Can Baseline [18F]FDG PET/CT Predict Response to Immunotherapy After 6 Months and Overall Survival in Patients with Lung Cancer or Malignant Melanoma? A Multicenter Retrospective Study

Aim: To assess the role of baseline 18F-fluorodeoxyglucose ([18F]FDG)-positron emission tomography/computed tomography (PET/CT) in predicting response to immunotherapy after 6 months and overall survival (OS) in patients with lung cancer (LC) or malignant melanoma (MM). Methods: Data from a multicenter, retrospective study conducted between March and November 2021 were analyzed. Patients >18 years old with a confirmed diagnosis of LC or MM, who underwent a baseline [18F]FDG-PET/CT within 1-2 months before starting immunotherapy and had a follow-up of at least 12 months were included. PET scans were examined visually and semiquantitatively by physicians at peripheral centers. The metabolic tumor burden (number of lesions with [18F]FDG-uptake) and other parameters were recorded. Clinical response was assessed at 3 and 6 months after starting immunotherapy, and OS was calculated as the time elapsing between the PET scan and death or latest follow-up. Results: The study concerned 177 patients with LC and 101 with MM. Baseline PET/CT was positive in primary or local recurrent lesions in 78.5% and 9.9% of cases, in local/distant lymph nodes in 71.8% and 36.6%, in distant metastases in 58.8% and 84%, respectively, in LC and in MM patients. Among patients with LC, [18F]FDG-uptake in primary/recurrent lung lesions was more often associated with no clinical response to immunotherapy after 6 months than in cases without any tracer uptake. After a mean 21 months, 46.5% of patients with LC and 37.1% with MM had died. A significant correlation emerged between the site/number of [18F]FDG foci and death among patients with LC, but not among those with MM. Conclusions: In patients with LC who are candidates for immunotherapy, baseline [18F]FDG-PET/CT can help to predict response to this therapy after 6 months, and to identify those with a poor prognosis based on their metabolic parameters. For patients with MM, there was only a weak correlation between baseline PET/CT parameters, response to therapy, and survival.

Impact of 68Ga-PSMA PET/CT in patients with metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide

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Background: 68Ga prostate specific membrane antigen positron emission tomography/computed tomography (68Ga-PSMA PET/CT) is a highly sensitive diagnostic tool to detect prostate metastatic sites even at low levels of Prostate Specific Antigen (PSA). We evaluated the impact of 68Ga-PSMA PET/CT in patients treated with enzalutamide as first-line therapy for mCRPC. Methods: In an observational prospective study, 67 consecutive mCRPC patients were treated with enzalutamide 160 mg once daily in first-line for mCRPC. 68Ga-PSMA PET/CT was performed at baseline, after 3 months, during follow-up and at PSA/clinical progression. Patients were evaluated on a monthly basis for serological PSA response and safety. We measured at baseline the sum of metabolic total volume (SMTV), mean standardized uptake volume (SSUVmean), maximum standardized uptake volume (SSUVmax) and total lesion activity (STLA), which is the product of SMTV and SSUVmean, for a maximum of 20 lesions. These parameters together with baseline PSA level, Eastern Cooperative Oncology Group performance status (ECOG PS), Gleason Score (GS) and age were analyzed by univariate and multivariate Cox regression models as potential predictors of progression-free survival (PFS) and overall survival (OS). Results: At the moment of the present analysis, 58 mCRPC patients were considered fully evaluable. The median age was 75 years (range, 47-91), ECOG PS was 0 in 47 cases (81%), 1-2 in 11 (19%), GS was <8 in 22 (38%), 8-10 in 36 (62%), the median baseline PSA was 2.66 µg/L (range 0.09-197). We observed a median SMTV of 5.73 cm3, median SSUVmax of 44.85, median SSUVmean of 25.80 and median STLA of 59.66. At the median follow-up of 52 months, median PFS was 28.9 months (95% CI 16.3-43.6), median OS was not reached (95% CI 36.8-not reached). In univariate analysis, SSUVmax and STLA were significant for PFS (p=0.015 and p=0.001, respectively) and OS (p=0.026 and p=0.019, respectively), while SSUVmean was significant only for OS (p=0.028). On multivariate analysis, STLA only remained significant for PFS (p<0.001) and OS (p=0.026). Conclusions: The assessment of mCRPC by 68Ga-PSMA PET/CT before starting enzalutamide was associated with longer median PFS and OS compared to prior studies using standard imaging only. STLA, expression of both volume and intensity of 68Ga-PSMA uptake, appeared the strongest parameter able to predict PFS and OS.

