From October 1999 to June 2007, 397 patients with node-positive breast cancer underwent BCS, adjuvant four cycles of AC followed by four cycles of taxane, and adjuvant radiotherapy (RT) in sequence at the National Cancer Center and Seoul National University Hospital, Korea.

All patients had BCS with axillary lymph node dissection or sentinel lymph node biopsy. The original pathologic report was reviewed to collect histologic data. All patients received four cycles of doxorubicin 60 mg/m² by slow intravenous push and then cyclophosphamide 600 mg/m² intravenous infusion over 30 minutes every 21 days followed by four additional 21-day cycles of taxane (paclitaxel 175 mg/m² intravenous or docetaxel 75 mg/m² intravenous as a 3-hour infusion on day 1 of each cycle).

Adjuvant RT was delivered after chemotherapy was completed. All patients underwent whole breast RT using 6-15 MV photons. Seven patients were treated with hypofractionated RT of 39 Gy using 3 Gy per fraction and the rest of the patients received conventional RT of 50-50.4 Gy at 1.8-2.0 Gy per fraction. An additional 9-16.2 Gy electron-boost using 1.8-3.0 Gy/fraction was delivered to the tumor bed. The addition of regional RT was decided at the discretion of the treating radiation oncologist’s assessment of regional failure risk. Two hundred and seventeen patients (54.7%) received 45-50.4 Gy at 1.8-2.0 Gy/fraction to the axillary and supraclavicular (SCL) regions. Among these patients, only one patient received additional RT to the internal mammary node (IMN) region.

Adjuvant hormonal therapy (HT) was given to most patients with estrogen receptor (ER)–positive or progesterone receptor (PR)–positive tumors. Three hundred and eight patients (77.6%) had ER-positive or PR-positive tumors. Among these patients, 251 received tamoxifen, 46 received aromatase inhibitors, 10 did not receive HT, and one patient had unavailable data. One patient received tamoxifen without hormonal receptor expression. If adjuvant HT was indicated, it was given with RT in most cases.

There were 71 patients (17.9%) with HER2-positive (immunohistochemistry 3+ or fluorescence in situ hybridization positive) tumors. Fifteen of these patients were treated with adjuvant trastuzumab and four patients received adjuvant lapatinib. Adjuvant trastuzumab or lapatinib were given on a 21-day cycle for one year and could be used with RT.

The interval between surgery and RT was defined as the time from the date of the first oncologic surgery to the first day of RT. The definition of ipsilateral breast tumor recurrence (IBTR) was recurrence of invasive breast cancer or ductal carcinoma in situ in the same breast treated with RT. Loco-regional recurrence (LRR) included IBTR, ipsilateral axillary lymph node recurrence, IMN recurrence, and SCL recurrence. Failure at any other site was considered a distant metastasis (DM). Each failure was scored as an event regardless of recurrence at other sites. Contralateral breast tumor recurrence was not counted as a failure but as a secondary malignancy. An event for DFS included IBTR, LRR and DM. The Kaplan-Meier method was used to calculate the actuarial rates of ipsilateral breast tumor recurrence-free survival (IBTRFS), loco-regional recurrence-free survival (LRRFS), distant metastasis-free survival (DMFS), DFS, and OS. Comparison between groups was performed by two-sided log-rank tests. Cox proportional hazards model was used for multivariate analysis and analysis of the effect of SRI on clinical outcomes. Maxstat, a maximal chi-square method in R 2.13.0 (R Development Core Team, Vienna, Austria, http://www.R-project.org) was used to identify optimal cut-off value of SRI for each outcome. Two-tailed null hypotheses of no difference were rejected if p-values were less than 0.05, or, equivalently, if the 95% confidence intervals (CIs) of hazard ratio estimates excluded 1. All statistical analyses, except Maxstat, were carried out using SPSS ver. 16.0 (SPSS Inc., Chicago, IL).

Table 1 summarizes the patient and tumor characteristics. The median age of patients at diagnosis was 45 years old (range, 22 to 73 years). Most patients had invasive ductal carcinoma (94.5%) according to the World Health Organization’s classification system. Positive or close resection margin was reported in 13.6% of all cases following the last surgery. There were 192 patients (48.9%) with histologic grade III tumor, 114 patients (31.6%) with extensive intraductal component (EIC), 314 patients (79.1%) with lymphovascular space invasion (LVI) and 137 patients (36.0%) with Ki-67 greater than 15%. The pathologic stage by American Joint Committee on Cancer (AJCC) seventh edition was IIA in 115 patients (29.0%), IIB in 131 patients (33.0%), IIIA in 98 patients (24.7%), IIIB in one patient (0.3%), and IIIC in 52 patients (13.0%).

