IBISCO TRIAL is a phase II trial aimed to demonstrate the improvement of pathological complete response (pCR) in Luminal B breast cancer (BC) patients treated with stereotactic radiation therapy (SBRT) as an anticipated boost associated with neoadjuvant chemotherapy (NAC).

As a secondary objective, histochemical and molecular analysis of the tumour and the inflammatory microenvironment will be performed.

IBISCO TRIAL is a phase II trial aimed to demonstrate the improvement of pCR in Luminal B breast cancer (BC) patients treated with stereotactic radiation therapy (SBRT) as an anticipated boost associated with neoadjuvant chemotherapy (NAC).

The primary endpoint will be evaluated on surgical specimen using the residual cancer burden (RCB) index.

Thirty patients with clinical stage T1-2 Luminal B BC, suitable for conservative surgery and with a clinical indication for NAC, will be enrolled in two years. An observation cohort will also be created with patients fulfilling inclusion criteria who refuse enrollment in the interventional cohort and for patients where SBRT boost appears not feasible after enrollment for technical issues.

As a secondary objective, histochemical and molecular analysis of the tumour and the inflammatory microenvironment will be performed.

After the completion of neoadjuvant treatments, surgery and adjuvant therapies (endocrine therapy and whole breast irradiation) will be performed as for clinical practice

Inclusion Criteria:

• Luminal B-like BC, cT1-2
• Indication for neoadjuvant chemotherapy

Exclusion Criteria:

• Pregnancy
• Breast feeding
• Patient not available for follow up