Aim: In breast carcinoma (BC), the relationship between the ploidy pattern and molecular subtyping is still unknown. We aim to investigate the prognostic impact of DNA ploidy within molecular subtypes of a large cohort of BC patients.
Methods: The series involved 520 BC patients with no neoadjuvant therapy and a median follow-up of 115.5 months. Immunohistochemical assessment of hormonal receptors, ERBB2 (HER2) status and Ki67 proliferative activity was the basis of the surrogate molecular subtyping. Ploidy was evaluated by DNA flow cytometry in fresh/frozen tumour samples. Kaplan-Meier (K-M) survival estimation was used for prognostic statistical analysis.
Results: Luminal A subtype had the lowest prevalence of disease recurrences (23.6 %) and deaths from disease (18.3 %), while Luminal B (42.2 %/37.9 %), Triple-negative (46.4 %/40.6 %), and HER2-positive (55.9 %/50.0 %) subtypes had the highest. The Triple-positive subtype shows an intermediate/low frequency of adverse events (29.4 % of disease recurrences and 17.6 % of deaths from disease). Luminal A tumours were mostly diploid (55.3 %), while Triple-negative and HER2-positive tumours showed a high incidence of aneuploidy (82.6 % and 88.2 %, respectively). Luminal B and Triple-positive tumours had an intermediate percentage of aneuploidy (63.8 % and 70.6 %, respectively). K-M survival curves showed that DNA aneuploidy is significantly associated with shorter disease-free survival and overall survival in Luminal A and Luminal B molecular subtypes.
Conclusion: DNA aneuploidy identifies a subset of Luminal BC patients with worse clinical outcome, potentially eligible for more aggressive adjuvant therapy.
Keywords: Breast carcinoma; DNA aneuploidy; Molecular subtyping; Prognosis; Survival analysis.
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