Complete metabolic response after Partially Ablative Radiotherapy (PAR) for bulky retroperitoneal liposarcoma: A case report

In the management of symptomatic inoperable retroperitoneal sarcomas (RPS), palliative radiotherapy (RT) is a potential treatment option. However, the efficacy of low doses used in palliative RT is limited in these radioresistant tumors. Therefore, exploring dose escalation strategies targeting specific regions of the tumor may enhance the therapeutic effect of RT in relieving or preventing symptoms. In this case report, we present the case of an 87-year-old patient with rapidly growing undifferentiated liposarcoma in the retroperitoneum, where surgical and systemic therapies were ruled out due to age and comorbidities. RT was administered using volumetric modulated arc therapy, delivering 20 Gy in 4 fractions twice daily to the macroscopic tumor and 40 Gy in 4 fractions twice daily (simultaneous integrated boost) to the central part of the tumor (Gross Tumor Volume minus 2 cm). An 18F-FDG-PET-CT scan performed after RT demonstrated a complete metabolic response throughout the entire tumor mass. Although the patient eventually succumbed to metastatic spread to the bone, liver, and lung after 9 months, no local disease progression or pain/obstructive symptoms were observed. This case highlights the technical and clinical feasibility of delivering ablative doses of RT to the central region of the tumor and suggests the potential for achieving a complete metabolic response and durable tumor control.

Potential Clinical Applications of Dedicated Prostate Positron Emission Tomography

The diagnosis of prostate cancer (PCa) is usually based on transrectal or transperineal biopsies (from 12 to 24 samples) in most cases after the performance of a dedicated MRI and/or transrectal ultrasound. A small-dedicated PET scanner could improve spatial resolution and increase sensitivity, allowing a precise detection and location of the PCa foci, thus allowing an image-guided biopsy. In this short review, we will focus our attention on the potential application of a dedicated prostate PET scanner and on the prototype that has been already assembled for this purpose.

Future Imaging of Prostate Cancer: Do We Need More Than PSMA PET/CT?

In the setting of prostate cancer (PCa), many different imaging modalities are available to correctly assess staging, restaging, treatment response and radio-ligand therapy recruitment. The introduction of fluoride or gallium-labelled prostate specific membrane antigen (PSMA) made a revolution in PCa management, also due to its possible theragnostic use. Nowadays PSMA-PET/CT is a fundamental tool for staging and restaging PCa. This review discusses the latest findings in PSMA imaging in PCa patients and the impact of PSMA imaging on the patients' management in primary staging, biochemical recurrence and in advanced prostate cancer, always keeping in mind the important theragnostic role of PSMA. This review tries also to assess the current role of other radiopharmaceuticals as Choline, FACBC or other radiotracers like gastrin-releasing peptide receptor targeting tracers and FAPI in different PCa settings.

68Ga-FAPI PET/CT Interobserver Agreement on Tumor Assessment: An International Multicenter Prospective Study

⁶⁸Ga-fibroblast activation protein inhibitors (FAPIs) are promising radiotracers for cancer imaging, with emerging data in the recent years. Nonetheless, the interobserver agreement on ⁶⁸Ga-FAPI PET/CT study interpretations in cancer patients remains poorly understood. Methods: ⁶⁸Ga-FAPI PET/CT was performed on 50 patients with various tumor entities (sarcoma [n = 10], colorectal cancer [n = 10], pancreatic adenocarcinoma [n = 10], genitourinary cancer [n = 10], and other types of cancer [n = 10]). Fifteen masked observers reviewed and interpreted the images using a standardized approach for local, local nodal, and metastatic involvement. Observers were grouped by experience as having a low (<30 prior ⁶⁸Ga-FAPI PET/CT studies; n = 5), intermediate (30-300 studies; n = 5), or high level of experience (>300 studies; n = 5). Two independent readers with a high level of experience and unmasked to clinical information, histopathology, tumor markers, and follow-up imaging (CT/MRI or PET/CT) served as the standard of reference (SOR). Observer groups were compared by overall agreement (percentage of patients matching SOR) and Fleiss κ with mean and corresponding 95% CI. We defined acceptable agreement as a κ value of at least 0.6 (substantial or higher) and acceptable accuracy as at least 80%. Results: Highly experienced observers agreed substantially on all categories (primary tumor: κ = 0.71; 95% CI, 0.71-0.71; local nodal involvement: κ = 0.62; 95% CI, 0.61-0.62; distant metastasis: κ = 0.75; 95% CI, 0.75-0.75), whereas observers with intermediate experience showed substantial agreement on primary tumor (κ = 0.73; 95% CI, 0.73-0.73) and distant metastasis (κ = 0.65; 95% CI, 0.65-0.65) but moderate agreement on local nodal stages (κ = 0.55; 95% CI, 0.55-0.55). Observers with low experience had moderate agreement on all categories (primary tumor: κ = 0.57; 95% CI, 0.57-0.58; local nodal involvement: κ = 0.51; 95% CI, 0.51-0.52; distant metastasis: κ = 0.54; 95% CI, 0.53-0.54). Compared with SOR, the accuracy for readers with high, intermediate, and low experience was 85%, 83%, and 78%, respectively. In summary, only highly experienced readers showed substantial agreement and a diagnostic accuracy of at least 80% in all categories. Conclusion: The interpretation of ⁶⁸Ga-FAPI PET/CT for cancer imaging had substantial reproducibility and accuracy among highly experienced observers only, especially for local nodal and metastatic assessments. Therefore, for accurate interpretation of different tumor entities and pitfalls, we recommend training or experience with at least 300 representative scans for future clinical readers.

