Using FDG-PET to Measure Early Treatment Response in Head and Neck Squamous Cell Carcinoma: Quantifying Intrinsic Variability in Order to Understand Treatment-Induced Change

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Fig 1.
Bland-Altman plots for baseline tumor SUV_max and SUV_mean. Graphs show the difference between the 2 baseline SUV measurements plotted against their average for SUV_max in the node (A), SUV_mean in the node (B), SUV_max in primary tumor (C), and SUV_mean in primary tumor (D). The solid line is the mean of differences, and dotted lines indicate the limits of agreement (mean of difference, ±1.96 × SD).

Table 1:

Patient characteristics

Patient No.	Sex	Age (yr)	Primary Site and Stage				HPV Status	Double-Baseline PET	Intratreatment PET	Days between PET2 and PET3
1	M	65	Base of tongue	T1	N2b	M0	+	Yes	Yes	17
2	M	50	Tonsil	T1	N2a	M0	+	Yes	No
3	M	44	Tonsil	T2	N2b	M0	Unknown	Yes	Yes	12
4	M	60	Tonsil	T1	N2b	M0	+	Yes	Yes	14
5	M	38	Nasopharynx	T2	N2	M0	Unknown	Yes	Yes	17
6	M	55	Base of tongue	T4	N0	M0	Unknown	Yes	Yes	13
7	M	53	Base of tongue	T4	N2c	M0	−	Yes	Yes	13
8	M	48	Tonsil	T2	N2b	M0	+	Yes	Yes	11
9	M	48	Tonsil	T2	N2b	M0	+	Yes	Yes	25
10	M	55	Tonsil	T1	N2b	M0	+	Yes	No
11	M	50	Tonsil	T1	N2c	M0	+	Yes	Yes	13
12	M	60	Tonsil	T2	N2b	M0	+	Yes	Yes	21
13	M	39	Tonsil	T3	N2b	M0	+	Yes	Yes	14
14	M	49	Soft palate	T2	N2c	M0	−	Yes	Yes	23
15	M	42	Tonsil	T4	N0	M0	+	Yes	Yes	13
16	M	68	Base of tongue	T2	N2b	M0	+	Yes	Yes	11
17	M	49	Base of tongue	T3	N0	M0	+	Yes	Yes	8

Table 2:

Means (SD, range) and intraclass coefficients for baseline and intratreatment SUV differences

	Baseline ΔSUV	Intratreatment ΔSUV	Baseline %ΔSUV	Intratreatment %ΔSUV	P Value^{^a}	ICC of SUV1 and 2^{^b}	ICC of SUV2 and 3^{^b}
Primary tumor
SUV_max	2.13 (2.65)	−2.92 (4.43)	12.6 (9.2)	15.2 (22.4)	.56	0.94 (0.76–0.97)	0.67 (0.27–0.87)
SUV_mean	1.27 (1.77)	−1.06 (2.24)	11.4 (10.5)	9.9 (22.6)	.81	0.91 (0.76–0.97)	0.67 (0.26–0.87)
Nodal metastasis
SUV_max	0.87 (0.61)	−1.84 (2.62)	7.6 (5.2)	14.5 (21.6)	.25	0.95 (0.86–0.98)	0.57 (0.11–0.83)
SUV_mean	0.61 (0.46)	−1.29 (1.47)	9.4 (8.0)	15.1 (21.8)	.30	0.93 (0.81–0.97)	0.46 (-0.03–0.78)

↵a P value for the paired test of whether the baseline %ΔSUV is different from the intratreatment %ΔSUV.
↵b SUV1 and 2 represent baseline-baseline ICC. SUV 2 and 3 represent baseline-intratreatment ICC.