Intrinsic subtypes and benefit from postmastectomy radiotherapy in node-positive premenopausal breast cancer patients who received adjuvant chemotherapy - results from two independent randomized trials.
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Date
2018-01-01ICR Author
Author
Laurberg, T
Tramm, T
Nielsen, T
Alsner, J
Nord, S
Myhre, S
Sørlie, T
Leung, S
Fan, C
Perou, C
Gelmon, K
Overgaard, J
Voduc, D
Prat, A
Cheang, MCU
Type
Journal Article
Metadata
Show full item recordAbstract
BACKGROUND: The study of the intrinsic molecular subtypes of breast cancer has revealed differences among them in terms of prognosis and response to chemotherapy and endocrine therapy. However, the ability of intrinsic subtypes to predict benefit from adjuvant radiotherapy has only been examined in few studies. METHODS: Gene expression-based intrinsic subtyping was performed in 228 breast tumors collected from two independent post-mastectomy clinical trials (British Columbia and the Danish Breast Cancer Cooperative Group 82b trials), where pre-menopausal patients with node-positive disease were randomized to adjuvant radiotherapy or not. All patients received adjuvant chemotherapy and a subgroup of patients underwent ovarian ablation. Tumors were classified into intrinsic subtypes: Luminal A, Luminal B, HER2-enriched, Basal-like and Normal-like using the research-based PAM50 classifier. RESULTS: In the British Columbia study, patients treated with radiation had an overall significant lower incidence of locoregional recurrence compared to the controls. For Luminal A tumors the risk of loco-regional recurrence was low and was further lowered by adjuvant radiation. These findings were validated in the DBCG 82b study. The individual data from the two cohorts were merged, the hazard ratio (HR) for loco-regional recurrence associated with giving radiation was 0.34 (0.19 to 0.61) overall and 0.12 (0.03 to 0.52) for Luminal A tumors. CONCLUSIONS: In both postmastectomy trials, patients with Luminal A tumors turned out to have a significant lower incidence of loco-regional recurrence when randomized to adjuvant radiotherapy, leaving no indication to omit postmastectomy adjuvant radiation in pre-menopausal high-risk patients with Luminal A tumors. It was not possible to evaluate the effect of radiotherapy among the other subtypes because of limited sample sizes.
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Subject
Humans
Carcinoma, Ductal, Breast
Breast Neoplasms
Lymphatic Metastasis
Neoplasm Recurrence, Local
Receptor, erbB-2
Receptors, Estrogen
Chemotherapy, Adjuvant
Radiotherapy, Adjuvant
Dose Fractionation
Lymph Node Excision
Mastectomy
Premenopause
Adult
Female
Research team
Genomic Analysis – Clinical Trials
Language
eng
Date accepted
2017-11-25
License start date
2018-01
Citation
Acta oncologica (Stockholm, Sweden), 2018, 57 (1), pp. 38 - 43
Publisher
TAYLOR & FRANCIS LTD