Recommendations for post-mastectomy radiation therapy after neo-adjuvant chemotherapy: an International Survey of Radiation Oncologists

Is There a Role for Post-Mastectomy Radiotherapy for T1-2N1 Breast Cancers With Node-Positive Pathology After Patients Become Node-Negative Pathology Following Neoadjuvant Chemotherapy?

Purpose: To assess the benefit of post-mastectomy radiotherapy (PMRT) in breast cancer (BC) patients with T1-2N1M0 who developed pathologically negative lymph nodes (ypN0) after undergoing neoadjuvant chemotherapy (NAC) and mastectomy.

Patients and Materials: Patients with T1-2 tumors and positive lymph node(s) who became pN0 after NAC and mastectomy were screened from our prospectively maintained database. The primary endpoint was recurrence-free survival (RFS), and the secondary endpoints were local recurrence-free survival (LRFS) and overall survival (OS). Propensity-score matching (PSM) was conducted for the comparison between PMRT and non-PMRT groups.

Results: Of the 142 eligible patients, 110 (77.5%) received PMRT, and 32 (22.5%) did not. The median follow-up time was 72 months. Univariate analyses showed that the 5-year RFS, LRFS, and OS rates were 88.7, 94.5, and 96.1, respectively, with PMRT and 72.4, 90.1, and 95.0% without PMRT (p = 0.028; p = 0.151; p = 0.971). Multivariate analyses established PMRT as a significant prognostic factor for RFS rate (HR, 0.411; 95% CI, 0.175–0.968; p = 0.042). After a PSM analysis (64 in the PMRT group vs. 32 in the non-PMRT group), PMRT remained significant, with improved RFS in univariate and multivariate analysis (with 5-year RFS rates of 90.1 vs. 72.4%, respectively, p = 0.016; HR, 0.323, 95%CI, 0.115–0.913, p = 0.033). In the subgroup of 48 (33.8%) patients with pathologic complete responses (pCR, ypT0, and ypN0) after NAC, PMRT did not affect RFS (HR, 0.226; 95% CI, 0.034–1.500; p = 0.123).

Conclusions: PMRT might benefit pT1-2N1M0 patients with pN0 after NAC. Patients with pCR might consider omitting PMRT. Prospective studies are needed to assess the effect of PMRT on this specific patient population.

Does post mastectomy radiotherapy reduce loco-regional recurrence rates in all clinical stages of breast cancer following a complete pathological response to neoadjuvant chemotherapy? A systematic review and meta-analysis of the literature

The role of post-mastectomy radiotherapy (PMRT) has not been qualified in contemporary cohorts that have achieved complete pathological response (pCR) following neoadjuvant chemotherapy (NAC). This systematic review evaluated loco-regional recurrence (LRR) rates following PMRT for patients with pCR or pathologically lymph node negative disease (ypN0) after NAC. We identified seven papers that described LRR in 415 patients with pCR following NAC. Pooled analysis demonstrated clear benefit of PMRT on LRR (OR: 0.2 [95% CI: 0.06–0.58; p = 0.003]) and this was most pronounced in stage III/IV disease (OR: 0.12 [95% CI: 0.04–0.44; p = 0.0012]), as well as of benefit in ypN0 disease. PMRT appears to be effective in reducing LRR following pCR or ypN0 in advanced breast cancer but requires further investigation.

The role of postmastectomy radiotherapy in clinically node-positive, stage II-III breast cancer patients with pathological negative nodes after neoadjuvant chemotherapy: an analysis from the NCDB

Purpose

The role of postmastectomy radiotherapy (PMRT) in clinically node-positive, stage II-III breast cancer patients with pathological negative nodes (ypN0) after neoadjuvant chemotherapy (NAC) remains controversial.

Methods

A total of 1560 clinically node-positive, stage II-III breast cancer patients treated with NAC and mastectomy who achieved ypN0 between 1998 and 2009 in the National Cancer Database were analyzed. The effects of PMRT on overall survival (OS) for the entire cohort and multiple subgroups were evaluated. Imputation and propensity score matching were used as sensitivity analyses to minimize biases.

