Tumor Sink Effect in 68Ga-PSMA-11 PET: Myth or Reality?

Andrei Gafita; Hui Wang; Andrew Robertson; Wesley R. Armstrong; Raphael Zaum; Manuel Weber; Farid Yagubbayli; Clemens Kratochwil; Tristan R. Grogan; Kathleen Nguyen; Fernando Navarro; Rouzbeh Esfandiari; Isabel Rauscher; Bjoern Menze; David Elashoff; Ebrahim S. Delpassand; Ken Herrmann; Johannes Czernin; Michael S. Hofman; Jeremie Calais; Wolfgang P. Fendler; Matthias Eiber

doi:10.2967/jnumed.121.261906

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FIGURE 1.
Study flowchart. mCRPC = metastatic castration-resistant prostate cancer; mHSPC = metastatic hormone-sensitive prostate cancer; Q = quintile.
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FIGURE 2.
SUV_mean of normal organs. Horizontal lines represent median value.
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FIGURE 3.
Examples of maximum-intensity-projection images of PSMA PET for each tumor load group. PSMA-positive tumor segmentation is highlighted in red.
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FIGURE 4.
SUV_mean of normal organs stratified by tumor load.

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TABLE 1.

Characteristics of Patients

Characteristics	Control (n = 50)	mHSPC (n = 81)	mCRPC (n = 275)
Age (y)	71 (69–74)	69 (63–72)	72 (66–76)
Weight (kg)	86 (80–99)	81 (75–92)	80 (72–92)
Injected activity (MBq)	185 (183–196)	128 (96–153)	155 (112–195)
Acquisition time (min)	60 (55–66)	65 (59–82)	60 (53–67)
PSA (ng/mL)*	0.4 (0.2–0.8)	4.0 (1–11)	130 (37–431)
PSMA-VOL (cm³)	0	7 (2–37)	563 (194–1,358)
Site of disease on PSMA-PET
Bone	0	70 (86%)	256 (93%)
Lymph nodes	0	34 (42%)	202 (74%)
Bone + lymph nodes	0	27 (33%)	183 (67%)
Viscera^†	0	10 (12%)	82 (30%)
Bone + lymph nodes + viscera	0	1 (1%)	59 (22%)

*Data missing for 10 patients.
↵^†Viscera include lung, liver, rectum, pancreas, peritoneal, brain and adrenal.
mHSPC = metastatic hormone-sensitive prostate cancer; mCRPC = metastatic castration-resistant prostate cancer; PSA = prostate-specific antigen.
Qualitative data are number and percentage; continuous data are median and IQR.

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TABLE 2.

Comparison of PSMA-VOL Groups and ⁶⁸Ga-PSMA Uptake in Normal Organs

			SUV_mean			SUV_max
Organ	Tumor load group	PSMA-VOL (cm³)	Median	Difference from control (%)	P	Median	Difference from control (%)	P
Salivary gland	Control	0	11.0 (10.0–12.4)	—	—	21.8 (19.3–26.2)	—	—
	Very low	<25	10.3 (8.3–13.7)	−6.4 (−15.2, +3.4)	0.189	22.9 (18.3–29.5)	+5.0 (−4.0, +14.2)	0.585
	Low	25–189	11.0 (9.1–12.9)	+0.5 (−9.8, +10.5)	0.239	21.9 (18.1–29.2)	+0.5 (−9.1, +9.9)	0.768
	Moderate	189–532	10.8 (9.1–12.0)	−1.8 (−9.8, +5.1)	0.195	23.4 (20.1–29.0)	+7.3 (−2.5, +18.0)	0.352
	High	532–1,355	8.3 (6.6–10.3)	−24.5 (−33.3, −17.0)	<0.001	18.3 (13.8–22.5)	−16.0 (−7.2, −25.5)	<0.001
	Very high	>1,355	6.8 (5.5–9.4)	−38.1 (−47.8, −29.7)	<0.001	16.0 (11.2–23.0)	−26.6 (−15.1, −38.9)	<0.001
Kidney	Control	0	34.7 (26.4–37.8)	—	—	59.8 (49.5–68.1)	—	—
	Very low	<25	30.3 (23.0–35.8)	−12.6 (−22.0, +2.2)	0.125	55.4 (43.8–69.5)	−7.4 (−17.8, +3.1)	0.394
	Low	25–189	26.7 (20.0–33.9)	−23.0 (−34.1, −13.5)	0.001	52.6 (37.3–69.7)	−12.0 (−22.9, −1.4)	0.054
	Moderate	189–532	26.5 (19.3–32.8)	−23.6 (−32.0, −15.2)	<0.001	54.2 (37.4–71.2)	−9.4 (−12.5, +3.0)	0.085
	High	532–1,355	24.0 (18.9–31.4)	−30.8 (−42.1, −20.3)	<0.001	47.7 (35.2–65.3)	−20.2 (−30.5, −9.8)	0.005
	Very high	>1,355	20.8 (15.1–23.6)	−40.0 (−50.3, −31.1)	<0.001	42.8 (31.4–52.8)	−28.4 (−39.4, −18.0)	<0.001
Liver	Control	0	4.4 (3.6–5.5)	—	—	9.5 (8.2–11.2)	—	—
	Very low	<25	3.8 (3.2–5.2)	−13.6 (−25.0, +1.6)	0.070	11.0 (8.5–12.4)	15.8 (+2.4, +25.9)	0.073
	Low	25–189	3.9 (3.1–4.5)	−11.4 (−20.3, −3.0)	0.010	10.1 (7.5–11.6)	+6.3 (−4.1, +15.2)	0.886
	Moderate	189–532	3.9 (3.3–4.8)	−11.4 (−22.0, −1.7)	0.033	9.9 (8.5–12.2)	+4.2 (−9.8, +17.1)	0.451
	High	532–1,355	3.7 (3.0–4.9)	−15.9 (−25.9, −16.1)	0.008	9.3 (7.6–11.6)	−2.1 (−11.8, +7.9)	0.842
	Very high	>1,355	2.5 (1.8–3.5)	−43.2 (−55.6, −30.8)	<0.001	7.8 (6.4–10.6)	−17.9 (−30.0, −4.2)	0.017
Spleen	Control	0	6.3 (4.6–8.2)	—	—	10.3 (8.2–13.4)	—	—
	Very low	<25	5.5 (4.2–6.8)	−12.7 (−25.5, +1.2)	0.074	10.9 (9.3–12.6)	+5.8 (−6.1, +17.6)	0.384
	Low	25–189	5.3 (4.5–7.6)	−14.9 (−30.0, +2.4)	0.175	10.2 (8.2–13.7)	−1.0 (−9.8, +8.0)	0.888
	Moderate	189–532	5.9 (4.4–7.8)	−6.3 (−18.9, +6.2)	0.422	11.0 (8.4–13.9)	+6.8 (−6.2, +19.3)	0.492
	High	532–1,355	4.8 (3.9–7.2)	−23.8 (−37.3, −6.8)	0.012	9.2 (7.5–12.9)	−10.7 (−23.9, +3.4)	0.271
	Very high	>1,355	4.1 (3.3–6.0)	−34.9 (−49.8, −21.3)	<0.001	9.1 (6.4–12.2)	−11.7 (−24.4, +1.9)	0.068