ITA-IMMUNO-PET: The Role of [18F]FDG PET/CT for Assessing Response to Immunotherapy in Patients with Some Solid Tumors

AIM

To examine the role of [18F]FDG PET/CT for assessing response to immunotherapy in patients with some solid tumors.

METHODS

Data recorded in a multicenter (n = 17), retrospective database between March and November 2021 were analyzed. The sample included patients with a confirmed diagnosis of a solid tumor who underwent serial [18F]FDG PET/CT (before and after one or more cycles of immunotherapy), who were >18 years of age, and had a follow-up of at least 12 months after their first PET/CT scan. Patients enrolled in clinical trials or without a confirmed diagnosis of cancer were excluded. The authors classified cases as having a complete or partial metabolic response to immunotherapy, or stable or progressive metabolic disease, based on a visual and semiquantitative analysis according to the EORTC criteria. Clinical response to immunotherapy was assessed at much the same time points as the serial PET scans, and both the obtained responses were compared.

RESULTS

The study concerned 311 patients (median age: 67; range: 31-89 years) in all. The most common neoplasm was lung cancer (56.9%), followed by malignant melanoma (32.5%). Nivolumab was administered in 46.3%, and pembrolizumab in 40.5% of patients. Baseline PET and a first PET scan performed at a median 3 months after starting immunotherapy were available for all 311 patients, while subsequent PET scans were obtained after a median 6, 12, 16, and 21 months for 199 (64%), 102 (33%), 46 (15%), and 23 (7%) patients, respectively. Clinical response to therapy was recorded at around the same time points after starting immunotherapy for 252 (81%), 173 (56%), 85 (27%), 40 (13%), and 22 (7%) patients, respectively. After a median 18 (1-137) months, 113 (36.3%) patients had died. On Kaplan-Meier analysis, metabolic responders on the first two serial PET scans showed a better prognosis than non-responders, while clinical response became prognostically informative from the second assessment after starting immunotherapy onwards.

CONCLUSIONS

[18F]FDG PET/CT could have a role in the assessment of response to immunotherapy in patients with some solid tumors. It can provide prognostic information and thus contribute to a patient's appropriate treatment. Prospective randomized controlled trials are mandatory.

Radiomics Analysis on [68Ga]Ga-PSMA-11 PET and MRI-ADC for the Prediction of Prostate Cancer ISUP Grades: Preliminary Results of the BIOPSTAGE Trial

Simple Summary

Radiomics analysis is used on magnetic resonance imaging – apparent diffusion coefficient (MRI-ADC) maps and [68Ga]Ga-PSMA-11 PET uptake maps to assess unique tumor traits not visible to the naked eye and predict histology-proven ISUP grades in a cohort of 28 patients. Our study’s main goal is to report imaging features that can distinguish patients with low ISUP grades from those with higher grades (ISUP one+) by employing logistic regression statistical models based on MRI-ADC and 68Ga-PSMA data, as well as assess the features’ stability under small contouring variations. Our findings reveal that MRI-ADC and [⁶⁸Ga]Ga-PSMA-11 PET imaging features-based models are equivalent and complementary for predicting low ISUP grade patients. These models can be employed in broader studies to confirm their ISUP grade prediction ability and eventually impact clinical workflow by reducing overdiagnosis of indolent, early-stage PCa.

Abstract

Prostate cancer (PCa) risk categorization based on clinical/PSA testing results in a substantial number of men being overdiagnosed with indolent, early-stage PCa. Clinically non-significant PCa is characterized as the presence of ISUP grade one, where PCa is found in no more than two prostate biopsy cores.MRI-ADC and [⁶⁸Ga]Ga-PSMA-11 PET have been proposed as tools to predict ISUP grade one patients and consequently reduce overdiagnosis. In this study, Radiomics analysis is applied to MRI-ADC and [⁶⁸Ga]Ga-PSMA-11 PET maps to quantify tumor characteristics and predict histology-proven ISUP grades. ICC was applied with a threshold of 0.6 to assess the features’ stability with variations in contouring. Logistic regression predictive models based on imaging features were trained on 31 lesions to differentiate ISUP grade one patients from ISUP two+ patients. The best model based on [⁶⁸Ga]Ga-PSMA-11 PET returned a prediction efficiency of 95% in the training phase and 100% in the test phase whereas the best model based on MRI-ADC had an efficiency of 100% in both phases. Employing both imaging modalities, prediction efficiency was 100% in the training phase and 93% in the test phase. Although our patient cohort was small, it was possible to assess that both imaging modalities add information to the prediction models and show promising results for further investigations.

