Impact of time to local recurrence on the occurrence of metastasis in breast cancer patients treated with neoadjuvant chemotherapy: A random forest survival approach.

BACKGROUND: We studied the relationship between time to ipsilateral breast tumor recurrence (IBTR) and distant metastasis-free survival (DMFS) in patients with breast cancer treated by neoadjuvant chemotherapy (NAC). METHODS: Between 2002 and 2012, 1199 patients with primary breast cancer were treated with NAC. Clinical, radiological and pathological data were retrieved from medical records. Multivariate analysis was performed with the random survival forest (RSF) method, to evaluate the relationship between time to local recurrence and DMFS. RESULTS: Time to IBTR, local recurrence and molecular subtype were the factors most strongly associated with DMFS. In the total population, DMFS increased linearly with recurrence time, up to 50 months. For recurrences after 50 months, DMFS was similar for all times to recurrence. Considering molecular subtypes separately, the threshold was similar for the TNBC subtype (50 months), but appeared to occur later for the luminal and HER2-positive subtypes (75 months). CONCLUSION: A threshold of 50 months seems to differentiate between early and late recurrences and could be used to guide the medical management of local breast tumour recurrences.