A Retrospective Multicenter Analysis of the Incidence of Bone-Only Disease at PSMA PET/CT in Castration Resistant Prostate Cancer Patients

PSMA PET/CT has unprecedented accuracy for localization of initial or recurrent prostate cancer (PC), which can be applied in a metastasis-directed therapy approach. PSMA PET/CT (PET) also has a role in the selection of patients for metastasis-directed therapy or radioligand therapy and therapy assessment in CRPC patients. The purpose of this multicenter retrospective study was to determine the incidence of bone-only metastasis in CRPC patients who underwent PSMA PET/CT for restaging, as well as identifying potential predictors of bone-only PET positivity. The study analyzed data from 179 patients from two centers in Essen and Bologna. Results showed that 20.1% of the patients had PSMA uptake only in the bone, with the most frequent lesions located in the vertebrae, ribs, and hip bone. Half half of the patients showed oligo disease in bone and may benefit from a bone-metastasis-directed therapy. Initial positive nodal status and solitary ADT were shown to be negative predictors of osseous metastasis. The role of PSMA PET/TC in this patient population needs to be further explored in terms of its role in the evaluation and adoption of bone-specific therapies.

PSMA-PET Guided Treatment in Prostate Cancer Patients with Oligorecurrent Progression after Previous Salvage Treatment

Background: Prostate Specific Membrane Antigen-Positron Emission Tomography (PSMA-PET) is used to select recurrent prostate cancer (PCa) patients for metastases-directed therapy (MDT). We aimed to evaluate the oncologic outcomes of second-line PSMA-guided MDT in oligo-recurrent PCa patients. Methods: we performed a retrospective analysis of 113 recurrent PCa after previous radical prostatectomy and salvage therapies with oligorecurrent disease at PSMA-PET (≤3 lesions in N1/M1a-b) in three high-volume European centres. Patients underwent second-line salvage treatments: MDT targeted to PSMA (including surgery and/or radiotherapy), and the conventional approach (observation or Androgen Deprivation Therapy [ADT]). Patients were stratified according to treatments (MDT vs. conventional approach). Patients who underwent MDT were stratified according to stage in PSMA-PET (N1 vs. M1a-b). The primary outcome of the study was Progression-free survival (PFS). Secondary outcomes were Metastases-free survival (MFS) and Castration Resistant PCa free survival (CRPC-FS). Kaplan-Meier analyses assessed PFS, MFS and CRPC-FS. Multivariable Cox regression models identified predictors of progression and metastatic disease. Results: Overall, 91 (80%) and 22 (20%) patients were treated with MDT and the conventional approach, respectively. The median follow-up after PSMA-PET was 31 months. Patients who underwent MDT had a similar PFS compared to the conventional approach (p = 0.3). Individuals referred to MDT had significantly higher MFS and CRPC-FS compared to those who were treated with the conventional approach (73.5% and 94.7% vs. 30.5% and 79.5%; all p ≤ 0.001). In patients undergoing MDT, no significant differences were found for PFS and MFS according to N1 vs. M1a-b disease, while CRPC-FS estimates were significantly higher in patients with N1 vs. M1a-b (100% vs. 86.1%; p = 0.02). At multivariable analyses, age (HR = 0.96) and ADT during second line salvage treatment (HR = 0.5) were independent predictors of PFS; MDT (HR 0.27) was the only independent predictor of MFS (all p ≤ 0.04) Conclusion: Patients who underwent second-line PSMA-guided MDT experienced higher MFS and CRPC-FS compared to men who received conventional management.

A novel tool for predicting the dose distribution of non-sealed 188 Re (Rhenium) resin in non-melanoma skin cancers (NMSC) patients

BACKGROUND

High-dose rate brachytherapy using a non-sealed ¹⁸⁸ Rhenium resin (¹⁸⁸ Re) is a recently approved treatment option for Non-Melanoma Skin Cancer (NMSC). The treatment goal is to deliver a personalized absorbed dose to the deepest point of neoplastic infiltration corresponding to the minimal target dose. The treatment consists of the application of a ¹⁸⁸ Re-based resin over a plastic foil placed on the target skin surface. However, there is no treatment planning tool to assess the ¹⁸⁸ Re activity needed for a personalized treatment.

PURPOSE

The paper aims to present a novel Monte Carlo (MC)-based tool for ¹⁸⁸ Re-based resin activity and dose calculation, experimentally validated using Gafchromic EBT3 films.

METHODS

MC simulations were carried out using FLUKA modeling density and composition of ¹⁸⁸ Re resin. The MC-based Look Up Table (LUT) was incorporated in an ad hoc developed tool. The proposed tool allows the personalized calculation of treatment parameters (i.e., acti×vity to be dispensed, the treatment duration and dose volume histograms), according to the target dimension. The proposed tool was compared using Bland-Altman analysis to the previous calculation approaches conducted using VARSKIN in a retrospective cohort of 76 patients. The tool was validated in ad hoc experimental set ups using a stack of calibrated Gafchromic EBT3 films covered by a plastic film and exposed using a homogenous activity distribution of ¹⁸⁸ Re eluate and a heterogeneous activity distribution of ¹⁸⁸ Re resin mimic the patient treatment.

RESULTS

The agreement between the proposed tool and VARSKIN was evaluated on the investigated cohort with median range of Target Area, Target Depth and Treatment Time equal to 4.8 [1.0-60.1] cm² , 1.1 [0.2-3.0] mm and 70 [21-285] min, with a median range of Target Dose (Gy) of 23.5 [10-54.9]. The calculated minimal target doses, ranged from 1% to 10% for intermediate target depths (1.2±0.7 mm), while showing significant differences in the estimation of superficial (maximal) target doses. The agreement between MC calculation and measurements at different plans in a stack of Gafchromic EBT3 films was within 10% for both the homogenous and heterogeneous activity distribution of ¹⁸⁸ Re. Worst agreements were observed for absorbed doses lower than 0.3 Gy.

