RW Treatment Patterns and Outcomes in Postmenopausal HR+/HER2- mBC Patients Treated With Palbociclib Plus Letrozole as Initial Endocrine Therapy at Community Oncology Practices in the U.S.

Number of Participants With Type of Metastatic Disease

In this outcome measure, number of participants with de novo metastatic and recurrent types of metastatic disease were recorded and reported.

Time frame: Baseline during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants With Sites of Metastatic Disease

Sites of metastatic disease included: locoregional site, adrenal gland, bone, brain, distant lymph nodes, gastrointestinal system, liver, lung, pleura, pericardial, and/or peritoneal cavity. A participant could have more than 1 metastatic site.

Time frame: Baseline during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants With Total Number of Metastatic Sites

In this outcome measure, number of participants with total number of metastatic sites ranging from 1 to \>3 were recorded and reported.

Time frame: Baseline during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants With Eastern Cooperative Oncology Group Performance Status (ECOG-PS) at the Time of Initiation of First-line Treatment

In this outcome measure, number of participants with ECOG at the time of initiation of first-line treatment were included. ECOG scale: 0= fully active/able to carry on all pre-disease activities without restriction; 1= restricted in physically strenuous activity but ambulatory and able to carry out work of a light and sedentary nature; 2= ambulatory and capable of all self-care, but unable to carry out any work activities, up and about \>50 percent (%) of waking hours; 3=capable of only limited self-care, confined to bed/chair \>50% of waking hours; 4=completely disabled, cannot carry on any self-care, totally confined to bed/chair.

Time frame: Pre-dose on Day 1 of treatment during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants With Comorbidities at the Time of Initiation of First-line Treatment

In this outcome measure, number of participants with various comorbidities at the time of initiation of first-line treatment were recorded and reported. Comorbidities included acquired immune deficiency syndrome/human immune virus (AIDS/HIV), cardiovascular disease, cerebrovascular disease, chronic pulmonary disease, congestive heart failure, connective tissue disease, dementia, depression, diabetes with chronic complications, diabetes without chronic complications, hemiplegia or paraplegia, hypertension, liver disease - mild, moderate, or severe, myocardial infarction, other hematologic malignancy, other non-hematologic malignancy, peptic ulcer disease, peripheral vascular disease, renal disease, thromboembolic events (arterial or venous), and other. One participant could have more than 1 comorbidity. Data with "0" values has not been reported in this outcome measure.

Time frame: Pre-dose on Day 1 of treatment during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Charlson Comorbidity Index (CCI) Score

CCI based on various comorbid conditions including myocardial infarction, congestive heart failure, peripheral vascular disease, cerebrovascular disease, dementia, chronic pulmonary disease, rheumatologic disease, peptic ulcer disease, hemiplegia or paraplegia, renal disease, AIDS/HIV, diabetes with and without chronic complications, liver disease (mild, moderate, or severe) was reported. CCI score range was from 0 to 14, where 0= low comorbid condition and 14= high comorbid condition, higher scores indicated more comorbidity.

Time frame: Day 1 of treatment during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants Who Received Chemotherapy (Neo/Adjuvant) and Hormonal Therapy

In this outcome measure, number of participants who received neo/adjuvant chemotherapy and hormonal (endocrine) therapy were recorded and reported. Neo/Adjuvant chemotherapy and hormonal therapy were the treatments administered before primary cancer treatment to enhance the outcome of primary treatment. Participants reported in rows below are not mutually exclusive.

Time frame: Baseline during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Duration of Adjuvant Therapy

Time frame: Baseline during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Time From Discontinuation of Adjuvant Therapy to Initiation of First-line Treatment

In this outcome measure, time from discontinuation (in months) of adjuvant therapy up to the initiation of first-line treatment of palbociclib combination was recorded and reported.

Time frame: Baseline during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants With Different Initial Palbociclib Dose

In this outcome measure, number of participants with different initial dose treatment patterns (125 milligram \[mg\]/day, 100 mg/day, and 75 mg/day) at palbociclib initiation were recorded and reported.