Combining liquid biopsy and functional imaging analysis in metastatic castration-resistant prostate cancer helps predict treatment outcome

Plasma tumour DNA (ptDNA) is a potential early noninvasive biomarker of treatment outcome in metastatic castration-resistant prostate cancer (mCRPC). Herein, we investigated whether pretreatment ptDNA levels reflect metabolic tumour burden in mCRPC and better predict treatment outcome in combination with functional imaging. Targeted next-generation sequencing was performed to estimate the ptDNA fraction from 102 mCRPC patients receiving abiraterone or enzalutamide. The maximum standardized uptake value (SUVmax), total lesion activity (TLA) and metabolic tumour volume (MTV) were evaluated on 18 F-fluorocholine positron emission tomography/computed tomography. We assessed a Weibull multiple regression model to determine the combined impact of clinical, molecular and imaging characteristics on overall survival (OS) and progression-free survival (PFS), and to obtain prognostic scores. A significant association was seen between ptDNA and SUVmax, MTV and TLA. For survival analysis, patients were randomly allocated into a training (n = 68) and a validation (n = 34) set. In the training set, multivariable analyses showed that ptDNA, MTV and serum lactate dehydrogenase together with visceral metastasis were independent predictors of both OS and PFS. Prognostic scores were generated, with the identification of three groups of patients with significantly different median OS (29.2, 15.9 and 8.7 months) and PFS (13.3, 7.7 and 3.2 months) probabilities. The differences in median survival between risk groups were confirmed in the validation cohort for both OS and PFS. In our study, we showed that integrating plasma DNA analysis with functional imaging may improve prognostic risk stratification and treatment selection in mCRPC.

Theragnostic in neuroendocrine tumors

In the last few decades, the incidence and prevalence of neuroendocrine tumors has been increasing. The theragnostic approach, that allows the diagnosis and treatment of different neoplasms with the same ligand, is a typical nuclear medicine tool. Applied for years, is also pivotal in neuroendocrine tumors (NETs) where it has improved the diagnostic accuracy and the therapeutic efficacy with impact on patient's survival. Theragnostic also allows the identification of important prognostic factors such as tumor location and burden, presence of liver metastases and intensity of somatostatin receptors (SSTR) expression to consider in new and possibly combined studies to ameliorate patient's outcome. Moreover, the possibility to evaluate receptor expression even in non-NET malignancies has de facto widened the possible indications for PRRT. We believe that this innovative therapeutic approach will be implemented in next years by radiomics and biological tumors characterization to better address PRRT applications.

Diagnostic and Prognostic Potential of 18F-FET PET in the Differential Diagnosis of Glioma Recurrence and Treatment-Induced Changes After Chemoradiation Therapy

Background

MRI-based differential diagnosis of glioma recurrence (GR) and treatment-induced changes (TICs) remain elusive in up to 30% of treated glioma patients. We aimed to determine ¹⁸F-FET PET diagnostic performance in this clinical scenario, its outcome dependency on established prognostic factors, optimal ¹⁸F-FET semi-quantitative thresholds, and whether ¹⁸F-FET parameters may instantly predict progression-free survival (PFS) and overall survival (OS).

Methods

We retrospectively analyzed 45 glioma patients treated with chemoradiation therapy (32 males; mean age: 51 years, glioma grade: n=26 WHO4; n=15 WHO3; n=4 WHO2) who underwent ¹⁸F-FET PET to resolve differential diagnosis of GR and TICs raised by MRI performed in the preceding 2 weeks and depicting any of the following changes in their radiation field: volumetric increase of contrast-enhancing lesions; new contrast-enhancing lesion; significant increase in T2/FLAIR non-enhancing lesion without reducing corticosteroids. ¹⁸F-FET PET outcome relied on evaluation of maximum tumor-to-brain ratio (TBRmax), time-to-peak (TTP), and time-activity curve pattern (TAC). Metabolic tumor volume (MTV) and total tumor metabolism (TTM) were calculated for prognostic purposes. Standard of reference was repeat MRI performed 4–6 weeks after the previous MRI. Non-parametric statistics tested ¹⁸F-FET-based parameters for dependency on established prognostic markers. ROC curve analysis determined optimal cutoff values for ¹⁸F-FET semi-quantitative parameters. ¹⁸F-FET parameters and prognostic factors were evaluated for PFS and OS by Kaplan-Meier, univariate, and multivariate analyses.