CONCLUSIONS

Our results support the implementation of our MC-based tool in the practical routine for calculating the ¹⁸⁸ Re resin activity and treatment parameters necessary for obtaining the prescribed minimal target dose. This article is protected by copyright. All rights reserved.

Histology and PSMA Expression on Immunohistochemistry in High-Risk Prostate Cancer Patients: Comparison with 68Ga-PSMA PET/CT Features in Primary Staging

PSMA-PET/CT is a suitable replacement for conventional imaging in the primary staging of PCa. The aim of this retrospective study was to assess the correlation between parameters discovered by PSMA PET/CT in primary staging and either prostate histopathology (pT) findings or PSMA-IHC expression in a cohort of biopsy-proven high-risk PCa candidates for surgery. Clinical information (age, iPSA-value, and grading group) and PSMA-PET/CT parameters (SUVmax, PSMA tumor volume [PSMA-TV], and total lesion [PSMA-TL]) were compared with pT (including histologic pattern, Gleason grade, and lymphovascular invasion [LVI]) and PSMA-IHC features, including visual quantification (VS) with a four-tiered score (0 = negative, 1+ = weak, 2+ = moderate, 3+ = strong), growth pattern (infiltrative vs expansive), and visual pattern (cytoplasmic vs membranous). In total, 44 patients were enrolled, with a median age of 67 (IQR 57-77); the median iPSA was 9.4 ng/dL (IQR 12.5-6.0). One patient (3%) was grading group (GG) 3, 27/44 (61%) were GG4, and 16/44 (36%) were GG5. PSMA-PET/CT detection rate for the presence of primary prostate cancer was 100%. Fused/poorly formed Gleason grade 4 features were predominant (22/44–50%); a cribriform pattern was present in 18/44 (41%) and acinar in 4/44 (9%). We found that lower PSMA-TVs were mostly related to acinar, while higher PSMA-TVs correlated with a higher probability to have a cribriform pattern (p-value 0.04). LVI was present in 21/44(48%) patients. We found that higher PSMA-TV and PSMA-TL are predictive of LVI p-value 0.002 and p-value 0.01, respectively. There was no correlation between PET-parameters and perineural invasion (PNI), probably because this was present in almost all the patients. Moreover, patients with high PSMA-TL values displayed the highest PSMA-IHC expression (VS3+) with a membranous pattern. In conclusion, PSMA-TV and PSMA-TL are predictors of a cribriform pattern and LVI. These conditions are mostly related to higher aggressiveness and worse outcomes.

Case report: PSMA PET/CT addresses the correct diagnosis in a patient with metastatic prostate cancer despite negative core biopsies and mpMRI. A diagnostic challenge

This is a case of [⁶⁸ Ga]Ga-Prostate-specific membrane antigen (PSMA)-11 PET/CT in a 73-years old patient presenting high Prostate Specific Antigen (PSA) levels despite both multi-parametric magnetic resonance imaging (mpMRI) and 12-core saturation biopsy negative for prostate cancer (Pca). This is a highly interesting case because, despite the advanced metastatic spread at initial presentation as showed by [⁶⁸Ga]Ga-PSMA-PET/CT, the primary Pca was detected by none of the diagnostic techniques (12 random sample biopsy, mpMRI, PSMA PET/CT). However, [⁶⁸Ga]Ga-PSMA-PET/CT showed a suspicious axillary lesion suitable for biopsy, which finally resulted as Pca metastasis. This case report is therefore a brilliant example of how [⁶⁸Ga]Ga-PSMA-PET/CT optimized patient's management.

Multicenter External Validation of a Nomogram for Predicting Positive Prostate-specific Membrane Antigen/Positron Emission Tomography Scan in Patients with Prostate Cancer Recurrence

BACKGROUND

A nomogram has recently been developed to predict ⁶⁸Ga-labeled prostate-specific membrane antigen (PSMA)-11 positron emission tomography (PET)/computed tomography (PSMA-PET) results in recurrent prostate cancer (PCa) patients.

OBJECTIVE

To perform external validation of the original nomogram in a multicentric setting.

DESIGN, SETTING, AND PARTICIPANTS

A total of 1639 patients who underwent PSMA-PET for prostate-specific antigen (PSA) relapse after radical therapy were retrospectively included from six high-volume PET centers. The external cohort was stratified according to clinical setting categories: group 1: first-time biochemical recurrence (n = 774); group 2: PSA relapse after salvage therapy (n = 499); group-3: biochemical persistence after radical prostatectomy (n = 210); and group-4: advanced-stage PCa before second-line systemic therapies (n = 124).

INTERVENTION

PSMA-PET in recurrent PCa.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

PSMA-PET detection rate was assessed in the overall population and in each subgroup. A multivariable logistic regression model was produced to evaluate the predictors of a positive scan. The performance characteristics of the model were assessed by quantifying the predictive accuracy (PA) according to model calibration. The Youden's index was used to find the best nomogram's cutoff. Decision curve analysis (DCA) was implemented to quantify the nomogram's clinical net benefit.

RESULTS AND LIMITATIONS

In the external cohort, the overall detection rate was 53.8% versus 51.2% in the original population. At multivariate analysis, International Society of Urological Pathology grade group, PSA, PSA doubling time, and clinical setting were independent predictors of a positive scan (all p ≤ 0.02). The PA of the nomogram was identical to the original model (82.0%); the model showed an optimal calibration curve. The best nomogram's cutoff was 55%. In the DCA, the nomogram revealed clinical net benefit when the threshold nomogram probabilities were ≥20%. The retrospective design is a major limitation.

CONCLUSIONS

The original nomogram exhibited excellent characteristics on external validation. The incidence of a false negative scan can be reduced if PSMA-PET is performed when the predicted probability is ≥20%.

PATIENT SUMMARY

A nomogram has been developed to predict prostate-specific membrane antigen/positron emission tomography (PSMA-PET) results for recurrent prostate cancer (PCa). The nomogram represents an easy tool in the decision-making process of recurrent PCa.