Time frame: Day 1 of treatment during data identification period of approximately 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Total Number of Treatment Cycles Received

Total number of cycles of treatment was the mean number of cycles received by participants prior to the discontinuation of initial treatment of metastatic breast cancer.

Time frame: From first-line treatment up to the discontinuation of initial treatment of metastatic breast cancer during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants With Dose Reductions

In this outcome measure, number of participants whose dose was reduced from 125 mg/day to 100 mg/day or from 125 mg/day to 75 mg/day, or from 100 mg/day to 75 mg/day were recorded and reported.

Time frame: From start to end of treatment during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants With Increased Dose Patterns

In this outcome measure, number of participants with increased dose patterns from 100 mg/day to 125 mg/day, 75 mg/day to 125 mg/day, and from 75 mg/day to 100 mg/day were recorded and reported.

Time frame: From start to end of treatment during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants With Any Treatment Interruptions

In this outcome measure, number of participants whose treatment was interrupted due to any reason (toxicity, no response, loss of response, disease progression (PD), prepare for alternative treatment strategy, participant choice or other) were recorded and reported.

Time frame: From start to end of treatment during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Frequency of CBC Testing During First Cycle of Treatment

In this outcome measure, mean of number of complete blood count (CBC) testing was recorded during first cycle of first line (1L) treatment. 1 cycle was of 28 days.

Time frame: During first cycle of first line treatment during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Frequency of Electrolyte Testing During First Cycle of First Line Treatment

In this outcome measure, mean of number of electrolyte testing was recorded during first cycle of first line treatment. 1 cycle was of 28 days.

Time frame: During first cycle of first line treatment during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Frequency of Liver Function Testing During First Cycle of First Line Treatment

In this outcome measure, mean of liver function testing was recorded during first cycle of first line treatment. 1 cycle was of 28 days.

Time frame: During first cycle of first line treatment during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Percentage of Participants With Progression Free Survival (PFS) at Month 6

PFS= time from 1L Palbociclib combination treatment initiation until clinician documented PD while on Palbociclib/death. Participants who discontinued 1L treatment due to toxicity, participant's choice/other reason were censored on date of discontinuation. PD=increase in visible disease \&/or presence of any new lesion; included cases where clinician indicated PD. Percentage of participants who were progression-free \& alive at 6 months following palbociclib initiation was calculated by Kaplan-Meier method. Event (PD/death) = any record of measurable increase in disease (size of lesion at initiation of palbociclib versus most recent scan), presence of new lesions (new sites based on most recent scan/biopsy), notation in participants electronic health record by treating physician that participant had progressed/recorded date of death. Participants were censored if they discontinued 1L treatment with palbociclib due to any reason other than PD/death (toxicity/participant request, etc).

Time frame: Month 6 during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Percentage of Participants With Progression Free Survival (PFS) at Month 12

PFS= time from 1L Palbociclib combination treatment initiation until clinician documented PD while on Palbociclib/death. Participants who discontinued 1L treatment due to toxicity, participant's choice/other reason were censored on date of discontinuation. PD=increase in visible disease \&/or presence of any new lesion; included cases where clinician indicated PD. Percentage of participants who were progression-free \& alive at 6 months following palbociclib initiation was calculated by Kaplan-Meier method. Event (PD/death) = any record of measurable increase in disease (size of lesion at initiation of palbociclib versus most recent scan), presence of new lesions (new sites based on most recent scan/biopsy), notation in participants electronic health record by treating physician that participant had progressed/recorded date of death. Participants were censored if they discontinued 1L treatment with palbociclib due to any reason other than PD/death (toxicity/participant request, etc).

