Incidence of febrile neutropenia during chemotherapy among patients with nonmyeloid cancer receiving filgrastim vs a filgrastim biosimilar

Figures & data

Figure 1 Sample selection and attrition flow diagram.

Table 1 Baseline patient characteristics by weighted and unweighted cycles

Characteristic	Unweighted			Weighteda
	Filgrastim-sndz (n=349)b	Filgrastim-ref (n=6,546)b	Stand. diff. (%)	Filgrastim-sndz (n=349)b	Filgrastim-ref (n=6,546)b	Stand. diff. (%)c
Observed cycle, n (%)
1	162 (46.4)	3,297 (50.4)	−7.9	174 (49.9)	3,115 (47.6)	4.7
2	61 (17.5)	1,116 (17.0)	1.1	56 (16.2)	1,110 (16.9)	−2.1
3	51 (14.6)	846 (12.9)	4.9	49 (14.0)	863 (13.2)	2.3
4	33 (9.5)	590 (9.0)	1.5	34 (9.9)	640 (9.8)	0.4
5	26 (7.4)	414 (6.3)	4.5	24 (6.7)	481 (7.3)	−2.4
6	16 (4.6)	283 (4.3)	1.3	12 (3.3)	338 (5.2)	−9.2
Mean age, years	60.9	64.8	−28.6	65.6	64.6	7.4
Male, n (%)	147 (42.1)	2,333 (35.6)	13.3	97 (27.9)	2,356 (36.0)	−17.5
Geographic region, n (%)
Northeastd	10 (2.9)	980 (15.0)	−43.5	141 (40.4)	2,576 (39.3)	2.2
Midwestd	106 (30.4)	1,624 (24.8)	12.5	–	–	–
South	178 (51.0)	3,168 (48.4)	5.2	171 (48.9)	3,182 (48.6)	0.5
West	55 (15.8)	773 (11.8)	11.5	37 (10.7)	788 (12.0)	−4.2
Otherd	0 (0.0)	1 (0.0)	−1.7	–	–	–
Insurance type, n (%)
Commercial	213 (61.0)	2,890 (44.1)	34.3	151 (43.2)	2,948 (45.0)	–3.7
Medicare	136 (39.0)	3,656 (55.9)	−34.3	198 (56.8)	3,598 (55.0)	3.7
Mean Quan–Charlson score	5.6	5.8	−7.2	5.9	5.8	7.3
Mean number of G-CSF doses	2.3	2.2	9.2	2.3	2.2	3.2
Mean length of cycle 1, days	20.9	21.5	−7.1	21.9	21.4	5.7
G-CSF prophylaxis, n (%)	159 (45.6)	3,379 (51.6)	−12.1	185 (53.0)	3,366 (51.4)	3.1
Cancer
None	4 (1.1)	52 (0.8)	3.6	1 (0.4)	53 (0.8)	–4.9
Lymphoid	38 (10.9)	366 (5.6)	19.4	12 (3.5)	388 (5.9)	–11.2
Solid	295 (84.5)	5,562 (85.0)	−1.2	304 (87.2)	5,563 (85.0)	6.5
Both	12 (3.4)	566 (8.6)	−22.0	31 (8.8)	542 (8.3)	1.9
Metastatic cancer	136 (39.0)	3,053 (46.6)	−15.5	171 (49.0)	3,022 (46.2)	5.6
Metastatic cancer to bone	45 (12.9)	883 (13.5)	−1.8	39 (11.3)	882 (13.5)	–6.7
Prior infection	142 (40.7)	3,164 (48.3)	−15.4	195 (56.0)	3,134 (47.9)	16.3
Prior radiation	30 (8.6)	1,003 (15.3)	−20.8	67 (19.2)	974 (14.9)	11.4
Prior surgery	138 (39.5)	2,490 (38.0)	3.1	142 (40.6)	2,495 (38.1)	5.2
Renal dysfunction	83 (23.8)	1,409 (21.5)	5.4	82 (23.5)	1,413 (21.6)	4.5
Hepatic dysfunction	81 (23.2)	1,953 (29.8)	−15.1	122 (34.9)	1,935 (29.6)	11.4
Prior use of G-CSF agents	56 (16.0)	2,151 (32.9)	−39.9	111 (31.7)	2,089 (31.9)	–0.5

Notes:

a Includes adjustment for covariate imbalance using inverse probability of treatment weighting and an adjustment for censored cycles using Kaplan–Meier estimates.

b Numbers in header row refer to the number of chemotherapy cycles.

c By convention, stand. diff. <10% indicates high between-cohort similarity for that variable. Bold text indicates stand. diff. >10%.

d Northeast/midwest/other regions are combined for weighted cohorts.

Abbreviations: G-CSF, granulocyte colony-stimulating factor; stand. diff., standardized difference.

Table 2 Adjusted incidence of febrile neutropenia by weighteda cycle

FN definition, n (%)	Filgrastim-sndz (n=349)b	Filgrastim-ref (n=6,546)b	Difference of percentages (90% CI)c
Neutropenia + fever	3 (0.81)	40 (0.61)	0.20 (−0.57 to 1.56)
Neutropenia + infection	4 (1.21)	87 (1.33)	–0.12 (−1.17 to 2.28)
Neutropenia + infection + fever	0 (0.0)	9 (0.14)	–0.14d

Notes:

a Includes adjustment for covariate imbalance using inverse probability of treatment weighting and an adjustment for censored cycles using Kaplan–Meier estimates.

b Numbers in header row refer to the number of chemotherapy cycles.

c CIs are based on the bias-adjusted bootstrap method with 10,000 bootstrap replications.

d CI is not displayed because the incidence of FN in the weighted filgrastim-sndz cohort is 0.

Abbreviation: FN, febrile neutropenia.