Adaptive Individualized high-dose preoperAtive (AIDA) chemoradiation in high-risk rectal cancer: a phase II trial

PURPOSE

To evaluate the pathological complete response (pCR) rate of locally advanced rectal cancer (LARC) after adaptive high-dose neoadjuvant chemoradiation (CRT) based on 18 F-fluorodeoxyglucose positron emission tomography/computed tomography (18 F-FDG-PET/CT).

METHODS

The primary endpoint was the pCR rate. Secondary endpoints were the predictive value of 18 F-FDG-PET/CT on pathological response and acute and late toxicity. All patients performed 18 F-FDG-PET/CT at baseline (PET0) and after 2 weeks during CRT (PET1). The metabolic PET parameters were calculated both at the PET0 and PET1. The total CRT dose was 45 Gy to the pelvic lymph nodes and 50 Gy to the primary tumor, corresponding mesorectum, and to metastatic lymph nodes. Furthermore, a sequential boost was delivered to a biological target volume defined by PET1 with an additional dose of 5 Gy in 2 fractions. Capecitabine (825 mg/m2 twice daily orally) was prescribed for the entire treatment duration.

RESULTS

Eighteen patients (13 males, 5 females; median age 55 years [range, 41-77 years]) were enrolled in the trial. Patients underwent surgical resection at 8-9 weeks after the end of neoadjuvant CRT. No patient showed grade > 1 acute radiation-induced toxicity. Seven patients (38.8%) had TRG = 0 (complete regression), 5 (27.0%) showed TRG = 2, and 6 (33.0%) had TRG = 3. Based on the TRG results, patients were classified in two groups: TRG = 0 (pCR) and TRG = 1, 2, 3 (non pCR). Accepting p < 0.05 as the level of significance, at the Kruskal-Wallis test, the medians of baseline-MTV, interim-SUVmax, interim-SUVmean, interim-MTV, interim-TLG, and the MTV reduction were significantly different between the two groups. 18 F-FDG-PET/CT was able to predict the pCR in 77.8% of cases through compared evaluation of both baseline PET/CT and interim PET/CT.

CONCLUSIONS

Our results showed that a dose escalation on a reduced target in the final phase of CRT is well tolerated and able to provide a high pCR rate.

The Impact of PSMA-PET on Oncologic Control in Prostate Cancer Patients Who Experienced PSA Persistence or Recurrence

Background: Prostate Specific Membrane Antigen-Positron Emission Tomography (PSMA-PET) is currently recommended to restage prostate cancer (PCa) and to guide the delivery of salvage treatments. We aim to evaluate the oncologic outcomes of patients with recurrent PCa who received PSMA-PET. Methods: 324 hormone-sensitive PCa with PSA relapse after radical prostatectomy who underwent PSMA-PET in three high-volume European Centres. Patients have been stratified as pre-salvage who never received salvage treatments (n = 134), and post-salvage, including patients who received previous salvage therapies (n = 190). Patients with oligorecurrent (≤3 lesions), PSMA-positive disease underwent PSMA-directed treatments: salvage radiotherapy (sRT) or Metastases-directed therapy (MDT). Patients with polirecurrent (>3 lesions) PSMA-positive disease were treated with systemic therapy. Patients with negative PSMA-PET were treated with sRT or systemic therapies or observation. The primary outcome of the study was Progression-free survival (PFS). Secondary outcomes were: Metastases-free survival (MFS) and Castration Resistant Pca free survival (CRPC-FS). Results: median follow up was 23 months. In the pre-salvage setting, the PFS, MFS and CRPC-FS estimates at 3 years were 66.2% vs. 38.9%, 95.2% vs. 73.7% and 94.9% vs. 93.1% in patients with negative vs. positive PSMA-PET, respectively (all p ≥ 0.2). In the post-salvage setting, the PFS, MFS and CRPC-FS estimates at 3 years were 59.5% vs. 29.1%, 92.7% vs. 65.1% and 98.8% vs. 88.8% in patients with negative vs. positive PSMA-PET, respectively (all p ≤ 0.01). At multivariable analyses, a positive PSMA-PET was an independent predictor of progression (HR = 2.15) and metastatic disease (HR 2.37; all p ≤ 0.03). Conclusion: PSMA-PET in recurrent PCa detects the site of recurrence guiding salvage treatments and has a prognostic role in patients who received previous salvage treatments.

CARE‑compliant stereotactic radiotherapy of urothelial nodal metastases: A case report

The aim of the present study was to report the case of a 58-year-old male patient with ureteral carcinoma who underwent ureteroileostomy treatment. At 2 years following surgery, six lymph node metastases (LNMs) were detected in the patient's para-aortic and pelvic regions using ¹⁸F-labeled fluoro-2-deoxyglucose (FDG) positron emission tomography (PET)/CT. All LNMs were treated using stereotactic body radiotherapy (SBRT; 35-40 Gy/5 fractions). At 3 months after radiotherapy, ¹⁸F-FDG-PET/CT examination revealed a complete radiological and metabolic response of all targeted treatment sites in the patient. In the 2 years following radiotherapy, another three same-dose SBRT treatments were performed on single or multiple LNMs, which were all detected in the abdomen and pelvis of the patient. Overall, a total of 11 LNMs were targeted in the patient and all exhibited complete radiological and metabolic response following treatment. The only treatment side effect reported by the patient was a slight and temporary loss of appetite. In patients with lymph node oligometastases there are two options for radiotherapy: i) Irradiation focusing on LNMs alone; and ii) prophylactic irradiation of the entire lymph node area combined with a boost on macroscopic lesions. In the patient discussed in the present study, the choice of irradiation focusing on LNMs alone made it possible to postpone systemic therapies and instead use an optimally tolerated treatment. The treatment outcome in this patient indicated that there was no radioresistance of urothelial LNMs.

