Jenna Fischer, who starred in “The Office,” said Tuesday that she underwent surgery and treatment for breast cancer earlier this year and is now “cancer free.”

Fischer, 50, wrote in an Instagram post that she was diagnosed with stage 1 triple-positive breast cancer in December. A routine mammogram in October 2023 had produced inconclusive results due to dense breast tissue, prompting a breast ultrasound and then a biopsy. 

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Triple-positive breast cancer is an aggressive form of the disease, but it is highly treatable and very responsive to therapies.

Fischer had lumpectomy surgery in January to remove the tumor. Although the cancer was caught early and did not spread to her lymph notes, she she underwent 12 weeks of chemotherapy beginning in February and three weeks of radiation in June. 

“I am happy to say that I was recently re-screened, and the treatments worked,” Fischer wrote. “I am cancer free. I will continue to be treated and monitored to help me stay that way.”

What is triple-positive breast cancer?

Healthy breast cells have receptors that bind to the hormones estrogen and progesterone to promote growth. A protein known as human epidermal growth factor 2, or HER2, also is involved in this process. 

Breast cancers that have atypically high levels of the HER2 protein are known as HER2-positive. Those that also have higher-than-usual levels of estrogen and progesterone receptors are known as triple-positive.

This subtype of HER2-positive breast cancer makes up 10% of all breast cancer diagnoses, according to the MD Anderson Cancer Center.

What are the symptoms? How is it detected? 

Triple-positive breast cancer has the same symptoms as other types of breast cancer, including the development of lumps in the breast or armpit. Other symptoms include a change in size or shape of the breast, nipple discharge, and skin that looks dimpled, puckered, scaly or inflamed. 

Mammograms can detect early-stage breast cancer that otherwise may go unnoticed. Suspicious lumps uncovered during breast cancer screenings are biopsied to determine whether they are cancerous.

Doctors may examine cancerous tumors with immunohistochemistry tests to determine if the cancer is driven by the estrogen receptor, the progesterone receptor, the HER2 receptor or a combination of the three — all being positive results in a diagnosis of triple-positive breast cancer.

How is triple-positive breast cancer treated? What are the survival rates?

Treatments include therapies used to treat HER2-positive and hormone receptor-positive breast cancers. 

Patients with tumors smaller than 2 centimeters typically receive surgery first, then chemotherapy with HER2-targeted therapy, according to the MD Anderson Cancer Center. Radiation therapy, and possibly hormone therapy may follow. 

Fischer said she followed this treatment route and is still being treated with infusions of Herceptin, a treatment for HER2-positive breast cancer, and a daily dose of Tamoxifen, an estrogen blocker.

The effectiveness of treatment for triple-positive breast cancer depends on its stage. A 2022 study found the five-year overall survival rate for triple-positive breast cancer was 96.7%. The five-year disease-free survival rate is 90%. The former rate includes people who are still receiving treatment for the disease. The latter only includes people who are no longer showing signs of cancer. 

Overall death rates for breast cancer have dropped by 44% since 1989, but racial disparities remain. Black women are less likely to be diagnosed with breast cancer but more likely to die of it than white women.