Because of mammography screening increasingly more women are diagnosed with centimeter or subcentimeter node-negative breast cancer (i.e., T1abN0); these tumors account for approximately 19% of all newly diagnosed breast cancers in Sweden. Although the long term relapse-free survival rates among patients with such tumors is as high as ≥90%, some reports suggest that certain patient subgroups may have rates <75%. Firmly established prognostic and predictive factors for patients with T1abN0 tumors are, however, lacking. This is a nationwide, register-based cohort study investigating prognostic and predictive factors in women with centimeter or subcentimeter breast cancer. The study hypotheses are: 1) Established prognostic and/or predictive factors in overall breast cancer are prognostic and/or predictive factors also in centimeter or subcentimeter node-negative breast cancer; 2) The established relative reduction in risk of recurrence and death of adjuvant treatment for overall breast cancer are similar in centimeter or subcentimeter node-negative breast cancer.

Inclusion Criteria:

1. Female.
2. Operated for centimeter or subcentimeter breast cancer.

Exclusion Criteria:

1. Previous breast cancer.
2. Metastatic breast cancer at diagnosis.

The study population consists of all Swedish women operated for centimeter or subcentimeter breast cancer who are included in the regional breast cancer registries (1977 to 2007) or the national breast cancer registry (2008 onwards).