Time frame: Month 12 during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Percentage of Participants With Progression Free Survival (PFS) at Month 18

PFS= time from 1L Palbociclib combination treatment initiation until clinician documented PD while on Palbociclib/death. Participants who discontinued 1L treatment due to toxicity, participant's choice/other reason were censored on date of discontinuation. PD=increase in visible disease \&/or presence of any new lesion; included cases where clinician indicated PD. Percentage of participants who were progression-free \& alive at 6 months following palbociclib initiation was calculated by Kaplan-Meier method. Event (PD/death) = any record of measurable increase in disease (size of lesion at initiation of palbociclib versus most recent scan), presence of new lesions (new sites based on most recent scan/biopsy), notation in participants electronic health record by treating physician that participant had progressed/recorded date of death. Participants were censored if they discontinued 1L treatment with palbociclib due to any reason other than PD/death (toxicity/participant request, etc).

Time frame: Month 18 during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Percentage of Participants With Progression Free Survival (PFS) at Month 24

PFS= time from 1L Palbociclib combination treatment initiation until clinician documented PD while on Palbociclib/death. Participants who discontinued 1L treatment due to toxicity, participant's choice/other reason were censored on date of discontinuation. PD=increase in visible disease \&/or presence of any new lesion; included cases where clinician indicated PD. Percentage of participants who were progression-free \& alive at 6 months following palbociclib initiation was calculated by Kaplan-Meier method. Event (PD/death) = any record of measurable increase in disease (size of lesion at initiation of palbociclib versus most recent scan), presence of new lesions (new sites based on most recent scan/biopsy), notation in participants electronic health record by treating physician that participant had progressed/recorded date of death. Participants were censored if they discontinued 1L treatment with palbociclib due to any reason other than PD/death (toxicity/participant request, etc).

Time frame: Month 24 during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Overall Survival (OS)

OS was defined as the interval from the initiation of first line palbociclib combination treatment until death. Participants who were alive at the time of data collection were censored on the last date of visit with their provider.

Time frame: From initiation of treatment up to death during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Percentage of Participants With Clinical Benefit Rate (CBR)

CBR was defined as the percentage of participants who achieved complete (where 'complete response' was recorded at any time on treatment) or partial response (where 'partial response' was recorded at any time on treatment), or stable disease at greater than equal to (\>=) 24 weeks on palbociclib combination therapy. Stable disease was defined as no evidence of complete or partial response, and no progression on palbociclib therapy for 24 weeks or greater. Complete response: Complete resolution of all visible disease. Partial response: Partial reduction in size of visible disease in some or all areas without any areas of increase in visible disease

Time frame: From initiation of treatment up to CR and PR and SD during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Objective Response Rate (ORR)

ORR was defined as the percentage of participants who achieved complete response (CR) or partial response (PR) on palbociclib combination therapy recorded from first dose of study treatment until disease progression due to any cause. Complete response: complete resolution of all visible disease. Partial response: partial reduction in size of visible disease in some or all areas without any areas of increase in visible disease.

Time frame: From initiation of treatment up to CR and PR and SD during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants With Stable Disease Lasting Greater Than (>) 24 Weeks

Stable disease was defined as no evidence of complete or partial response, and no progression on palbociclib therapy for 24 weeks or greater. Complete response: Complete resolution of all visible disease. Partial response: Partial reduction in size of visible disease in some or all areas without any areas of increase in visible disease.

Time frame: From initiation of treatment up to end of treatment during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Number of Participants Who Received Drug Regimen Post Discontinuation of Initial Endocrine-Based Therapy

In this outcome measure, number of participants who received drug regimen after discontinuation of initial endocrine-based therapy were recorded and reported.

Time frame: Post discontinuation of initial endocrine-based therapy during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)

Duration of Discontinued Therapy

Discontinuation referred to a treatment persistence terminal event other than regimen change or switch, disease progression, or death. Participants who had a termination of palbociclib for reasons other than regimen change or switch, disease progression, or death were recorded and reported as discontinued.

Time frame: Up to 24 months after palbociclib treatment initiation during data identification of approximatively 4 years (from the data retrieved and observed retrospectively over a duration of 5.7 months)