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

PURPOSE: Whole-pelvis (WP) radiation therapy (radiation) improved biochemical relapse-free survival (bRFS) compared with prostate bed (PB)-only radiation in the Radiation Therapy Oncology Group 0534, but was performed in an era prior to positron emission tomography (PET) staging. Separately, 18F-fluciclovine PET/CT-guided postprostatectomy radiation improved 3-year bRFS versus radiation guided by conventional imaging alone. We hypothesized that patients who were changed from WP to PB-only radiation after PET would have bRFS that was: (a) no higher than patients initially planned for PB-only radiation; and (b) lower than patients planned for WP radiation without PET guidance. METHODS AND MATERIALS: We conducted a post hoc analysis of a prospective, randomized trial comparing conventional (arm 1) versus PET-guided (arm 2) postprostatectomy radiation. In arm 2, pre-PET treatment field decisions were recorded and post-PET fields were defined per protocol; pathologic node negative (pN0) without pelvic or extrapelvic PET uptake received PB-only radiation. Three-year bRFS was compared in patients planned for WP with change to PB-only radiation (arm 2 [WP:PB]) vs arm 2 patients planned for PB-only with final radiation to PB-only (arm 2 [PB:PB]) and arm 1 pN0 patients treated with WP radiation (arm 1 [WP]) using the Z test and log-rank test. Demographics were compared using the chi-square test, Fisher exact test, or analysis of variance, as appropriate. RESULTS: We identified 10 arm 2 (WP:PB), 31 arm 2 (PB:PB) and 11 arm 1 (WP) patients. Androgen deprivation was used in 50.0% of arm 2 (WP:PB) and 3.2% of arm 2 (PB:PB) patients, P < .01. Median preradiation prostate-specific antigen was higher in arm 2 (WP:PB) vs arm 2 (PB:PB) patients (0.4 vs 0.2 ng/mL, P = .03); however, there were no significant differences in T stage, Gleason score, or margin positivity. Three-year bRFS was 80% in arm 2 (WP:PB) vs 87.4% in arm 2 (PB:PB), P = .47, respectively. Arm 1(WP) patients had significantly worse 3-year (23%) bRFS vs arm 2 (WP:PB), P < .01. CONCLUSIONS: Patients initially planned for WP radiation with field decision change to PB-only radiation after PET showed (1) no significant difference in 3-year bRFS compared with patients initially planned for PB-only radiation; and (2) improved bRFS compared with patients receiving WP radiation without PET guidance. PET-guided volume de-escalation in selected patients may be 1 approach to mitigating toxicity without compromising outcomes.

Prospective investigation of amino acid transport and PSMA-targeted positron emission tomography for metastatic lobular breast carcinoma.

PURPOSE: To explore the feasibility of imaging amino-acid transport and PSMA molecular pathways in the detection of metastatic breast invasive lobular carcinoma (ILC) and if there is superior detection compared to standard-of-care imaging [computed tomography (CT)/bone scan, or 18F-FDG positron-emission-tomography (PET)-CT]. METHODS: 20 women with de-novo or suspected metastatic ILC underwent two PET-CT scans with 18F-fluciclovine and 68Ga-PSMA-11 on separate days. Uptake per patient and in 3 regions per patient - ipsilateral axillary lymph node (LN), extra-axillary LN (ipsilateral supraclavicular or internal mammary), or distant sites of disease - was compared to standard-of-care imaging (CT/bone scan in 13 patients and 18F-FDG PET-CT in 7 patients). Results were correlated to a composite standard of truth. Confirmed detection rate (cDR) was compared using McNemar's test. Mean SUVmax of 18F-fluciclovine and 68Ga-PSMA-11 in the most avid lesion for each true positive metastatic region and intact primary lesion were compared by t-test. RESULTS: The cDR for standard-of-care imaging was 5/20 patients in 5/60 regions. 68Ga-PSMA-11 PET-CT detected metastasis in 7/20 patients in 7/60 regions. 18F-fluciclovine PET-CT detected metastasis in 9/20 patients in 12/60 regions. The cDR for 18F-fluciclovine PET-CT was significantly higher versus standard-of-care imaging on the patient and combined region levels, while there were no significant differences between 68Ga-PSMA-11 and standard-of care imaging. 18F-fluciclovine cDR was also significantly higher than 68Ga-PSMA-11 on the combined region level. Mean SUVmax for true positive metastatic and primary lesions with 18F-fluciclovine (n = 18) was significantly greater than for 68Ga-PSMA-11 (n = 11) [5.5 ± 1.8 versus 3.5 ± 2.7 respectively, p = 0.021]. CONCLUSION: In this exploratory trial, 18F-fluciclovine PET-CT has a significantly higher cDR for ILC metastases compared to standard-of-care imaging and to 68Ga-PSMA-11. Mean SUVmax for true positive malignancy was significantly higher with 18F-fluciclovine than for 68Ga-PSMA-11. Exploratory data from this trial suggests that molecular imaging of amino acid metabolism in patients with ILC deserves further study. CLINICAL TRIAL REGISTRATION: Early phase (I-II) clinical trial (NCT04750473) funded by the National Institutes of Health (R21CA256280).

