Bone Metastasis Free Fraction Curves of Breast Cancer Patients According To pTNM Stage. Bone metastasis free fractions are shown for patients with invasive breast cancer patients according to pTNM stage. Each curve shows the bone metastasis-free fraction of patients as follows: in situ (black square), stage I (open circle), stage IIA (gray circle), stage IIB (black circle), stage IIIA (open triangle), stage IIIB (black inverted triangle), and stage IV other than bone (open square). Point marks indicate events. Oblique straight lines indicate 3% per person-year (solid) and 1% per person-year (dotted) lines.