Real-world treatment patterns of palbociclib and blood count monitoring in patients with advanced breast cancer in Japan

Figures & data

Table 1. Definition of the first-line treatment for each patient with advanced breast cancer.

	Gap period between adjuvant endocrine therapy & its subsequent therapies	Definition
No adjuvant endocrine therapy record^†	–	The first therapy following a record of metastasis
Adjuvant endocrine therapy record^‡	Gap of >12 months	The first therapy following a 12-month gap period
	Gap of ≤12 months	The first therapy following the adjuvant endocrine therapy^§

† Patients had no record of breast cancer treatment during a 180-day lookback period before the earliest metastasis record identified during the study period.

‡ Adjuvant endocrine therapy was defined as the earliest endocrine therapy with a start date within 365 days of the latest breast cancer surgery record identified during the study period.

§ To minimize misclassification of line of therapy, the following patients were not included in the analysis: patients treated with the same hormonal therapy in both adjuvant endocrine therapy and the first-line treatment; patients treated with letrozole in adjuvant endocrine therapy and anastrozole in the first-line treatment; and patients treated with anastrozole in adjuvant endocrine therapy and letrozole in the first-line treatment.

Table 2. Baseline demographic and clinical characteristics of patients initiating palbociclib treatments.

Characteristic	n = 1074
Sex, n (%)
Male	7 (0.7)
Female	1067 (99.3)
BMI (kg/m^2), mean (SD)	23.3 (4.4)
Age, median (minimum, maximum)
At the start of the first-line for advanced breast cancer	63 (31, 90)
At initiation of palbociclib lines	64 (32, 92)
Year of initiation of palbociclib lines, n (%)
2017	19 (1.8)
2018	443 (41.2)
2019	353 (32.9)
2020	259 (24.1)
Gonadotrophin releasing hormone (GnRH) analogues prescribed concomitantly with palbociclib, n (%)
Goserelin or leuprorelin	146 (13.6)
Charlson Comorbidity Index, mean (SD)	7.9 (2.1)
Adjuvant endocrine therapy record
No	515 (48.0)
Yes	559 (52.0)
Adjuvant endocrine therapy record with ≥12 months gap period	68 (6.3)
Adjuvant endocrine therapy record with <12 months gap period	491 (45.7)
With aromatase inhibitors^†	314 (56.2)
With tamoxifen^†	220 (39.4)
With others^†	30 (5.4)
Chemotherapy record prior to palbociclib treatment in advanced breast cancer setting
Yes	195 (18.2)
No	879 (81.8)

† The overall number of treatment lines (denominator) is the sum of those with adjuvant endocrine therapy record with a ≥12-month and <12-month gap period (n = 559). Some adjuvant endocrine therapy was prescribed with more than one therapy (e.g., aromatase inhibitors, tamoxifen and others).

SD: Standard deviation.

Figure 1. Distribution of palbociclib treatments in the first- through fourth- or later-line treatments.

There was one patient who was prescribed palbociclib before December 2017 and was included in the total figure only.

Figure 2. Endocrine therapies prescribed in combination with palbociclib in each treatment line.

This figure shows the results of the number of patients who were prescribed endocrine therapies in combination with palbociclib in the first three treatment lines (n = 843 out of 1074 patients). The results in the fourth or later treatment lines are not shown. The ‘other’ include patients prescribed ≥1 endocrine therapies and those prescribed medroxyprogesterone.

Figure 3. A 6-month palbociclib treatment continuation in combination with endocrine therapies in each treatment line.

This figure shows the results of 6-month palbociclib treatment continuation in the first three treatment lines (n = 843 out of 1074 patients). Results in the fourth or later treatment lines are not shown.

Table 3. Initial and final daily dose of palbociclib.

Initial dose (n, %)	Final dose			Treatment duration^†
	Dose	n	%	Median, days
125 mg/day (881, 82.0)	125 mg/day	296	33.6	224.0
	100 mg/day	271	30.8	265.0
	75 mg/day	288	32.7	432.0
	Other	26	3.0	356.0
100 mg/day (139, 12.9)^‡	100 mg/day	58	41.7	216.0
	75 mg/day	74	53.2	251.0
	Other	6	4.3	398.0
75 mg/day (41, 3.8)^‡	75 mg/day	37	90.2	279.0
	Other	2	4.9	126.0
Other (13, 1.2)^§	–	–	–	–

† Treatment duration represents days from palbociclib treatment initiation to the final palbociclib treatment.

‡ Treatment lines with dose escalation were excluded from the analysis for the final dose, which were 1 and 2 treatment lines for 100 and 75 mg/day, respectively.

§ Nonrecommended daily dose or dose reductions are grouped in ‘other’.

Figure 4. Timing of palbociclib dose reduction from 1 to 20 weeks of the treatment initiation.

This figure shows the timing of palbociclib dose reduction in the first 20 weeks of the treatment initiation (n = 588 out of 1074 patients), and results in later weeks are not shown.

Figure 5. Blood tests performed during palbociclib treatments in 1–20 weeks.

(A) Timing and (B) blood tests.