Tamoxifen reduces cancer by 40%?

Hi moskitoe:

It sounds like your mother has not yet had her lumpectomy. Therefore, her risk of recurrence (loco-regional and distant) following lumpectomy and radiation cannot be accurately ascertained at this time.

As I noted in your other thread, you are putting the cart before the horse. Your mother cannot make informed decisions about the potential benefit of systemic treatment (e.g., tamoxifen) until after her surgery. This is because the results of the surgical pathology may affect understanding of her recurrence risk.

Despite her current diagnosis of intermediate grade DCIS based on biopsy, that may not be her final diagnosis. According to the American Society of Clinical Oncologists ("ASCO"), among patients with apparently pure DCIS by minimally-invasive biopsy (e.g., core-needle, invasive disease is found "10% to 20% of cases overall, approximately half of which are limited to micro invasive cancer" ("T1mi", where Tumor ≤ 1 mm in greatest dimension).

(As an example of this, I was diagnosed with DCIS on both sides. However, the surgical pathology on my right side found a 1.5 mm IDC, plus a few areas of microinvasion. On the left, the extent of the DCIS was much greater than appreciated from either mammography or MRI.)

As you will appreciate, invasive breast cancer can have a different recurrence risk as compared with pure DCIS, and leads to consideration of distant recurrence risk in treatment decisions.

Even if no invasive disease is found, the grade, extent, and/or architecture of the DCIS may differ in material ways from what biopsy shows and this may alter understanding of local recurrence risk. The size of the surgical margins is also a factor.

Please understand that this forum is not an appropriate source of information regarding your mother's baseline recurrence risk or her residual risk after lumpectomy plus radiation:

(1) After her surgical pathology is available, please seek expert professional medical advice from a Radiation Oncologist ("RO") about her residual local recurrence risk after lumpectomy plus radiation.

(2) Then, with that information in hand, please seek expert professional medical advice from a Medical Oncologist ("MO") about by how much tamoxifen can potentially reduce that risk. Request an explanation of how that information is derived.

Unfortunately, members of this community often provide inaccurate information. Therefore, all information you get here (including from me) should be verified with your mom's medical oncologist and radiation oncologist to ensure she receives accurate, current, case-specific expert professional medical advice regarding her risk of recurrence and the potential benefits of treatment.

Informed decisions should be based on case-specific expert professional medical advice.

BarredOwl

Hi Barred Owl -

You are absolutely correct ... it should be 9. I somehow subtracted 6 from 15 and got 11. No idea how, LOL. I do agree it is premature to be estimating risk prior to surgery and did specify that we were talking about averages, and that individual cases may vary. Her question though was about what an average risk reduction of 40% would mean in the context of lumpectomy and radiation having brought it down already, and the clarification of relative risk vs. absolute risk in a generic sense would be useful prior to being given exact numbers.

For what it’s worth, 40 was the average number given to me by my team as well, but as you say, what really matters is the risk to a particular individual.