Postmastectomy Radiation Therapy Improves Survival of N1 Breast Cancer Patients

S8 Purpose/Objective(s): Randomized trials testing hypofractionated radiation therapy (HFRT) after breast conservative surgery have reported similar efficacy and toxicity compared with conventional fractionated radiation therapy (CFRT). To evaluate the efficacy and toxicity of HFRT after mastectomy, we conducted a phase III randomized trial in June 2008, the interim analysis of the enrolled patients was reported here. Materials/Methods: Breast cancer patients who had 4 or more positive nodes and/or tumor size more than 5 cm were randomly assigned after mastectomy to 50 Gy in 25 fractions over 5 weeks (CFRT) versus 43.5 Gy in 15 fractions over 3 weeks (HFRT), respectively, to the chest wall and supraclavicular nodal region. Four hundred fifty-five women were recruited from 2008 to 2012. There were 223 in CFRT group and 232 in HFRT group. All patients had at least 6-month follow-up and 100% received a median of 6 (range, 3-10) cycles of chemotherapy, including 115 (25.3%) neoadjuvant chemotherapy. Three hundred fifty-nine (78.9%) received hormonal therapy and 67 (14.7%) received anti-Her-2 targeted therapy. The following variables were well balanced between CFRT and HFRT groups, including menopausal status, disease stage, histology grade, estrogen receptor, progesterone receptor and Her-2 expressions, hormonal and targeted therapy. Toxicities were scaled with CTC3.0 criteria. KaplanMeier method and Chi-square test were used to compare the differences. Results: The median age of the patients was 48 years (range, 24-74 years). With a median follow-up in survivors of 33 months (range, 6-62 months), 13 locoregional recurrences (LRR), 71 distant metastases (DM), and 32 deaths have occurred. The 3-year LRR, DM, disease-free survival (DFS) and overall survival (OS) rates were 3.9%, 18.3%, 80.1% and 92.5%, respectively. There were no differences in 3-year LRR (2.5% vs 5.2%, p Z 0.153), DM (17.5% vs 18.9%, p Z 0.609), DFS (80.6% vs79.7%, p Z 0.542), and OS (93.7% vs 91.2%, p Z 0.797) between CFRT and HFRT groups. Sixty-nine (15.2%) and 36 patients (7.9%) developed grade 2 and grade 3 dermatitis. Six patients (1.3%) had grade 2 pneumonitis. None had grade 3 or more pneumonitis. Sixty-six patients (14.5%) had grade 1-2 arm edema and 9 (2.0%) had grade 1-2 shoulder symptoms. No brachial plexopathy occurred. The incidence of grade 2 and grade 3 dermatitis were significantly lower in HFRT than in CFRT group (10.8% vs 19.7% and 4.3% vs 11.7%, p < 0.0001). There were no differences in the occurrence of pneumonitis, arm edema and shoulder symptoms between CFRT and HFRT groups. Conclusions: At 3 years median follow-up, 43.5 Gy in 15 fractions is comparable to 50 Gy in 25 fractions for breast cancer patients after mastectomy, in terms of efficacy and toxicity, except that patients with HFRT had lower rate of dermatitis. Author Disclosure: S. Wang: None. Y. Song: None. X. Liu: None. J. Jin: None. W. Wang: None. Z. Yu: None. Y. Liu: None. H. Ren: None. H. Fang: None. Y. Li: None.

18 Postmastectomy Radiation Therapy Improves Survival of N1 Breast Cancer Patients Y. Tsai, H. Cheng, B. Yu, C. Horng, C. Chen, J. Jian, N. Chu, M. Tsou, M. Liu, and A. Huang; Koo Foundation Sun Yat-Sen Cancer Center, Taipei, Taiwan Purpose/Objective(s): This study is to evaluate the survival benefits of post-mastectomy radiation therapy (PMRT) in T1-2N1 breast cancer patients. Materials/Methods: Between 1990 and 2007, 716 breast cancer patients with 1-3 positive lymph nodes treated with mastectomy were included in this study. Among them, 283 patients had PMRT to the chest wall and regional lymphatics according to risk factors and patient’s preference. Patients with or without PMRT were evaluated for their locoregional recurrence-free survival (LRFS), metastasis-free survival (MFS), diseasefree survival (DFS), and overall survival (OS). Propensity Score Analysis (PSA) was performed in attempt to balance the biased covariates that might affect treatment outcomes. Results: With a median follow-up of 80 months, PMRT significantly improved 10 year LRFS, MFS, DFS and OS in retrospective and

