Association between regional nodal irradiation and breast cancer recurrence-free interval for patients with low-risk, node-positive breast cancer
Menée auprès de 1 169 patientes atteintes d'un cancer du sein de stade pT1-2pN1 diagnostiqué entre 2005 et 2014 (âge : 40-79 ans ; durée médiane de suivi : 9,2 ans), cette étude analyse l'association entre une irradiation régionale ganglionnaire et une amélioration de l'intervalle sans récidive
Purpose/Objective(s): Randomized clinical trials have shown that regional nodal irradiation (RNI) in patients with unselected N1 breast cancer improves breast cancer-specific survival. However, the benefit of RNI in women with biologically low risk, N1 breast cancer is uncertain. We conduct a population-based study to determine if RNI is associated with improved breast cancer recurrence-free interval (BCRFI) in this population. Materials/Methods: Patients aged 40-79 with pT1-2pN1 (node-positive) breast cancers diagnosed from 2005 to 2014 were identified. Inclusion criteria were modeled off the TAILOR RT study, which is a randomized non-inferiority clinical trial designed to assess the value of RNI in low-risk N1 patients. Eligible patients had BCS (breast-conserving surgery) or mastectomy & axillary lymph node dissection (ALND) with 1-3 positive nodes, BCS and sentinel lymph node biopsy (SLNB) with 1-2 positive nodes, or mastectomy and SLNB with 1 positive node. Additionally, patients had Luminal A breast cancers, as approximated by: estrogen receptor positive (Allred 6-8/8), progesterone receptor positive (Allred 6-8/8), human epidermal growth factor receptor 2 (HER2)-negative, and grade 1-2 immunohistochemical testing. All patients were prescribed hormonal treatment. The primary endpoint of BCRFI, which was the time to any breast cancer recurrence or breast cancer-related death, was analyzed using multivariate competing risks analysis. Results: The cohort included 1,169 women with a median follow-up of 9.2 years. Radiation treatments were: none (151 treated with mastectomy alone), breast-only (133) and locoregional (885). Patients undergoing RNI were younger (median 58 versus 62 years), more likely to have 2-3 macroscopic lymph nodes involved and more often received chemotherapy (all p<0.05). The 10-year estimate of BCRFI was 90% without RNI versus 90% with RNI (p=0.5). On multivariable analysis, RNI was not a significant predictor of BCRFI (HR=1.0, p=0.9). Conclusion: In this retrospective analysis, RNI was not associated with improved BCRFI for women with biologically low risk, N1 breast cancer. We advocate accrual to the ongoing TAILOR RT study.
International Journal of Radiation Oncology, Biology, Physics 2021