Thank you for the opportunity to present to the committee today, and thank you for taking the time to review an issue so important to women's health.

I'm a breast medical oncologist in Toronto. I speak with patients and their families about breast cancer every single day, and I see how this disease and its treatment impacts them. We are all committed to ensuring the best possible outcomes for women and for people with breast cancer.

My academic focus is in knowledge translation or guideline implementation. Through this work, I was invited to participate as a knowledge expert on the task force. The 2024 draft guidelines state as follows:

Breast cancer screening is a personal choice.

Women aged 40 to 74 should be provided information about the benefits and harms of screening to make a screening decision that aligns with their values and preferences. If someone in this age range is aware of this information and wants to be screened, they should be offered mammography screening every 2 to 3 years.

This information should be accessible and shared in absolute numbers. It should include how age, family history, race and ethnicity, and breast density (if known) may impact the benefits and harms of screening.

The task force invited four experts: a medical oncologist, a radiation oncologist, a radiologist and a breast oncology surgeon. There were two to three patient partners. All provided input on the three main systematic review questions: inclusion criteria for each study, outcomes of importance and protocols. Randomized trials and observational and quasi-experimental studies were included.

The task force investigated, among others, the following outcomes: breast cancer mortality, stage distribution and treatment morbidity. We often hear about the benefits of early detection. We are told that if we can find cancer earlier, there is less chance of death from breast cancer or less intensive therapies. It might be surprising, but early detection is not always necessarily an assurance of either of these. More and more, we know that the biology of disease or how aggressive the cancer is factors into prognosis.

Outcomes of harms, including additional testing showing no cancer and overdiagnosis, were also looked at. Overdiagnosis means the biopsy-proven detection of a pre-cancer or cancer that would otherwise never have caused the individual any symptoms or problems in their lifetime. This occurs for older women and is also well documented in younger women.

All studies that met inclusion criteria and additional studies submitted to the portal were reviewed by the evidence synthesis team. The team included two radiology experts and a GP-oncologist. All studies were rated for certainty, i.e., how likely they are to represent the truth, through something called the GRADE methodology. Once the data analysis was completed, the evidence was displayed to our working group, and we reviewed and discussed the data.

In key question three, the task force undertook a systematic review related to the values and preferences for women ages 40 to 74 for screening. This showed that the majority of women aged 40 to 49 felt that the harms outweigh the benefits for screening; however, members of the task force working group agreed that there is large variability in women's values.

The task force met separately to look at the evidence in totality, looking at all included study results and comparing them. One of the criticisms of the task force is that certain studies were not considered. It is normal in the scientific method of a systematic review to question why some results are outliers compared to others. This does not mean that they are dismissed. The task force cannot base its recommendation on only one or two studies; they must look at the evidence in totality.

Everything above that I have stated are the facts as I know them. To be clear, what follows is my personal opinion.

I think it is commendable to have guidelines state specifically that personal risk factors, benefits and harms should be clearly communicated to women to inform a decision and that the decision they make should be respected.

The alternative suggested by many critical of the task force is to systematically screen all women starting at 40. I have concerns that this is not respectful to the range of values that different women hold about the benefits and harms of screening. Some women will want to screen, and others won't. Both sets of values should be respected.

I went into this process with an open mind of what the data would demonstrate. I truly believe that the task force went into this with open minds as well. The science shows us that there are both benefits and harms to breast screening. In individuals not at high risk, there is equipoise and substantial uncertainty. There is more uncertainty than the public may think.

Sometimes science gives us an answer we didn't expect or we don't want, but we should still listen to it. In medical practice, when there is close equipoise or uncertainty, the best thing to do is have a shared discussion with each individual patient in front of us and respect their decision.

Thank you.