So I'm due to start tamoxifen but am questioning it.

It sounds like you are thinking things through and are striving for enough information to make your decision. It is great that your DCIS was found before it turned into IDC and had a larger risk of spreading through the lymph or blood systems. I had IDC and wanted to take all steps I could so that I could avoid a spread - although nothing is guaranteed in this BC world. I can accept what happens if I have done my job to prevent it. I also lost my extra weight to remove that extra estrogen. So now I can look forward. I had a lot of side effects from Arimidex and changed to Tamoxifen on my MO's recommendation. My side effects are few and inconsistent - occasional sleeplessness, leg & foot cramps. If it is recommended by your oncologists, you might consider trying the tamoxifen and seeing how you react. You can always stop! Best wishes!

Hi:

The National Comprehensive Cancer Center (NCCN) guidelines (Version 3_2015) (still current as of this date) indicate the following re menopausal status:

"Reasonable criteria for determining menopause include any of the following:
• Prior bilateral oophorectomy . . ."

Regarding the treatment of pure DCIS, the NCCN guidelines for "Breast Cancer" state:

"Risk reduction therapy for ipsilateral breast following breast-conserving surgery:

Consider tamoxifen for 5 years for:
• Patients treated with breast-conserving therapy (lumpectomy) and radiation therapy (category 1), especially for those with ER-positive DCIS. . .

According to the NCCN Panel, tamoxifen may be considered as a strategy to reduce the risk of ipsilateral breast cancer recurrence in women with ER-positive DCIS treated with breast-conserving therapy (category 1 for those undergoing breast-conserving surgery followed by radiation therapy; category 2A for those undergoing excision alone). The benefit of tamoxifen for ER-negative DCIS is not known."

[Edit: Please see further message below regarding additional options]

There is a very recent 2015 abstract and related article regarding some results from the NRG Oncology/NSABP B-35 trial of anastrozole (an aromatase inhibitor) vs tamoxifen in postmenopausal women with ER-receptor or PgR-receptor positive (by IHC analysis) DCIS and no invasive BC who had undergone a lumpectomy with clear resection margins:

Abstract: http://meetinglibrary.asco.org/content/146144-156

Article: http://www.onclive.com/conference-coverage/asco-20...

BarredOwl

Hi CAMommy:

This topic was recently discussed in another thread, and I have edited by my post above and provide the following regarding some additional options for completeness. The use of aromatase inhibitors for pure DCIS does not appear to be discussed in the guidelines for the treatment of "Breast Cancer" from the National Comprehensive Cancer Center (NCCN), Professional Version 3-2015. That guideline document features tamoxifen for risk reduction therapy for the ipsilateral breast following breast-conserving surgery. However, it refers to a second NCCN guideline for "Breast Cancer Risk Reduction" (version 2-2015) with respect to risk reduction therapy for the contralateral breast. The second guideline document discusses several options for post-menopausal women, including tamoxifen, raloxifene, and the Aromatase Inhibitors exemestane (Aromasin) and anastrozole (Arimidex).

Although the guideline for "Breast Cancer Risk Reduction" (version 2-2015) notes that "Exemestane and anastrozole are not currently FDA approved for breast cancer risk reduction," it does include these drugs as available choices:

"The NCCN experts serving on the Breast Cancer Risk Reduction Panel have included exemestane and anastrozole as choices of risk-reduction agent for most postmenopausal women desiring non-surgical risk-reduction therapy (category 1). This is based on the results of the MAP.3 trial and the IBIS-II trial."

Here are the cited trial reports:

MAP.3 Trial:

(Text): http://www.nejm.org/doi/full/10.1056/NEJMoa1103507...

(Pdf): http://www.nejm.org/doi/pdf/10.1056/NEJMoa1103507

Correction: http://www.nejm.org/doi/full/10.1056/NEJMx110056

IBIS-II Trial:

http://dx.doi.org/10.1016/S0140-6736(13)62292-8

As noted above, there is also this recent abstract from the NRG Oncology/NSABP B-35 trial of anastrozole (an aromatase inhibitor) vs tamoxifen in post-menopausal women with ER-receptor or PgR-receptor positive DCIS who had undergone a lumpectomy with clear resection margins:

NRG Oncology/NSABP B-35 trial:

Abstract: http://meetinglibrary.asco.org/content/146144-156

Article: http://www.onclive.com/conference-coverage/asco-20...

Article: http://www.ascopost.com/ViewNews.aspx?nid=29595

In post-menopausal women, consideration of a variety of factors, including risk/benefit profiles, will be factored in when choosing tamoxifen, raloxifene, or an aromatase inhibitor (exemestane (Aromasin), anastrozole (Arimidex)).

BarredOwl

Hi CAMommy:

IBIS-II Trial:

http://dx.doi.org/10.1016/S0140-6736(13)62292-8

The number of deaths reported as 18 and 17 include deaths from all causes, not just breast cancer per Table 2. Deaths from breast cancer were 2 (n = 1920) in the treatment arm and 0 (n = 1944) in the placebo arm. I am not sure what that means, but with such small numbers, it seems possible that the result may not be meaningful (possibly just due to chance)?

BarredOwl