Women under the age of 40 are more likely than older patients to have breast cancers diagnosed at a later stage and more aggressive tumor types, according to research published on May 22 for the 2020 American Society of Breast Surgeons virtual meeting.
Researchers from Allegheny General Hospital in Pittsburgh compared breast cancer tumor and patient statistics of more than 50,000 women in the U.S. with breast cancer. Younger patients had unique cancer features, needs, and concerns regarding treatment, including a higher rate of triple-negative cancers and positive human epidermal growth factor receptor 2 (HER2) status.
"In today's age of precision medicine and ever-evolving breast cancer treatments, understanding tumor biology and optimizing therapeutic interventions based on this is a reality and critical to improving outcomes," stated Dr. Kelly Krupa, resident researcher and lead study author, in a press release.
The authors wanted to study younger patients' breast cancer stage at diagnosis, tumor biology, treatments, and outcomes to see whether patients under the age of 40 received and benefited from more aggressive treatment than older women.
They analyzed data from 54,799 patients with breast cancer, which accounted for all female patients with known HER2 receptor status in the National Cancer Database from 2010 to 2014. A little under half (48%) of the women were under 40 years old, while the remaining women were 40 or older.
| Breast cancer characteristics by patient age | ||
| Under 40 | 40 or older | |
| Stage 1 | 37% | 62% |
| Stage 2 | 46% | 30% |
| Stage 3 | 13% | 6% |
| Stage 4 | 4% | 3% |
| HER2 positive | 23% | 13% |
| Estrogen-receptive negative | 27% | 15% |
| Undergo chemotherapy | 84% | 43% |
Younger women consistently presented for care with significantly higher clinical and pathologic stages of breast cancer than patients age 40 or older. The authors also found a statistically significant relationship between age and presenting stage.
Younger women also had more tumor characteristics associated with more aggressive cancer. Patients under the age of 40 were significantly more likely to have moderately differentiated tumors, poorly differentiated tumors, and undifferentiated tumors (grades 2-4) than well-differentiated tumors (grade 1).
A greater percentage of younger women were HER2 positive, a signal of more aggressive cancer. Furthermore, almost 20% of younger women had triple-negative breast cancer, compared with about half that percentage in older patients.
Treatments varied significantly by age as well. Younger women had a greater likelihood of undergoing chemotherapy, while patients aged 40 or older were more likely to receive radiation therapy.
While mortality did not differ between the two groups of patients, Krupa noted that younger women may have unique concerns, including living longer with side effects, wondering how their cancer status affects younger siblings and relatives, and the implications of cancer treatment on family planning.
The authors cautioned they didn't have the data to determine whether genetics or other risk factors differed between the two cohorts of patients. Nevertheless, they concluded that the tumor and patient characteristics of younger women with breast cancer are different enough to treat women under 40 as a unique population.
"A consistent body of research finds breast cancers in younger patients share many common attributes," Krupa stated. "With its large patient sampling and comprehensive examination of tumor features, treatments, and outcomes, this study adds to the growing body of research on tumor characteristics of a younger population."
