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.

Primary outcomes

1. Number of Participants According to Year of Initial Diagnosis of Breast Cancer

   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 according to their year of initial diagnosis of breast cancer were reported.

2. Number of Participants With American Joint Committee on Cancer (AJCC) Stage Status

   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)

   AJCC stages included: stage l (T1N0M0), stage IIA (T0N1M0, T1N1M0, T2N0M0), stage IIB (T2N1M0, T3N0M0), stage IIIA (T0N2M0, T1N2M0, T2N3M0, T3N1 or N2M0), stage IIIB (T4 any NM0, any TN3M0), stage IIIC (any TN3M0), stage IV (any T any NM1), and unknown. T0 = early form of tumor, T1 = less than (<) 2 centimeter (cm), T2 =2-5 cm, T3 = greater than (>) 2 cm, T4 = large sized, N0 = not spread to lymph node (LN), N1 = spread to LN 1 to 3, N2= spread to LN 4 to 9, N3 = spread >10 axillary LN, M0 = no metastasis, M1= metastasis.

3. Number of Participants With Node Status

   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)

   In this outcome measure, number of participants with node status ranging from N0 to Nx were recorded and reported. N0= No regional lymph node involvement (no cancer found in the lymph nodes), N1-N3= involvement of regional lymph nodes (number and/or extent of spread), and Nx = regional lymph nodes cannot be evaluated. N2 included N2A, and N2B stages; N3 included N3A, N3B, and N3C stages.

4. Number of Participants With Menopausal Status

   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)

   In this outcome measure, number of participants with menopausal status were recorded and reported. Menopausal status included pre-menopausal, peri-menopausal and post-menopausal.

5. Number of Participants With Type of Metastatic Disease

   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)

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

6. Number of Participants With Sites of Metastatic Disease

   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)

   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.

7. Number of Participants With Total Number of Metastatic Sites

   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)

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

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

   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)

   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.

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

   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)

   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.

10. Charlson Comorbidity Index (CCI) Score

    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)

    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.

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

    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.

12. 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)

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

    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)

    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.

14. Number of Participants With Different Initial Palbociclib Dose

    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)

    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.

15. Total Number of Treatment Cycles Received

    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)

    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.

16. Number of Participants With Dose Reductions

    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)

    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.

17. Number of Participants With Increased Dose Patterns

    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)

    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.

18. Number of Participants With Any Treatment Interruptions

    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)

    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.

19. Frequency of CBC Testing During First Cycle of Treatment

    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)

    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.

20. Frequency of Electrolyte Testing During First Cycle of First Line Treatment

    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)

    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.

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

    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)

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

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

    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)

    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).

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

    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)

    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).

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

    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)

    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).

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

    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)

    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).

26. Overall Survival (OS)

    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)

    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.

27. Percentage of Participants With Clinical Benefit Rate (CBR)

    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)

    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

28. Objective Response Rate (ORR)

    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)

    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.

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

    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)

    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.

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

    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)

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

31. Duration of Discontinued Therapy

    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)

    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.