Results

¹⁸F-FET PET sensitivity, specificity, positive predictive value, negative predictive value were 86.2, 81.3, 89.3, 76.5%, respectively; higher diagnostic accuracy was yielded in IDH-wild-type glioma patients compared to IDH-mutant glioma patients (sensitivity: 81.8 versus 88.9%; specificity: 80.8 versus 81.8%). KPS was the only prognostic factor differing according to ¹⁸F-FET PET outcome (negative versus positive). Optimal ¹⁸F-FET cutoff values for GR were TBRmax ≥ 2.1, SUVmax ≥ 3.5, and TTP ≤ 29 min. PFS differed based on ¹⁸F-FET outcome and related metrics and according to KPS; a different OS was observed according to KPS only. On multivariate analysis, ¹⁸F-FET PET outcome was the only significant PFS factor; KPS and age the only significant OS factors.

Conclusion

¹⁸F-FET PET demonstrated good diagnostic performance. ¹⁸F-FET PET outcome and metrics were significantly predictive only for PFS.

Flare phenomenon in prostate cancer: recent evidence on new drugs and next generation imaging

Over the years, an increasing proportion of metastatic prostate cancer patients has been found to experience an initial bone flare phenomenon under both standard therapies (androgen deprivation therapy, chemotherapy, radiotherapy, abiraterone, enzalutamide) and novel agents (immunotherapy, bone-targeting radioisotopes). The underlying biological mechanisms of the flare phenomenon are still elusive and need further clarification, particularly in relation to different types of treatment and their treatment response assessment. Flare phenomenon is often underestimated and, in some cases, can negatively affect clinical outcome. In cases with suspected bone flare, the treatment should be continued for a minimum of 12 more weeks before further decisions about efficacy can be taken. Physicians and patients should be aware of this effect to avoid unwarranted anxiety and inadequate early discontinuation of treatment. This review aims at highlighting new evidence on flare phenomenon arising after the introduction of new drugs extending across the biochemical, radiographic and clinical spectrum of the disease.

Combining molecular and functional imaging in metastatic castration-resistant prostate cancer (mCRPC)

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Background: Recently, plasma tumour DNA (ptDNA) has been identified as a potential early noninvasive biomarker of treatment response in mCRPC patients ( Conteduca, Br J Cancer 2020). In this study, we sought to determine whether pre-treatment ptDNA could accurately reflect metabolic tumor burden in mCRPC and if it could be in combination with functional imaging could provide better prognostication. Methods: Between October 2011 and June 2016, 102 plasma samples from mCRPC patients treated with abiraterone or enzalutamide were collected. Targeted next-generation sequencing was performed to determine baseline ptDNA fraction. Maximum standardized uptake value (SUVmax), total lesion activity (TLA), and metabolic tumour volume (MTV) were calculated on 18F-fluorocholine positron emission tomography/computed tomography. A Weibull multiple regression model was adopted to evaluate the combined impact of clinical, molecular and imaging features on overall survival (OS) and to obtain a prognostic score. Each variable was allotted a “partial score” that depended on the size of the regression coefficient. Total scores ranged between 0 and 5.85 and assigned patients to 3 different risk groups according to 18-months survival probability: group I, >70%; group II 30%-70%; and group III, <30%. We estimated OS probabilities by the exponential model and by the Kaplan-Meier method. Results: We observed a significant association between ptDNA levels dichotomized as below or above median plasma tumor fraction (low ptDNA≤0.188 versus high ptDNA>0.188) and median SUVmax (p<0.0001), MTV (p=0.0005) and TLA (p<0.0001). Patients were randomly divided into a training set (n=68) and a validation set (n=34). In the training cohort, we performed a multivariable analysis showing that visceral metastasis, serum LDH, MTV and ptDNA were independent predictors of OS [HR=2.64, 95%CI 1.32-5.26, p=0.006; HR=3.69, 95%CI 1.98-6.87, p<0.0001; HR=1.91, 95%CI 1.13-3.21, p=0.015; and HR=2.64, 95%CI 1.32-5.26, p=0.003, respectively]. In the training set, median OS was significantly different among the 3 risk groups (risk group I, 29.2 months [95% CI, 18.3 to 37.0 months]; risk group II, 15.9 months [95% CI, 10.6 to 24.0 months]; and risk group III, 8.7 months [95% CI, 6.3 to 15.4 months]; p<0.0001). Similar results were observed in the validation set groups (risk group I, 23.4 months [95% CI, 8.1 to 38.5 months]; risk group II, 13.3 months [95% CI, 3.7 to 18.0 months]; and risk group III, 7.3 months [95% CI, 2.6 to 11.8 months]; p=0.001). Conclusions: Integrating plasma DNA analysis with functional imaging may improve prognostic risk stratification and treatment selection in mCRPC patients. A larger prospective evaluation is now warranted.