[18F]F-Poly(ADP-Ribose) Polymerase Inhibitor Radiotracers for Imaging PARP Expression and Their Potential Clinical Applications in Oncology.

Including poly(ADP-ribose) polymerase (PARP) inhibitors in managing patients with inoperable tumors has significantly improved outcomes. The PARP inhibitors hamper single-strand deoxyribonucleic acid (DNA) repair by trapping poly(ADP-ribose)polymerase (PARP) at sites of DNA damage, forming a non-functional "PARP enzyme-inhibitor complex" leading to cell cytotoxicity. The effect is more pronounced in the presence of PARP upregulation and homologous recombination (HR) deficiencies such as breast cancer-associated gene (BRCA1/2). Hence, identifying HR-deficiencies by genomic analysis-for instance, BRCA1/2 used in triple-negative breast cancer-should be a part of the selection process for PARP inhibitor therapy. Published data suggest BRCA1/2 germline mutations do not consistently predict favorable responses to PARP inhibitors, suggesting that other factors beyond tumor mutation status may be at play. A variety of factors, including tumor heterogeneity in PARP expression and intrinsic and/or acquired resistance to PARP inhibitors, may be contributing factors. This justifies the use of an additional tool for appropriate patient selection, which is noninvasive, and capable of assessing whole-body in vivo PARP expression and evaluating PARP inhibitor pharmacokinetics as complementary to the currently available BRCA1/2 analysis. In this review, we discuss [18F]Fluorine PARP inhibitor radiotracers and their potential in the imaging of PARP expression and PARP inhibitor pharmacokinetics. To provide context we also briefly discuss possible causes of PARP inhibitor resistance or ineffectiveness. The discussion focuses on TNBC, which is a tumor type where PARP inhibitors are used as part of the standard-of-care treatment strategy.

Advances in Radioligand Theranostics in Oncology.

Theranostics with radioligands (radiotheranostics) has played a pivotal role in oncology. Radiotheranostics explores the molecular targets expressed on tumor cells to target them for imaging and therapy. In this way, radiotheranostics entails non-invasive demonstration of the in vivo expression of a molecular target of interest through imaging followed by the administration of therapeutic radioligand targeting the tumor-expressed molecular target. Therefore, radiotheranostics ensures that only patients with a high likelihood of response are treated with a particular radiotheranostic agent, ensuring the delivery of personalized care to cancer patients. Within the last decades, a couple of radiotheranostics agents, including Lutetium-177 DOTATATE (177Lu-DOTATATE) and Lutetium-177 prostate-specific membrane antigen (177Lu-PSMA), were shown to prolong the survival of cancer patients compared to the current standard of care leading to the regulatory approval of these agents for routine use in oncology care. This recent string of successful approvals has broadened the interest in the development of different radiotheranostic agents and their investigation for clinical translation. In this work, we present an updated appraisal of the literature, reviewing the recent advances in the use of established radiotheranostic agents such as radioiodine for differentiated thyroid carcinoma and Iodine-131-labeled meta-iodobenzylguanidine therapy of tumors of the sympathoadrenal axis as well as the recently approved 177Lu-DOTATATE and 177Lu-PSMA for differentiated neuroendocrine tumors and advanced prostate cancer, respectively. We also discuss the radiotheranostic agents that have been comprehensively characterized in preclinical studies and have shown some clinical evidence supporting their safety and efficacy, especially those targeting fibroblast activation protein (FAP) and chemokine receptor 4 (CXCR4) and those still being investigated in preclinical studies such as those targeting poly (ADP-ribose) polymerase (PARP) and epidermal growth factor receptor 2.

