Your Tamoxifen Questions Answered

Taryn Hillin
7 min readOct 6, 2023
Photo by Angiola Harry on Unsplash

Let’s talk about Tamoxifen.

If you’ve been diagnosed with hormone-receptor-positive breast cancer you’ve probably heard of Tamoxifen (and if you’re pre-menopausal you’ve probably been prescribed Tamoxifen).

For those who don’t know, Tamoxifen is a SERM — a selective estrogen receptor modulator. And it does exactly what the name implies, it gets in the way of your estrogen receptors (including the ones your cancer cells can use) and prevents cells from responding to the hormone.

Due to this mechanism, Tamoxifen comes with a host of side effects — often related to the induction of menopause — like hot flashes, low sex drive, vaginal dryness / or discharge, depression (25% of women on Tamoxifen are also on an anti-depressant), joint and muscle pain, blurred vision, liver problems and a tiny risk of endometrial cancer.

Since Tamoxifen is prescribed mainly to pre-menopausal women*, they’re often young — 20s, 30s, 40s — and therefore the side effects can greatly disrupt their Quality of Life and set them up for issues later on. Not only that, Tamoxifen is prescribed for 5 years to 10 years, making the decision to stay on it … a LONG one.

Here’s the thing. Tamoxifen is a VERY effective drug at reducing the risk of breast cancer recurrence. Indeed, it’s often said to “reduce breast cancer recurrence risk by half”, yet some studies show that 25% to 35% of women prescribed Tamoxifen as adjuvant therapy stop taking it (usually for harsh side effects). Those numbers climb closer to 50% in high-risk women prescribed Tamoxifen as a prophylactic (i.e. to prevent breast cancer in the first place).

So what’s going on? Surely taking Tamoxifen has many upsides, the greatest one being preventing breast cancer from recurring and becoming metastatic (which is incurable). Yet, it seems for many women the downsides just aren’t worth it.

To take or not to take Tamoxifen is a personal decision and a tough one. I can’t understate that enough. It seems, to me, that breast cancer patients are faced with a lot of statistical analysis on whether or not they need to be on this drug, without much clarity. It’s difficult to weigh the pros and cons of a drug that may make your life miserable, and possibly cause more health issues, but purports to “cut your cancer risk by 50%” if you don’t know your baseline risk.

“If someone had Stage 2 [breast cancer], they’re probably not questioning whether or not to take hormone therapy,” says Dr. Tiffany Troso-Sandoval, an oncologist at Memorial Sloan Kettering specializing in Breast and Gynecological cancers who I turned to for guidance on this subject. “But a lot of the patients who might have DCIS or LCIS may be wondering, do I really need to take this?” [DCIS, Ductal Carcinoma In Situ, is seen as pre-cancer/Stage 0/Benign, in that it may never turn into active cancer. LCIS Lobular carcinoma in situ also is not considered cancer].

And this seems to be the crux of the issue, the RISK of the drug, versus the RISK of the cancer.

But when it comes to breast cancer this can be a difficult question to answer, due to the sheer number of variables involved. Not to mention that some hormone-receptor-positive cancers can recur LONG after 5 years, adding yet another layer of whether or not to extend hormone therapy.

I want to dive into that question, “Do I Really Need To Take Tamoxifen?” because so many women have reached out to me and asked. But, here’s my caveat, no amount of Googling or online articles can tell you that answer effectively. It will all come down to your individual cancer and your individual risk. Hopefully, the explainer below can be a valuable resource to have a conversation with your doctor.

Answering the Question: Do I REALLY Need Tamoxifen?

Turns out there are ways to measure the risk in numbers.

In Troso-Sandoval’s practice, they use the Oncotype DX test to help women understand their risk of recurrence based on several factors: how aggressive the cancer is, how estrogen-sensitive it is, and whether hormone therapy decreases that risk enough. “Based on that test, we can get a percentage risk of recurrence and give that to the patient,” she says. “But it’s all relative”.

For example, if your baseline risk is 5% and you cut it to 2% is that worth it? Probably. But if your baseline risk is 2% and you’re cutting it to 1%, is that still worth it? Both of those are cutting by 50%, but a 1% reduction might not outweigh the harsh side effects.

Dr. Troso-Sandoval says this type of test, Oncotype DX, should be the Standard of Care for anyone with Stage I breast cancer or higher. (She says there’s also a version that can be used for DCIS, but it’s less common).

