Multicenter open-label, phase II trial, to evaluate the efficacy and safety of nal-IRI in patients with HER2-negative breast cancer, who have documented Central Nervous System (CNS) progression following Whole Brain Radio Therapy (WBRT), Stereotactic Radiosurgery (SRS) and/or surgery, as determined by the Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) criteria.

This is an international, prospective, open-label, multicenter, single arm, two-stage Simon Design phase II clinical trial, with the primary objective of assessing the efficacy of nal-IRI single agent in a cohort of HER2-negative metastatic breast cancer (MBC) patients with CNS involvement.

Eligible patients will have histologically proven diagnosis of adenocarcinoma of the breast, they must have progressed to at least one prior chemotherapy regimen in the metastatic setting and must have been progressed in CNS to previous local treatment (Surgery and/or WBRT and/or SRS) showing at least one measurable lesion in the CNS (symptomatic meningeal carcinomatosis is not permitted). Eligible patients must have been previously received at least treatment with taxanes (either in the neo/adjuvant or in the metastatic scenario). Patients could not be eligible if they are candidates for a local treatment with a radical intention.

Patients will be accrued in a two-stage design. Considering a drop-out rate of 10%, the accrual goal will be a total of 63 patients in both stages (first stage will include 23 evaluable patients and the second stage will include 33 more evaluable patients).

Inclusion Criteria:

1. Female or male patients > 18 years

2. Patients must have a diagnosis of metastatic breast cancer.

3. Patients should have been pretreated with taxanes at any time prior to the study enrolment if not formally contraindicated.

4. At least one prior chemotherapy regimen for advanced disease.

5. Evidence of new brain metastases and/or stable or progressive brain metastases following previous WBRT and/or SRS and/or surgery.

6. At least one brain lesion needed to be measurable for new and progressive metastases (≥10 mm on T1-weighted, gadolinium-enhanced magnetic resonance imaging). For stable brain metastases at least one extracerebral lesion need to be measurable.

7. HER2 negative breast cancer defined as 0 - 1+ by immunohistochemistry or FISH negative result.

8. ECOG performance status <2.

9. Life expectancy >12 weeks.

10. Patients must have sufficient organ and marrow function as defined below:

    a. Hematopoietic parameters: i. Absolute neutrophil count ≥ 1,5 x 109/L ii. Platelets ≥ 100 x 109/L iii. Haemoglobin ≥ 9 mg/dL b. Hepatic parameters: i. Total bilirubin ≤ 1.5 mg/dL ii. AST (SGOT)/ALT (SGPT) ≤ 2.5 X institutional upper limit of normal c. Renal parameters: i. Creatinine ≤ 1.5 X institutional upper limits of normal, OR ii. Creatinine clearance ≥ 60 mL/min/1.73 m2 for pts w/ creatinine levels > institutional normal.

11. Participants of childbearing potential must agree to use at least efficient contraception method (even though it is recommendable for them to use a highly effective method) prior to study entry and for the duration of study participation as well as a negative serum pregnancy test within 7 days of study enrolment and at the end of treatment visit.

12. Ability to understand and the willingness to sign a written informed consent.

Exclusion Criteria:

1. Patients must not have previously received nal-IRI or any other form of irinotecan, conventional or liposomal.
2. Patients who have received prior anti-cancer treatment with chemotherapy, endocrine therapy, immunotherapy or radiotherapy within 3 weeks (6 weeks for nitrosoureas or mitomycin-C) prior to starting study treatment.
3. Radiation therapy encompassing more than 30% of bone marrow.
4. Significant chronic gastrointestinal disorder with diarrhea as a major symptom (i.e Crohn's disease, ulcerative colitis, malabsorption, or grade ≥ 2 diarrhea of any etiology at baseline)
5. Have a serious concomitant systemic disorder (e.g. active infection including HIV, or cardiac disease) incompatible with the study (at the discretion of investigator), previous history of bleeding diathesis, or treatment with Sintrom.
6. Patients who have symptomatic lymphangitis, dyspnoea at rest or meningeal carcinomatosis. (Patients with asymptomatic involvement may be enrolled in the study.)
7. Patients must be recovered from any clinically relevant toxic effects of any prior surgery, radiotherapy or other therapy intended for the treatment of breast cancer. For peripheral neuropathy, up to CTCAE (v4.0) Grade 2 is acceptable for patients with pre-existing condition.
8. Patients may not be receiving any other investigational or anticancer agents while on the study.
9. History of other malignancies, which could affect compliance with the protocol or interpretation of the results. Patients with malignancies diagnosed more than 5 years prior to study day 1, adequately treated carcinoma in situ of the cervix or basal or squamous cell skin are generally eligible.
10. Pregnant or lactating women.
11. NYHA Class III or IV congestive heart failure, ventricular arrhythmias or uncontrolled blood pressure. Or known abnormal ECG with clinically significant abnormal findings.
12. Active infection or an unexplained fever >38.5°C (excluding tumoral fever), which in the physician's opinion might compromise the patient's health.
13. Patients with other significant disease or disorders that, in the Investigator's opinion, would exclude the patient from the study.
14. Current use or any use in the last two weeks of strong CYP3A-enzyme inducers/inhibitors and/or strong UGT1A inhibitors
15. Known hypersensitivity to any of the components of nanoliposomal irinotecan (nal-IRI) other liposomal irinotecan formulations or irinotecan.

It is not planned