Imaging Molecular Targets and Metabolic Pathways in Breast Cancer for Improved Clinical Management: Current Practice and Future Perspectives.

Breast cancer is the most frequently diagnosed cancer and leading cause of cancer-related deaths worldwide. Timely decision-making that enables implementation of the most appropriate therapy or therapies is essential for achieving the best clinical outcomes in breast cancer. While clinicopathologic characteristics and immunohistochemistry have traditionally been used in decision-making, these clinical and laboratory parameters may be difficult to ascertain or be equivocal due to tumor heterogeneity. Tumor heterogeneity is described as a phenomenon characterized by spatial or temporal phenotypic variations in tumor characteristics. Spatial variations occur within tumor lesions or between lesions at a single time point while temporal variations are seen as tumor lesions evolve with time. Due to limitations associated with immunohistochemistry (which requires invasive biopsies), whole-body molecular imaging tools such as standard-of-care [18F]FDG and [18F]FES PET/CT are indispensable in addressing this conundrum. Despite their proven utility, these standard-of-care imaging methods are often unable to image a myriad of other molecular pathways associated with breast cancer. This has stimulated interest in the development of novel radiopharmaceuticals targeting other molecular pathways and processes. In this review, we discuss validated and potential roles of these standard-of-care and novel molecular approaches. These approaches' relationships with patient clinicopathologic and immunohistochemical characteristics as well as their influence on patient management will be discussed in greater detail. This paper will also introduce and discuss the potential utility of novel PARP inhibitor-based radiopharmaceuticals as non-invasive biomarkers of PARP expression/upregulation.

Actinium-225-PSMA radioligand therapy of metastatic castration-resistant prostate cancer (WARMTH Act): a multicentre, retrospective study.

BACKGROUND: Actinium-225 (225Ac) prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) is a novel therapy for metastatic castration-resistant prostate cancer (mCRPC). We aimed to report the safety and antitumour activity of 225Ac-PSMA RLT of mCRPC in a large cohort of patients treated at multiple centres across the world. METHODS: This retrospective study included patients treated at seven centres in Australia, India, Germany, and South Africa. We pooled data of consecutive patients of any age and Eastern Cooperative Oncology Group performance status with histopathologically confirmed adenocarcinoma of the prostate who were treated with one or more cycles of 8 MBq 225Ac-PSMA RLT administered intravenously for mCRPC. Previous lines of mCRPC treatment included taxane-based chemotherapy, androgen-receptor-axis inhibitors, lutetium-177 (177Lu) PSMA RLT, and radium-223 dichloride. The primary outcomes were overall survival and progression-free survival. FINDINGS: Between Jan 1, 2016, and May 31, 2023, 488 men with mCRPC received 1174 cycles of 225Ac-PSMA RLT (median two cycles, IQR 2-4). The mean age of the patients was 68·1 years (SD 8·8), and the median baseline prostate-specific antigen was 169·5 ng/mL (IQR 34·6-519·8). Previous lines of treatment were docetaxel in 324 (66%) patients, cabazitaxel in 103 (21%) patients, abiraterone in 191 (39%) patients, enzalutamide in 188 (39%) patients, 177Lu-PSMA RLT in 154 (32%) patients, and radium-223 dichloride in 18 (4%) patients. The median follow-up duration was 9·0 months (IQR 5·0-17·5). The median overall survival was 15·5 months (95% CI 13·4-18·3) and median progression-free survival was 7·9 months (6·8-8·9). In 347 (71%) of 488 patients, information regarding treatment-induced xerostomia was available, and 236 (68%) of the 347 patients reported xerostomia after the first cycle of 225Ac-PSMA RLT. All patients who received more than seven cycles of 225Ac-PSMA RLT reported xerostomia. Grade 3 or higher anaemia occurred in 64 (13%) of 488 patients, leukopenia in 19 (4%), thrombocytopenia in 32 (7%), and renal toxicity in 22 (5%). No serious adverse events or treatment-related deaths were recorded. INTERPRETATION: 225Ac-PSMA RLT shows a substantial antitumour effect in mCRPC and represents a viable therapy option in patients treated with previous lines of approved agents. Xerostomia is a common side-effect. Severe bone marrow and renal toxicity are less common adverse events. FUNDING: None.