68Ga-PSMA-11 PET/CT-Guided Stereotactic Body Radiation Therapy Retreatment in Prostate Cancer Patients with PSA Failure after Salvage Radiotherapy

(1) Purpose: To investigate the role of ⁶⁸Ga-PSMA-11 PET/CT in guiding retreatment stereotactic body radiation therapy (SBRT) in prostate cancer (PCa) patients in biochemical recurrence (BCR) after salvage radiotherapy (S-RT). (2) Methods: We retrospectively evaluated PCa patients previously treated with S-RT on the prostate bed and with proven serum prostate antigen (PSA) failure after S-RT. In all patients (pts), ⁶⁸Ga-PSMA-11 PET/CT was positive in the prostate bed only and guided retreatment SBRT. All retreatments were performed by applying the same radiotherapy protocol (median dose of 18 Gy/3 fractions; IQR 18-21 Gy). The median follow-up was 27 months (range 4-35 months). (3) Results: 38 consecutive patients were considered in this analysis. The overall median PSA level before RT was 1.10 ng/mL (IQR 0.82-2.59). PSA decreased at 3 and 6 months after treatment, with a median value of 0.60 ng/mL (IQR 0.31-0.96; p < 0.001) and 0.51 ng/mL (IQR 0.29-1.17; p < 0.001), respectively. Overall, biochemical recurrence-free survival (b-RFS) was 15.0 months (95% CI 13-23). Grade-1 toxicity was reported in 31.6% of patients (12/38). (4) Conclusion: These results confirm that ⁶⁸Ga-PSMA-11-PET/CT is able to identify the site of recurrence in patients who have failed S-RT, thus supporting the use of metastases-directed radiotherapy as a safe and effective treatment.

Targeted Alpha Therapy in mCRPC (Metastatic Castration-Resistant Prostate Cancer) Patients: Predictive Dosimetry and Toxicity Modeling of 225Ac-PSMA (Prostate-Specific Membrane Antigen)

Radioligand therapy is a type of internal radiotherapy combining a short-range radioisotope labeled to a carrier with a high affinity for a specific receptor expressed on tumor cells. Targeted alpha therapy (TAT) combines a high-linear energy transfer (LET) emitter (²²⁵Ac) with a prostate-specific membrane antigen (PSMA) carrier, specifically binding tumor cells in patients with metastatic castration-resistant prostate cancer. Although the antitumor activity of ²²⁵Ac-PSMA is well-documented, this treatment is nowadays only used as salvage therapy because the high incidence of xerostomia limits the therapeutic window. Thus, methods to reduce salivary toxicity and models able to describe xerostomia incidence are needed. We recently studied the efficacy of salivary gland protectors administered in combination with ¹⁷⁷Lu-PSMA therapy. Starting from these data, we performed a predictive dosimetric evaluation of ²²⁵Ac-PSMA to assess the impact of salivary gland protectors in TAT. ²²⁵Ac-PSMA predictive dosimetry was performed in 13 patients treated with ¹⁷⁷Lu-PSMA. Sequential whole-body planar images were acquired 0.5–1, 16–24, 36–48, and 120 h post-injection. ¹⁷⁷Lu time-activity curves were corrected for ²²⁵Ac physical decay and assumed in equilibrium for all daughters. The OLINDA/EXM spherical model was used for dose estimation of the parotid and submandibular glands. The dose for each daughter was calculated and summed for the total dose estimation. The biologically effective dose formalism was extended to high-LET emitters. For the total biologically effective dose formalism extended to high-LET emitters, including the contribution of all daughter isotopes, the brachytherapy formalism for a mixture of radionuclides was implemented. Equivalent doses in 2 Gy/fraction (EQD2) were then calculated and compared with the normal tissue complication probability model derived from external beam radiotherapy for grade ≥2 xerostomia induction. Median predictive doses were 0.86 Bd_RBE5/MBq for parotid glands and 1.05 Bd_RBE5/MBq for submandibular glands, with a 53% reduction compared with previously published data. The results show that the radiobiological model implemented is conservative, as it overestimates the complication rate with respect to the clinical data. Our data shows the possibility of reducing salivary gland uptake in TAT with the coadministration of organ protectors, but these results should be confirmed for TAT with ²²⁵Ac-PSMA by carrying out prospective trials with defined toxicity endpoints and dosimetry procedures.

