Evidence of meeting #122 for Health in the 44th Parliament, 1st Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was women.
A recording is available from Parliament.
Conservative
Laila Goodridge Conservative Fort McMurray—Cold Lake, AB
Mr. Chair, it is effectively a slight amendment to the motion that was put on notice on June 3 by my colleague, Dr. Ellis. It just updates the dates. Otherwise, it is identical.
If you would prefer, I could amend the original motion, but I thought this was cleaner and simpler.
Liberal
The Chair Liberal Sean Casey
Your only option now is to challenge the chair because there are two issues.
Number one, if you were moving Dr. Ellis's motion, you couldn't because you aren't Dr. Ellis. Number two, the motion that you moved is not identical, so it requires 48 hours' notice, which hasn't been given.
The motion is out of order. Unless there's a challenge forthcoming, we're going to move to Dr. Hanley, please, for five minutes.
Conservative
Laila Goodridge Conservative Fort McMurray—Cold Lake, AB
I will ask for unanimous consent of the committee to move the motion.
Liberal
The Chair Liberal Sean Casey
Does Ms. Goodridge have unanimous consent to move the motion that has not been put on notice?
There is no unanimous consent.
We'll go to Dr. Hanley, please, for five minutes.
Liberal
Brendan Hanley Liberal Yukon, YT
Thank you.
I want to thank all the witnesses and I want to thank Ms. Goodridge for bringing this study into a priority lineup. It is an extremely important study and very timely.
Dr. Gordon, you're a very compelling witness, I have to say.
Most of my five minutes will be probably devoted to just drilling down on a few issues.
Can you talk to me about interval cancers and their relative importance?
Having been versed in this over many years, you might say that the traditional thinking is that aggressive cancers do not lend themselves to screening because almost by definition they appear between screening intervals and often the younger the woman, the more aggressive the cancer. This applies to other types of cancers of course, which is maybe one of the limitations of screening.
Maybe you could clarify what you think of that based on what we know today, especially with the technology that we have today.
Is this becoming a more outdated phenomenon?
Volunteer Medical Advisor, Clinical Professor at University of British Columbia, Dense Breasts Canada
Let me just define this for the others.
An interval cancer is one that turns up after a woman's last mammogram was read as negative. It's usually found as a lump. Interval cancers are more often the aggressive ones, the HER2-positive and so on. They are the rapidly growing cancers. They often present larger—already spread to the lymph nodes—than screen-detected cancers and they do have a worse prognosis.
There are two categories of interval cancers. There are the ones we just mentioned, which are the rapidly growing cancers. Even when you look at her recent mammogram, she didn't have dense breasts and she had the easy kind of mammogram to read, but it really wasn't there. It developed so fast that, let's say, her mammogram was negative, six months later she has another mammogram when she shows up with this lump and, oh my goodness, there's a lump that's easy to see on her mammogram. That's one kind. That's the kind that just grew so fast that it wasn't there on the mammogram. The other kind of interval cancer is the one that was there when she had her mammogram, but it was hidden in her normal dense tissue.
Breast density refers to the amount of breast tissue—glandular and fibrous tissue, but let's just call it breast tissue—compared to fat. All women have both in their breasts, but the proportions vary tremendously. Someone's breasts are all fat and then some have a little bit of dense tissue, some have more and then there's the highest category of dense tissue where there's hardly any fat and it's all dense tissue.
The reason that's important is that normal, dense breast tissue on a mammogram is white and fat is black. All lumps, including cancers, are white. If a woman has a fatty breast, it's a dark gray or black-looking mammogram and even the smallest little white cancer jumps out at you like a star in the sky.
If a woman has a very dense breast and it's all white, you're going to miss even a big cancer. In fact, 50% of cancers are missed in the densest tissue.
I'm going to let you get a word in edgewise.
Liberal
Brendan Hanley Liberal Yukon, YT
I have less than two minutes left, but I appreciate the fulsome explanation.
I want to focus on the U.S. and the way the recommendations are now in the U.S. preventive task force versus Canada.
You do acknowledge that we have included observational studies in the Canadian guidelines for the first time, but also that they are weighted differently from clinical trials. There's almost a time consideration because clinical trials, almost by definition, are older. The RCT has always been the gold standard of trials.
Do you see there is a process that is happening differently in the U.S. versus Canada? Should we be looking at processes that are potentially different, to emulate the U.S.? I'd also note that the U.K. has not changed from 50. As far as I know, the U.S. is perhaps one of the first to include the 40.
Volunteer Medical Advisor, Clinical Professor at University of British Columbia, Dense Breasts Canada
What the U.S. did differently from Canada was that they took greater weight of the data showing an increasing incidence in younger women and the incidence of breast cancer in racialized women. But the Americans didn't get it perfect either. They're only saying to screen every two years. They clearly don't weight the harms to the extent that our task force does.
Liberal
Brendan Hanley Liberal Yukon, YT
Dr. Nadler, we won't have time for you to speak to this. If you're able to table a response to that, to the difference between the U.S. approach and the Canadian approach, I think that would be very useful.
Am I out of time, Chair?
Liberal
The Chair Liberal Sean Casey
Dr. Nadler, please take 30 seconds to offer your perspective. If that's not enough, feel free to follow up in writing.
Breast Medical Oncologist and Implementation Scientist, As an Individual
Thank you.
The incidence change in Canada was different from the incidence in the United States. That may be one reason.
Dr. Paula Gordon explained the difference in the two types of interval cancers. It's important to understand, exactly as Dr. Gordon said, that this is why screening doesn't help for some interval cancers. The more aggressive ones appear between screens. Although screening does help for some, it doesn't help for all.
Another important thing about interval cancers or detecting cancer early is that we don't necessarily know that screening will change the outcomes. This is something called length-time bias. A more slowly growing cancer will sit and wait and not present as a lump until a screen. A more aggressive cancer will show up in between screens. Obviously, when we look back at retrospective studies, it looks like screening catches all the very slow-growing cancers and it looks like all the fast-growing ones are in people who don't have screening, but that's because they're fast, and they show up as interval cancers. That's called length-time bias. It's a very important bias. We don't dismiss studies because of it, but we always have to think that this bias is there. The task force has to look at all of that data as systematically and as methodically as possible.
Finally, with regard to the U.S., they actually acknowledge in their guidelines that the recommendation doesn't actually improve EDI, or equity and diversity. They actually say in their guidelines that starting everybody at 40 doesn't actually improve the disparities.
We all call for more research in that area.
Liberal
Liberal
Conservative
Laila Goodridge Conservative Fort McMurray—Cold Lake, AB
Could we get unanimous consent to get an answer from Dr. Gordon on that?
Liberal
Volunteer Medical Advisor, Clinical Professor at University of British Columbia, Dense Breasts Canada
I'll be quick.
Yes, what Dr. Nadler says is true, but we do know that the size and the nodal status still matter even for aggressive tumours. In fact, sometimes it matters even more. As I said, the five-year survival rate for stage one triple-negative cancer is 96%. Stage 3 is 47%.
We also use modelling. It's not all about anecdotal cases of some women who didn't benefit. It's true that not all women will benefit to the same extent as others, but if you don't screen, you don't find the cancer in the first place to know whether it is high grade or not.
Liberal
The Chair Liberal Sean Casey
I would like to thank all our witnesses for being with us here today and for being so patient as we worked through several challenges that interrupted and delayed your testimony. Your expertise is evident. We are extremely grateful that you were here with us to kick off this study and for the depth and breadth of information that has been provided. Thank you so much for being with us.
Is it the will of the committee to adjourn the meeting?