Prognostic Value of PSMA PET/CT in Prostate Cancer.

Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein expressed in the majority of prostate cancer (PCa). PSMA has an enzymatic function that makes metabolic substrates such as folate available for utilization by PCa cells. Intracellular folate availability drives aggressive tumor phenotype. PSMA expression is, therefore, a marker of aggressive tumor biology. The large extracellular domain of PSMA is available for targeting by diagnostic and therapeutic radionuclides, making it a suitable cellular epitope for theranostics. PET imaging of radiolabeled PSMA ligands has several prognostic utilities. In the prebiopsy setting, intense PSMA avidity in a prostate lesion correlate well with clinically significant PCa (csPCa) on histology. When used for staging, PSMA PET imaging outperforms conventional imaging for the accurate staging of primary PCa, and findings on imaging predict post-treatment outcomes. The biggest contribution of PSMA PET imaging to PCa management is in the biochemical recurrence setting, where it has emerged as the most sensitive imaging modality for the localization of PCa recurrence by helping to guide salvage therapy. PSMA PET obtained for localizing the site of recurrence is prognostic, such that a higher lesion number predicts a less favorable outcome to salvage radiotherapy or surgical intervention. Systemic therapy is given to patients with advanced PCa with distant metastasis. PSMA PET is useful for predicting response to treatments with chemotherapy, first- and second-line androgen deprivation therapies, and PSMA-targeted radioligand therapy. Artificial intelligence using machine learning algorithms allows for the mining of information from clinical images not visible to the human eyes. Artificial intelligence applied to PSMA PET images, therefore, holds great promise for prognostication in PCa management.

Integrated Genomic Analysis of Primary Prostate Tumor Foci and Corresponding Lymph Node Metastases Identifies Mutations and Pathways Associated with Metastasis.

Prostate cancer is a highly heterogeneous disease and mortality is mainly due to metastases but the initial steps of metastasis have not been well characterized. We have performed integrative whole exome sequencing and transcriptome analysis of primary prostate tumor foci and corresponding lymph node metastases (LNM) from 43 patients enrolled in clinical trial. We present evidence that, while there are some cases of clonally independent primary tumor foci, 87% of primary tumor foci and metastases are descended from a common ancestor. We demonstrate that genes related to oxidative phosphorylation are upregulated in LNM and in African-American patients relative to White patients. We further show that mutations in TP53, FLT4, EYA1, NCOR2, CSMD3, and PCDH15 are enriched in prostate cancer metastases. These findings were validated in a meta-analysis of 3929 primary tumors and 2721 metastases and reveal a pattern of molecular alterations underlying the pathology of metastatic prostate cancer. We show that LNM contain multiple subclones that are already present in primary tumor foci. We observed enrichment of mutations in several genes including understudied genes such as EYA1, CSMD3, FLT4, NCOR2, and PCDH15 and found that mutations in EYA1 and CSMD3 are associated with a poor outcome in prostate cancer.

Prostate Cancer Skeletal Metastasis: A Spontaneous Evolution from Osteolytic to Osteoblastic Morphology without Treatment.

Skeletal metastases due to prostate cancer (PCa) are more commonly osteoblastic than osteolytic. In the rarer cases of osteolytic skeletal metastasis of PCa, transition to osteoblastic phenotype occurs following treatment, which indicates successful healing. In this report, we present a case of spontaneous osteolytic to osteoblastic evolution of PCa skeletal metastasis without treatment in a patient with recurrence of PCa. Our patient is a 59-year-old male who had a robotic radical prostatectomy in July 2014 for a T2c adenocarcinoma of the prostate gland (Gleason score = 4 + 3). He had adjuvant pelvic radiotherapy in January 2015 due to prostate-specific antigen (PSA) persistence. PSA began to rise in October 2015. An 18 F-fluciclovine positron emission tomography/computed tomography (PET/CT) scan obtained in June 2017 at a PSA of 0.5 ng/mL was negative. Repeat 18 F-fluciclovine PET/CT of February 2020 at PSA of 3.72 ng/mL showed prostate bed recurrence and a nonavid osteolytic left inferior pubic ramus lesion. 18F radiohybrid prostate-specific membrane antigen ( 18 F-rhPSMA) PET/CT scan of August 2020 performed as part of an ongoing clinical trial confirmed local prostate bed recurrence with a low-grade radiotracer uptake in the osteolytic left inferior pubic ramus bone lesion. Without salvage therapy, 18 F-fluciclovine PET/CT of October 2020 and March 2022 shows progressive sclerosis in the left pubic ramus lesion. An osteolytic to osteoblastic transition of a bone lesion as shown in this patient calls for a rethink in our understanding of untreated PCa skeletal metastasis progression. This case provides novel insight into the understanding of the temporal evolution of skeletal metastasis and calls for further research.

