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Oct 8, 2021 04:27PM
Elle, diagnoses of 3rd primaries are so rare that I doubt that there are any studies. I've looked for them but have never found them.
The reason 3rd primaries are so rare is not because they don't happen - you'll find quite a few people on this site - but because the group of patients who could possibly develop a 3rd primary is very small. Approx. 12.5% of women develop breast cancer a first time; the percent who develop BC two times is a just a small percent of the original 12.5%. Looking at those of us who do develop BC twice, many opt for a BMX at the time of the second diagnosis. While this doesn't eliminate the risk of a 3rd primary, it reduces the risk to something in the range of 1%-2%. So within this already small group, the number who continue to have one or two natural breasts after the second diagnosis is small - and these are the women a researcher would want to look at to determine the risk of a 3rd primary. Therefore developing a research study to follow these women, to see if they are diagnosed a 3rd time, would be difficult and costly, since these patients are hard to find and there would never be a critical mass of patients in any one location.
Having said that, while I've never found data on 3rd diagnoses, I suspect that your doctor is wrong when he said that your risk is no different than any other woman. It is well established that once we've been diagnosed one time, our risk to be diagnosed a second time is higher than the risk of any other woman. There's no one reason why this is true; to the best of my understanding, it's more of a generalized risk based on the fact that if your cells went wonky one time, they probably are more likely (than the average woman) to go wonky again. And if your breast tissue has shown itself to be a friendly environment for the development of cancer cells one time, then it's more likely to do that again. In other words, for each of us, whatever the reason we developed breast cancer the first time, well, that reason might still be there and might cause breast cancer to develop again.
When it comes to a 3rd diagnosis, the factors that made us higher risk for a second diagnosis still remain. And in fact having a second diagnosis probably confirms that those factors are still relevant and remain at play in our bodies. So my gut reaction when I got my second diagnosis was that this probably meant that I was very high risk for a 3rd diagnosis.
I'm a stats person and I really wish that there were stats on this - I'd be thrilled to be proven wrong. I don't generally put much weight on anecdotes, but with nothing else to go on, I will say that in 15 years on this site I have been surprised by the number of people I've seen return with 3rd diagnoses, particularly relative to the number I've seen return with 2 diagnoses.
This is not what you want to hear, and I stress that it's just my guess and my opinion, however there are some facts and logic behind my thinking.