Valeur pronostique des sous-types moléculaires et du Ki67 pour les cancers du sein indemnes d’envahissement ganglionnaire après mastectomie : expérience de l’institut Curie–hôpital René-Huguenin et revue de la littérature

Abstract

PurposeTo evaluate the prognostic value of Ki67 expression, breast cancer molecular subtypes and the impact of postmastectomy radiotherapy in breast cancer patients with pathologic negative lymph nodes (pN0) after modified radical mastectomy. Patients and methodsSix hundred and ninety-nine breast cancer patients with pN0 status after modified radical mastectomy, treated between 2001 and 2008, were identified from a prospective database in a single institution. Tumours were classified by intrinsic molecular subtype as luminal A or B, HER2+, and triple-negative using estrogen, progesterone, and HER2 receptors. Multivariate Cox analysis was used to determine the risk of locoregional recurrence associated with intrinsic subtypes and Ki67 expression, adjusting for known prognostic factors. ResultsAt a median follow-up of 56months, 17 patients developed locoregional recurrence. Five-year locoregional recurrence-free survival and overall survival in the entire population were 97%, and 94.7%, respectively, with no difference between the postmastectomy radiotherapy (n=191) and no-postmastectomy radiotherapy (n=508) subgroups. No constructed subtype was associated with an increased risk of locoregional recurrence. A Ki67 above 20% was the only independent prognostic factor associated with increased locoregional recurrence (hazard ratio, 4.18; 95% CI, 1.11 to 15.77; P<0.0215). However, postmastectomy radiotherapy was not associated with better locoregional control in patients with proliferative tumours. ConclusionKi67 expression but not molecular subtypes are predictors of locoregional recurrence in breast cancer patients with negative lymph nodes after modified radical mastectomy. The benefit of adjuvant radiotherapy in patients with proliferative tumours should be further investigated in prospective studies.