Correlation between [68Ga]Ga-FAPI-46 PET Imaging and HIF-1α Immunohistochemical Analysis in Cervical Cancer: Proof-of-Concept.

Hypoxia leads to changes in tumor microenvironment (upregulated CAFs) with resultant aggressiveness. A key factor in the physiological response to hypoxia is hypoxia-inducible factor-1alpha (HIF-1α). [68Ga]Ga-FAPI PET imaging has been demonstrated in various cancer types. We hypothesized that [68Ga]Ga-FAPI PET may be used as an indirect tracer for mapping hypoxia by correlating the image findings to pathological analysis of HIF-1α expression. The [68Ga]Ga-FAPI PET/CT scans of women with cancer of the cervix were reviewed and the maximum and mean standardized uptake value (SUVmax and SUVmean) and FAPI tumor volume (FAPI-TV) were documented. Correlation analysis was performed between PET-derived parameters and immunohistochemical staining as well as between PET-derived parameters and the presence of metastasis. Ten women were included. All patients demonstrated tracer uptake in the primary site or region of the primary. All patients had lymph node metastases while only six patients had distant visceral or skeletal metastases. The mean SUVmax, SUVmean, and FAPI-TV was 18.89, 6.88, and 195.66 cm3, respectively. The average FAPI-TV for patients with additional sites of metastases was higher than those without. Immunohistochemistry revealed varying intensities of HIF-1α expression in all tested samples. There was a positive correlation between the presence of skeletal metastases and staining for HIF-1α (r=0.80;p=0.017). The presence of skeletal metastasis was correlated to the HIF-1⍺ staining (percentage distribution). Furthermore, the FAPI-TV was a better predictor of metastatic disease than the SUVmax.

Aberrant Vascular Anatomy Associated With Artifactual Focal Avidity in the Liver on PSMA PET.

ABSTRACT: 68 Ga-prostate-specific membrane antigen (PSMA) PET/CT is a valuable tool for staging and restaging of prostate cancer. Prostate-specific membrane antigen expression is not specific to prostate cancer, as it is expressed in normal tissues as well as in neoplastic and nonneoplastic processes. Awareness of the broad possibility of lesions with PSMA avidity is necessary to recognize normal variants and avoid potential pitfalls in image interpretation. We present a series of cases showing physiologic focal PSMA avidity in hepatic segment IVb. We correlate this uptake with aberrant hepatic vasculature. The awareness of this variant is important for accurate image interpretation to prevent additional invasive procedures, undue treatment escalation, and denial of curative treatment to patients.

225Ac-PSMA-617 radioligand therapy of de novo metastatic hormone-sensitive prostate carcinoma (mHSPC): preliminary clinical findings.