The other test often used is the Breast Cancer Index (BCI).

“BCI is the second half of treatment analysis,” she says. This test is a DNA analysis of cancer cells looking at propagation and hormone sensitivity, that gives a patient (and their doctor) two answers: what is the percentage risk of recurrence in 5 years or 10 years AND will more hormone therapy be beneficial? (The answer is a binary Yes/No.)

For example, someone could have a high risk of recurrence, but the test shows hormone therapy would not be helpful. “This is a bad scenario because it means I don’t have a drug to give you” explains Troso-Sandoval. On the flip side, the result could be an 8% risk of recurrence, but YES hormone therapy is helpful.

Again patients are left with a statistical analysis, so I asked what is the cutoff here of low-risk versus high-risk? Troso-Sandoval suggested anything above 5% risk is a reason to stay on the drug.

This takes me back to compliance. As a non-BC patient looking at these numbers, a 5% risk *seems* low — and I imagine patients who just finished treatment see a low number and think, “This drug simply isn’t worth it.” But that’s because we don’t have the depth of knowledge oncologists do regarding data on this test. So I looked up some data to put this in context.

A study from Yale School of Medicine of 240 women showed the median BCI score was 4.6%, with a range of 1.0%-17.1%. Seeing these scores puts a 5% score into a different context than imagining scores of 80% or 90%, which just don’t happen. In the Yale study “high-risk” was considered 5.0%-17.1%.

This is why it’s imperative to have doctors take the time to translate these risk numbers with their patients.

After my conversation, I started to think that the decision to stay on Tamoxifen may rest on a better explanation of the risks, the testing, and a deeper understanding (empathy) of what patients have to sacrifice to stay on the drug. Industry stats show patients say they are more likely to stay on the drug (compliance) when given a BCI score.

Data shows that women who stopped taking hormonal therapy early were 35% to 56% more likely to have a recurrence than women who didn’t stop taking the medicine early. A good stat to know if you’re considering ending the drug early.

Of course, that means there are women out there who don’t take Tamoxifen and don’t get recurrence. This is the difficult part about any adjuvant cancer therapy — you must ask yourself “Which bucket will I be in?” No easy task. I think this question is especially difficult if you’re facing a DCIS / LCIS / Atypical Hyperplasia situation, where it may never become cancer anyway.

If you are struggling with this decision please make sure your doctor is offering tests like Oncotype and BCI and clearly explaining what the numbers mean and what your true risk of recurrence is.

Mitigating Tamoxifen Side Effects

As for those on it, there are ways to mitigate the side effects. These tips come from Dr. Troso-Sandoval at MSKCC. She is running a Facebook page for cancer patients called “Winning the Cancer Journey” which you should definitely join. (Obviously, none of this is medical advice, it is for educational purposes only, and you must discuss everything with your own doctor).

  • For joint and bone health, make sure Vitamin D levels are adequate (the 40 ng/mL to 60 ng/mL range), sometimes taking calcium, magnesium, Turmeric, and Fish Oil (Omega 3) is helpful.
  • Try to stretch, exercise, and especially do weight-bearing exercises.
  • For hot flashes, put a mini fan in every room. Have a fan blowing on your neck at night.
  • There are drugs doctors can prescribe for hot flashes and night sweats, like Gabapentin and certain anti-depressants. Ask your doctor about them, but also when deciding to go on a medication ask yourself, how life-altering is it? How intrusive is it?
  • For other symptoms, like both vaginal dryness and excess vaginal discharge (which are normal), try a product like Replense. Even excess discharge can be the body overcompensating for dryness, so while it seems counterintuitive it’s not.
  • There are also some non-mainstream tests that can help analyze how your body metabolizes Tamoxifen (which plays a role in how much of it your body is getting and processing) from Genomind. You can ask your doctor about these tests.

Hope this is helpful, feel free to share your experience with Tamoxifen below.

*Post-menopausal women diagnosed with hormone receptor-positive Breast Cancer are more likely to be put on an Aromatase Inhibitor. Some studies are looking at ovary suppression + AI in pre-menopausal women as well. Side effects like bone and joint pain may be worse on an AI.

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Taryn Hillin

Writer, journalist, media strategist. Sony TV Diverse Writers '21; Universal Writers '22; Formerly of HuffPost, Fusion, TMZ, and VP Strategy ENTITY. Yale grad.