What Characterizes Breast Cancer in Adolescent and Young Adult Patients?

Researchers looked at the characteristics of breast cancer found in patients under 40 years old.

Patients under the age of 40 years with breast cancer tend to have more advanced and more aggressive disease, including higher incidence of HER2-positive breast cancer and triple-negative breast cancer (TNBC), according to a new study published online ahead of print on August 2 in Annals of Surgical Oncology. These patients also tend to undergo more aggressive treatment.

Breast cancer is relatively rare among younger individuals, with 1.8% of all diagnoses occurring in patients aged 20 to 34 years old and 8.7% occurring in those aged 35 to 44 years old. Adolescent and young adult (AYA) patients, representing those aged 15 to 39 years old, are relatively understudied.

“Breast cancer is the leading cause of cancer-related death among females in this age category,” wrote study authors led by Brittany L. Murphy, MD, MS, of the Mayo Clinic in Rochester, Minnesota.

The authors aimed to characterize the patient and treatment characteristics of AYA patients, using the National Cancer Database. They identified a total of 46,265 AYA patients with stages 0-3 breast cancer diagnosed between 2010 and 2015 and compared these with 169,423 patients aged 40 to 49 years.

AYA patients presented with higher stage disease. Among those patients aged 15 to 29 years, 48.2% presented with clinical stage 2 breast cancer and 17.3% presented with stage 3 disease. For those aged 30 to 39 years, those rates were 43.8% for stage 2 and 13.6% for stage 3; for the control patients aged 40 to 49 years, the rates were 29.9% and 7.7%, respectively (P < 0.001 for each pairwise comparison).

HER2-positive disease was more common among younger patients as well. In those aged 15 to 29 years, 29.9% had HER2-positive breast cancer; in those aged 30 to 39 years, that rate was 25.5%, while it was 18.6% in those aged 40 to 49 years (P < 0.001).

TNBC was also more common. In the three age groups, the rate of TNBC was 23.7%, 20.9%, and 13.8%, respectively (P < 0.001). More patients in the 40 to 49 years group presented with hormone receptor-positive/HER2-negative disease.

Among patients who were treated with primary surgery, AYA patients were more likely to undergo mastectomy (69.2%) than patients in their forties (49.5%; P < 0.001). Mastectomy was most common among the youngest group, at 75.4%, compared to those aged 30 to 39 years (68.5%; P < 0.001). Similarly, AYA patients were more likely to be treated with chemotherapy if they had invasive disease than patients aged 40 to 49 years (P < 0.001).

The treatment decisions, according to the authors, “may reflect recommendations and/or patient preferences for more aggressive treatment based on age rather than tumor biology.”

Experts note that the management of breast cancer in younger patients is complicated by considerations such as fertility preservation and pregnancy, and by the fact that AYA patients are underrepresented in most clinical trials. In Annals of Surgical Oncology earlier this year, authors led by Pridvi Kandagatla, MD of the University of Michigan, wrote that management of breast cancer in younger patients requires a multidisciplinary approach.

 “Future trials and studies should focus on increasing treatment options for young cancer patients,” they wrote.