Theragnostics in prostate cancer

Prostate-specific membrane antigen (PSMA) is a molecular target for both imaging diagnostics and therapeutics, i.e., a theragnostics target. There has been a growing body of evidence supporting PSMA theragnostics approaches in the management of prostate cancer (PCa) for tailored precision medicine. Tumor characterization through PSMA-ligand PET imaging is crucial for assessing the molecular signature and eligibility for PSMA radioligand therapy. Recent U.S. Food and Drug Administration (FDA) approval of two new drug applications for PSMA PET imaging contribute to reinforce PSMA as an oncologic blockbuster. Additionally, relevant progress in the PSMA treatment has been made in the last five years. [¹⁷⁷Lu]Lu-PSMA-617 radioligand therapy for patients with progressive PSMA-avid metastatic castration-resistant PCa (mCRPC) significantly increased overall survival and radiographic progression-free survival, according to the results of an international, prospective, open label, multicenter, randomized, phase III study (VISION trial). The objective of this comprehensive review is to highlight the recent advances in PCa theragnostics, focusing on actual clinical applications and future perspectives.

Lung uptake detected by 68Ga-PSMA-11 PET/CT in prostate cancer patients with SARS-CoV-2: a case series

Coronavirus disease 2019 (COVID-19) pathology is associated with neoangiogenesis and interstitial pneumonia. ⁶⁸Ga-PSMA-11-PET/CT is able to image in vivo PSMA (Prostate-Specific Membrane Antigen) expression on both prostate cancer (PCa) cells and neovasculature endothelial cells. The aim of the case series was to explore pulmonary PSMA expression not related to cancer in patients with PCa and concomitant COVID-19. In this retrospective, multicenter case series, patients who underwent ⁶⁸Ga-PSMA-11-PET/CT for PCa and concomitant proven COVID-19 infection were analyzed. Patients were stratified according to ⁶⁸Ga-PSMA-11 intensity of uptake in the lung (SUV_max). Low uptake: < blood pool; mild-to-moderate uptake: > blood pool and < liver; intense uptake: > liver. Potential correlation between pulmonary ⁶⁸Ga-PSMA-11 uptake not related to PCa and CT patterns typical for COVID-19 was assessed. Nine patients were included, all of them presenting abnormal ⁶⁸Ga-PSMA-11 uptake, at different grades: 2/9 low, 6/9 mild-to-moderate, 1/9 high. Uptake distribution was generally bilateral, peripheral and posterior, positively matching with ground-glass CT alterations in 7/9 (78%) patients, while mismatch was observed in 2/9 (22%). 1/9 patients presented PCa lung metastases at ⁶⁸Ga-PSMA-11. ⁶⁸Ga-PSMA-11-PET/CT detected increased PSMA uptake within the lung, not related to PCa, matching with CT typical COVID-19 patterns in almost all patients. Further studies are needed to evaluate the role of ⁶⁸Ga-PSMA-11 PET in COVID-19 patients and the potential role of PSMA overexpression as a biomarker for neoangiogenesis, in both oncological and infective disorders.

PET/CT variants and pitfalls in prostate cancer: What you might see on PET and should never forget

2-deoxy-2-[¹⁸F]fluorodeoxyglucose (FDG) positron emission tomography (PET) gained an impressive role in the diagnostic management of many oncological diseases, even though its use in imaging prostate cancer (PC) is limited to selected cases, mostly advanced stage of PC and selection for prostate specific antigen membrane (PSMA) radioligand therapy (RLT). In the past years, several PET tracers have been developed for both staging and restaging PC. The three most employed PET molecules in daily practice are [¹¹C] or [¹⁸F]F-Choline, [¹⁸F]F-Fluciclovine (Anti-1- amino-3-[18F]Fluorocyclobutane-1-Carboxylic Acid, also known as (Anti-[¹⁸F]FACBC), [⁶⁸Ga]Ga-PSMA and recently FDA approved the first Fluorinated PSMA-based named [¹⁸F]F-DCFPyl. Each one has its own physiological and peculiarity which are worth exploring. Moreover, an increasing number of case reports and studies have reported tracers' variants, pitfalls, or even non-prostatic diseases (benign and malignant) incidentally detected. In prostate oncology, PET can be performed with several indications in different stages of disease, as highlighted in the EAU Guidelines on PC. A correct scan interpretation depends on the knowledge of both the physiological distribution of the tracers and the uptake of possible variants and pitfalls. The aim of this critical review is to provide a comprehensive knowledge of physiological distribution of these three tracers, as well as an updated overview of variants and pitfalls.

Current and Emerging Clinical Applications of PSMA PET Diagnostic Imaging for Prostate Cancer

Prostate-specific membrane antigen (PSMA) is highly expressed on most prostate cancer (PCa) cells, and several PSMA ligands for PET imaging are now available worldwide. ⁶⁸Ga-PSMA-11 has already received U.S. Food and Drug Administration and European Medicines Agency approval, and use of PSMA PET is currently suggested by several international guidelines for investigating PCa in different clinical settings. In primary PCa, PSMA PET has been shown to be superior to cross-sectional imaging for the detection of pelvic lymph nodes and distant metastases with subsequent clinical management changes. Additionally, it might also have a role in intraprostatic tumor localization, especially when combined with multiparametric MRI. In a setting of PCa recurrence, higher detection rates have been observed than for any other available imaging techniques, especially at low prostate-specific antigen values. Furthermore, PSMA PET consistently led to a shift in clinical management, thus increasing the proportion of radiotherapy, surgery, or other focal therapies at the expense of systemic options or no treatment. In oligometastatic disease after radical surgery, PSMA PET may be relevant in guiding a metastasis-directed therapy approach, as preliminary data seem to suggest a benefit in terms of progression-free survival after treatment of PSMA PET-positive lesions. As a staging and gatekeeping technique, PSMA PET represents a reliable whole-body imaging procedure in combination with second-line therapy of castration-resistant PCa, as well as being pivotal when assessing patients eligible for radioligand therapy such as ¹⁷⁷Lu-PSMA. This critical review aims at providing a comprehensive overview of the latest literature on the current or emerging main indications, as well as a general outlook on the recommended interpretation criteria for PSMA PET imaging.

