True recurrence versus new primary: an analysis of ipsilateral XXXX recurrences after breast-conserving therapy.

@entity1 @entity5 @entity0
PURPOSE: Ipsilateral @entity0 recurrence (IBTR) can occur in 5-20% of @entity1 with @entity0 treated with breast-conserving therapy. Two entities of IBTR have been described: true recurrence (TR), suggested to be regrowth of disease at the @entity5 bed, and new primary (NP), distinct from the index lesion in histology and location. This study compared survival outcomes between two @entity1 cohorts classified clinically as having either TR or NP. METHODS AND MATERIALS: Between 1989 and 1999, 6,020 @entity1 were referred to the BC Cancer Agency with newly diagnosed pT1-2, N0-1, M0 @entity0 , treated with breast-conserving surgery. Of these, 289 @entity1 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 @entity5 location. Of 289 @entity1 , 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 @entity1 than in NP @entity1 (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, @entity0 -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 @entity1 with IBTR classified as true recurrence compared to new primary. Non-statistically significant trends for less favorable survival were observed for @entity1 with TR. Further investigation of the hypothesis that TR and NP @entity5 are distinct entities with different survival prognoses will require standardized pathology review and molecular analyses.
