Background:
The influence of intrinsic tumor subtypes on outcome of patients with small (T1a/b)
breast cancer remains still unclear.
Patients and methods:
This is a prospective cohort register study including 1008 patients with small T1a/b
breast cancer treated between 2003 and 2011. Tumors were grouped by biological characteristics
in four different subtypes: luminal A, luminal B, human epidermal growth factor receptor
2 (HER2) enriched, and triple negative breast cancer (TNBC).
Results:
The median follow-up time was 6.5 years. From 919 eligible patients 408 (44.4%) were
classified luminal A, 246 (26.8%) luminal B, 183 (19.9%) HER2 enriched, and 82 (8.9%)
TNBC. A total of 305 (34.2%) patients were treated with systemic therapy. Patients
receiving systemic therapy were significantly younger, had lymph nodes metastasis,
higher tumor grade, negative HR and positive HER2 status. Patients with luminal A
tumors demonstrated the best survival rate and it was improved by systemic therapy.
In the opposite, the survival rate of patients with luminal B cancer, HER2 enriched
tumors and TNBC was improved by addition of systemic treatment. The effect of systemic
treatment was significant in Luminal B (p = 0.040) and HER2 overexpressing tumors
(p = 0.016). Treatment effect of systemic therapy in HER2 enriched tumors remained
significant even after adjustment of other prognostic factors (HR = 0.43, CI 0.19
– 0.98; p = 0.047). Notably, tumor size was not associated with patients' survival
and treatment decision.
Conclusion:
The treatment decision of small breast cancer should be made by biological subtype
and not by tumor size or lymph node status.
