Abstract P5-20-15: Dosing patterns and economic burden of drug wastage among postmenopausal women with HR+/HER2- metastatic breast cancer receiving palbociclib
Authors: Dalal AA , Gagnon-Sanschagrin P , Burne R , Guerin A , Gauthier G , Small T , Niravath P 
Published: February 2018

Abstract
Background: Dose modification related to adverse event is common in the treatment of metastatic breast cancer (mBC). Based on the dosage form and strengths available, dose modification may lead to drug wastage when the dose cannot be split or saved for later use. This study aimed to describe dosing patterns and to estimate the economic burden of drug wastage associated with dose modifications in postmenopausal women with HR+/HER2- mBC receiving palbociclib.
Methods: Postmenopausal adult women diagnosed with HR+/HER2- mBC were identified from the Truven administrative claims database (2006Q1–2015Q4). Regimens received following mBC diagnosis were identified – patients who received a palbociclib-based regimen during one of their first three lines of therapy for mBC were included in the study. Palbociclib starting daily dose, average daily dose, and dosing patterns (dosing modifications and sequences) were reported. A dose modification was defined as a change (decrease/increase) of ≥25mg daily compared to the preceding dose. The economic burden of drug wastage was estimated by multiplying the number of days with drug wastage (i.e., days with overlapping palbociclib prescriptions due to dosage change) by the average cost reimbursed by payers for one unit of palbociclib. Descriptive analyses were conducted separately by line of therapy for mBC.
Results: A total of 473 patients received palbociclib in first (214), second (157), or third (120) line of therapy for mBC. Patients were observed to receive palbociclib for an average of 4.3 months in first line and 4.1 months in second and third line of therapy. The majority of patients started palbociclib on the recommended 125 mg dose and remained on that dose until the end of observation. Dosing patterns and sequences are summarized in Table 1. Among the 214 patients who used palbociclib in first line, 38 (17.8%) had a dose modification – among these, 6 (15.8%) patients had an overlap in prescription fills (average overlap of 9.2 days). This potential drug wastage resulted in an average cost of $4,376 per patient over a period of approximately 4 months following treatment initiation. Results were consistent in second and third lines of therapy, with higher proportions of patients with drug wastage in later lines of therapy.
Conclusion: Over a short observation period, dose modifications, mostly dose reductions, were relatively frequent, and potential resulting drug wastage was associated with a substantial economic burden.
Table 1: Palbociclib dosing patterns and sequences First lineSecond lineThird lineStarting dose (mg daily), N (%) 757 (3.3)3 (1.9)3 (2.5)10015 (7.0)17 (10.8)4 (3.3)125 - recommended dose192 (89.7)137 (87.3)113 (94.2)Average dose on treatment, mean±SD [median]119.52±11.27 [125]115.95±13.61 [125]116.85±13.30 [125]Dose sequencing (mg daily), N (%) 125163 (76.2)96 (61.1)74 (61.7)125→10021 (9.8)29 (18.5)26 (21.7)125→100→756 (2.8)8 (5.1)7 (5.8)125→100→1250 (0.0)1 (0.6)1 (0.8)125→752 (0.9)3 (1.9)4 (3.3)125→75→1000 (0.0)0 (0.0)1 (0.8)10010 (4.7)9 (5.7)1 (0.8)100→752 (0.9)7 (4.5)3 (2.5)100→1253 (1.4)0 (0.0)0 (0.0)100→75→1000 (0.0)1 (0.6)0 (0.0)753 (1.4)3 (1.9)3 (2.5)75→1002 (0.9)0 (0.0)0 (0.0)75→100→1251 (0.5)0 (0.0)0 (0.0)75→1251 (0.5)0 (0.0)0 (0.0)
Citation Format: Dalal AA, Gagnon-Sanschagrin P, Burne R, Guerin A, Gauthier G, Small T, Niravath P. Dosing patterns and economic burden of drug wastage among postmenopausal women with HR+/HER2- metastatic breast cancer receiving palbociclib [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-20-15.