High dose brachytherapy with non sealed 188Re (rhenium) resin in patients with non-melanoma skin cancers (NMSCs): single center preliminary results

Background and aim

High dose brachytherapy using a non sealed ¹⁸⁸Re-resin (Rhenium-SCT®, Oncobeta® GmbH, Munich, Germany) is a treatment option for non-melanoma skin cancer (NMSC). The aim of this prospective study was to assess the efficacy and the safety of a single application of Rhenium-SCT® in NMSC.

Materials and method

Fifty consecutive patients (15F, 35 M, range of age 56–97, mean 81) showing 60 histologically proven NMSCs were enrolled and treated with the Rhenium-SCT® between October 2017 and January 2020. Lesions were located on the face, ears, nose or scalp (n = 46), extremities (n = 9), and trunk (n = 5). Mean surface areas were 7.0 cm² (1–36 cm²), mean thickness invasion was 1.1 mm (0.2–2.5 mm), and mean treatment time was 79 min (21–85 min). Superficial, mean, and target absorbed dose were 185 Gy, 63 Gy, and 31 Gy respectively. Patients were followed-up at 14, 30, 60, 90, and 180 days posttreatment, when dermoscopy and biopsy were performed. Mean follow-up was 20 months (range 3–33 months). Early skin toxicity was classified according to Common Terminology Criteria for Adverse Events (CTCAE). Cosmetic results were evaluated after at least 12 months according to Radiation Therapy Oncology Group (RTOG) scale.

Results

At 6 months follow-up, histology and dermoscopy were available for 54/60 lesions, of which 53/54 (98%) completely responded. One patient showed a 1-cm² residual lesion that was subsequently surgically excised. Twelve months after treatment, 41/41 evaluable lesions were free from relapse. Twenty four months after treatment, 23/24 evaluable lesions were free of relapse. In 56/60 lesions early side effects, resolving within 32 days were classified as grades 1–2 (CTCAE). In the remaining 4/60 lesions, these findings were classified as grade 3 (CTCAE) and lasted up to 8–12 weeks but all resolved within 90 days. After at least 12 months (12–33 months), cosmetic results were excellent (30 lesions) or good (11 lesions).

Conclusion

High dose brachytherapy with Rhenium-SCT® is a noninvasive, reasonably safe, easy to perform, effective and well-tolerated approach to treat NMSCs, and it seems to be a useful alternative option when surgery or radiation therapy are difficult to perform or not recommended. In our population 98% of the treated lesions resolved completely after a single application and only one relapsed after 2 years. Larger patients’ population and longer follow-up are needed to confirm these preliminary data and to find the optimal dose to administer in order to achieve complete response without significant side effects.

Detection rate, pattern of relapse and influence on therapeutic decision of PSMA PET/CT in patients affected by biochemical recurrence after radical prostatectomy, a retrospective case series

AIMS

⁶⁸Ga-Prostate-specific membrane antigen (PSMA) PET/CT is widely used in patients with biochemical recurrence (BCR) after radical prostatectomy. We collected data about patients staged with PSMA PET/CT after BCR (PSA < 1 ng/ml) in four different institutes. Impact of baseline features (Gleason score, risk classification, PSA at recurrence, PSA doubling time and time to recurrence) was explored to understand predictive factors of (PSMA) PET/CT positivity. Impact of restaging on following treatment approaches was reported.

RESULTS

92 patients were included. PSMA PET/CT detection rate was 56.5% and low-volume disease (≤ 3 non-visceral lesions) was detected in 52.2% of patients. After positive scan, 13.5% of patients still lies on observation, ADT alone was administered in 30.8% of cases, Stereotactic body RT (SBRT) alone was delivered to 44.2% of patients and 11.5% of patients underwent concomitant SBRT and ADT. Seven patients underwent conventional salvage prostate bed RT. Chi-squared test showed a higher rate of positive PSMA PET/CT for patients with Gleason score > 7 (p = 0.004) and TTR < 29.5 months (p = 0.003).

CONCLUSIONS

PSMA PET/CT showed a high detection rate. This influenced clinical management in a significant percentage of patients, allowing treatment tailoring on the basis of imaging.

Predictive Role of MRI and 18F FDG PET Response to Concurrent Chemoradiation in T2b Cervical Cancer on Clinical Outcome: A Retrospective Single Center Study

Tumor response in locally advanced cervical cancer (LACC) is generally evaluated with MRI and PET, but this strategy is not supported by the literature. Therefore, we compared the diagnostic performance of these two techniques in the response evaluation to concurrent chemoradiotherapy (CCRT) in LACC. Patients with cervical cancer (CC) stage T2b treated with CCRT and submitted to MRI and PET/CT before and after treatment were enrolled in the study. All clinical, pathological, therapeutic, radiologic and follow-up data were collected and examined. The radiological response was analyzed and compared to the follow-up data. Data of 40 patients with LACC were analyzed. Agreement between MRI and PET/CT in the evaluation response to therapy was observed in 31/40 (77.5%) of cases. The agreement between MRI, PET/CT and follow-up data showed a Cohen kappa coefficient of 0.59 (95% CI = 0.267-0.913) and of 0.84 (95% CI = 0.636-1.00), respectively. Considering the evaluation of primary tumor response, PET/CT was correct in 97.5% of cases, and MRI in 92.5% of cases; no false negative cases were observed. These results suggest the use of PET/CT as a unique diagnostic imaging tool after CCRT, to correctly assess residual and progression disease.

