Detection Rate of 18F-rhPSMA-7.3 PET in Patients with Suspected Prostate Cancer Recurrence at PSA Levels <1 ng/mL: Data from the Phase 3 SPOTLIGHT Study

PURPOSE/OBJECTIVE(S)

Novel molecular imaging agents yield potential for localization of disease in patients with biochemical recurrence of prostate cancer when PSA levels are still low, and may facilitate early intervention with selective therapy to optimize outcomes. Radiohybrid (rh) positron emission tomography (PET) radiopharmaceutical, 18F-rhPSMA-7.3, is a novel high affinity prostate-specific membrane antigen (PSMA)-targeting ligand with potential for low bladder activity. The SPOTLIGHT study (NCT04186845) evaluated the diagnostic performance of 18F-rhPSMA-7.3 in men with suspected prostate cancer recurrence. Here, we report findings from a post-hoc analysis of SPOTLIGHT data, which determined the 18F-rhPSMA-7.3 detection rates (DR) at low-very low PSA levels.

MATERIALS/METHODS

Patients enrolled in SPOTLIGHT underwent PET 50-70 min after IV administration of 296 MBq 18F-rhPSMA-7.3. Scans were evaluated by 3 blinded central readers, with the majority read representing agreement between ≥2 independent readers. For the present analysis, all patients with an evaluable 18F-rhPSMA-7.3 PET and who had a baseline PSA <1 ng/mL were selected. Overall (patient-level) and regional DR by majority read were determined, stratifying DR according to the patients' baseline PSA level (<0.2, ≥0.2 - <0.3, ≥0.3 - <0.5, and ≥0.5 - <1 ng/mL).

RESULTS

In total, 389 patients (median [range] PSA, 1.10 [0.03-135] ng/mL, 84 with intact prostate) had an evaluable 18F-rhPSMA-7.3 scan. The overall DR was 83% (322/389) by majority read. Of the 389 patients with an evaluable 18F-rhPSMA-7.3 scan, 188 had a baseline PSA <1 ng/mL and were eligible for the present analysis. Despite low patient numbers in some PSA categories, moderate to high DR were observed, with the patient-level DR shown to increase with increasing baseline PSA (see table). Overall, 68% (128/188) of patients with a PSA <1 ng/mL and 64% (77/121) of patients with a PSA <0.5 ng/mL had a positive 18F-rhPSMA-7.3 scan by majority read. Regional DR were broadly consistent across all PSA categories. Of note, extrapelvic lesions were observed in 21% (25/121) of patients with a PSA <0.5 ng/mL and 27% (51/188) of all patients with a PSA <1 ng/mL.

CONCLUSION

Among this cohort of patients with low-very low PSA levels, more than two-thirds were found to have positive 18F-rhPSMA-7.3 scans. Of clinical significance, over a quarter of patients had extrapelvic findings. 18F-rhPSMA-7.3 PET may be a useful tool for treatment planning in patients with early biochemical recurrence of prostate cancer where curative salvage therapy is of prime consideration.

Biochemical Relapse-Free Survival in Post-Prostatectomy Patients Receiving 18F-Fluciclovine-Guided Prostate Bed Only Radiation: Post-Hoc Analysis of a Prospective Randomized Trial

PURPOSE/OBJECTIVE(S)

Whole pelvis (WP) radiation therapy (XRT) significantly improved biochemical relapse free survival (bRFS) compared to prostate-bed (PB)-only XRT in RTOG 0534, yet increased toxicity and was performed in an era prior to PET staging (Pollack et al, Lancet, 2022). Separately, 18F-fluciclovine PET/CT (PET)-guided post-prostatectomy XRT demonstrated improved bRFS compared to XRT guided by conventional imaging alone. We hypothesized that patients whose decisions were changed from whole pelvic XRT to PB-only XRT after PET imaging would have bRFS that was (a) not significantly different than patients initially planned for PB-only XRT, and (b) significantly improved over patients planned for WP XRT without PET guidance.

MATERIALS/METHODS

We conducted a post-hoc analysis of a prospective, randomized, single-institution trial comparing conventional (Arm A) v. PET-guided (Arm B) post-prostatectomy XRT. For patients randomized to Arm B, pre-PET treatment field decisions were recorded, and post-fluciclovine fields were rigidly defined per protocol: pN0 patients with no pelvic or extrapelvic PET uptake received PB-only XRT. Three- and four-year bRFS were compared in patients initially planned for WP with change to PB-only XRT [Arm B (WP→PB)] v Arm B patients initially planned for PB-only with final XRT to PB-only [Arm B(PB→PB)] & Arm A patients treated with whole pelvic XRT [Arm A(WP)] using Z test and log-rank test. Demographics were compared using Chi-square test, Fisher's exact test, or ANOVA as appropriate.

