V5: Does Residual Cancer Burden Predict Local Recurrence After Neoadjuvant Chemotherapy?

The extent of residual disease after neoadjuvant chemotherapy (NAC) can be quantified by the Residual Cancer Burden (RCB), a prognostic tool commonly utilized to estimate survival outcomes in breast cancer. This study investigates the association between RCB and locoregional recurrence (LRR). 


Methods: We retrospectively reviewed 532 women who underwent NAC between 2010 and 2016.  Relapse in the ipsilateral breast, skin/subcutis, chest wall, pectoralis or regional lymph nodes was considered a LRR.  The LRR cumulative incidence (LRCI) was estimated using the Fine and Gray competing risks model, with LRR defined as the event of interest and death as the competing risk. The association of LRCI with prognostic variables was evaluated.


Results:

Overall, 29 (5.5%) patients developed a LRR after a median follow-up of 65 months.  Site of recurrence included ipsilateral breast, pectoralis, post-operative skin/subcutis, and regional lymph nodes.  The 5-year cumulative incidence of LRR by RCB was: RCB-0 (0.9%), RCB-1 (3.2%), RCB-2 (6.0%), and RCB-3 (12.9%). Univariately, LRCI varied significantly by RCB (p=0.010), and multivariable analysis using the competing risks model showed a significant association between LRCI with both increasing RCB and by tumor phenotype (p=0.039).  RCB-3 patients were at increased risk of local relapse compared to RCB-0 (HR 13.60 CI [2.29-80.95] p=0.036).  77.5% of RCB-2 patients did not experience a recurrence compared to only 53% of RCB-3.  Subjects with HR+/HER2- phenotype were at lower risk for LRR compared with HER2+ cancers (p< 0.039).  3.5% of the mastectomy group had a LRR compared with 9.6% of those after lumpectomy.  This was not statistically significant in the multivariable model (p=0.081). 
 


Conclusions:

Our results suggest that RCB is associated with the incidence of LRR and has a potential role in influencing clinical decisions regarding indications for adjuvant therapy.