PFS is the time from the date of randomization to the date of the first documentation of objective progression of disease (PD)or death due to any cause in absence of documented PD. Participants lacking an evaluation of tumor response after randomization had their PFS time censored on the date of randomization with the duration of a day. Participants with documentation of PD or death after a long interval (2 or more incomplete or non-evaluable assessments) since the last tumor assessment were censored at the time of last objective assessment that did not show PD. The length of PFS was calculated as PFS time (months) =[progression/death date(censor date) - randomization date + 1]/30.4. Progression is defined using Response Evaluation Criteria in Solid Tumors(RECIST v1.1) a 20% increase in the sum of diameters of target lesions and the sum must also demonstrate an absolute increase of at least 5mm or unequivocal progression of existing non-target lesions or the appearance of new lesions.

The intent-to-treat (ITT) population or full analysis set included all participants who were randomized, with study intervention, regardless of whether participants received the study intervention or received a different drug from that to which they were randomized.

OS is defined as the time from date of randomization to date of death due to any cause. In the absence of confirmation of death, survival time was censored to last date the participant was known to be alive. For participants lacking survival data beyond the date of their last follow-up, the OS time was censored on the last date they were known to be alive. Participants lacking survival data beyond randomization were to have their OS times be censored at randomization. The length of OS was calculated as OS time (months) = [death date (censor date) - randomization date + 1]/30.4.

The ITT population or full analysis set included all participants who were randomized, with study intervention, regardless of whether participants received the study intervention or received a different drug from that to which they were randomized.

OS is defined as the time from date of randomization to date of death due to any cause. In the absence of confirmation of death, survival time was censored to last date the participant was known to be alive. For participants lacking survival data beyond the date of their last follow-up, the OS time was censored on the last date they were known to be alive. Participants lacking survival data beyond randomization were to have their OS times be censored at randomization. The length of OS was calculated as OS time (months) = [death date (censor date) - randomization date + 1]/30.4.

The ITT population or full analysis set included all participants who were randomized, with study intervention, regardless of whether participants received the study intervention or received a different drug from that to which they were randomized.

One-, Two- or Three-year Survival Probability is defined as the probability of survival 1 year, 2 or 3 years after the date of randomization based on the Kaplan-Meier estimate. Survival time was censored to last date the participant is known to be alive.

The ITT population or full analysis set included all participants who were randomized, with study intervention, regardless of whether participants received the study intervention or received a different drug from that to which they were randomized.

OR is defined as the overall complete response (CR) or partial response (PR) according to the RECIST version 1.1 Objective Response Rate (ORR) is defined as the proportion of participants with CR or PR relative to all randomized participants and randomized participants with measurable disease at baseline. Participants who do not have on-study radiographic tumor re-evaluation, who received anti-tumor treatment other than the study medication prior to reaching a CR or PR, or who died, progressed, or dropped out for any reason prior to reaching a CR or PR were counted as non-responders in the assessment of ORR. Per response evaluation criteria in solid tumors criteria (RECIST v1.1) for target lesions and assessed by MRI: Complete Response (CR), Disappearance of all target lesions; Partial Response (PR), ≥30% decrease in the sum of the longest diameter of target lesions (longest for non-nodal and short axis for nodal target lesions); Overall Response (OR) = CR + PR.

The ITT population or full analysis set included all participants who were randomized, with study intervention, regardless of whether participants received the study intervention or received a different drug from that to which they were randomized. Randomized participants with measurable disease at baseline was also included.

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 was used. DR was calculated as [the date response ended (ie, date of PD or death) - first CR or PR date + 1)]/30.4. Kaplan-Meier estimate of median of the DR is provided below. No inferential statistical analysis were done for DR. The DR was only calculated for the participants with a CR or PR.

The ITT population or full analysis set included all participants who were randomized, with study intervention, regardless of whether participants received the study intervention or received a different drug from that to which they were randomized.

CBR is defined as the overall complete response (CR), partial response (PR) , or stable disease (SD) ≥24 weeks according to the RECIST version 1.1. Clinical Benefit Response Rate (CBRR) is defined as the proportion of participants with CR, PR, or SD ≥24 weeks relative to all randomized participants and randomized participants with measurable disease at baseline. Participants who do not have on-study radiographic tumor re-evaluation, who received antitumor treatment other than the study medication prior to reaching a CR or PR, a best response of SD ≥24 weeks, or who died, progressed, or dropped out for any reason prior to reaching a CR or PR and a best response of SD ≥24 weeks was counted as non-responders in the assessment of CBR. Per RECIST v1.1 for target lesions and assessed by MRI: CR, disappearance of all target lesions; PR, ≥30% decrease in the sum of the longest diameter of target lesions; OR = CR + PR.

