Biological subtype predicts risk of locoregional recurrence after mastectomy and response to post-mastectomy radiation in a large, national database
Menée à partir de données portant sur 5 673 patientes atteintes d'un carcinome mammaire de stade I-III traité par mastectomie entre 2000 et 2009 (durée médiane de suivi : 50,1 mois), cette étude met en évidence une association entre le sous-type biologique de la tumeur et la réponse à une radiothérapie adjuvante ou le risque de récidive locorégionale
Purpose : To evaluate loco-regional recurrence (LRR) after mastectomy and impact of post-mastectomy radiation (PMRT) by breast cancer subtype.
Methods and Materials : Between 2000-2009, 5673 patients with stage I-III breast carcinoma underwent mastectomy and nodal evaluation; 30% received PMRT. Isolated LRR (iLRR) and LRR were compared across groups defined by biological subtype and receipt of trastuzumab: luminal A (estrogen-ER/progesterone-PR+, HER2-, low/intermediate grade), luminal B (ER/PR+, HER2-, high grade), HER2 with trastuzumab, HER2 without trastuzumab, and triple negative (TN; ER-, PR-, HER2-). LRR hazard ratios (HR) were estimated with multivariable Fine and Gray models. The effect of PMRT on LRR was evaluated with Fine and Gray models stratified by propensity for PMRT.
Results : With a median follow-up of 50.1 months, there were 19 iLRR and 109 LRR events. HER2 patients with trastuzumab had no iLRR and only a single LRR. Compared with luminal A patients, TN patients had significantly greater adjusted risk of iLRR (HR 14.10; 95%CI 2.97-66.90), with a similar trend among luminal B (HR 4.94; 95%CI 0.94-25.82) and HER2 patients without trastuzumab (HR 4.41; 95%CI 0.61-32.11). While PMRT reduced LRR, the effect of PMRT varied by subgroup with the greatest and smallest effects seen among luminal A (HR 0.17; 95%CI 0.05-0.62) and TN patients (HR 0.59; 95%CI 0.25-1.35), respectively.
Conclusions : TN patients had the highest risk of LRR and the least benefit from PMRT; these patients may benefit from alternate treatment strategies. In contrast, in the era of HER2-directed therapy, the role of local therapy may need to be reassessed among HER2 patients.
International Journal of Radiation Oncology • Biology • Physics , résumé, 2014