Tamoxifen to prevent contralateral BC after SMX?

MEM127

Hi - Looking for some input. I was diagnosed with DCIS, right side, grade 3, ER/PR negative. I had a lumpectomy in January and did not get clear margins. The DCIS was more extensive than they anticipated and there was also additional DCIS that was grade 2, ER+ (vs. grade 3, ER-). The grade 3 was much more extensive, but there was still the smaller DCIS there that was connected to it. At the same time as the lumpectomy, I had an excisional biopsy on the left breast, which thankfully was benign. My small breast couldn't do another lumpectomy, so I had a MX on the right last week. When I talked with the surgeon before the MX, she said I wouldn't need any follow up treatment - no hormones or radiation. But she called after the surgery (which went well, clear margins, etc.) she said I had the option of taking Tamoxifen to prevent cancer developing in the left breast down the road. I guess I'm a little confused at this point - originally, it was supposed to be a lumpectomy plus 4 weeks of radiation, no tamoxifen because it was ER-. Then it was SMX, no radiation, no tamoxifen. But now she has suggested tamoxifen, but didn't seem to push it, really presented it as just an option that I should balance against side effects, etc. She estimated the chance of a new breast cancer on the left side to be at 15% without tamoxifen, maybe 12% with it. For 3% I don't think I'm inclined to do it. But - now a tiny part of me is second guessing my decision to go with the SMX vs DMX (now that it's already done - how's that for Monday morning quarterbacking!). Before, after talking with both the breast surgeon and the plastic surgeon, I felt comfortable that there was no cancer on the left, that I had DCIS, not invasive cancer, and basically there was no need to be so aggressive (no family history of BC, over 50, peri-menopausal), so single was the way to go and if I got it on the left down the road, I'd just deal with it then. I'm still mostly comfortable with that, but I'll be happier after reconstruction when I feel less deformed and lopsided (not having a great day today). Sorry to lay this all out in rambling form. Any thoughts on taking Tamoxifen when the majority of the DCIS was ER negative?

Beesie

MEM,

Have you see a Medical Oncologist? An MO is the doctor who should be advising you about this.

Based on the studies I've seen, it shows that breast cancer patients (including those who've had DCIS) appear to have between a 60% to 100% increase in breast cancer risk (100% increase equating to double the risk) vs. the general population, and those a TN first primary breast cancer may have a higher risk than that. For you, the average 50 year old has about an 11% remaining lifetime risk of breast cancer so a 100% increase in risk would put your risk at 22%. This risk is spread over your remaining lifetime, so maybe 35-40 years.

Second Primary Breast Cancer Occurrence According to Hormone Receptor Status https://www.ncbi.nlm.nih.gov/pmc/articles/PMC27209...

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Estrogen receptor, progesterone receptor, and HER2-neu expression in first primary breast cancers and risk of second primary contralateral breast cancerhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC41444...

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Hormone receptor status of a first primary breast cancer predicts contralateral breast cancer risk in the WECARE study populationhttps://breast-cancer-research.biomedcentral.com/a...

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Contralateral breast cancer risk according to first breast cancer characteristics among United States women from 1992 to 2015. https://ascopubs.org/doi/abs/10.1200/JCO.2019.37.1...

As for Tamoxifen, earlier studies have shown that during the years you take it, it can reduce your new primary risk by at least 50%. Recent studies suggest that this benefit continues for many years after you stop taking it, up to 20 years, although the overall risk reduction benefit is a bit less, and the benefit is specific to ER+ cancers. Your first diagnosis was ER-; a second diagnosis could be either ER+ or ER- but Tamoxifen will only reduce your risk for the ER+.

Tamoxifen for prevention of breast cancer: extended long-term follow-up of the IBIS-I breast cancer prevention trial https://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(14)71171-4/fulltext

Like you, I had a UMX. I was 49 and my diagnosis was ER+/PR- DCIS-Mi. At the time my MO told me that my risk to develop a new primary would be approx. double that of the average woman my age who had never been diagnosed with breast cancer. He said the decision on taking Tamoxifen as a preventative for my contralateral breast was up to me, but he recommended against. His reasoning was that with my cancer being PR-, I would not get the full risk reduction benefit from Tamoxifen. He also felt that my highest risk years were at least 10 years ahead of me - for all women, our risk to be diagnosed is highest during our 60s and 70s - and at that time there were no studies to suggest that Tamoxifen's risk reduction benefit would extend that long. The standard at that time was 5 years of Tamoxifen - there were no studies released yet on the efficacy of 10 years of Tamoxifen. So his feeling was that if I wanted to take Tamox., it would be better to start when I was a bit older. With the research that has come out in the years since, I wouldn't be surprised if he would now be more favorable to someone taking Tamoxifen in a situation like mine. The difference for you is that your current diagnosis is ER-/PR-, and for that twist I think you really need to talk to an MO.

The good news is that because you are looking at Tamoxifen as a preventative, there is no urgency to this decision. You could start now, or in 3 months, or in 3 years. So you have time to make up your mind and decide what you want to do.

MEM127

Thank you Bessie! I’ve got some reading to do.