True Recurrence Versus New Primary: An Analysis of Ipsilateral Breast Tumor Recurrences After Breast-Conserving Therapy

Purpose: Ipsilateral breast tumor recurrence (IBTR) can occur in 5-20% of women with early-stage breast cancer treated with breast-conserving therapy. Two entities of IBTR have been described: true recurrence (TR), suggested to be regrowth of disease at the tumor bed, and new primary (NP), distinct from the index lesion in histology and location. This study compared survival outcomes between two patient cohorts classified clinically as having either TR or NP. Methods and Materials: Between 1989 and 1999, 6,020 women were referred to the BC Cancer Agency with newly diagnosed pT1-2, N0-1, M0 invasive breast cancer, treated with breast-conserving surgery. Of these, 289 patients had pathologically confirmed IBTR. Retrospective analysis was performed, and a set of decision rules was applied to classify cases as TR or NP based on change in histology, grade, hormone receptor status, and tumor location. Of 289 patients, 129 (45%) were classified as having TR and 139 (48%) as having NP; 21 (7%) were unclassified. Results: The distributions of age at diagnosis, age at recurrence, and histopathologic factors were similar in the TR and NP cohorts (all p > 0.05). The mean time to recurrence was shorter in TR patients than in NP patients (4.8 years vs. 6.3 years, p = 0.001). Treatment of the IBTR did not differ between the two groups. In the TR and NP cohorts, breast cancer-specific survival was 55.7% vs. 61.3% (p = 0.93), and overall survival was 43.7% vs. 54.8% (p = 0.53). Conclusions: Time to recurrence is significantly shorter in patients with IBTR classified as true recurrence compared to new primary. Non-statistically significant trends for less favorable survival were observed for patients with TR. Further investigation of the hypothesis that TR and NP tumors are distinct entities with different survival prognoses will require standardized pathology review and molecular analyses.