Contralateral BC Survival Stats

I've done a lot of research on bilateral BC, most studies look at both synchronous (what I had) and asynchronous (what you had) bilateral BC. From what I found, there is a very slight increase in risk of distant recurrence when bilateral, but the main risk is still the worse side's diagnosis. So, in my case, the risk of distant recurrence (stage IV) is about the same as a woman who had one-sided grade 1, low oncotype IDC, even though I had it in both breasts. Your risk would be about the same as any woman who had grade 3 IDC (although the risk would vary based on your oncotype vs others, of course).

Most of us never find out a reason. It could be environmental, some genetic mutation that hasn't been discovered yet, or, as my RO said, just bad luck.

All I can recommend is you do what you can to reduce the probability of recurrence going forward. There's lots of good research about that. I found Box 2 in the below link to be a short-and-sweet synopsis.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5318212/

Being diagnosed with breast cancer increases the risk that we will be diagnosed again, with a second primary breast cancer, unrelated to the first. There is no clear explanation as to why this is and likely the explanation is different for everyone, just as the cause our breast cancers is different for everyone. But what it comes down to is that since our bodies allowed for the development of breast cancer cells previously, and since our breasts presented a friendly environment for those cancer cells, it makes sense that it might happen again, and that our risk to develop a new primary is in fact greater than the risk of the average woman to develop a first breast cancer.

What this doesn't say anything about is the aggressiveness of the cancer. Nor does it address the timing of the discovery of the cancer. So while some of us might develop breast cancer twice (or even 3 or 4 times), each breast cancer might be an easily treatable non-aggressive cancer. And if the second cancer is found early - particularly if it is found while still DCIS - it might be virtually harmless.

Over the years I've seen lots of women return to this site with a new primary, sometimes just a few years after the first diagnosis but sometimes as much as 20 years later. In some cases, especially if the first diagnosis was DCIS or a tiny Stage IA, the second diagnosis might be more serious and therefore present a greater risk. But at least as often, the second diagnosis is less serious.

A recurrence generally presents a increased risk of mets. A new primary does not - with a new primary, the risk of mets for each diagnosis is assessed separately and each is unaffected by the other. That said, the overall survival rate for those diagnosed twice is lower than it is for those who have a single diagnosis of breast cancer. This makes sense, since there is a separate mortality risk associated with each breast cancer diagnosis. Additionally, it appears that being treated twice plays into the increased mortality risk, from two standpoints. First is the added toxicity of two rounds of treatments. Second is that some treatments might not be available to treat the second cancer because they were used for the first and cannot be given again.

TheLadyGrey, in your case, with DCIS being your second diagnosis, none of these factors come into play. There is virtually no mortality risk associated with a diagnosis of DCIS. There are no treatments that you would normally get for this second diagnosis that you cannot get because you've had the treatment before. And to my understanding, you aren't doubling up on any of the treatments you had for your first diagnosis (thereby increasing the impact on your body). So there is no reason why your DCIS diagnosis would affect your prognosis from your first diagnosis, and there is nothing about this second diagnosis that if affected by your first.

Some info on second primaries: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6025574/#!po=32.6087

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2720990/

https://www.ncbi.nlm.nih.gov/pubmed/14659121

I was diagnosed at 60 and then again at 63. Both were HR+, small, the first grade 1 the second grade 3. I may have done better had I taken the anti-hormone treatment first round, but I didn't...too scared of it. Now I am on it; 8 years out for first one and 6 years out for the second one. Hoping for the best. You just never know....but does anyone? My sister is stage 4 and today, with her chemo pill working and not giving her any problems, she almost got killed by a falling tree limb. You just never know.