Clinical value of negative 68Ga-PSMA PET/CT in the management of biochemical recurrent prostate cancer patients

PURPOSE

To evaluate the clinical value of ⁶⁸Ga-PSMA PET/CT negativity in patients with biochemical recurrent prostate cancer (BCR).

METHODS

One hundred three BCR patients (median age, 70 years; median PSA, 0.47 ng/mL) with negative ⁶⁸Ga-PSMA PET/CT, followed up for at least 1 year, were retrospectively identified in a database of 1003 consecutive patients undergoing ⁶⁸Ga-PSMA PET/CT for BCR. Clinical recurrence (CR) was determined or excluded on follow-up imaging selected as per clinical practice. Clinical recurrence-free survival (CRFS) was computed from the date of negative ⁶⁸Ga-PSMA PET/CT to the date of evident disease; frequencies of CRFS were described as per ISUP patient subset (subset 1: ISUP grades 1 and 2; subset 2: ISUP grade 3; subset 3: ISUP grades 4 and 5) and other conventional variables.

RESULTS

In 57 patients out of 103 (55.3%), CR was detected in the prostatic fossa (45.6%), nodes (38.6%), and bone (15.8%). The median CRFS was 15.4 months (range, 12.1-20.5), with a CRFS at 12 months in 61.4% of cases (range, 50.9-70.4) whereas the 24-month CRFS was 34.8% (range, 24-45.8). ISUP subset 1 benefited from significantly longer CRFS compared to subset 2 and subset 3 (median CRFS, 20.5 months, 12.6 months, and 12.1 months, respectively). ISUP subset 3 had significantly poorer 24-month CRFS (9.3%) compared to subset 1 (47.8%) and subset 2 (33.5%). At the univariate and multivariate analyses, the ISUP subset was the only significant risk factor for clinical relapse; ISUP subset 3 and subset 2 patients held a higher risk of CR compared to subset 1 patients (HR of 2.75 [1.35-5.57] for subset 3 versus subset 1; HR of 2.08 [1.11-3.88] for subset 2 versus subset 1).

CONCLUSION

⁶⁸Ga-PSMA PET/CT negativity in early BCR patients (PSA < 0.5 ng/mL) with low-grade primary prostate cancer (ISUP1 and 2) may support the exploration of a clinical surveillance approach in future prospective studies.

A Whole Body Dosimetry Protocol for Peptide-Receptor Radionuclide Therapy (PRRT): 2D Planar Image and Hybrid 2D+3D SPECT/CT Image Methods

