Is Tamoxifen needed after a BMX?

My MO said Tamoxifen would not be necessary after my BMX since nothing invasive was found. No one I have seen thinks HER2 testing is necessary for DCIS (because all DCIS is HER2+ at some point, I believe), so I don't know my status.

"I thought the BMX gave women a 1-2% chance of recurrence and that the Tamox only reduced that risk by a half of a percent."

Yes, that is generally correct.  The exception would be if someone had particularly close margins after the MX - in that case, the risk of recurrence would be higher, particularly if the DCIS was high grade and aggressive, and that could justify the Tamoxifen. KrisLiz, it sounds as though this is your situation, and that would be why your MO put you on Tamoxifen. Having close margins changes your pathology vs. others who've have a MX or BMX for DCIS and who have clear surgical margins.  So even if you have the same diagnosis as someone else, if they had clear margins after a MX, their risk of recurrence is quite different than yours and that can lead to a different recommendation. 

All DCIS, regardless of the pathology, is pre-invasive, and that's a critical difference vs. invasive cancer. Regardless of how aggressive one's DCIS might have been, if it was pure DCIS, then theoretically (unless something was missed in the pathology), there is no risk of distant recurrence, i.e. no risk of mets. This is big and very signficant and it eliminates the reason why someone who has a BMX for invasive cancer might be prescribed Tamoxifen.

The risks that do come with having a highly aggressive DCIS are that 1) there is a greater risk that some invasive cancer might be found hidden in with the DCIS, 2) there is a greater risk that the DCIS will evolve to become invasive cancer within a shorter period of time, and 3) there is a greater risk that the DCIS might be wide spread and therefore more likely to recur.  After a MX, if the final pathology is pure DCIS and if the margins are acceptably large, then all of those risks have been addressed and pretty much eliminated.  So after a MX, assuming pure DCIS and clear margins, the risk of a local recurrence will be ~ 1% - 2%, regardless of whether one had an aggressive pathology or whether one had a less aggressive pathology. 

With a recurrence risk of only 1% - 2%, the benefit that you'll get from Tamoxifen will be a 0.5% - 1.0% risk reduction (a 50% reduction of the recurrence risk). Tamoxifen's risk of serious side effects is in the range of 1% to possibly as high as 3%, if you have other health issues that might be triggered by the Tamoxifen.  Approx. 50% - 60% of women experience some quality of life side effects from Tamoxifen, sometimes minor but sometimes debilitating. 

I think that for someone who is at risk of mets, or for someone who has a high risk of local recurrence, Tamoxifen is a terrific drug that can cut that risk in half.  In these siutations, the risk of side effects is minor compared to the benefits that someone will get from Tamoxifen.

But for someone who's had a BMX for DCIS and who's had clear margins and therefore only has a 1% - 2% risk of local recurrence?  From everything I've read about DCIS recurrence risk and about Tamoxifen side effects, personally I think that you will be putting your health at greater risk by taking Tamoxifen than by not taking it. There are very few black and white issues in the world of breast cancer, but to me, this one come about as close as anything. But yes, this is just my own personal opinion as a patient and not a medical professional of any sort.

By the way, I had a single MX for 7+cm of high grade DCIS with comedonecrosis, and I had a microinvasion of IDC. My oncologist said that for my MX side, there was absolutely no way that he would recommend Tamoxifen for exactly the reasons I've explained here. (My microinvasion does give me a very slight risk of mets, but it's so low that it doesn't warrant Tamoxifen.) The only reason for me to consider Tamoxifen was because I am high risk to be diagnosed with BC again, in my remaining breast. But even for this, my oncologist recommended against Tamoxifen.  He explained his rationale and then sent me away to think about it. I was really surprised - I'd expected that he would prescribe Tamoxifen. But I went away and thought about it, and more importantly, did my research, and ended up agreeing with him. So I never took Tamoxifen, despite having had only a single MX. And I'm not alone. Having been on this board for 7 years now, I'd say that it's about 50/50 as to whether women who've had a single MX for DCIS end up on Tamoxifen or not. 

ShaneOak, it should be in the pathology report.

The pathology report might specifically mention all of the margins or it might make a more general statement, such as saying that "all margins are greater than 4mm" or "anterior margin is 2mm and all other margins are 5mm or greater" or something like that.  My MX pathology report noted two margins that were relatively close (1mm and 2mm) and then said that all the rest were 6mm or greater. 

The margins are: Lateral margin (outside margin, i.e. towards your underarm);  Medial margin (inside margin, i.e. towards the center of your chest);  Superior margin (top margin);  Inferior margin (bottom margin);  Anterior margin (front margin);  Posterior margin (back margin). 

Further to my earlier post, here is an article that summarizes a lot of what is currently known about DCIS and mastectomies:

The Impact of Surgery on Ductal Carcinoma In Situ Outcomes: The Use of Mastectomy

And here are some of the key points from this article that are relevant to this discussion:

Possible higher recurrence rate with close margins: "Few patients are considered to have sufficiently high risk to justify PMRT (postmastectomy radiation therapy), but based on clinical parameters such as extent of disease, high grade, positive margins, or young age, radiation may occasionally be given. This recommendation is supported by two studies, which reported long-term recurrence rates of 16% and 11% for mastectomy margins of less than or equal to 2 mm. In contrast, we have found an 8-year locoregional recurrence rate below 2% in women with close or positive margins after mastectomy without radiation. These few and discrepant studies support a selective use of PMRT for DCIS."

Long term recurrence rate overall for MX for DCIS: "Clinical outcomes following mastectomy for DCIS are excellent, with both clinical trial and population-based studies consistently reporting a 1%–2% rate of local recurrence with long-term follow-up..."

Lack of need for Tamoxifen after a MX for DCIS: "Systemic hormonal therapy has a limited role following mastectomy for DCIS....Given the low rate of ipsilateral breast events in women following mastectomy for DCIS, tamoxifen does not confer a significant benefit to the ipsilateral breast. Thus, the greatest impact of systemic hormonal therapy after mastectomy for DCIS may be to the contralateral breast, with younger women with longest life expectancy likely to benefit most."

I'm so glad to have read this- I had umx and thank goodness had no micro invasion and clean margins( although not huge) so no tamoxifen or radiation. Mo calculated my risk for the remaining breast at 14% rather than the 11% of the general population. So all things considered, I was pretty fortunate :-/