The Impact of Monosodium Glutamate on 68Ga-PSMA-11 Biodistribution in Men with Prostate Cancer: A Prospective Randomized, Controlled Imaging Study

Wesley R. Armstrong; Andrei Gafita; Shaojun Zhu; Pan Thin; Kathleen Nguyen; Rejah Alano; Stephanie Lira; Kiara Booker; Linda Gardner; Tristan Grogan; David Elashoff; Martin Allen-Auerbach; Magnus Dahlbom; Johannes Czernin; Jeremie Calais

doi:10.2967/jnumed.120.257931

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FIGURE 1.
Study flowchart.
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FIGURE 2.
Set of images of 73-y-old patient after radiation therapy (initial PSA, 16 ng/mL; biopsy Gleason score, 8; pT2c) and concurrent androgen hormone treatment, currently presenting for rising PSA value (6.27 ng/mL). After enrollment, patient was randomized to oral ingestion arm and received 18.9 g of MSG before second ⁶⁸Ga-PSMA-11 injection. PSMA PET/CT images revealed multifocal prostate involvement, common iliac right and external iliac right pelvic lymph nodes, and multiple bone lesions. Maximum-intensity-projection images show overall decline in ⁶⁸Ga-PSMA-11 accumulation within normal organs as well as tumor lesions on MSG scan relative to control scan. Axial view images display relevant case example of bone lesion with significant PSMA decrease after MSG administration (SUV_max from 18.6 to 9.2). p.i. = after injection.
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FIGURE 3.
SUV_mean (A) and SUV_max (B) of salivary glands, kidneys, and tumor lesions in control and MSG studies in oral ingestion and swishing arms.
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FIGURE 4.
Median changes in ⁶⁸Ga-PSMA11 activity in saliva between control and MSG groups at 0, 10, 30, 45, and 100 min after tracer injection for oral ingestion arm (A) and swishing arm (B).

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TABLE 1

Patient Characteristics

Characteristic	Data
Age (y)	72 (56–81)
Time since diagnosis of PCa (y)	7 (0.6–21)
PSA at diagnosis (ng/mL)	36 (2.5–308)
Gleason score at diagnosis^*
<8	7 (44%)
≥8	8 (50%)
T stage at diagnosis^*
T1	1 (6%)
T2	11 (66%)
T3	3 (18%)
M status at diagnosis^{^†}
M0	15 (94%)
M1	1 (6%)
Primary treatment^{^‡}
Prostatectomy ± lymphadenectomy	7 (49%)
Local radiotherapy	6 (42%)
Systemic treatment	1 (7%)
Salvage treatment
None	9 (56%)
Radiotherapy	3 (19%)
Systemic treatment	4 (25%)
Indication for scan
Primary staging	2 (12%)
Biochemical recurrence	7 (42%)
Metastatic restaging	7 (42%)
PSA at time of PSMA (ng/mL)	6.2 (0.2–53.7)

↵* Data missing for 1 patient.
↵^† M1 was defined as metastatic disease (distant metastases).
↵^‡ Data missing for 2 patients.
Qualitative data are number and percentage (total n = 16); continuous data are median and range.

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TABLE 2

PSMA PET Findings

	Swishing		Oral ingestion
Study arm	Control	MSG	Control	MSG
⁶⁸Ga-PSMA-11 PET/CT+
Prostate/prostate bed (T+)	4 (50%)	4 (50%)	5 (63%)	5 (63%)
Pelvic LN (N1)	1 (13%)	1 (13%)	2 (25%)	2 (25%)
Extrapelvic LN (M1a)	1 (13%)	1 (13%)	1 (13%)	1 (13%)
Bone (M1b)	2 (25%)	1 (13%)	3 (38%)	3 (38%)
Visceral (M1c)	0	0	0	0
⁶⁸Ga-PSMA-11 TNM pattern
PSMA T0 N0 M0	2 (25%)	2 (25%)	1 (13%)	1 (13%)
PSMA T+ N0 M0	3 (38%)	3 (38%)	2 (25%)	2 (25%)
PSMA T0 N1 M0	0	0	0	0
PSMA T+ N1 M0	1 (13%)	1 (13%)	1 (13%)	1 (13%)
PSMA T+ N0 M1	0	0	1 (13%)	1 (13%)
PSMA T0 N0 M1	2 (25%)	2 (25%)	2 (25%)	2 (25%)
PSMA T0 N1 M1	0	0	0	0
PSMA T+ N1 M1	0	0	1 (13%)	1 (13%)

Data are number and percentage.

