A Study of Palbociclib (PD-0332991) + Letrozole vs. Letrozole For 1st Line Treatment Of Postmenopausal Women With ER+/HER2- Advanced Breast Cancer (PALOMA-2)

PFS is defined as the time from the date of randomization to the date of the first documentation of objective tumor progression as per Response Evaluation Criteria In Solid Tumors Criteria (RECIST v1.1) or death due to any cause in the absence of documented PD, whichever occurs first. If tumor progression data include more than 1 date, the first date will be used. PFS (in months) will be calculated as (first event date − randomization date +1)/30.4. Progression is defined using RECIST v1.1, as a 20% increase in the sum of diameters of target measurable lesions above the smallest sum observed (over baseline if no decrease in the sum is observed during therapy), with a minimum absolute increase of 5 mm, or unequivocal progression of pre-existing non-target lesions, or the appearance of new lesions.

Objective Response (OR) is defined as the overall complete response (CR) or partial response (PR) according to the RECIST v1.1. Objective Response Rate (ORR) is defined as proportion of patients with CR or PR relative to all randomized patients with measurable disease at baseline. Patients who do not have on-study radiographic tumor re-evaluation, who received anti-tumor treatment, or who died, progressed/ dropped out for any reason prior to reaching a CR or PR were counted as non-responders in the assessment of ORR. Per RECIST v1.1, CR: Complete disappearance of target lesions with exception of nodal disease. All target nodes must decrease to normal size (short axis <10mm). PR: ≥30% decrease under baseline of the sum of diameters of all target measurable lesions.The short diameter is used in the sum for target nodes, while the longest diameter is used in the sum for all other target lesions. Stable Disease: neither sufficient shrinkage nor increase to qualify for disease progression.

The OR is defined as the overall CR or PR according to the RECIST v1.1. ORR is defined as proportion of patients with CR or PR relative to all randomized patients with measurable disease at baseline. Patients who do not have on-study radiographic tumor re-evaluation, who received anti-tumor treatment, or who died, progressed/ dropped out for any reason prior to reaching a CR or PR were counted as non-responders in the assessment of ORR. Per RECIST v1.1, CR: Complete disappearance of target lesions with exception of nodal disease. All target nodes must decrease to normal size (short axis <10mm). PR: ≥30% decrease under baseline of the sum of diameters of all target measurable lesions. The short diameter is used in the sum for target nodes, while the longest diameter is used in the sum for all other target lesions. Stable Disease: neither sufficient shrinkage nor increase to qualify for disease progression.

DR is defined as the time from the first documentation of objective tumor response (CR or PR) to the first documentation of disease progression or to death due to any cause, whichever occurs first. If tumor progression data included more than 1 date, the first date will be used. DR was calculated as [the date response ended (i.e. date of PD or death) - first CR or PR date + 1)]/30.4. DR would only be calculated for the subgroup of patients with an objective tumor response. Per RECIST v1.1, CR: Complete disappearance of target lesions with exception of nodal disease. All target nodes must decrease to normal size (short axis <10mm). PR: ≥30% decrease under baseline of the sum of diameters of all target measurable lesions.The short diameter is used in the sum for target nodes, while the longest diameter is used in the sum for all other target lesions. Stable Disease: neither sufficient shrinkage nor increase to qualify for disease progression.

DC is defined as the overall CR, PR, or stable disease (SD) ≥24 weeks according to the RECIST version 1.1. Disease Control Rate (DCR) is defined as the patients with CR, PR, or SD ≥24 weeks relative to all randomized participants. Participants who do not have on-study radiographic tumor reevaluation, who received anti-tumor treatment, a best response of SD≥24 weeks, or who died, progressed,or dropped out for any reason prior to achieving reaching a CR or PR and a best response of SD≥24 weeks was counted as non-responders in DCR. Per RECIST v1.1, CR: Complete disappearance of target lesions with exception of nodal disease. All target nodes must decrease to normal size (short axis <10mm). PR: ≥30% decrease under baseline of the sum of diameters of all target measurable lesions. The short diameter is used in the sum for target nodes, while the longest diameter is used in the sum for all other target lesions. SD: neither sufficient shrinkage nor increase to qualify for disease progression

PFS survival by biomarker status by Investigator assessment. Progression is defined using RECIST v1.1, as a 20% increase in the sum of the longest diameter of target lesions, or a measurable increase in a non-target lesion, or the appearance of new lesions.

