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Abstract
Purpose: This study aimed to identify high-risk factors for regional recurrence in patients with breast cancer with pathologically negative lymph nodes.

Methods and materials: We retrospectively analyzed 3800 patients with stage pT1-pT3 breast cancer and pathologically negative lymph nodes between 2004 and 2012. All patients underwent upfront surgery with curative intent. Adjuvant systemic treatments were administered to most patients (96.7%) based on contemporary guidelines.

Results: After a median follow-up of 83 months (range, 7-175 months), the estimated 10-year cumulative incidence rate of regional recurrence was 2.0%. Multivariate competing risk analysis revealed that high histologic grade, positive lymphovascular invasion, and stage pT2-3 were significant risk factors for any regional recurrence. Patients with ≥2 risk factors showed a significantly higher 10-year cumulative incidence rate of any regional recurrence than those with 1 or no risk factors (5.5% vs 1.2%; P < .001). When the number of retrieved lymph nodes was less than 10, the difference in the incidence rate of regional recurrence between patients with ≥2 risk factors and those with 1 or no risk factors was greater (6.6% vs 1.3%, respectively; P < .001). The 10-year disease-free survival was worse in patients with ≥2 risk factors than in those with 1 or no risk factors (84.7% vs 90.0%, respectively; P < .001). Patients with ≥2 risk factors also showed worse 10-year overall survival than did those with 1 or no risk factors (91.3% vs 97.0%, respectively; P < .001).

Conclusions: Overall, the cumulative incidence rate of any regional recurrence was low at 10 years. However, patients with ≥2 risk factors showed an increased risk of any regional recurrence and worse disease-free survival, particularly when the number of retrieved lymph nodes was less than 10.

Affiliations

Sang-Won Kim  1 , Won Kyung Cho  2 , Doo Ho Choi  2 , Haeyoung Kim  2 , Oyeon Cho  3 , Won Park  4 , Mison Chun  5
1 Department of Radiation Oncology, Konyang University College of Medicine, Daejeon, Republic of Korea; Myunggok Medical Research Institute, Konyang University College of Medicine, Daejeon, Republic of Korea.
2 Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
3 Department of Radiation Oncology, Ajou University School of Medicine, Suwon, Republic of Korea.
4 Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. Electronic address: wonro.park@samsung.com.
5 Department of Radiation Oncology, Ajou University School of Medicine, Suwon, Republic of Korea. Electronic address: chunm@ajou.ac.kr.