Purpose  

The objective of this study was to examine the association of: (i) diagnosis at age ≤35, (ii) first-degree family history of breast or ovarian cancer (BOC) and (iii) a research based definition of genetic risk, with tumor characteristics, treatment and survival in breast cancer (BC).

Patients and methods  

Consenting female participants in the population-based Ontario Familial Breast Cancer Registry diagnosed with primary invasive BC between 1996 and 1998 were followed prospectively until 2005.

Results  

Among 967 women, 105 were ≤35 years old at diagnosis and 686 were classified as genetic risk cases, including 349 with a first-degree family history. Individuals diagnosed at age ≤35 were more likely to self-detect tumors, to present with inflammatory BC, to have invasive ductal carcinoma of no special type, high T stage, and tumors with lymphovascular invasion (LVI), high grade and negative estrogen receptors. Younger women were more likely to receive chemotherapy and less likely to receive hormonal therapy. Diagnosis ≤35 years old was associated with significantly reduced distant recurrence free survival, an effect that did not persist after adjustment for tumor and treatment related variables. Poor outcomes were restricted to younger women with hormone responsive BC. Family history was associated with increased rates of mammographic detection of BC, lower tumor stage and less frequent inflammatory BC, but had no association with BC outcomes.

Conclusion  

Women diagnosed with BC at age ≤35 have more aggressive tumors; these adverse tumor characteristics, rather than age, lead to poor outcomes. Family history was not associated with survival.