The benefit of postmastectomy radiotherapy (PMRT) in breast cancer patients with 1-3 positive lymph nodes (LNs) is unclear. We compared outcomes and evaluated prognostic factors in patients with 1-3 positive LNs having PMRT or not.
We retrospectively reviewed records of breast cancer patients who had mastectomy in our institution between 2003 and 2011. The patients with neoadjuvant systemic therapy were excluded. A total of 120 patients with pN1 disease were identified. PMRT was given in 24 patients (PMRT group) and not in 96 patients (non-PMRT group). PMRT encompassed chest wall and supraclavicular fossa, and median dose was 50.4 (range, 50–60) Gy in daily dose of 1.8 (range, 1.8-2) Gy. The primary end-point was 5-year disease-free survival (DFS). To explore the influence of LN status on DFS, we included the ratio of positive LNs (LNR). The cut-off value of LNR was selected as 0.1, which showed maximum difference in DFS between PMRT and non-PMRT groups.
The median follow-up times were 60.8 (range, 8.6-129.5) months for entire patients, and 59.9 (range, 25.2-115.6) months and 63.1 (range, 8.6-129.5) months for PMRT and non-PMRT groups, respectively. At 5-year, locoregional recurrence-free survival, distant metastasis-free survival, DFS, and overall survival rates were 97.1%, 92.2%, 91.3%, and 97.4%, respectively. Between PMRT and non-PMRT groups, 5-year DFS rates were not different, 89.4% and 91.8% (p = 0.722). Comparing with non-PMRT group, PMRT group had more unfavorable characteristics, such as 2-3 positive LNs (75.0% vs. 43.8%, p = 0.006) and higher LNR (66.7% vs. 34.4%, p = 0.004). In the univariate analysis, the higher LNR showed a trend of worse DFS (p = 0.087), while the number of positive LNs or other variables did not have significant associations with DFS. According to the multivariate analysis, the higher LNR was associated with a trend of worse DFS (p = 0.107).
In this study, PMRT group showed comparable outcomes with non-PMRT group, though more patients with unfavorable tumor characteristics underwent PMRT. The LNR rather than the absolute number of involved LNs showed a possibility to be considered as a useful parameter to make a decision to perform PMRT in breast cancer patients with 1-3 positive LNs.
Clinical trial identification
All authors have declared no conflicts of interest.