TORONTO -- As a national shortage of a common drug used to treat breast cancer threatens to drag on for another two months, a top oncologist is urging patients to visit their doctor to find alternatives.

In August, an “anticipated shortage” of the anti-estrogen drug Tamoxifen was reported to Health Canada by two of the three manufacturers in Canada. The companies cited a “disruption” in the manufacturing process as the reason for the setback.

Months later, the anticipated shortage became a reality with manufacturers announcing an “actual shortage” in October and patients reporting difficulty filling their prescriptions at pharmacies across the country.

The disruption has led to widespread concern among the thousands of Canadians who take the oral medication to treat breast cancer, as well as other less common cancers. It’s also used to prevent the recurrence of cancer.

According to the Canadian Cancer Society, Tamoxifen is the most commonly used anti-estrogen drug given to cancer patients as part of hormonal therapy. Because the medication is also used to prevent the return of cancer, patients often take the drug for up to 10 years.

Dr. Leta Forbes, a medical oncologist and the provincial head of systemic treatment at Cancer Care Ontario, said the risk of pausing treatment due to the drug shortage will depend on the individual.

“Every patient has an individual risk depending on the type of cancer that they’ve had so we recommend that they speak to their health-care professional about what the risks are of a temporary pause in their treatment or what alternatives there could be that they could be switched to in the interim,” she told CTV’s Your Morning on Wednesday.

Forbes said there are other oral tablets that can be given to patients who are past menopause as well as injections that can be given in the meantime.

For some patients who have a very low risk of recurrence, Forbes said they may not have to take any alternative medication during the shortage.

In a statement to CTV News, a spokesperson for Health Canada said they have identified an “international supply” of the drug and they’re working to make it available to Canadians “as soon as possible as a short-term measure to manage the supply gap.”

According to the agency’s website, which lists reported shortages, the estimated end date for the Tamoxifen shortage is Jan. 31, 2020.