International Journal of Radiation Oncology  Biology  Physics Oral Scientific Abstract 18; Table Propensity Score Analysis For Patients With or Without Postmastectomy Radiation Therapy (PMRT)

Age 40 >40 Tumor stage T1 T2 LVI None/focal Prominent ER status Positive Negative LN (+) number 1-2

No PMRT (N Z 248)

PMRT (N Z 248)

P value

67 181

74 174

.4895

110 138

105 143

.6505

183 53

79 67

.1794

160 85

166 81

.6558

197

193

.6631

propensity score-matched analyses. Multivariate analysis in PSA patients revealed that no PMRT (HR 5.7, p < 0.0001), negative ER status (HR 2.6, p Z 0.0035), age  40 (HR 2.4, p Z 0.0077), T2 disease (HR 2.4, p Z 0.0177) and prominent LVI (HR 2.1, p Z 0.0238) were risk factors of locoregional recurrence (LRR). Independent risk factors associated with MFS and DFS are age  40, T2 disease, no adjuvant chemotherapy and no PMRT. The risk factors associated with overall survival were no adjuvant chemotherapy (HR 6.7, p < 0.0001), age  40 (HR 2.4, p Z 0.0013), negative ER status or no adjuvant hormonal therapy (HR 2.0, p Z 0.0097), T2 disease (HR 1.7, p Z 0.045), and no PMRT (HR 1.9, p Z 0.0284). Conclusions: PMRT significantly improved 10 year LRFS, MFS, DFS and OS in N1 breast cancer patients who had other risk factors associated with LRR, such as age  40 years, prominent LVI, T2 disease, and negative ER status. Author Disclosure: Y. Tsai: None. H. Cheng: None. B. Yu: None. C. Horng: None. C. Chen: None. J. Jian: None. N. Chu: None. M. Tsou: None. M. Liu: None. A. Huang: None.

19 Margin Status and the Risk of Local Recurrence (LR) in Patients With Early-Stage Breast Cancer Treated With Breast-Conserving Therapy (BCT) A.L. Russo,1 A. Niemierko,2 N.L. Wong,3 N. Arvold,3 J. Wong,3 J.R. Bellon,3 R.S. Punglia,3 J.E. Brock,4 and J.R. Harris3; 1Harvard Radiation Oncology Program, Boston, MA, 2Biostatistics, Department of Radiation Oncology, Massachusetts General Hospital, Boston, MA, 3 Department of Radiation Oncology, Brigham and Women’s Hospital/ Dana-Farber Cancer Institute, Boston, MA, 4Department of Pathology, Brigham and Women’s Hospital, Boston, MA Purpose/Objective(s): LR after BCT for invasive breast cancer (IBC) is associated with decreased survival. A positive surgical margin is associated with an increased risk of LR; however, there is controversy about whether a close margin (>0 mm and <2 mm) from invasive carcinoma or DCIS confers an increased risk of LR compared with a negative margin (2 mm). Materials/Methods: We reviewed the medical records of 906 women with early-stage IBC treated with BCT at our institution between 1/1998 and 10/2006. Final margin status was coded as: 1) negative (n Z 729), 2) close (n Z 85), or 3) close (n Z 84)/positive (n Z 8) but having no additional tissue to take according to the surgeon. The 8 positive/no additional tissue margins included 2 with DCIS at one margin, 4 with invasive carcinoma at one margin, and 2 with invasive carcinoma at two margins. There were significant differences in baseline characteristics by margin status with respect to tumor size, number of positive nodes, grade, LVI, EIC, and reexcision status, with the no additional tissue group having slightly less favorable characteristics. Ninety-one percent of patients received adjuvant systemic therapy. Fisher’s exact test was used to compare crude rates of LR by margin status. Actuarial rates of LR were calculated using the Kaplan-