PROMETEO II is a single-arm window of opportunity trial to evaluate biologic and
anti-proliferative effects of palbociclib and letrozole in HR+/HER2-negative operable breast
cancer (BC) patients with residual disease after neoadjuvant chemotherapy (NAC) and help to
identify biomarkers for better patient selection.
This is a single-arm window of opportunity trial to evaluate biologic and anti-proliferative
effects of palbociclib and letrozole in HR+/HER2-negative operable BC patients with residual
disease after NAC and help to identify biomarkers for better patient selection.
The primary endpoint will be the Complete Cell Cycle Arrest (CCCA) determined by Ki67<2.7%,
centrally assessed at surgery after 4 weeks of palbociclib and letrozole.
Tumor measurement will be performed by magnetic resonance imaging (MRI) for disease
evaluation at screening at the end of NAC. The biopsy after chemotherapy will only be done if
the tumor is equal or larger than 1 cm in its greatest diameter by MRI. Ki67% ≥ 10% after NAC
by local determination will be necessary to be included in the study.
Patients will be administered palbociclib at a dose of 125 mg once daily, day 1 to day 21
followed by 7 days off treatment in a 28-day cycle and letrozole: oral, 2.5 mg per day
continuously, one cycle of treatment.
After finalization of the neoadjuvant treatment, patients will undergo surgery. Surgery
specimens will be collected for histological examination and biomarker analysis
The end of the study is defined as the date of post-surgery visit and will take place 4 weeks
(+/- 7days) after the surgery in order to monitor the patient's safety and collect the
1. Written and signed informed consent for all study procedures according to local
regulatory requirements prior to beginning specific protocol procedures.
2. Female patients age ≥ 18 years.
3. Pre and post-menopausal women.
4. ECOG (Eastern Cooperative Oncology Group) Performance Status of 0 to 1.
5. Histologically confirmed non-metastatic primary HR-positive/HER2 negative breast
cancer with all the following characteristics:
- Breast cancer eligible for surgery.
- ER-positive and/or progesterone receptor (PgR) positive and HER2-negative tumor
by American Society of Clinical Oncology (ASCO) /College of American Pathologists
(CAP) guidelines, ER and PgR defined as IHC nuclear staining >1% and HER2
negative and Ki-67 >10%, locally assessed.
- Ki67% ≥ 10% after neoadjuvant chemotherapy locally assessed.
- A lesion that can be accurately and serially measured in at least 1 dimension and
for which the longest diameter is ≥ 1 cm as measured by MRI after neoadjuvant
6. Completed ≥80% total dose of an anthracycline/taxane-based neoadjuvant regimen
planned. The allowed chemotherapy regimens will be AC (cyclophosphamide, doxorubicin)
or EC (epirubicin, cyclophosphamide) 4 cycles followed by weekly paclitaxel x 12 or AC
or EC 4 cycles followed by docetaxel 4 cycles. It would be acceptable to change the
administration sequence to paclitaxel followed by AC/EC. AC can be given either a
standard dose or in a dose dense schedule. Paclitaxel could be administered as a
solvent-based or Nanoparticle albumin-bound (Nab) formulation.
7. Availability of a recent formalin-fixed paraffin-embedded (FFPE) tumor sample before
NAC and a research tumor biopsy after NAC. Minimal sample requirements are to have at
least 2 tumor cylinders with a minimal tissue surface of 10 mm2 tissue, containing at
least 10% tumor cells and having enough tissue to do at least 2 cuts of 10 μm each.