PURPOSE: 225Ac-PSMA-617 has demonstrated good anti-tumor effect as a treatment option for metastatic castration-resistant prostate cancer (mCRPC) patients. No study has previously assessed treatment outcome and survival following 225Ac-PSMA-617 treatment of de novo metastatic hormone-sensitive prostate carcinoma (mHSPC) patients. Based on the potential side effects that are known and explained to the patients by the oncologist, some of the patients refused the standard treatment and are seeking alternative therapies. Thus, we report our preliminary findings in a retrospective series of 21 mHSPC patients that refused standard treatment options and were treated with 225Ac-PSMA-617. METHODS: We retrospectively reviewed patients with histologically confirmed de novo treatment-naïve bone ± visceral mHSPC that were treated with 225Ac-PSMA-617 radioligand therapy (RLT). Inclusion criteria included an Eastern Cooperative Oncology Group (ECOG) performance status of 0 to 2, treatment-naive bone ± visceral mHSPC, and patients refusal for ADT ± docetaxel, abiraterone acetate, or enzalutamide. We evaluated the response to treatment using prostate-specific antigen (PSA) response and the progression-free survival (PFS) and overall survival (OS) as well as the toxicities. RESULTS: Twenty-one mHSPC patients were included in this preliminary work. Following treatment, twenty patients (95%) had any decline in PSA and eighteen patients (86%) presented with a PSA decline of ≥ 50% including 4 patients in whom PSA became undetectable. A lower percentage decrease in PSA following treatment was associated with increased mortality and shorter progression-free survival. Overall, administration of 225Ac-PSMA-617 was well tolerated. The commonest toxicity seen was grade I/II dry mouth observed in 94% of patients. CONCLUSIONS: Given these favorable results, randomized prospective multicenter trials assessing the clinical value of 225Ac-PSMA-617 as a therapeutic agent for mHSPC administered either as monotherapy or administered concomitant with ADT are of interest.

A Discordant Pattern of Uptake on 68 Ga-PSMA PET/CT Versus 18 F-Fluciclovine PET/CT in Radiation-Induced Hepatitis : Implications for Early Postradiotherapy Imaging-Based Response Assessment.

ABSTRACT: A 62-year-old woman with right-sided invasive lobular breast carcinoma completed external beam radiotherapy 6 weeks before undergoing a 68 Ga-PSMA PET/CT and 18 F-fluciclovine PET/CT scan as part of an ongoing clinical trial (NCT04750473) assessing the performance of these molecular imaging modalities in invasive lobular breast carcinoma. The 68 Ga-PSMA PET/CT demonstrated a band-like area of increased radiotracer uptake in the dome of the right lobe of the liver anteriorly, whereas 18 F-fluciclovine PET/CT done a day later revealed photopenia in the corresponding area of the liver. The external beam radiotherapy plan confirmed that the radiotherapy field overlaid the region of the hepatic discordant radiotracer uptake on the PET/CT scans.

Impact of 18 F-Fluciclovine PET/CT Findings on Failure-Free Survival in Biochemical Recurrence of Prostate Cancer Following Salvage Radiation Therapy.

PURPOSE: We aimed to evaluate the impact of 18 F-fluciclovine PET/CT imaging on failure-free survival (FFS) post-salvage radiotherapy (SRT) for prostate cancer (PCa) recurrence. METHODS: Seventy-nine patients were recruited in a phase 2/3 clinical trial to undergo 18 F-fluciclovine PET/CT before SRT for PCa. Four patients with extrapelvic disease were excluded. All patients were followed up at regular intervals up to 48 months. Treatment failure was defined as a serum prostate-specific antigen level of ≥0.2 ng/mL above the nadir after SRT, confirmed with an additional measurement, requiring systemic treatment or clinical progression. Failure-free survival was computed and compared between patients grouped according to 18 F-fluciclovine PET/CT imaging findings. RESULTS: Eighty percent (60/75) of patients had a positive finding on 18 F-fluciclovine PET/CT, of which 56.7% (34/60) had prostate bed-only uptake, whereas 43.3% (26/60) had pelvic nodal ± bed uptake. Following SRT, disease failure was detected in 36% (27/75) of patients. There was a significant difference in FFS between patients who had a positive versus negative scan (62.3% vs 92.9% [ P < 0.001] at 36 months and 59.4% vs 92.9% [ P < 0.001] at 48 months). Similarly, there was a significant difference in FFS between patients with uptake in pelvic nodes ± bed versus prostate bed only at 36 months (49.8% vs 70.7%; P = 0.003) and at 48 months (49.8% vs 65.6%; P = 0.040). Failure-free survival was also significantly higher in patients with either negative PET/CT or prostate bed-only disease versus those with pelvic nodal ± prostate bed disease at 36 (78% vs 49.8%, P < 0.001) and 48 months (74.4% vs 49.8%, P < 0.001). CONCLUSIONS: Findings on pre-SRT 18 F-fluciclovine PET/CT imaging, even when acted upon to optimize the treatment decisions and treatment planning, are predictive of post-SRT FFS in men who experience PCa recurrence after radical prostatectomy. A negative 18 F-fluciclovine PET/CT is most predictive of a lower risk of failure, whereas the presence of pelvic nodal recurrence portends a higher risk of SRT failure.