RESULTS

We identified 10 Arm B (WP→PB), 31 Arm B (PB→PB), and 25 Arm A (WP) patients. Androgen deprivation was used in 50.0% of Arm B (WP→PB) and 3.2% of Arm B (PB→PB) patients, p<0.01. Mean pre-XRT PSA was significantly higher (1.56 v 0.32 ng/mL, respectively, p<0.01) in Arm B (WP→PB) v Arm B (PB→PB) patients, however, there was no significant difference in extracapsular extension (p = 1.00), seminal vesical invasion (p = 1.00), Gleason score ≥8 (p = 0.58) or margin positivity (p = 0.73) between cohorts. Three- and four-year bRFS was 80% in Arm B (WP→PB) & 87.4% in Arm B (PB→PB), p = 0.47, respectively. Arm A (WP) patients had significantly worse three- (35.2%) and four-year (13.2%) bRFS compared to Arm B (WP→PB), p<0.01.

CONCLUSION

Patients initially planned for WP XRT whose treatment field decisions were changed to PB-only XRT after PET guidance had, in this post-hoc analysis, (a) relapse rates not significantly different than patients initially planned for PB-only XRT and (b) improved relapse rates over patients treated with WP XRT without PET guidance. PET-guided volume de-escalation in selected patients may be one approach to mitigating excess toxicity seen with WP XRT without compromising outcomes and warrants further exploration.

Diagnostic Performance of 18F-rhPSMA-7.3 PET in Men with Newly Diagnosed High-Risk Prostate Cancer and Negative Conventional Imaging

PURPOSE/OBJECTIVE(S)

The LIGHTHOUSE study (NCT04186819) evaluated high affinity radio hybrid (rh) prostate-specific membrane antigen (PSMA)-targeted PET radiopharmaceutical, 18F-rhPSMA-7.3, in patients across a range of prostate cancer (PCa) risk groups. Here, we report findings from a subgroup with high/very high-risk PCa who had no evidence of nodal or metastatic disease on conventional imaging.

MATERIALS/METHODS

Treatment-naïve patients scheduled for radical prostatectomy (RP) plus pelvic lymph node (PLN) dissection underwent PET 50-70 min after IV administration of 296 MBq 18F-rhPSMA-7.3. Local readers interpreted the scans prior to RP (performed ≤60 d post-PET) and ahead of a blinded read by 3 central readers. If the local read indicated M1 disease, verification (biopsy, surgery, or confirmatory follow-up imaging) of PET-positive M1 lesions was attempted before treatment. The present analysis evaluates the 18F-rhPSMA-7.3 sensitivity and specificity for detection of PLN metastases in all high/very high-risk patients with negative conventional imaging at baseline who underwent 18F-rhPSMA-7.3 PET and subsequent surgery. Histopathology was used as the standard of truth (SoT). Additionally, the M1 verified detection rate (VDR; % of patients with true positive (TP) M1 lesions using histopathology or follow-up imaging as SoT out of all patients scanned) was assessed in an extended population of all patients who had 18F-rhPSMA-7.3 PET regardless of surgery.

RESULTS

The sensitivity and specificity for PLN detection among 174 men with very/high-risk PCa and negative conventional imaging ranged from 24-33% and 92-96%, respectively, across readers (Table 1a). Across readers, M1 lesions were identified in 28-51 of the 197 patients in the extended population, giving an overall M1 detection rate of 14-26%. Of the identified lesions, 16-25 were successfully verified (predominantly using follow-up imaging as SoT) as TP, providing a M1 VDR of 8.1-13% (Table 1).

CONCLUSION

18F-rhPSMA-7.3 PET provides clinically useful information on the presence of both N1 and M1 disease prior to surgery in high/very high-risk PCa patients who were staged N0 M0 on conventional imaging. Specifically, up to 13% of such patients had verified TP M1 lesions. 18F-rhPSMA-7.3 may guide treatment, potentially helping such patients avoid ultimately futile surgery.

Feasibility of Hyperfunctioning Parathyroid Gland Localization Using [18F]fluciclovine PET/CT

PURPOSE

To evaluate the ability of anti-1-amino-3-anti-1-amino-3-[¹⁸F]fluorocyclobutane-1-carboxylic acid ([¹⁸F]fluciclovine) positron emission tomography/X-ray computed tomography (PET/CT) in comparison to Technetium-99m 2-methoxy isobutyl isonitrile ([^99mTc]sestamibi) single-photon emission computed tomography/CT (SPECT/CT) for the localization of hyperfunctioning parathyroid glands in patients with hyperparathyroidism.

