Mother, Community Leader with Breast Cancer Has Remarkable Response to Immunotherapy

Nancy Arsenault was taking a lunch break from driving her elementary school bus route in her hometown of Stow, Massachusetts, when she began to experience double vision.

She had been first diagnosed with pre-invasive breast cancer in 2006, which recurred in 2011. In 2019, she developed an invasive breast cancer in her chest wall and underwent endocrine therapy and surgery. She hoped that the cancer was finally stable.

But as the situation quickly worsened, Arsenault went to the nearest hospital emergency room where they found that a tumor in her skull bone was pushing against optical nerves, causing the change in vision.

“I was shocked,” Arsenault remembers.

Further imaging and tests performed by her team at Dana-Farber’s Breast Oncology Program showed the cancer had metastasized to other parts of the body too. Radiation was administered to the tumor in her skull, and her physician, Erica Mayer, MD, MPH, sent material from her tumor for molecular testing.

It was a stressful period. Three of Arsenault’s four children — her triplets — were in their senior year of high school and she was helping them apply for colleges, all while dealing with remote and hybrid learning at the school and at home. The fourth was in her freshman year at college, attending classes virtually. But the staff at Dana-Farber did everything they could to make the process easy.

“They really listened to me,” Arsenault says. “I completely trusted them.”

Arrival at Dana-Farber

Arsenault began seeing the Dana-Farber team in 2019 when she developed a new breast cancer in her chest wall and needed endocrine therapy along with another surgery in June 2020. When they learned the cancer spread to Arsenault’s bones in the fall, Mayer and her team entered her into a clinical trial. The trial was testing treatment with a targeted therapy called palbociclib in addition to endocrine therapy.

After radiation and with ongoing systemic therapy, Arsenault’s symptoms rapidly improved. But then, in 2021, her cancer began to worsen. Undeterred, Mayer sent her tumor for molecular testing again. The test revealed a biomarker that told her Arsenault could benefit from treatment by the immunotherapy pembrolizumab. Arsenault’s breast cancer was found to have a high tumor mutational burden (TMB), meaning there was a high number of mutations in her tumor cells.

“This is a rare marker in breast cancer,” explains Mayer. “But as a part of our EMBRACE (Ending Metastatic Breast Cancer for Everyone) program, led by Nancy Lin, MD, we perform genomic profiling for all of our patients with metastatic breast cancer and can detect these less common breast cancer features.”

Living her life

The pembrolizumab treatment has been remarkably effective and is a testament to the personalized delivery of care that Dana-Farber specializes in. She has had a remarkable response to therapy and “the tumor in my skull shrunk so much that it is no longer visible on an MRI,” Arsenault says. The success has enabled her to go on serving her Stow, Massachusetts community, of which she is a stalwart member.

Arsenault co-founded the only local, independent, newspaper in Stow 15 years ago. The paper is still in print today although Arsenault has since stepped away.

“This town is full of stories,” Arsenault says.

She has also worked as a bus driver ferrying children to and from the local schools, and although she gave that up after her most recent incident, she has recently been elected to the Stow Planning Board and delivers Meals on Wheels in the town. With the work and time that she has put into improving her community, she easily won election to her first town board.

 “The cancer will never be totally gone,” Arsenault notes — but her treatment regimen keeps the cancer from spreading, which has allowed her to continue to be mother to her children who are all in college now. “I don’t think about it unless it’s my treatment day,” she says.

What she does think about daily is the message her team delivered at the start of treatment.

“They told me the goal is not just that I live, but that I continue to live my life. And my life is full and busy and what defines me. Every day I realize that what they have hoped to achieve, is truly happening,” says Arsenault.

Arsenault stays busy at home with board responsibilities, wood to stack for the winter, and college sporting events to attend around New England. The ability to do these things were enabled by her personalized treatment.

“Nancy is a dynamo,” says Mayer. “We’re always so impressed with her energy, focus, and desire to make the world a better place for her family, town, and other patients with breast cancer.”