A Tale of 3 Tracers: Contrasting Uptake Patterns of 18F-Fluciclovine, 68Ga-PSMA, and 18F-FDG in the Uterus and Adnexa.

ABSTRACT: A 41-year-old woman with invasive lobular carcinoma of the breast underwent sequential 68Ga-PSMA-11 PET/CT and 18F-fluciclovine PET/CT as part of an ongoing clinical trial (NCT04750473). 68Ga-PSMA PET/CT showed increased radiotracer uptake in the uterine endometrium and left adnexa. 18F-fluciclovine PET/CT showed increased radiotracer uptake in a leiomyomatous uterus. A clinical 18F-FDG PET/CT demonstrated radiotracer uptake in the endometrium and a circumferential area of uptake in the left adnexa, a pattern more similar to the 68Ga-PSMA uptake pattern. This case highlights the discordance in the uptake pattern of 2 radiotracers approved for prostate cancer imaging but increasingly used in non-prostate malignancies imaging.

Imaging of Invasive Fungal Infections- The Role of PET/CT.

Over the last decades, the population at risk for invasive fungal disease (IFD) has increased because of medical therapy advances and diseases compromising patients' immune systems. The high morbidity and mortality associated with invasive fungal disease in the immunocompromised present the challenge of early diagnosis of the IFD and the need to closely monitor the infection during treatment. The definitive diagnosis of invasive fungal disease based on culture or histopathological methods often has reduced diagnostic accuracy in the immunocompromised and may be very invasive. Less invasive and indirect evidence of the fungal infection by serology and imaging has been used for the early diagnosis of fungal infection before definitive results are available or when the definitive methods of diagnosis are suboptimal. Imaging in invasive fungal disease is a non-invasive biomarker that helps in the early diagnosis of invasive fungal disease but helps follow-up the infection during treatment. Different imaging modalities are used in the workup to evaluate fungal disease. The different imaging modalities have advantages and disadvantages at different sites in the body and may complement each other in the management of IFD. Positron emission tomography integrated with computed tomography with [18F]Fluorodeoxyglucose (FDG PET/CT) has helped manage IFD. The combined functional data from PET and anatomical data from the CT from almost the whole body allows noninvasive evaluation of IFD and provides a semiquantitative means of assessing therapy. FDG PET/CT adds value to anatomic-based only imaging modalities. The nonspecificity of FDG uptake has led to the evaluation of other tracers in the assessment of IFD. However, these are mainly still at the preclinical level and are yet to be translated to humans. FDG PET/CT remains the most widely evaluated radionuclide-based imaging modality in IFD management. The limitations of FDG PET/CT must be well understood, and more extensive prospective studies in uniform populations are needed to validate its role in the management of IFD that can be international guidelines.

Molecular Imaging of Tuberculosis.

Despite the introduction of many novel diagnostic techniques and newer treatment agents, tuberculosis (TB) remains a major cause of death from an infectious disease worldwide. With about a quarter of humanity harboring Mycobacterium tuberculosis, the causative agent of TB, the current efforts geared towards reducing the scourge due to TB must be sustained. At the same time, newer alternative modalities for diagnosis and treatment response assessment are considered. Molecular imaging entails the use of radioactive probes that exploit molecular targets expressed by microbes or human cells for imaging using hybrid scanners that provide both anatomic and functional features of the disease being imaged. Fluorine-18 fluorodeoxyglucose (FDG) is the most investigated radioactive probe for TB imaging in research and clinical practice. When imaged with positron emission tomography interphase with computed tomography (PET/CT), FDG PET/CT performs better than sputum conversion for predicting treatment outcome. At the end of treatment, FDG PET/CT has demonstrated the unique ability to identify a subset of patients declared cured based on the current standard of care but who still harbor live bacilli capable of causing disease relapse after therapy discontinuation. Our understanding of the pathogenesis and evolution of TB has improved significantly in the last decade, owing to the introduction of FDG PET/CT in TB research. FDG is a non-specific probe as it targets the host inflammatory response to Mycobacterium tuberculosis, which is not specifically different in TB compared with other infectious conditions. Ongoing efforts are geared towards evaluating the utility of newer probes targeting different components of the TB granuloma, the hallmark of TB lesions, including hypoxia, neovascularization, and fibrosis, in TB management. The most exciting category of non-FDG PET probes developed for molecular imaging of TB appears to be radiolabeled anti-tuberculous drugs for use in studying the pharmacokinetic characteristics of the drugs. This allows for the non-invasive study of drug kinetics in different body compartments concurrently, providing an insight into the spatial heterogeneity of drug exposure in different TB lesions. The ability to repeat molecular imaging using radiolabeled anti-tuberculous agents also offers an opportunity to study the temporal changes in drug kinetics within the different lesions during treatment.