Results

Of the entire 1560 eligible patients, 903 (57.9%) received PMRT and 657 (42.1%) didn’t. At a median follow-up of 56.0 months, no statistical difference was observed for OS between two groups by univariate and multivariate analyses (P = 0.120; HR 1.571, 95% CI 0.839-2.943). On subgroup analyses, PMRT significantly improved OS in patients with clinical stage IIIB/IIIC disease, T3/T4 tumor, or residual invasive breast cancer after NAC (P < 0.05). This improvement in OS remained significant after sensitivity analyses for the propensity score-matched patients.

Conclusions

This study demonstrated that PMRT showed a heterogeneous effect in clinically node-positive, stage II-III breast cancer patients with ypN0 following NAC. PMRT improved OS for patients with clinical stage IIIB/IIIC disease, T3/T4 tumor, or residual invasive breast tumor after NAC. In the absence of definitive conclusions from prospective studies, including the ongoing NSABP B-51 trial, our findings may help identify specific groups of women with clinically node-positive, stage II-III breast cancers who could benefit from PMRT after NAC.

Indications for Postmastectomy Radiation After Neoadjuvant Chemotherapy in ypN0 and ypN1-3 Axillary Node-Positive Women

INTRODUCTION

Downstaging with neoadjuvant chemotherapy (NAC) might obscure indications for postmastectomy radiation (PMRT). The degree of downstaging that results in local-regional recurrence (LRR) rates low enough to omit PMRT remains controversial. We examined the rate of LRR in women who received NAC who underwent mastectomy without PMRT.

PATIENTS AND METHODS

Between 2004 and 2013, 81 women with stage I to IIIA breast cancer had NAC and mastectomy; 48 patients (59%) were clinical N0 and 33 patients (41%) were clinical N1; median age was 45 years; 33 patients (41%) had hormone receptor-positive (HR⁺)HER2^-, 21 patients (26%) HR⁺HER2⁺, 19 patients (23%) HR^- HER2^-, and 7 patients (9%) HR^-HER2⁺ disease. We explored how LRR rates varied with age, BRCA status, Grade, receptor status, clinical N status, pathologic response, lymphovascular invasion, and mastectomy margins. Median follow-up was 4.9 years.

RESULTS

After NAC, 35 patients (43%) had a pathologic complete response (pCR), 33 patients (41%) were ypN0, and 13 patients (16%) were ypN1-3+. There were 8 LRRs (6 chest wall, 1 axillary, 1 supraclavicular node). The 5-year cumulative incidence of LRR was 8% for all patients, 3% for pCR, 16% for ypN0, 10% for ypN1-3+, 6% for HR⁺HER2^-, 25% for HR⁺HER2⁺, 0% for HR^-HER2^-, and 0% for HR^-HER2⁺. LRR was 31% in the ypN0 and 33% in the ypN1-3+ HR⁺HER2⁺ women, and 12% in the ypN0 and 0% in the ypN1 to ypN3+ HR⁺HER2^- patients.

CONCLUSION

This study is unique. All HER2⁺ patients received trastuzumab and LRR was analyzed according to treatment response, clinicopathologic factors, and receptor status. pCR patients including young women and clinical stage IIIA had low LRR rates. However, ypN0 and ypN1-3+ HR⁺HER2⁺ patients had higher rates of LRR compared with other receptor subgroups and on the basis of limited data should be considered for PMRT.

Postmastectomy radiation therapy after neoadjuvant chemotherapy: review and interpretation of available data

Postmastectomy radiotherapy (PMRT) has been shown to decrease locoregional recurrence and improve overall survival in patients with tumors greater than 5 cm or positive nodes. Because neoadjuvant chemotherapy (NAC) can cause significant downstaging, the indications for PMRT in the setting of NAC remain controversial and thus careful consideration of clinical stage at presentation, pathologic response to NAC, and other clinical characteristics, such as grade and biomarker status is required. The current review synthesizes both prospective and retrospective data to provide evidence for recommending PMRT after NAC for patients presenting with cT3-4 disease, cN2-3 disease, and residual nodal disease, as well as rationale for omitting PMRT in patients with cT1-2N0-1 disease who achieve a pathologic complete response. Other scenarios, including nodal complete response in the presence of other risk factors, are also explored. The topics of pre-NAC clinical staging and pathologic axillary nodal staging are reviewed, and radiation portal design is briefly discussed.