The ITT population or full analysis set included all participants who were randomized, with study intervention, regardless of whether participants received the study intervention or received a different drug from that to which they were randomized. Randomized participants with measurable disease at baseline was also included.

Ctrough was defined as steady-state predose concentration. Observed directly from data. For palbociclib, a steady-state trough was to be defined as a predose plasma concentration following at least 8 consecutive days of 125 mg daily dose without dosing interruption and the time window for the PK collection was to be between 22 and 26 hours after the dose (the day prior to PK collection) and no more than 1 hour post-dose on the day of PK collection.

The participants who were treated with Palbociclib + fulvestrant (with or without goserelin) or placebo + fulvestrant (with or without goserelin) and have at least one measured plasma drug concentration. The geometric mean and coefficient of variation was not estimable for Cycle 1/Day 15 and Cycle 2/Day 15 for the reporting arm placebo plus fulvestrant.

Ctrough was defined as steady-state predose concentration. Observed directly from data. For fulvestrant, a steady-state trough was to be defined when a patient had received all prior planned doses and the sample was collected predose.

The 40 participants who participated in the early safety review, who are treated with palbociclib + fulvestrant ± goserelin or placebo + fulvestrant ± goserelin and have at least one measured plasma drug concentration.

Ctrough was defined as steady-state predose concentration. Observed directly from data. For goserelin, a steady-state trough was to be defined when a patient had received all prior planned doses and the sample was collected predose.

The 40 participants who participated in the early safety review, who are treated with palbociclib + fulvestrant ± goserelin or placebo + fulvestrant ± goserelin and have at least one measured plasma drug concentration.

The EORTC-QLQ-C30 is a 30-item questionnaire composed of five multi-item functional subscales (physical, role, emotional, cognitive , and social functioning), three multi-item symptom scales (fatigue, nausea/vomiting, and pain), a global quality of life (QOL) subscale, and six single item symptom scales assessing other cancer-related symptoms (dyspnea, sleep disturbance, appetite loss, constipation, diarrhea, and the financial impact of cancer). The questionnaire employs 28 4-point Likert scales with responses from "not at all" to "very much" and two 7-point Likert scales for global health and overall QOL. Responses to all items are then converted to a 0 to 100 scale. For functional and global QOL scales, higher scores represent a better level of functioning/QOL. For symptom-oriented scales, a higher score represents more severe symptoms. A 10-point or higher change in scores from baseline is considered clinically significant.

The PRO -evaluable population is defined as a subset of ITT participants, who have completed a baseline and at least one post -baseline PRO assessment prior to end of study treatment. Analysis based on repeated measures mixed-effects model with an intercept term, treatment, time, treatment-by-time, and baseline as covariate.

The EORTC-QLQ-C30 is a 30-item questionnaire composed of five multi-item functional subscales (physical, role, emotional, cognitive , and social functioning), three multi-item symptom scales (fatigue, nausea/vomiting, and pain), a global quality of life (QOL) subscale, and six single item symptom scales assessing other cancer-related symptoms (dyspnea, sleep disturbance, appetite loss, constipation, diarrhea, and the financial impact of cancer). The questionnaire employs 28 4-point Likert scales with responses from "not at all" to "very much" and two 7-point Likert scales for global health and overall QOL. Responses to all items are then converted to a 0 to 100 scale. For functional and global QOL scales, higher scores represent a better level of functioning/QOL. For symptom-oriented scales, a higher score represents more severe symptoms. A 10-point or higher change in scores from baseline is considered clinically significant.

The PRO -evaluable population is defined as a subset of ITT participants, who have completed a baseline and at least one post -baseline PRO assessment prior to end of study treatment. Analysis based on repeated measures mixed-effects model with an intercept term, treatment, time, treatment-by-time, and baseline as covariate.

The EORTC-QLQ-BR23 is a 23-item breast cancer-specific companion module to the EORTC-QLQ-C30 and consists of four functional scales (body image, sexual functioning, sexual enjoyment, future perspective) and four symptom scales (systemic side effects, breast symptoms, arm symptoms, upset by hair loss). QLQ-BR23 questionnaire employs 4-point scales with responses from 'not at all' to 'very much'. All scores are converted to a 0 to 100 scale. For functional scales, higher scores represent a better level of functioning.

The PRO -evaluable population is defined as a subset of ITT participants, who have completed a baseline and at least one post -baseline PRO assessment prior to end of study treatment. Analysis based on repeated measures mixed-effects model with an intercept term, treatment, time, treatment-by-time, and baseline as covariate.

The EORTC-QLQ-BR23 is a 23-item breast cancer-specific companion module to the EORTC-QLQ-C30 and consists of four functional scales (body image, sexual functioning, sexual enjoyment, future perspective) and four symptom scales (systemic side effects, breast symptoms, arm symptoms, upset by hair loss). QLQ-BR23 questionnaire employs 4-point scales with responses from 'not at all' to 'very much'. All scores are converted to a 0 to 100 scale. For symptom-oriented scales, a higher score represent more severe symptoms.

