GPP13: Local recurrence according to whether pathologic complete response has been achieved after neoadjuvant chemotherapy and breast conserving surgery
Introduction: With the help of radiotherapy, it has been widely accepted that one breast cancer mortality can be avoided by reducing 4 local recurrences in early breast cancer after breast conserving surgery (BCS). However, while pathologic complete response (pCR) is being used as a surrogate endpoint for survival analysis in many clinical studies after neoadjuvant chemotherapy (NAC), few data has been presented on the oncologic outcome regarding local recurrence. In this study, we retrospectively reviewed the ipsilateral breast tumor recurrence (IBTR) rate after NAC and BCS to assess if there is a difference depending on pathologic response and explore the feasibility of treatment de-escalation, such as whole breast irradiation.
Method: Clinical records of 967 patients were review retrospectively from 2007 Jan to 2019 Dec who were diagnosed with breast cancer and underwent NAC from a single center in Seoul, South Korea. IBTR rate and IBTR-free survival (IBTR-FS) was compared between pCR and non-pCR groups. Cases of systemic recurrence were excluded when the event occurred and none of the cases were followed afterwards. Result: Two-hundred and twenty-seven patients who underwent NAC followed by BCS were included in the analysis. The median follow-up was 54 months. Of these, 88 patients (38.8%) achieved pCR and 139 patients (61.2%) had residual tumor after NAC (non-pCR). IBTR occurred in 3 patients (3.4%) among 88 pCR patients, while it occurred in 9 patients (6.4%) in 139 non-pCR group patients (p=0.377, fisher’s exact test). The patients who achieved pCR had a numerically lower IBTR than those with residual disease (HR 0.58; 95% CI, 0.19-1.80; P=0.343). Among the 51 patients with hormone receptor negative (HR-) and HER2 positive (HER2+) subtype, none of 33 patients with pCR experienced IBTR, whereas 4 of 18 patients with residual tumor had IBTR. Of these, the pCR group had a significantly longer IBTR-FS than the non-pCR group (log-rank p=0.043).
Conclusion: The IBTR rate was numerically higher in the non-pCR group, almost twice as high as the pCR group, although without statistical significance. Within the HR-HER2+, the IBTR-FS of the pCR was prolonged significantly compared to that of the non-pCR. Since these patients generally show good response to anti-HER2 therapy combined with chemotherapy, the patients with invasive residual disease after HER2-targeted therapy may have had high risk of local recurrence. By contrast, the group of patients with pCR may have very low risk of local recurrence, in which de-escalation of radiotherapy could be suggested. Because the study is limited in its small number, a larger scale study is warranted in order to better convey the effects of pCR on local recurrence.