Experts say leaked messages present false link between gender-affirming care and cancer

Hundreds of messages from an internal chat board for an international group of transgender health professionals were leaked in a think tank report last week and framed as revealing serious health risks associated with gender-affirming care, including cancer. But experts say this correlation is false and oversimplifies the complex role of hormones in the body.

The report was released by Environmental Progress, a think tank focused on energy and environmental policy and founded by Michael Shellenberger, a writer who has previously been critical of gender-affirming care and said he wants to shut down the World Professional Association for Transgender Health. The report claims that two particular messages from the WPATH system — where any of the organization’s more than 2,700 member clinicians can go to discuss care — suggest a connection between hormone therapy and cancer.

In one, a doctor writes about a 16-year-old patient who developed two benign liver tumors after several years of taking birth control and one year of gender-affirming testosterone. In another, a different doctor recalled a colleague who died of liver cancer after nearly a decade of taking testosterone. That doctor wrote that, “To the best of my knowledge, [the cancer] was linked to his hormone treatment.” The doctor also noted that they didn’t have any other details because the patient had died.

But experts say that these individual anecdotes are being purposefully misinterpreted — the benign liver tumors the first patient developed are known to be a rare side effect linked to birth control use. And they add that the report inaccurately paints a picture of a larger pattern for which there is no clear evidence.

“When you hear of a one-off case, you have to balance that against the tens of thousands of people who’ve been on testosterone and are doing well,” said Carl Streed, a physician, president of the United States Professional Association for Transgender Health, and WPATH board member.

WPATH president and physician Marci Bowers confirmed that the leaked messages were from the organization’s internal message board. “We are the professionals who best know the medical needs of trans and gender diverse individuals — and stand opposed to individuals who misrepresent and de-legitimize the diverse identities and complex needs of this population through scare tactics,” she wrote in a statement about the leak.

Experts don’t debate that hormones in general can contribute to a person’s risk of cancer. Conditions like breast cancer can occur when there is “unchecked hormone action,” meaning that a hormone has been overproduced in the body so much that its effects can’t be counteracted by other hormones, said Simon Knott, a researcher and co-director of the Applied Genomics Shared Resource Cancer Institute at Cedars-Sinai. But no matter a person’s sex or gender, everybody has certain levels of both estrogen and testosterone in their body. To adjust the ratio of those levels to change one’s physical appearance — as with gender-affirming treatment — will not typically create a problem, as those levels stay within a normal range for the human body.

“To say that any one hormone that’s given to an individual is going to drive tumors — it’s pretty naive,” Knott said.

Using estrogen alone as a form of hormone therapy for menopausal cisgender women can create unchecked hormonal action. Researchers learned about an increased risk of endometrial cancer associated with this treatment from studies with thousands of participants. Research on this scale does not exist for gender-affirming hormones, but smaller studies don’t show a clear correlation. And a systematic review of literature last year found that there was not enough evidence to say there’s an association between testosterone therapy for trans men and liver tumors.

A 2019 study in the Netherlands did show an increased risk for breast cancer in trans women receiving hormone therapy compared to cisgender men. But experts say this isn’t the most useful comparison, and the trans women in that study still had a lower risk of breast cancer compared to cis women.

“When you have breast tissue then you can have cancer of that tissue. And that’s all we’re seeing,” said Joshua Safer, the executive director of the Mount Sinai Center for Transgender Medicine and Surgery and a WPATH board member.

That logic may work in the opposite direction, too. Last year, Knott and colleagues published a small study analyzing breast tissue from trans men and cis women. They found that testosterone therapy may actually protect against breast cancer.

Various types of hormone treatments have been used safely in treatments like birth control for “decades and decades and decades,” Safer said.

Still, experts do want to see more studies specifically on transgender people who do have cancer. Some providers tell their trans patients to stop taking hormone therapy when they have cancer out of an abundance of caution, said Scout, the executive director of the National LGBT Cancer Network, who has no first name. This can be incredibly upsetting for patients who are then unable to present as their true gender.

In order for clinicians to make more informed decisions, there needs to be a broader inclusion of trans people in research, experts say, starting with the inclusion of gender identity and expression in patients’ electronic health records in addition to sex.

“We have more data gaps than we have data points,” Scout said. “Our concerns are medical mistrust, not being able to find safety at providers, and that leading to delayed diagnosis, and that also leading to worse experiences of care.”

In the meantime, providers who prescribe gender-affirming hormones and other treatment for trans people continue to communicate with patients directly about any potential risks. Streed always talks through a patient’s personal risk for developing blood clots when prescribing estrogen, and about testosterone’s potential effect on cholesterol levels.

“People are saying that any risk is unacceptable, and that is not how medicine works,” Streed said. Oral contraceptives are another type of hormone therapy involving estrogen, meaning there’s a risk patients will develop blood clots or benign tumors. Yet birth control is prescribed widely, and the first over-the-counter version will begin arriving in stores later this month.

The report on the leaked messages made numerous other claims about the dangers of gender-affirming care. But experts say none of the messages offer any evidence against continuing to safely provide gender-affirming care.

“When you read through [the leaked messages], it really is clinicians having conversations with each other trying to understand, ‘What would you do in this situation? This is what I’m thinking,’” said Streed, who read the entire report. “It all sounds like it’s pretty much conversations that I would expect among clinicians about clinical care.”

Erin Reed, an independent trans journalist who covers legislation and other news related to transgender people, also combed through the entire report and identified 216 instances of “errors, misrepresentation of data and citations, misrepresentations of the actual leaked material, and more,” she wrote.

Experts say it’s important to understand the source of any information in order to avoid misinformation about gender-affirming care. All the major medical associations — including the American Medical Association, the American College of Physicians and the American Academy of Pediatrics — support gender-affirming care.

They also worry that attacks and threats on providers may not only affect what research gets done, but what reliable information is accessible online for people who want to learn more. After Boston Children’s Hospital received bomb threats over providing gender-affirming care, more than 20 hospitals scrubbed information about these services from their websites.

But in the wake of the report on the leaked messages, Safer says that it’s more important than ever for clinics to publish and promote the evidence for gender-affirming care. “If the trusted site isn’t even there,” he said, “that’s going to be a problem.”