The beginning of the COVID-19 pandemic brought stress and uncertainty for many Australians - but for Jayme Gurishic those feelings were exacerbated by the shock of a cancer discovery.

The Melbourne legal worker's world was turned upside down when she was diagnosed with stage-two breast cancer at just 27.

"I still remember the time, it was 2.06pm ... I received a phone call and the doctor said, 'I'm so sorry, you have invasive breast cancer'," Ms Gurishic told AAP.

"I genuinely thought there had to have been a mix-up, they can't have the right results."

Due to COVID-19 restrictions, she was forced to undergo chemotherapy, hormone treatment and radiation therapy in hospital alone.

"I remember receiving a text message from the hospital the day before my first chemo session advising that due to the situation with COVID-19 that patients were unable to have anyone present with them in the oncology lounge or during treatment," Ms Gurishic said.

"So for my very first chemo session, which was six hours long, and every other chemo session after that, I was unable to have any family member attend or friends with me every Tuesday morning for three months."

For breast cancer organisations, the pandemic had another concerning impact: a reduction in routine screening, which could have a lingering effect on the timely diagnosis and treatment of the disease.

In 2020/21, almost 1.7 million women aged 50 to 74 were screened in the BreastScreen Australia program, a drop on the 1.8 million screened the previous year and 1.9 million in 2018/19, according to figures from the Australian Institute of Health and Welfare.

The age-standardised participation rate in the program fell from 54 per cent in 2018-19 to 47 per cent in 2020-21.

National Breast Cancer Foundation chief executive officer Cleola Anderiesz said the full impact of delayed screenings was unknown.

"We do not yet know the implication of delays (if any) on future breast cancer diagnosis and outcomes," she said.

"In 2022, more than 20,000 Australians will be diagnosed with breast cancer and over 3,200 people will die from this disease.

"Each death is one death too many, and research is critical to better understand, prevent, detect and treat breast cancer and ultimately end deaths from breast cancer."

In honour of Breast Cancer Awareness Month, which begins today, the foundation has launched its #BREASTfast campaign to boost research and achieve the goal of zero deaths from breast cancer.

The five-year survival rate for women diagnosed with breast cancer is 91.8 per cent, while for men the survival rate is 86.5 per cent.