White House chief of staff Susie Wiles is opening up about the grueling reality of fighting breast cancer while holding one of Washington's most demanding jobs, revealing that some days simply getting out of bed and going to work took all the strength she had.

In an op-ed published Sunday in USA Today, Wiles described what it was like to undergo chemotherapy while continuing to lead the White House staff for President Donald Trump. 

The disease occupied her thoughts from the moment she woke up and sometimes even while she slept, she wrote.

"Fighting cancer is brutal and unrelenting," Wiles wrote. Questions about treatment, test results and what might come next could overtake even a strong mind. At times, she acknowledged, they overtook hers.

CANCER-RELATED BRAIN FOG MAY IMPROVE WITH 2 SIMPLE TREATMENTS, SCIENTISTS SAY

Some days, Wiles said, she poured her strength into fighting the disease. On others, getting out of bed, getting dressed and going to work was its own test. "Most days, I carried the full weight of both," she wrote.

Work gave her a purpose beyond appointments, scans and side effects. "Cancer can make your world very small," Wiles wrote. She said she pushed herself to stay focused on the people who depended on her, even as she knew others might question whether she could still lead effectively.

KAI TRUMP REVEALS HOW FAMILY RALLIED AROUND MOM VANESSA AMID BREAST CANCER BATTLE: ‘IT’S A LONG JOURNEY’

The treatment did take a toll on her stamina, mobility and, at times, her focus. Wiles said she could not always be everywhere she wanted to be. Colleagues inside and outside the White House stepped in, while her two daughters, extended family, friends and medical team helped carry her through the illness.

Wiles made clear that working through treatment would not be right or possible for everyone. For her, she wrote, the job helped her hold on to a sense of who she was beyond the disease.

CANCER SURVIVORS MAY SEE SURPRISING BENEFITS FROM ONE SPECIFIC EXERCISE, STUDY SAYS

After successful surgery, pathology showed no residual cancer, Wiles wrote. She said she now faces the work of rebuilding what treatment took from her.

"Chemotherapy is, in a word, a b----," she wrote.

DOLLY PARTON’S PRIVATE CANCER BATTLE HIGHLIGHTS WHY SOME PATIENTS DON’T SHARE THEIR DIAGNOSES

In a post on X Sunday, Wiles said she rarely writes about herself but wanted to share what it was like to fight cancer while continuing to do a job she loves.

"Cancer tried to make my world smaller. I was determined not to let it," she wrote, adding that she hoped her account could offer strength to someone still fighting the disease.

VANESSA TRUMP REVEALS BREAST CANCER DIAGNOSIS IN EMOTIONAL STATEMENT: 'I AM STAYING FOCUSED AND HOPEFUL'

Wiles announced Sept. 16 that she was cancer free after receiving clear pathology results following an appointment at the Mayo Clinic. She had disclosed her early-stage breast cancer diagnosis in March.

Trump praised Wiles during her treatment, saying in a prerecorded May tribute that she was winning her cancer battle. Wiles thanked him for his kindness and compassion, and credited her family, friends, colleagues and doctors with helping her through the ordeal.

For others going through treatment, Wiles offered a message of hope. "Cancer does not have to take away who you are," she wrote. She said that for her, life beyond the disease includes serving Trump and the country and being a mother, grandmother and friend.

One of those daughters, Katie Wiles, responded to her mother’s account on X. "A strong woman isn’t loud in her strength; she’s steady and unshakable," she wrote. "You are our champion. So incredibly proud of you, Mom."