Can I Continue Gender-Affirming Hormone Therapy During Treatment?
Ash Davidson never imagined his gender transition would lead to a breast cancer diagnosis, but a few weeks after chest-flattening “top surgery” his surgeon told him they found a breast tumor. He then had to navigate a stage I invasive ductal carcinoma diagnosis during the early stages of his transition.
Transitioning can be both joyous and difficult, Davidson says. “Adding a cancer diagnosis on top of that was unfathomable.” Luckily, he was able to continue testosterone therapy while going through chemotherapy and radiation. But not everyone can, since gender-affirming hormone therapy (GAHT) helps some breast tumors grow.
Breast cancer can and does impact transgender and nonbinary (TGNB) people, regardless of their sex assigned at birth. A breast cancer diagnosis can disrupt someone’s transition, especially if they’re taking GAHT. Oncologists may suggest they stop GAHT altogether, depending on their breast cancer type and the oncologist’s knowledge of transgender health — but that isn’t always necessary. Here’s what you need to know.
Current guidelines for GAHT during treatment
Currently, there are no set guidelines for doctors on how to navigate GAHT for transgender people diagnosed with breast cancer. “Those of us who treat a lot of trans individuals with breast cancer — of which there are only a handful globally — have a consensus on what to do,” says Alison Berner, PhD. Berner is an oncology lecturer at Queen Mary University of London and the clinical lead for the UK Cancer and Transition Service, a pan-cancer clinic for gender-diverse people in the UK. “We’ve published it in the American Society of Clinical Oncology journal, but it’s not based on a formal clinical trial,” she says.
Without formal guidelines, Berner says shared decision-making between you, your gender-affirming care team, and your oncology team is important when deciding how to approach GAHT during treatment. Choosing whether or not to continue GAHT can depend on the biology of the tumor, “the person’s current effects from hormones, their long-term goals, and their appetite for risk,” Berner says.
GAHT and hormone receptor-positive breast cancer
If a breast tumor is hormone receptor-positive, then the hormones estrogen or progesterone (or both) fuel the cancer. Adding extra hormones to your body through GAHT — whether that’s estrogen, progesterone, or even testosterone — may complicate treatment. The body naturally turns a small amount of testosterone into estrogen, which is why taking testosterone can fuel hormone receptor-positive cancer.
Key takeaways:
If you’re taking estrogen and/or progesterone as part of your GAHT, your doctor may advise you to stop during cancer treatment. There are options, though, if you choose to continue GAHT.
If you’re taking testosterone as part of your GAHT, you should be able to continue taking it during cancer treatment. Your doctor may advise switching to gel formulations, and adding another drug, depending on the specifics of your tumor.
TGNB people taking estrogen and progesterone
For TGNB people assigned male at birth (amab), breast cancer is relatively rare. When cases do arise, they are more likely to be hormone receptor-positive. TGNB people taking estrogen and progesterone must balance the benefits of GAHT with the risks it poses to hormone receptor-positive cancer.
Estrogen receptor-positive breast cancer
If a transfeminine or non-binary person has an estrogen receptor-positive tumor, “then it’s a conversation about stopping or lowering estrogen therapy, knowing that we’ve got a really clear biological reason that it could be harmful,” Berner says.
Some trans people may decide they want to continue taking estrogen for their quality of life, while other people need to continue GAHT if they’ve had bottom surgery. In these cases, Berner generally wouldn’t suggest treating the cancer with an anti-estrogen therapy. “There’s no point in giving someone estrogen, then taking it away.”
There may be other treatment options if a TGNB person decides to continue estrogen GAHT. For example, for metastatic estrogen receptor-positive breast cancer, Berner says they could bypass the first-line treatment of CDK4/6 inhibitor and anti-estrogen therapy and go straight to chemotherapy. “They do need to accept that in doing that, they lose a line of therapy,” she adds.
If a TGNB person stops gender-affirming estrogen therapy for cancer treatment, it may just be a temporary pause. They may be able to restart GAHT if the cancer is cut out during surgery. For hormone receptor-positive breast cancers, doctors typically prescribe an anti-estrogen therapy like tamoxifen for 5-10 years after treatment. But that doesn’t have to be the case if you’re trans. “People can choose to take hormones again if it improves their quality of life,” Berner says.
And no matter what they decide about estrogen GAHT, trans and non-binary people can continue taking testosterone-lowering therapy as normal.
Progesterone receptor-positive breast cancer
About half of all hormone receptor-positive breast cancers have both estrogen and progesterone receptors, while about 2–8% have only progesterone receptors. Progesterone, similar to estrogen, can help fuel the growth of hormone receptor-positive tumors. So if a TGNB person has a hormone receptor-positive tumor and they’re taking progesterone, they may be advised to stop, says Berner.
TGNB people taking testosterone
TGNB people taking testosterone GAHT may be able to continue taking it during cancer treatment, depending on how their body uses testosterone.
In some cases, testosterone could actually work against breast cancer. In other cases, it can help fuel estrogen receptor-positive cancer. This doesn’t mean you have to stop testosterone GAHT, but it may mean you need different cancer treatment. And for some people, it might help to switch from testosterone injections to a daily gel.
Androgen receptor-positive breast cancer
The same way some tumors have estrogen receptors, they can also have androgen receptors. Androgen receptors are what allow androgen hormones like testosterone to affect cells and tissues. Recent research suggests that androgen receptors in breast tumors may have anti-estrogen effects.