The median follow-up duration of all patients was 65 months (range, 9 to 137 months). During follow-up, there were 12 cases of IBTR, 20 cases of LRR, 45 cases of DM, and 24 deaths. The actuarial 6-year IBTRFS was 96.9%, LRRFS 93.8%, DMFS 87.6%, DFS 85.5%, and OS 93.9%.

The median interval between surgery and RT was 6.7 months (range, 5.6 to 10.3 months). Because the association between SRI as a continuous variable and clinical outcomes should be confirmed before finding an optimal cut-off value using maximal chi-square method, a Cox proportional hazard model was performed to estimate the association of SRI with each clinical outcome (Table 2). An increase of SRI was related to worse DMFS (p=0.002), DFS (p=0.003), and OS (p=0.008). The optimal cut-off value of SRI for DMFS and DFS was 7 months by maximal chi-square method (p=0.024 and p=0.016, respectively) (Figs. 1 and 2). Even though the optimal cut-off value of SRI for OS was 7.5 months, it was not statistically significant (p=0.255). When a SRI of 7 months was applied, there were 275 patients in the group with a SRI ≤ 7 months and 122 patients in the group with SRI > 7 months. The 6-year actuarial DMFS for patients with SRI > 7 months was 81% versus 91% for patients with SRI ≤ 7 months (p=0.003), and DFS was 78% versus 89% (p=0.002), respectively (Table 3).

Table 3 provides univariate and multivariate analyses of prognostic factors for 6-year outcomes. Patients younger than 40 years old, ER-negative, and PR-negative tumors showed poor prognosis in IBTRFS and LRRFS. The 6-year IBTRFS for patients age < 40 years versus ≥ 40 years was 93% versus 98% (p=0.001) and the 6-year LRRFS was 91% versus 95% (p=0.037), respectively. The 6-year IBTRFS for patients with ER-negative tumors versus ER-positive tumors was 93% versus 99% (p=0.001) and the 6-year LRRFS was 87% versus 97% (p < 0.001), respectively. PR-negative tumors showed worse 6-year IBTRFS than PR-positive tumors (93% for PR-negative vs. 99% for PR-positive, p < 0.001) and worse 6-year LRRFS (89% for PR-negative vs. 97% for PR-positive, p < 0.001). Histology, tumor size, tumor grade, resection margin, EIC, LVI, HER-2, menopause status, Ki-67, nodal stage and stage group did not have an impact on IBTRFS and LRRFS.

Tumor size, tumor grade, ER status, PR status, nodal stage, and stage group were analyzed as prognosticators for the 6-year DMFS and DFS. Larger tumors were a poor prognostic factor for DMFS (95% for tumor size ≤ 2 cm vs. 82% for tumor size > 2 cm, p < 0.001) and for DFS (93% for tumor size ≤ 2 cm vs. 81% for tumor size > 2 cm, p=0.001). Higher tumor grade negatively affected DMFS (100% for grade I vs. 92% for grade II vs. 82% for grade III, p=0.003) and DFS (100% for grade I vs. 91% for grade II vs. 79% for grade III, p=0.006). ER-negative tumors showed worse 6-year DMFS than ER-positive tumors (79% for ER-negative vs. 91% for ER-positive, p < 0.001) and 6-year DFS (75% for ER-negative vs. 90% for ER-positive, p < 0.001). The 6-year DMFS for patients with PR-negative tumors versus PR-positive tumors was 83% versus 90% (p=0.029) and the 6-year DFS was 78% versus 89% (p=0.001), respectively. Higher nodal stage was a negative prognosticator for DMFS (94% for N1 vs. 80% for N2 vs. 72% for N3, p < 0.001) and DFS (91% for N1 vs. 77% for N2 vs. 72% for N3, p < 0.001). Higher stage group presented poorer prognosis for DMFS (94% for stage II vs. 77% for stage III, p < 0.001) and DFS (99% for stage II vs. 86% for stage III, p < 0.001).

Larger tumor (97% for tumor size ≤ 2 cm vs. 91% for tumor size > 2 cm, p=0.012), ER-negative tumor (96% for ER-positive vs. 88% for ER-negative, p < 0.001), higher nodal stage (99% for N1 vs. 87% for N2 vs. 85% for N3, p < 0.001), and higher stage group (99% for stage II vs. 86% for stage III, p < 0.001) negatively affected OS.

A multivariate analysis was performed to exclude confounding factors for outcomes. In multivariate analysis, patients younger than 40 years old had a worse prognosis for IBTRFS; tumor size more than 2 cm had worse prognosis for DMFS; nodal stage was an independent prognostic factor for OS. A SRI of greater than 7 months, however, lost its prognostic significance on multivariate analysis.