year, thousands of people signed petitions demanding the province pay for the drug treatment. One advocate, Dartmouth lawyer Jim Connors, died in April.

The drug is expected to help 150 people in the province and cost the government $5.3 million a year.

NDP health critic Dave Wilson said the government could have saved itself some of that money if it had acted on an NDP suggestion four years ago to fund a colorectal screening program.

"If it's caught early, we can reduce the number of people who would need Avastin, and hence lower the cost for this program," Wilson said.

The province has committed to setting up a colorectal screening program later this year.

Quebec, Ontario, Saskatchewan, British Columbia, and Newfoundland and Labrador include Avastin in their provincial drug programs.