Predictive accuracy and clinical benefit of a nomogram aimed to predict 68Ga-PSMA PET/CT positivity in patients with prostate cancer recurrence and PSA < 1 ng/ml external validation on a single institution database

PURPOSE

To perform an external validation of a recently published nomogram aimed to predict positive ⁶⁸Ga-PSMA-11 PET/CT in patients with biochemical recurrence (BCR) after radical prostatectomy (RP) by Rauscher et al. (Eur Urol 73(5):656-661, 2018).

METHODS

Overall, 413 PCa patients with BCR after RP (two consecutive PSA ≥ 0.2 ng/ml) and PSA value between 0.2 and 1 ng/ml were included. A multivariable logistic regression model was produced to assess the predictors of positive ⁶⁸Ga-PSMA-11 PET/CT results. The performance characteristics of the model were assessed by quantifying the predictive accuracy, according to model calibration. Yuden's index was used to find the best nomogram's cut-off. Finally, decision curve analysis (DCA) was implemented to quantify the nomogram's clinical value.

RESULTS

In the external cohort, the overall detection rate of ⁶⁸Ga-PSMA-11 PET/CT was 44% vs. 64.7% in the original population. At multivariate analysis, PSA at ⁶⁸Ga-PSMA-11 PET/CT (OR: 7.06, p < 0.001) and ongoing ADT at time of ⁶⁸Ga-PSMA-11 PET/CT (OR: 2.07, p = 0.03) were the only independent predictors of PET/CT positivity. The predictive accuracy of nomogram was suboptimal and comparable to that reported in the original model (64% vs. 67%, respectively). The calibration plot indicated suboptimal concordance. The best nomogram's cut-off to predict positive ⁶⁸Ga-PSMA-11 PET/CT was 35% (AUC = 0.61). In DCA, the nomogram revealed clinical net benefit when the threshold probabilities of positive ⁶⁸Ga-PSMA-11 PET/CT is > 35%.

CONCLUSION

We assessed similar suboptimal predictive accuracies in the external cohort compared to the original one. PSA and ongoing ADT were confirmed as positive predictors, and the most informative nomogram cut-off resulted 35%.

Alternative and New Radiopharmaceutical Agents for Lung Cancer

BACKGROUND

FDG PET/CT imaging has an established role in lung cancer (LC) management. Whilst it is a sensitive technique, FDG PET/CT has a limited specificity in the differentiation between LC and benign conditions and is not capable of defining LC heterogeneity since FDG uptake varies between histotypes.

OBJECTIVE

To get an overview of new radiopharmaceuticals for the study of cancer biology features beyond glucose metabolism in LC.

METHODS

A comprehensive literature review of PubMed/Medline was performed using a combination of the following keywords: "positron emission tomography", "lung neoplasms", "non-FDG", "radiopharmaceuticals", "tracers".

RESULTS

Evidences suggest that proliferation markers, such as 18F-Fluorothymidine and 11CMethionine, improve LC staging and are useful in evaluating treatment response and progression free survival. 68Ga-DOTA-peptides are already routinely used in pulmonary neuroendocrine neoplasms (NENs) management and should be firstly performed in suspected NENs. 18F-Fluoromisonidazole and other radiopharmaceuticals show a promising impact on staging, prognosis assessment and therapy response in LC patients, by visualizing hypoxia and perfusion. Radiolabeled RGD-peptides, targeting angiogenesis, may have a role in LC staging, treatment outcome and therapy. PET radiopharmaceuticals tracing a specific oncogene/signal pathway, such as EGFR or ALK, are gaining interest especially for therapeutic implications. Other PET tracers, like 68Ga-PSMA-peptides or radiolabeled FAPIs, need more development in LC, though, they are promising for therapy purposes.

CONCLUSION

To date, the employment of most of the described tracers is limited to the experimental field, however, research development may offer innovative opportunities to improve LC staging, characterization, stratification and response assessment in an era of increased personalized therapy.

Non-FDG PET/CT in Diagnostic Oncology: a pictorial review

Positron emission tomography/computed tomography (PET/CT) is currently one of the main imaging modalities for cancer patients worldwide. Fluorodeoxyglucose (FDG) PET/CT has earned its global recognition in the modern management of cancer patients and is rapidly becoming an important imaging modality for patients with cardiac, neurological, and infectious/inflammatory conditions.

Despite its proven benefits, FDG has limitations in the assessment of several relevant tumours such as prostate cancer. Therefore, there has been a pressing need for the development and clinical application of different PET radiopharmaceuticals that could image these tumours more precisely. Accordingly, several non-FDG PET radiopharmaceuticals have been introduced into the clinical arena for management of cancer. This trend will undoubtedly continue to spread internationally. The use of PET/CT with different PET radiopharmaceuticals specific to tumour type and biological process being assessed is part of the personalised precision medicine approach.

The objective of this publication is to provide a case-based method of understanding normal biodistribution, variants, and pitfalls, including several examples of different imaging appearances for the main oncological indications for each of the new non-FDG PET radiopharmaceuticals. This should facilitate the interpretation and recognition of common variants and pitfalls to ensure that, in clinical practice, the official report is accurate and helpful.

Some of these radiopharmaceuticals are already commercially available in many countries (e.g. ⁶⁸Ga-DOTATATE and DOTATOC), others are in the process of becoming available (e.g. ⁶⁸Ga-PSMA), and some are still being researched. However, this list is subject to change as some radiopharmaceuticals are increasingly utilised, while others gradually decrease in use.