PROCEDURES

Four patients with hyperparathyroidism underwent 60-minutes sequential neck and thorax PET/CT after [¹⁸F]fluciclovine (352 ± 28 MBq) injection. Lesion uptake and target-to-background ratios (TBR) were compared with [^99mTc]sestamibi (798 ± 27 MBq) SPECT/CT in the same patient.

RESULTS

Both techniques detected 4/5 hyperfunctioning parathyroid glands identified at surgery. The highest [¹⁸F]fluciclovine uptake and TBRs were at 5-9 min with rapid washout. [^99mTc]sestamibi had significantly higher TBRs compared with [¹⁸F]fluciclovine (5-9 min) for blood pool (10.9 ± 4.7 vs 1.3 ± 0.6; p < 0.01) and reference muscle backgrounds (5.8 ± 3.0 vs 1.7 ± 0.6; p < 0.01), with non-significant trend for thyroid tissue background (1.3 ± 0.5 vs 1.1 ± 0.5; p = 0.73).

CONCLUSION

Hyperfunctioning parathyroid glands can be detected on [¹⁸F]fluciclovine PET/CT at early imaging, but conspicuity (TBR) is better with [^99mTc]sestamibi. [¹⁸F]fluciclovine PET/CT does not seem promising in the detection of hyperfunctioning parathyroid glands.

Another “great mimicker”: FDG-PET/CT imaging findings of sarcoid-like reaction

Sarcoid-like reaction (SLR) is a cause of non-caseating granulomas in some of the cancer patients with otherwise no signs or symptoms of sarcoidosis. SLR has been described in a variety of solid organ malignancies, including breast and lung cancer. SLR may result in hypermetabolic activity in 18-fludeoxyglucose positron emission tomography (PET)/CT scan, resulting in false positive reporting for malignancy. The purpose of this case series is to expose residents/practising physicians who interpret PET/CT to a series of cases illustrating findings of SLR.

The use of the diagnostic radionuclide ascites scan to facilitate treatment decisions for hepatic hydrothorax

A 44-year-old man had an intractable right-sided pleural effusion due to cirrhosis, despite the absence of abdominal ascites. Instillation of Tc-99m macroaggregated serum albumin under CT guidance into the peritoneal space demonstrated transdiaphragmatic communication. This finding indicated the necessity for decompressing the portal system to treat the hydrothorax. The diagnostic radionuclide ascites scan may play an important role in the treatment approach to such patients.

Hospital 2000: the interface of radiology within a combined "complementary-allopathic" medicine framework

The field of radiology can play a crucial role in the movement beyond allopathic and complementary medicine to a true combination approach. Radiologists are proponents of minimal invasiveness and are familiar with the overreliance on diagnostic imaging tests. Their experience can be used to design appropriate applications for technology and to plan research methods to explore the questions raised by a combination medicine paradigm.

The integrative hospital explored via acupuncture

To integrate complementary and allopathic medicine within a single hospital requires close attention to models of health care delivery, economics, and medical philosophy. The practice of acupuncture can be used as a heuristic device to examine these issues and how solutions may apply to other complementary modalities in the creation of such a hospital facility.

Effective amplification of 20-kb DNA by reverse transcription PCR

Polymerase chain reaction has been applied to the amplification of long DNA fragments from a variety of sources, including genomic, mitochondrial, and viral DNAs. However, polymerase chain reaction amplification from cDNA templates produced by reverse transcription has generally been restricted to products of less than 10 kilobases. In this paper, we report a system to effectively amplify fragments up to 20 kilobases from human coronavirus 229E genomic RNA. We demonstrate that the integrity of the RNA template and the prevention of false priming events during reverse transcription are the critical parameters to achieve the synthesis of long cDNAs. The optimization of the polymerase chain reaction conditions enabled us to improve the specificity and yield of product but they were not definitive. Finally, we have shown that the same reverse transcription polymerase chain reaction technology can be used for the amplification of extended regions of the dystrophin mRNA, a cellular RNA of relatively low abundance.

Archaebacterial DNA polymerases tightly bind uracil-containing DNA

We show that archaebacterial DNA polymerases are strongly inhibited by the presence of small amounts of uracil-containing DNA. Inhibition appears to be competitive, with the DNA polymerase exhibiting approximately 6500-fold greater affinity for binding the inhibitor than a DNase I-activated DNA substrate. All six archaebacterial DNA polymerases tested were inhibited, while no eubacterial, eukaryotic, or bacteriophage enzymes showed this effect. Only a small inhibition resulted when uracil was present as the deoxynucleoside triphosphate, dUTP. The rate of DNA synthesis was reduced by approximately 40% when dUTP was used in place of dTTP for archaebacterial DNA polymerases. Furthermore, an incorporated dUMP served as a productive 3'-primer terminus for subsequent elongation. In contrast, the presence of an oligonucleotide containing as little as a single dUrd residue was extremely inhibitory to DNA polymerase activity on other primer-template DNA.