Differences in Failure-Free Survival After Salvage Radiotherapy Guided by Conventional Imaging Versus 18F-Fluciclovine PET/CT in Postprostatectomy Patients: A Post Hoc Substratification Analysis of the EMPIRE-1 Trial.

The EMPIRE-1 (Emory Molecular Prostate Imaging for Radiotherapy Enhancement 1) trial reported a survival advantage in recurrent prostate cancer salvage radiotherapy (SRT) guided by 18F-fluciclovine PET/CT versus conventional imaging. We performed a post hoc analysis of the EMPIRE-1 cohort stratified by protocol-specified criteria, comparing failure-free survival (FFS) between study arms. Methods: EMPIRE-1 randomized patients to SRT planning via either conventional imaging only (bone scanning plus abdominopelvic CT or MRI) (arm A) or conventional imaging plus 18F-fluciclovine PET/CT (arm B). Randomization was stratified by prostate-specific antigen (PSA) level (<2.0 vs. ≥ 2.0 ng/mL), adverse pathology, and androgen-deprivation therapy (ADT) intent. We subdivided patients in each arm using the randomization stratification criteria and compared FFS between patient subgroups across study arms. Results: Eighty-one and 76 patients received per-protocol SRT in study arms A and B, respectively. The median follow-up was 3.5 y (95% CI, 3.0-4.0). FFS was 63.0% and 51.2% at 36 and 48 mo, respectively, in arm A and 75.5% at both 36 and 48 mo in arm B. Among patients with a PSA of less than 2 ng/mL (mean, 0.42 ± 0.42 ng/mL), significantly higher FFS was seen in arm B than arm A at 36 mo (83.2% [95% CI, 70.0-91.0] vs. 66.5% [95% CI, 51.6-77.8], P < 0.001) and 48 mo (83.2% [95% CI, 70.0-91.0] vs. 56.2% [95% CI, 40.5-69.2], P < 0.001). No significant difference in FFS between study arms in patients with a PSA of at least 2 ng/mL was observed. Among patients with adverse pathology, significantly higher FFS was seen in arm B than arm A at 48 mo (68.9% [95% CI, 52.1-80.8] vs. 42.8% [95% CI, 26.2-58.3], P < 0.001) though not at the 36-mo follow-up. FFS was higher in patients without adverse pathology in arm B versus arm A (90.2% [95% CI, 65.9-97.5] vs. 73.1% [95% CI, 42.9-89.0], P = 0.006) at both 36 and 48 mo. Patients in whom ADT was intended in arm B had higher FFS than those in arm A, with the difference reaching statistical significance at 48 mo (65.2% [95% CI, 40.3-81.7] vs. 29.1 [95% CI, 6.5-57.2], P < 0.001). Patients without ADT intent in arm B had significantly higher FFS than patients in arm A at 36 mo (80.7% [95% CI, 64.9-90.0] vs. 68.0% [95% CI, 51.1-80.2]) and 48 mo (80.7% [95% CI, 64.9-90.0] vs. 58.6% [95% CI, 41.0-72.6]). Conclusion: The survival advantage due to the addition of 18F-fluciclovine PET/CT to SRT planning is maintained regardless of the presence of adverse pathology or ADT intent. Including 18F-fluciclovine PET/CT to SRT leads to survival benefits in patients with a PSA of less than 2 ng/mL but not in patients with a PSA of 2 ng/mL or higher.