8. Adequate organ function determined within 28 days prior to enrollment, defined as
- Absolute neutrophil count (ANC) ≥ 1.5 x 109/L
- Platelet count ≥ 100 x 109/L
- Hemoglobin ≥ 9 g/dL (red blood cell transfusion and/or erythropoietin
• Serum creatinine ≤ 1.5 x upper limit of normal (ULN), or 24-hour creatinine
clearance ≥ 60 mL/min for subject with creatinine levels >1.5 x ULN. (Note:
Creatinine clearance does not need to be determined if the baseline serum
creatinine is within normal limits. Creatinine clearance should be calculated per
- Serum bilirubin ≤ 1.5 x ULN OR direct bilirubin ≤ ULN for a subject with
total bilirubin level > 1.5 x ULN
- Aspartate aminotransferase (AST) ≤ 2.5 x ULN
- Alanine aminotransferase (ALT) ≤ 2.5 x ULN Coagulation International
normalization ratio (INR) or prothrombin time (PT) ≤ 1.5 x ULN
9. Serum or urine pregnancy test must be negative within 7 days prior to randomization in
women of childbearing potential. If the urine pregnancy test is positive or cannot be
confirmed as negative, a serum pregnancy test will be required. Pregnancy testing does
not need to be pursued in patients who are judged as postmenopausal before
randomization, as determined by local practice, or who have undergone bilateral
oophorectomy, total hysterectomy, or bilateral tubal ligation. Women of childbearing
potential randomized to the treatment must use adequate contraception for the duration
of protocol treatment.
10. Absence of any psychological, familial, sociological or geographical condition
potentially hampering compliance with the study protocol and follow-up schedule; those
conditions should be discussed with the patient before registration in the trial.
11. Resolution of all acute toxic effects of prior anti-cancer therapy to NCI CTCAE
version 5.0 Grade ≤ 1 (except alopecia or other toxicities not considered a safety
risk for the patient at investigator´s discretion).
1. Non-operable, locally advanced breast cancer (inoperable stage III) after NAC.
2. Bilateral or metastatic invasive breast cancer at the time of the diagnosis.
3. Multicentric or multifocal breast cancer before NAC.
4. Known severe hypersensitivity reactions to compounds similar to palbociclib or to
excipients or to endocrine treatments.
5. History of any previous treatment using Aromatase inhibitors (AI) o selective estrogen
receptor modulator (SERMs) in the past 5 years.
6. Prior therapy with palbociclib or any cyclin-dependent kinase (CDK) inhibitor.
7. Concurrent treatment with other experimental drugs. Participation in another clinical
trial with any investigational not marketed drug within 30 days prior to
8. Patients receiving any medications or substances that are strong inhibitors or
inducers of CYP3A isoenzymes within 7 days of randomization.
9. Any surgery (not including minor procedures such as primary tumor core biopsy, fine
needle aspiration) within 4 weeks of start of study treatment; or not fully recovered
from any side effects of previous procedures.
10. Sentinel lymph node biopsy is not allowed before NAC.
11. Diagnosis of any previous malignancy within the last 3 years, except for adequately
treated basal cell carcinoma, or squamous cell skin carcinoma, or in situ cervical
12. Malabsorption syndrome or other condition that would interfere with enteric
13. Clinically significant history of liver disease, including viral or other hepatitis,
current alcohol abuse, or cirrhosis.
14. Uncontrolled electrolyte disorders (eg, hypocalcemia, hypokalemia, hypomagnesemia).
15. Any of the following within 6 months of randomization: myocardial infarction,
severe/unstable angina, ongoing cardiac dysrhythmias of NCI CTCAE version 5.0 Grade
≥2, atrial fibrillation of any grade, coronary/peripheral artery bypass graft,
symptomatic congestive heart failure, cerebrovascular accident including transient
ischemic attack, or symptomatic pulmonary embolism.
16. Corrected QT interval (QTc) greater than 480 msec or a family or personal history of
long or short QT syndrome, Brugada syndrome or know history of QTc prolongation, or
Torsade de Pointes (TdP).
17. Uncontrolled current illness including, but not limited to, ongoing or active
infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac
arrhythmia, diabetes, or psychiatric illness/social situations that would limit
compliance with study requirements. Ability to comply with study requirements is to be
assessed by each investigator at the time of screening for study participation.