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TABLE 3

Comparison of ⁶⁸Ga-PSMA11 Uptake in Normal Organs in Control and MSG Scans

	SUV_mean				SUV_max
Site	Control	MSG	Change	P	Control	MSG	Change	P
Oral ingestion (n = 8)
Lacrimal glands	5.5 ± 2.3	2.6 ± 0.9	−50.9% ± 6.5%	0.001	9.9 ± 4.7	4.3 ± 1.6	−55.5% ± 6.1%	0.002
Parotid glands	10.9 ± 4.1	6.9 ± 3.3	−32.9% ± 22.6%	0.002	19.0 ± 6.6	13.2 ± 6.2	−34.1% ± 21.7%	0.020
Submandibular glands	15.9 ± 5.7	6.6 ± 2.5	−58.9% ± 8.9%	<0.001	29.0 ± 10.5	10.4 ± 3.7	−63.2% ± 9.9%	<0.001
Salivary glands	12.1 ± 4.6	6.8 ± 3.1	−45.5% ± 14.6%	0.004	29.0 ± 10.5	13.5 ± 5.9	−53.4% ± 11.1%	<0.001
Liver	4.6 ± 0.5	2.1 ± 0.3	−54.2% ± 5.3%	<0.001	10.7 ± 1.3	5.5 ± 0.4	−50.1% ± 8.3%	<0.001
Spleen	8.1 ± 2.0	3.0 ± 0.9	−62.8% ± 6.9%	<0.001	13.7 ± 3.5	5.3 ± 1.5	−61.5% ± 8.6%	<0.001
Kidney	34.5 ± 14.8	17.4 ± 8.8	−51.5% ± 13.7%	<0.001	63.6 ± 25.0	32.7 ± 16.6	−51.3% ± 13.3%	<0.001
Urinary bladder	16.0 ± 8.7	69.1 ± 34.3	+371.6% ± 300.2%	0.004	33.7 ± 23.9	184.2 ± 97.5	+593.2% ± 659.5%	0.003
Total tumor lesions	6.6 ± 3.5	3.5 ± 2.1	−45.0% ± 19.0%	0.023	21.5 ± 19.8	8.2 ± 8.7	−55.7% ± 22.0%	0.061
Swishing (n = 8)
Lacrimal glands	6.5 ± 1.6	6.0 ± 2.5	+4.9% ± 22.0%	0.625	12.3 ± 3.2	11.1 ± 4.6	−5.2% ± 25.0%	0.556
Parotid glands	11.7 ± 2.2	12.0 ± 2.7	+0.1% ± 8.4%	0.917	22.2 ± 6.1	22.5 ± 6.0	+1.9% ± 10.4%	0.792
Submandibular glands	12.8 ± 3.5	13.4 ± 3.6	+5.6% ± 6.8%	0.061	21.3 ± 7.0	22.6 ± 7.3	+7.7% ± 11.6%	0.188
Salivary glands	11.5 ± 2.3	11.9 ± 2.9	+1.6% ± 7.8%	0.521	25.8 ± 6.0	26.6 ± 7.2	+4.3% ± 12.3%	0.442
Liver	4.1 ± 0.8	4.3 ± 0.9	+5.7% ± 17.3%	0.317	9.8 ± 1.3	10.4 ± 3.0	+5.3% ± 15.7%	0.321
Spleen	6.1 ± 2.0	6.3 ± 1.7	+6.2% ± 18.6%	0.458	10.8 ± 3.9	10.1 ± 2.6	−0.3% ± 15.2%	0.622
Kidney	30.1 ± 8.0	30.1 ± 5.8	+ 1.9% ± 13.9%	0.958	57.1 ± 15.9	57.6 ± 13.6	+3.4% ± 15.8%	0.782
Urinary bladder	20.2 ± 13.5	24.2 ± 8.3	+36.5% ± 41.4%	0.357	50.6 ± 42.4	56.4 ± 20.2	+52.0% ± 70.0%	0.651
Total tumor lesions	4.9 ± 1.1	5.4 ± 1.6	7.8% ± 13.8%	0.125	12.5 ± 7.7	15.0 ± 11.3	12.6% ± 27.8%	0.196

Data are average ± SD.

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TABLE 4

Comparison of SUV_mean and SUV_max Derived from Control and MSG Scans

Parameter	Control	MSG	Change (%)	P
Oral ingestion (n = 7)
SUV_mean	5.4 (3.9, 11.4)	3.3 (1.9, 3.8)	−37.8 (−67.3, −32.5)	0.018
SUV_max	10.7 (6.5, 46.8)	5.1 (2.6, 9.7)	−52.3 (−70.0, −48.5)	0.018
Swishing (n = 6)
SUV_mean	4.9 (4.2, 5.5)	5.7 (4.1, 6.3)	13.8 (−4.0, 15.4)	0.116
SUV_max	9.0 (7.8, 14.8)	11.9 (6.7, 17.5)	17.9 (−14.0, 33.3)	0.173