The PRO -evaluable population is defined as a subset of ITT participants, who have completed a baseline and at least one post -baseline PRO assessment prior to end of study treatment. Analysis based on repeated measures mixed-effects model with an intercept term, treatment, time, treatment-by-time, and baseline as covariate.

The EuroQol-5D (version 3L) is a brief self-administered, validated instrument consisting of 2 parts. The first part consists of 5 descriptors of current health state (mobility, self care, usual activities, pain/discomfort, and anxiety/ depression); a participant is asked to rate each state on a three level scale (1=no problem, 2=some problem, and 3=extreme problem) with higher levels indicating greater severity/ impairment Published weights are available that allow for the creation of a single summary score called the EQ-5D index, which basically ranges from 0 to 1 with low scores representing a higher level of dysfunction and 1 as perfect health. The second part consists of the EQ-5D general health status as measured by a visual analog scale (EQ-5D VAS). EQ-5D VAS measures the participant's self-rated health status on a scale from 0 (worst imaginable health state) to 100 (best imaginable health state).

The PRO -evaluable population is defined as a subset of ITT participants, who have completed a baseline and at least one post -baseline PRO assessment prior to end of study treatment. Analysis based on repeated measures mixed-effects model with an intercept term, treatment, time, treatment-by-time, and baseline as covariate.

The EuroQol-5D (version 3L) is a brief self-administered, validated instrument consisting of 2 parts. The second part consists of the EQ-5D general health status as measured by a visual analog scale (EQ-5D VAS). EQ-5D VAS measures the participant's self-rated health status on a scale from 0 (worst imaginable health state) to 100 (best imaginable health state).

The PRO -evaluable population is defined as a subset of ITT participants, who have completed a baseline and at least one post -baseline PRO assessment prior to end of study treatment. Analysis based on repeated measures mixed-effects model with an intercept term, treatment, time, treatment-by-time, and baseline as covariate.

A time to event analysis was pre-specified for pain. An analysis of TTD in pain defined as time between baseline and first occurrence of increase of ≥10 points in pain. Deterioration will be defined increase in score of 10 points or greater from baseline. The Kaplan-Meier estimates of quartiles (time to deterioration) with 95% CI is mentioned below.

The PRO -evaluable population is defined as a subset of ITT participants, who have completed a baseline and at least one post -baseline PRO assessment prior to end of study treatment.

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.

The as-treated (AT) population or safety analysis set included all participants who received at least 1 dose of study intervention, with treatment assignments designated according to actual study intervention received.

Number of participants with shifts from Grade ≤2 at baseline values to post-baseline values (shift to Grade 3 or 4) were reported as per NCI-CTCAE, V4.0 graded from Grade 1 to 5. Grade 1: Mild; asymptomatic/ mild symptoms; clinical/diagnostic observations only; intervention not indicated. Grade 2: Moderate; minimal, local/noninvasive intervention indicated. Grade 3: Severe/medically significant but not immediately life-threatening; hospitalization/prolongation of hospitalization indicated. Grade 4: Life-threatening consequences; urgent intervention indicated. Shifts in lab parameter from Grade ≤2 at baseline to Grade 3 or 4 postbaseline (for parameters Anemia, Hemoglobin increased, Neutrophil count decreased, Platelet count decreased, and White blood cell count decreased) were reported.

The as-treated (AT) population or safety analysis set included all participants who received at least 1 dose of study intervention, with treatment assignments designated according to actual study intervention received.

Number of participants with shifts from Grade ≤2 at baseline values to post-baseline values (shift to Grade 3 or 4) were reported as per NCI-CTCAE, V4.0 graded from Grade 1 to 5. Grade 1: Mild; asymptomatic/ mild symptoms; clinical/diagnostic observations only; intervention not indicated. Grade 2: Moderate; minimal, local/noninvasive intervention indicated. Grade 3: Severe/medically significant but not immediately life-threatening; hospitalization/prolongation of hospitalization indicated. Grade 4: Life-threatening consequences; urgent intervention indicated. Shifts in lab parameter from Grade ≤2 at baseline to Grade 3 or 4 postbaseline (for parameters ALT increased, ALP increased, AST increased, Blood bilirubin increased, Creatinine increased, Hypercalcemia, Hyperkalemia, Hypermagnesemia, Hypernatremia, Hypoalbuminemia, Hypocalcemia, Hypokalemia, Hypomagnesemia, and Hyponatremia) were reported.

The as-treated (AT) population or safety analysis set included all participants who received at least 1 dose of study intervention, with treatment assignments designated according to actual study intervention received.