Prediction nomogram for 68Ga-PSMA-11 PET/CT in different clinical settings of PSA failure after radical treatment for prostate cancer

OBJECTIVE

The objective of this study was to develop a clinical nomogram to predict gallium-68 prostate-specific membrane antigen positron emission tomography/computed tomography (⁶⁸Ga-PSMA-11-PET/CT) positivity in different clinical settings of PSA failure.

MATERIALS AND METHODS

Seven hundred three (n = 703) prostate cancer (PCa) patients with confirmed PSA failure after radical therapy were enrolled. Patients were stratified according to different clinical settings (first-time biochemical recurrence [BCR]: group 1; BCR after salvage therapy: group 2; biochemical persistence after radical prostatectomy [BCP]: group 3; advanced-stage PCa before second-line systemic therapies: group 4). First, we assessed ⁶⁸Ga-PSMA-11-PET/CT positivity rate. Second, multivariable logistic regression analyses were used to determine predictors of positive scan. Third, regression-based coefficients were used to develop a nomogram predicting positive ⁶⁸Ga-PSMA-11-PET/CT result and 200 bootstrap resamples were used for internal validation. Fourth, receiver operating characteristic (ROC) analysis was used to identify the most informative nomogram's derived cutoff. Decision curve analysis (DCA) was implemented to quantify nomogram's clinical benefit.

RESULTS

⁶⁸Ga-PSMA-11-PET/CT overall positivity rate was 51.2%, while it was 40.3% in group 1, 54% in group 2, 60.5% in group 3, and 86.9% in group 4 (p < 0.001). At multivariable analyses, ISUP grade, PSA, PSA doubling time, and clinical setting were independent predictors of a positive scan (all p ≤ 0.04). A nomogram based on covariates included in the multivariate model demonstrated a bootstrap-corrected accuracy of 82%. The nomogram-derived best cutoff value was 40%. In DCA, the nomogram revealed clinical net benefit of > 10%.

CONCLUSIONS

This novel nomogram proved its good accuracy in predicting a positive scan, with values ≥ 40% providing the most informative cutoff in counselling patients to ⁶⁸Ga-PSMA-11-PET/CT. This tool might be important as a guide to clinicians in the best use of PSMA-based PET imaging.

18F-FDG PET/CT and Urothelial Carcinoma: Impact on Management and Prognosis-A Multicenter Retrospective Study

Objectives: To evaluate the ability of ¹⁸F-labeled fluoro-2-deoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) to predict survivorship of patients with bladder cancer (BC) and/or upper urinary tract carcinoma (UUTC). Materials: Data from patients who underwent FDG PET/CT for suspicion of recurrent urothelial carcinoma (UC) between 2007 and 2015 were retrospectively collected in a multicenter study. Disease management after the introduction of FDG PET/CT in the diagnostic algorithm was assessed in all patients. Kaplan-Meier and log-rank analysis were computed for survival assessment. A Cox regression analysis was used to identify predictors of recurrence and death, for BC, UUTC, and concomitant BC and UUTC. Results: Data from 286 patients were collected. Of these, 212 had a history of BC, 38 of UUTC and 36 of concomitant BC and UUTC. Patient management was changed in 114/286 (40%) UC patients with the inclusion of FDG PET/CT, particularly in those with BC, reaching 74% (n = 90/122). After a mean follow-up period of 21 months (Interquartile range: 4–28 mo.), 136 patients (47.4%) had recurrence/progression of disease. Moreover, 131 subjects (45.6%) died. At Kaplan-Meier analyses, patients with BC and positive PET/CT had a worse overall survival than those with a negative scan (log-rank < 0.001). Furthermore, a negative PET/CT scan was associated with a lower recurrence rate than a positive examination, independently from the primary tumor site. At multivariate analysis, in patients with BC and UUTC, a positive FDG PET/CT resulted an independent predictor of disease-free and overall survival (p < 0,01). Conclusions: FDG PET/CT has the potential to change patient management, particularly for patients with BC. Furthermore, it can be considered a valid survival prediction tool after primary treatment in patients with recurrent UC. However, a firm recommendation cannot be made yet. Further prospective studies are necessary to confirm our findings.

Future Perspective of the Application of Positron Emission Tomography-Computed Tomography-MR Imaging in Musculoskeletal Disorders

Fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) is the imaging method of choice in sarcoma patients. PET may help in diagnosis, grading, staging, biopsy guidance, monitoring response to therapy, restaging for recurrence, and prognosis. 18F-FDG-PET/MRI combines the higher tissue contrast of MRI in the study of soft-tissue lesions and the peculiarities of PET imaging that allow the characterization of tissues. The use of 18F-FDG-PET/MRI in these patients has reduces the radiation dose, which is of great importance, particularly in children. Data support the routine use of 18F-FDG-PET either using CT or MRI in patients with sarcoma.

Radioguided surgery with β radiation: a novel application with Ga68

Radio Guided Surgery is a technique helping the surgeon in the resection of tumors: a radiolabeled tracer is administered to the patient before surgery and then the surgeon evaluates the completeness of the resection with a handheld detector sensitive to emitted radiation. Established methods rely on γ emitting tracers coupled with γ detecting probes. The efficacy of this technique is however hindered by the high penetration of γ radiation, limiting its applicability to low background conditions. To overtake such limitations, a novel approach to RGS has been proposed, relying on β⁻ emitting isotopes together with a dedicated β probe. This technique has been proved to be effective in first ex-vivo trials. We discuss in this paper the possibility to extend its application cases to ⁶⁸Ga, a β⁺ emitting isotope widely used today in nuclear medicine. To this aim, a retrospective study on 45 prostatic cancer patients was performed, analysing their ⁶⁸Ga-PSMA PET images to asses if the molecule uptake is enough to apply this technique. Despite the expected variability both in terms of SUV (median 4.1, IQR 3.0–6.1) and TNR (median 9.4, IQR 5.2–14.6), the majority of cases have been found to be compatible with β-RGS with reasonable injected activity and probing time (5 s).