This systematic review evaluated neoadjuvant endocrine therapy (NET) in ER-positive DCIS, synthesizing evidence from prospective and retrospective studies on biological outcomes (Ki-67, PR expression) and radiological outcomes (lesion volume reduction).
Four early-phase trials showed consistent Ki-67 and PR suppression with NET, and aromatase inhibitors produced measurable radiologic downsizing in some cohorts; however, pathologic complete response was uncommon and occult invasive disease was found at surgery in a subset of cases.
- All included trials were early-phase with high heterogeneity, precluding meta-analysis. - Short-term surrogate endpoints (Ki-67 suppression, radiologic volume reduction) are unvalidated as predictors of long-term prevention of invasive transformation. - Occult invasive disease found at surgery highlights risks of non-operative approaches with current data.
NET in ER-positive DCIS shows biological activity but should not replace surgery — it is best used now as a tool to assess tumor biology. Non-operative endocrine strategies require validation from ongoing trials (COMET, LORETTA, RECAST, HORNEO01) before any clinical adoption.
