Disseminated tumor cells predict efficacy of regional nodal irradiation in early stage breast cancer
Menée en France à partir d'échantillons de moelle osseuse prélevés sur 620 patientes atteintes d'un cancer du sein de stade localisé (durée médiane de suivi : 11,7 ans), cette étude met en évidence une association entre la détection de cellules tumorales disséminées et le risque élevé de récidive locorégionale après irradiation des ganglions lymphatiques régionaux
Background : The disseminated tumor cells (DTC) are collected in the bone marrow and are the witness of micrometastatic spread. We previously reported that DTC could be a predictive factor of the efficacy of regional node irradiation (IMN/SCN: internal mammary nodes & supra-infra clavicular nodes). In this article, we report the long-term results (>10 years) on the impact of DTC status in early-stage breast cancer.
Methods : Patients with localized breast cancer were eligible for this prospective cohort. DTC was obtained from a medullary iliac crest sample performed prior to any primary therapy. DTC status was prospectively assessed by pathologists. Irradiation volumes were defined per standard of care. Cumulative incidence rates and hazard ratio were obtained using both Cox and Fine-Gray models. Interaction tests were performed to confirm the predictive value of DTC status in a multivariate analysis.
Results : 620 patients with localized breast cancer were included. Overall, 94 patients (15.2%) were DTC-positive. After a median follow-up of 11.7 years, 47 patients (7.6%) experienced a locoregional relapse.
DTC detection was associated with a higher risk of locoregional relapse in univariate and multivariate analyses (Cox, HR=3.26, 95%CI=[1.6;5.7], p=0.001).
In the multivariate subgroup analysis, IMN/SCN irradiation significantly reduced locoregional relapse for DTC-positive patients comparing to DTC-negative patients (interaction test: HR=0.3, 95%CI [0.1;0.9], p=0.02). IMN/SCN was the only irradiation volume with a impact on locoregional relapse in patients, according to their DTC status, and the predictive value of DTC status for the benefit of locoregional irradiation was independent of the locoregional nodal status.
Conclusion : This long-term analysis confirms the predictive impact of DTC status on the efficacy of regional radiotherapy on locoregional relapse in early breast cancer. After further studies, DTC status could be a decision tool to better tailor adjuvant radiation therapy in early stage breast cancer patients.
International Journal of Radiation Oncology • Biology • Physics , résumé, 2017