“For many years, we thought giving testosterone to someone when there are androgen receptors on a tumor may help the tumor grow,” Berner says. “But it appears to act in opposition to estrogen.” So, in tumors that are estrogen receptor-positive and androgen receptor-positive, testosterone therapy can continue during cancer treatment.
Testosterone and aromatase
Testosterone therapy can stop the ovaries from making estrogen, which is good in the case of estrogen receptor-positive breast cancer. But an enzyme that the body makes naturally, called aromatase, converts a small amount of testosterone into estrogen. So although testosterone may lower estrogen levels from the ovaries, it also triggers a smaller increase in the production of estrogen.
If a person is taking an anti-estrogen therapy that blocks estrogen receptors, like tamoxifen or fulvestrant, then the extra estrogen made by aromatase doesn’t matter. Sometimes a doctor will recommend an aromatase inhibitor because of insurance coverage or guidelines based on evidence in cis women. In this case, Berner suggests that people taking weekly testosterone injections switch to a daily testosterone gel.
“We know from observations in our clinic that peak testosterone from injections is when you get a lot of conversion to estrogen,” she says. Using a daily gel doesn’t lead to the same testosterone highs and lows, so less of it is converted to estrogen but you do need to monitor levels.
GAHT and hormone receptor-negative breast cancer
If a breast tumor is hormone receptor-negative, extra hormones from GAHT may not be a problem. But there may be a risk for TGNB people with triple-negative breast cancer who are taking testosterone.
Key takeaways:
If you’re taking estrogen and/or progesterone as part of your GAHT, you should be able to continue taking these hormones during cancer treatment.
If you’re taking testosterone as part of your GAHT and have triple-negative breast cancer, you may be advised to stop during cancer treatment.
TGNB people taking estrogen and progesterone
For trans and non-binary people diagnosed with breast cancer that isn’t hormone receptor-positive — like triple-negative breast cancer — Berner says GAHT can continue as normal. “We wouldn’t block [estrogen] in a cis woman in that situation,” she says.
TGNB people taking testosterone
In the case of triple-negative breast cancer — unlike estrogen receptor-positive breast cancer — androgen receptors may help tumors grow, Berner says. This means any extra testosterone added to the body from GAHT may be helping the tumor, too. So for trans and non-binary people taking testosterone GAHT who are diagnosed with triple-negative breast cancer with androgen receptors, “I would be more cautious with continuing testosterone.” She says the data isn’t as strong as it is for estrogen-related breast cancer, though, so more research is needed.
Other things to consider
A breast cancer diagnosis can change other aspects of transgender healthcare. In many cases, it removes the option of fertility preservation. And TGNB people who have had gender-affirming surgery to remove their ovaries may experience severe menopause symptoms from cancer treatment.
Fertility preservation
A breast cancer diagnosis may disrupt plans for fertility preservation, especially if a TGNB person hasn’t stored sperms or eggs before starting GAHT. The time a person needs to stop GAHT before their reproductive system is ready for them to freeze their sperm or eggs can range from 1-2 weeks to 6 months, Berner says. Some people can’t wait this long before starting chemo. This often takes fertility preservation off the table. Still, it’s important to talk to your oncology team if fertility preservation is important to you.
Menopause symptoms
Like cis women, TGNB people may experience menopause symptoms like hot flashes, mood swings, and sleep problems due to cancer treatment. “It seems to be worse if they have their ovaries out,” Berner says. She says it’s an area of unmet need that needs to be addressed with more research
Davidson faced intense side effects of tamoxifen while continuing GAHT post-treatment, including increased depression, anxiety, and joint and muscle pain. He says because of the lack of research on how tamoxifen mixes with fluctuating testosterone from GAHT, he felt like a guinea pig and “the unknowns were scary.” Unable to manage the side effects, Davidson and his oncologist ultimately decided together that he’d stop taking tamoxifen.
How to advocate for yourself during treatment
If you’ve recently been diagnosed with breast cancer and are on GAHT, it can help to seek out an LGBTQ-friendly cancer care provider who has experience working with trans and non-binary people. But this is not accessible to everyone. So you may need to advocate for yourself with your oncology team if you want to continue GAHT.
Berner has some advice:
Schedule a time to meet with your oncologist to talk only about GAHT, and go to that meeting informed. “Talk about the importance of continuing GAHT and the benefits it has on your physical and mental health,” she says.
Ask your oncology team to look over the evidence that’s out there, like Berner’s recent review of breast cancer care for TGNB people.
Ask your oncology team to think about what they would recommend to cis people taking hormones, which can inform how they should advise trans people taking GAHT.
Encourage your team to talk with outside experts, like those at the UK Cancer and Transition Service. “We’re happy to be contacted internationally to give advice,” Berner says.
Seek support if your cancer treatment will interrupt your GAHT. Check to see if local LGBT+ groups offer resources for people with cancer, or look for community online like through The Cancer Network’s LGBT+ peer support groups.
Davidson encourages TGNB people navigating a breast cancer diagnosis to ask for help from their support network and to not be afraid to take up space in the doctor's office. “Your care is just as real and just as important as anyone else's," he says. “You deserve to be treated with care, compassion, and dignity. Don’t ever let anyone tell you differently.”