Breast cancer survivor urges self-awareness: 'Know your body and what normal is'

Rachel O'Mahony was 38 years old when a routine corporate health screening changed the course of her life. She mentioned to the examining doctor that she'd been experiencing some breast tenderness—nothing alarming, nothing that kept her up at night. The doctor found no lumps during the physical exam but suggested an ultrasound if she wanted peace of mind. She decided to pursue it.

About a week before her appointment with the breast surgeon, O'Mahony felt a small, pea-sized lump while scratching her underarm in bed. The discovery startled her, but she wasn't deeply frightened. She felt well, had energy, showed no signs of illness. When she saw the consultant, he performed a needle biopsy and breast examination, then ordered a triple assessment—mammogram, ultrasound, and core biopsy together. He seemed confident there was nothing to worry about.

Ten days later, in early December 2007, the diagnosis arrived: breast cancer. The mammogram had been clear. The ultrasound had been clear. Only the core biopsy revealed the truth. Her particular cancer was small but aggressive, and it had already moved into her lymph nodes—the detail that frightened her most, the question of how far it had already traveled. O'Mahony described the moment as an out-of-body experience, as though she were watching someone else receive the news from a distance. The consultant was kind and reassuring. He promised her she would be home for Christmas.

The treatment plan unfolded quickly. A mastectomy was scheduled, followed by reconstruction using muscle from her back—a long, demanding surgery. She came home on Christmas Eve and spent six weeks recovering before meeting with her oncologist to learn what came next: chemotherapy, radiotherapy, and hormone therapy. Her cancer was HER2-positive, a classification that made her eligible for a clinical trial testing a new drug. She and her husband Declan researched carefully, then agreed she would participate, provided she could be monitored closely and withdraw if necessary. The trial began on February 4th, 2008—World Cancer Day, a date she would never forget.

From February through June 2009, O'Mahony endured chemotherapy every two weeks. She found it grueling, leaving her sick and depleted, though she noticed that by the second week of each cycle, the fog would lift enough for her to meet a friend for coffee, to reclaim small pieces of normalcy. After chemotherapy came 30 days of radiotherapy, followed by herceptin—a targeted drug she called a wonder drug—administered every three weeks until April 2009. For years afterward, she received bone-strengthening injections to counteract chemotherapy's side effects. Fifteen years later, she remained cancer-free.

But O'Mahony's story is shadowed by loss. Her mother was diagnosed with cancer in 2010, three years after Rachel's diagnosis, and died seven months later. Her aunt had died in 1998 at 54, her cancer discovered only after it had spread to her lungs; the primary tumor was never found. O'Mahony knows the other side of cancer, the side where treatment fails and time runs out. She is acutely aware that her survival was not inevitable.

Today, working as a patient advocate at the Lambe Institute in Galway, O'Mahony channels her experience into helping others navigate diagnosis and treatment. She emphasizes a single, powerful truth: people must know their own bodies well enough to recognize when something changes. They must be their own advocates, the only ones who truly understand what is normal for them. When something feels wrong, they must speak to their doctor. She points to the Irish Cancer Society's resources and stresses the importance of research and clinical trials—the very mechanisms that gave her access to targeted treatment, that continue to refine cancer care toward less toxic, more effective therapies. The advances she has witnessed in 15 years suggest that future patients may avoid chemotherapy altogether, receiving instead precisely targeted treatments tailored to their specific cancer. For O'Mahony, that possibility justifies everything she endured.