Positive is defined as H-Score ≥1 and negative as H-Score <1. H-Score is calculated as the sum of the % of cells at each level of staining intensity (0, 1+, 2+, and 3+) multiplied by the staining intensity value: H-Score = (% at 0)*0 + (% at 1+)*1 + (% at 2+)*2 + (% at 3+)*3. H-Score values range from 0 to 300.

ER stands for estrogen receptor and Rb stands for retinoblastoma susceptibility gene product.

Triplicate 12-lead ECG measurements (each recording separated by approximately 2 minutes) were performed and sent to a central laboratory for blinded manual adjudication. The average was calculated. The time corresponding to beginning of depolarization to repolarization of the ventricles (QT interval) was adjusted for RR interval using QT and RR from each ECG by Fridericia's formula (QTcF = QT divided by cube root of RR), by Bazette's formula (QTcB = QT divided by square root of RR) and corrected QT interval according to study-specific criteria (QTcS). Time-matched change from baseline values were reported for QTc analysis population.

Triplicate 12-lead ECG measurements (each recording separated by approximately 2 minutes) were performed and sent to a central laboratory for blinded manual adjudication. The average was calculated. The time corresponding to beginning of depolarization to repolarization of the ventricles (QT interval) was adjusted for RR interval using QT and RR from each ECG by Fridericia's formula (QTcF = QT divided by cube root of RR), by Bazette's formula (QTcB = QT divided by square root of RR) and corrected QT interval according to study-specific criteria (QTcS). Percentage of participants with post-baseline maximum absolute values and maximum increase from baseline were summarized for the safety analysis population.

Summary of Plasma Palbociclib Within-Patient Mean Steady-State Trough Concentrations.

The EuroQol EQ-5D is a 6-item instrument designed to assess health status in terms of a single index value or utility score. It contains 5 descriptors of current health state (mobility, self-care, usual activities, pain or discomfort, and anxiety or depression) with each dimension having 3 levels of function (1=no problem, 2=some problem, and 3=extreme problem). The scores on the 5 descriptors are summarized to create a single summary score. An overall utility score is calculated based on these domains, with a range score from 0 (worse health scenario) to a maximum of 1.0 (best health scenario).

FACT is a modular approach to assess participant health-related quality of life using a 'core' set of questions (FACT-G) as well as a cancer site-specific module. The FACT-G is a 27-item compilation of general questions divided into 4 domains: Physical Well-Being, Social/Family Well-Being, Emotional Well-Being, and Functional Well-Being. The FACT-B consisted of the FACT-G (27-item) and a breast-specific module: a 10-item instrument designed to assess participant concerns relating to breast cancer. For all questions, participants were asked to respond to a five-level scale where 0=not at all, 1=a little bit, 2=somewhat, 3=quite a bit, and 4=very much. FACT-B total score = Physical Well-Being + Social/Family Well-Being + Emotional Well-Being + Functional Well-Being + Breast Cancer Subscale. As each of the items ranges from 0-4, the range of possible scores is 0-144, with 0 being the worst possible score and 144 the best.

An AE is any untoward medical occurrence in a clinical investigation patient administered a product or medical device; the event need not necessarily have a causal relationship with the treatment or usage. An SAE is any untoward medical occurrence at any dose that results in death; is life-threatening; requires hospitalization; results in persistent or significant disability or in congenital anomaly/birth defect. Severity will be graded by the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE), Version 4.0.