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. 2015 Jun;56(6):855-61.
doi: 10.2967/jnumed.115.156133. Epub 2015 Apr 16.

Biodistribution and radiation dosimetry for a probe targeting prostate-specific membrane antigen for imaging and therapy

Ken Herrmann  1 , Christina Bluemel  2 , Martina Weineisen  3 , Margret Schottelius  3 , Hans-Jürgen Wester  4 , Johannes Czernin  5 , Uta Eberlein  2 , Seval Beykan  2 , Constantin Lapa  2 , Hubertus Riedmiller  6 , Markus Krebs  6 , Saskia Kropf  7 , Andreas Schirbel  2 , Andreas K Buck  2 , Michael Lassmann  2
Affiliations

Biodistribution and radiation dosimetry for a probe targeting prostate-specific membrane antigen for imaging and therapy

Ken Herrmann et al. J Nucl Med. 2015 Jun.

Abstract

Prostate-specific membrane antigen (PSMA) is a promising target for diagnosis and treatment of prostate cancer. EuK-Subkff-(68)Ga-DOTAGA ((68)Ga-PSMA Imaging & Therapy [PSMA I&T]) is a recently introduced PET tracer for imaging PSMA expression in vivo. Whole-body distribution and radiation dosimetry of this new probe were evaluated.

Methods: Five patients with a history of prostate cancer were injected intravenously with 91-148 MBq of (68)Ga-PSMA I&T (mean ± SD, 128 ± 23 MBq). After an initial series of rapid whole-body scans, 3 static whole-body scans were acquired at 1, 2, and 4 h after tracer injection. Time-dependent changes of the injected activity per organ were determined. Mean organ-absorbed doses and effective doses were calculated using OLINDA/EXM.

Results: Injection of 150 MBq of (68)Ga-PSMA I&T resulted in an effective dose of 3.0 mSv. The kidneys were the critical organ (33 mGy), followed by the urinary bladder wall and spleen (10 mGy each), salivary glands (9 mGy each), and liver (7 mGy).

Conclusion: (68)Ga-PSMA I&T exhibits a favorable dosimetry, delivering organ doses that are comparable to (kidneys) or lower than those delivered by (18)F-FDG.

Keywords: 68Ga; PET; PSMA; dosimetry; prostate cancer.

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Conflict of interest statement

No other potential conflict of interest relevant to this article was reported.

Figures

FIGURE 1
FIGURE 1
Sequential scan of 70-y-old patient (P3; PSA level, 101.2 ng/mL) with initial diagnosis of prostate cancer (dotted arrow) showing high tumor-to-background ratio. Maximum-intensity projections (upper row) and axial slices (middle and lower rows) at different time points are displayed ([A] early rapid scan, [B] 1-h scan, [C] 2-h scan, [D] 4-h scan). Primary prostate cancer (middle row; 1-h SUVmax, 55.0) as well as numerous iliacal (lower row; 1-h SUVmax, 57.0) and mediastinal lymph node metastases (upper row; 1-h SUVmax, 31.4) can be depicted immediately after injection and up to 4 h.
FIGURE 2
FIGURE 2
Sequential patient scan (P1) of 67-y-old patient with biochemical relapse (PSA level, 6.7 ng/mL) 1.8 y after curative radiotherapy. Maximum-intensity projections (upper row) and axial slices (middle and lower row) of early rapid scan (A) and scans after 1 h (B), 2 h (C), and 4 h (D) show increased uptake in rib metastasis (A–D, arrows) and physiologic uptake in lacrimal glands, salivary glands, liver, spleen, kidneys, and slightly in bowel (A–D). Red dotted arrow in A depicts unspecific uptake in left subclavian vein.
FIGURE 3
FIGURE 3
Time–activity curves for P1 for all organs showing uptake, for whole body, and for blood. For blood, percentage of activity is given per liter of blood.
FIGURE 4
FIGURE 4
Temporal variation of SUVmax–body weight in visible lesions in P1 (red), P3 (light blue), P4 (green), and P5 (blue). P1-l1 = bone lesion; P3-l1 = lymph node mediastinal; P3-l2 = tumor tissue prostate; P3-l3 = lymph node iliacal; P4-l4 = lymph node; P5-l1 = tumor tissue prostate; P5-l2 = bone lesion.
See this image and copyright information in PMC

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