It estimates there could be between 1,300 and 2,600 missed or undiagnosed breast cancer cases based on Cancer Australia data released this week.
The number of rescheduled appointments and the closure of BreastScreen across some states meant screening fell by roughly 98 per cent in April 2020 compared to April 2018 statistics.
In April 2020, around 1,100 screening mammograms were performed, compared to more than 74,000 in April 2018, according to data from the Australian Institute of Health and Welfare.
Meanwhile, diagnostic and investigative surgeries dropped by up to a third in the first wave of COVID-19.
Foundation chief executive Sarah Hosking said there should be investment in researching the significant impact of COVID-19 and delays in detection.
"With the expected increase in hard-to-treat breast cancer diagnoses in years to come, the time is now to re-focus on accomplishing zero breast cancer deaths and the additional funding required to reach that goal," Professor Hosking said.
"Breast cancer will not wait for COVID-19 to end."
BreastScreen Victoria said while services were closed temporarily at the start of the pandemic, most re-opened within weeks and have continued to screen throughout 2020 and 2021.
BreastScreen Victoria’s GP advisor Dr Alia Kaderbhai says women are being encouraged to book appointments for screenings particularly during October, which is Breast Cancer Awareness Month.
"Regular breast screening is a check of your breast tissue for the presence of breast cancer," she said in a new video for clients and GPs.
"You can view it like any other health check. And once it's done, most women don't have to think about it again for another two years ... early detection is so important in being able to treat cancer successfully."