Cancers & treatments·Regimen libraryFirst line

CDK4/6 inhibitor + aromatase inhibitor

Checked 2026-09-09

HR-positive, HER2-negative advanced breast cancer, first line (and adjuvant abemaciclib or ribociclib for high-risk early disease)

One cycle

every 28 days

28-day cycle, until progression (adjuvant: 2 years abemaciclib, 3 years ribociclib)Oral Daily oral course

Components

Drug	Dose	Route	Days
Palbociclib 125 mg or ribociclib 400-600 mg once daily Small-molecule CDK4/6 inhibitor	days 1-21 of 28	Oral	D1-21
Abemaciclib (alternative) Small-molecule CDK4/6 inhibitor	150 mg twice daily continuously	Oral	D1-28
Letrozole Small-molecule aromatase inhibitor	2.5 mg once daily	Oral	D1-28

Cycles

until progression (adjuvant: 2 years abemaciclib, 3 years ribociclib)

28-day cycle

Emetogenicity

Minimal (<10%)

G-CSF

Not routine

Notes

Ribociclib: ECG for QTc at baseline, day 14 and cycle 2; avoid QT-prolonging drugs.
Abemaciclib: diarrhoea in most patients, start loperamide at first loose stool.

Used in

HR-positive / HER2-negative breast cancer

Trials

PALOMA-2 MONALEESA-2 MONARCH 3 monarchE NATALEE

Products

RibociclibPalbociclibAbemaciclibLetrozole (and other aromatase inhibitors)

Source

MONALEESA-2, NEJM 2016; NCCN Breast Cancer

Reference doses for a typical adult from the cited protocol or label. Doses are adjusted for renal and hepatic function, age, performance status and prior toxicity, and institutional protocols vary. Verify against the current label and your local protocol before treating. Not medical advice.