Magnetic resonance cholangiography

Magnetic resonance cholangiography (MRC) can be performed with data from a routine imaging protocol, without the need for additional pulse sequences or special equipment. We studied three patients with obstructive jaundice who underwent magnetic resonance imaging (MRI) of the liver. T2-weighted fat suppressed fast spin-echo sequences were processed with a maximum intensity projection algorithm to create three-dimensional images of the dilated portions of the biliary tree. Results were correlated with endoscopic retrograde cholangiopancreatography and computed tomography. These images compared favorably with those acquired on scanners in which special breath-holding gradient echo protocols are used.

Selective RNA amplification: a novel method using dUMP-containing primers and uracil DNA glycosylase

The application of PCR to a wide variety of biological problems and molecular techniques has gained wide acceptance. RNA-PCR, a technique in which first-strand cDNA synthesis is followed by PCR amplification, has enabled detection and characterization of rare transcripts. One problem confronting the researcher involves specific amplification of transcribed sequences in the presence of small amounts of genomic DNA of identical sequence. We describe a novel technique, selective RNA amplification, which will specifically amplify RNA sequences in a background of homologous DNA. The method involves first-strand cDNA synthesis from a specific dUMP-containing oligonucleotide that contains unique user-defined 5' sequence (adapter sequence) not found in the message of interest. RNA template is degraded using RNase H, which is specific for RNA/DNA hybrids. This is followed by second-strand synthesis using a gene-specific primer (GSP). The original adapter primer is digested with uracil DNA glycosylase (UDG) to prevent its participation in subsequent amplification. PCR is then performed using the GSP and a second primer corresponding to the unique adapter sequence. In this paper, we apply this method to the amplification of RNA derived from human papilloma virus sequences. Using Southern analysis, we demonstrate specific amplification of 10(5) molecules of an in vitro-transcribed RNA. Denatured DNA of identical sequence and concentration was not amplified using the RNA-specific method. The method could eliminate the need for stringent purification of RNA and enables amplification of rare messages from RNA preparations containing homologous DNA of identical sequence and size.

Uracil DNA glycosylase-mediated cloning of polymerase chain reaction-amplified DNA: application to genomic and cDNA cloning

A simple and rapid method for cloning of amplification products directly from the polymerase chain reaction (PCR) has been developed. The method is based on the addition of a 12-base dUMP-containing sequence (CUACUACUACUA) to the 5' end of PCR primers. Incorporation of these primers during PCR results in the selective placement of dUMP residues into the 5' end of amplification products. Selective degradation of the dUMP residues in the PCR products with uracil DNA glycosylase (UDG) disrupts base pairing at the termini and generates 3' overhangs. Annealing of 3' protruding termini to vector DNA containing complementary 3' ends results in chimeric molecules which can be transformed, with high efficiency, without in vitro ligation. Directional cloning of PCR products has also been accomplished by incorporating different dU-containing sequences at the end of each PCR primer. Substitution of all dT residues in PCR primers with dU eliminates cloning of aberrant "primer dimer" products and enriches cloning of genuine PCR products. The method has been applied to cloning of inter-Alu DNA sequences from human placental DNA. Using a single primer, DNA sequences between appropriately oriented Alu sequences were amplified and cloned. Cloning of cDNA for the glyceraldehyde-3'-phosphate dehydrogenase gene from rat brain RNA was also demonstrated. The 3' end region of this gene was amplified by the 3' RACE method and the amplified DNA was cloned after UDG digestion. Characterization of cloned DNAs by sequence analysis showed accurate repair of the cloning junctions. The ligase-free cloning method with UDG should prove to be a widely applicable procedure for rapid cloning of PCR-amplified DNA.

Patients with an implanted cardioverter defibrillator: a new challenge

The AICD has become the "gold standard" of tachydysrhythmia management. Since its approval in October 1985, nearly 12,000 patients have been implanted with the device (statistic from Cardiac Pacemakers, Inc., February 15, 1990). The use of this device is expected to increase for patients who are at risk for sudden cardiac death. Future device technology is advancing rapidly with the addition of more programmable options, such as shock energy output and a programmable delay feature for nonsustained VT patients. Both of these options currently are incorporated into a clinical investigational device, the VENTAKP. The emergency nurse must be aware of the device's specific operation and be prepared to interact safely and effectively to assist the AICD patient.