Isolated sternal involvement in breast cancer: is it truly stage IV disease?

There is no consensus regarding treatment for patients with breast cancer and isolated sternal involvement. Though classified as AJCC stage IV, this group of patients may have prolonged distant disease free survival.

Retrospective case series of 8 patients with isolated sternal recurrence. Information regarding age, menopausal status, hormonal receptor status, HER2 status, initial treatment, time to sternal recurrence, treatment of sternal involvement, and outcome was obtained.

Median follow-up, 6 years. Seven of 8 diagnosed with metachronous sternal recurrence at a median of 3 years from initial breast cancer diagnosis, 1 with sternal involvement at initial diagnosis. Seven of 8 are alive, with one death from metastatic breast cancer 10 years after sternal recurrence. Six of 8 are without evidence of distant spread, 2 in continuous complete remission (CR) at 7 and 14 years from sternal recurrence.

While a small cohort, the excellent survival of the group identifies this as a distinct subset of metastatic disease, requiring special treatment considerations. Isolated sternal involvement could represent direct local-regional extension rather than systemic spread.