Peptide-receptor-radionuclide-therapy (PPRT) is a targeted therapy that combines a short-range energy radionuclide with a substrate with high specificity for cancer cell receptors. After injection, the radiotracer is distributed throughout the entire body, with a higher uptake in tissues where targeted receptors are overexpressed. The use of beta/gamma radionuclide emitters enables therapy imaging (beta-emission) and post-therapy imaging (gamma-emission) to be performed at the same time. Post-treatment sequential images permit absorbed dose calculation based on local uptake and wash-in/wash-out kinetics. We implemented a hybrid method that combines information derived from both 2D and 3D images. Serial whole-body images and blood samples are acquired to estimate the absorbed dose to different organs at risk and to lesions disseminated throughout the body. A single 3D-SPECT/CT image, limited to the abdominal region, overcomes projection overlap on planar images of different structures such as the intestines and kidneys. The hybrid 2D+3D-SPECT/CT method combines the effective half-life information derived from 2D planar images with the local uptake distribution derived from 3D images. We implemented this methodology to estimate the absorbed dose for patients undergoing PRRT with ¹⁷⁷Lu-PSMA-617. The methodology could, however, be implemented with other beta-gamma radiotracers. To date, 10 patients have been enrolled into the dosimetry study with ¹⁷⁷Lu-PSMA-617 combined with drug protectors for kidneys and salivary glands (mannitol and glutamate tablets, respectively). The median ratio between kidney uptake at 24 h evaluated on planar images and 3D-SPECT/CT is 0.45 (range:0.32-1.23). The comparison between hybrid and full 3D approach has been tested on one patient, resulting in a 1.6% underestimation with respect to full 3D (2D: 0.829 mGy/MBq, hybrid: 0.315 mGy/MBq, 3D: 0.320 mGy/MBq). Treatment safety has been confirmed, with a mean absorbed dose of 0.73 mGy/MBq (range:0.26-1.07) for kidneys, 0.56 mGy/MBq (0.33-2.63) for the parotid glands and 0.63 mGy/MBq (0.23-1.20) for submandibular glands, values in accordance with previously published data.

Multimodal Approach to Outcome Prediction in Metastatic Castration-Resistant Prostate Cancer by Integrating Functional Imaging and Plasma DNA Analysis

PURPOSE

Biomarkers for treatment personalization in metastatic castration-resistant prostate cancer (mCRPC) could help improve patient outcomes. Multiple tests on blood have reported associations with poorer outcome, including serum lactate dehydrogenase (LDH), chromogranin A (CGA), neutrophil:lymphocyte ratio (NLR), and, recently, copy number (CN) of androgen receptor (AR) in plasma DNA. Biologic data suggest an association between choline uptake and AR signaling. We aimed to integrate 18F-fluorocholine (FCH) uptake on positron emission tomography/computed tomography (PET/CT) scanning with plasma AR CN and other routinely obtained circulating biomarkers to evaluate their association with outcome.

MATERIALS AND METHODS

We determined plasma AR CN by digital droplet polymerase chain reaction from 105 mCRPC samples collected before abiraterone (n = 65) or enzalutamide (n = 40) therapy in the before (n = 26) and after (n = 79) chemotherapy settings. Pretreatment serum LDH, CGA, and NLR were also measured. FCH-PET/CT scan was performed at baseline, and maximum standardized uptake value (SUVmax), total lesion activity (TLA), and metabolic tumor volume (MTV) were calculated. Main end points were the correlation of FCH-PET/CT parameters with circulating biomarkers and their impact on outcome.

RESULTS

Plasma AR CN gain was observed in 27 patients (25.7%), and it correlated significantly with higher median SUVmax, TLA, and MTV values ( P < .001). Kaplan-Meier curves showed significantly worse progression-free survival and overall survival in patients with plasma AR gain and higher SUVmax, TLA, and MTV values ( P < .001 in each prognostic group). Conversely, no association was reported for prostate-specific antigen response. On multivariable analysis of overall survival, we showed as independent factors AR gain (hazard ratio [HR], 1.92; 95% CI, 1.07 to 3.47; P = .029), presence of visceral metastasis (HR, 3.04; 95% CI, 1.66 to 5.58; P = < .001), LDH (HR, 2.95; 95% CI, 1.72 to 5.05; P < .001), NLR (HR, 3.51; 95% CI, 2.14 to 5.74; P < .001), serum CGA (HR, 3.36; 95% CI, 1.99 to 5.67; P < .001), and MTV (HR, 2.09; 95% CI, 1.25 to 3.50; P = .005).

CONCLUSION

Our results indicate the potential usefulness of integrating functional imaging with plasma DNA analysis and other noninvasive biomarkers as a tool to improve treatment selection for CRPC. A larger prospective evaluation is warranted.

Prognostic value of 18F-choline PET/CT metabolic parameters in patients with metastatic castration-resistant prostate cancer treated with abiraterone or enzalutamide

PURPOSE

The role of 18F-choline positron emission tomography/computed tomography (FCH-PET/CT) in patients with metastatic castration-resistant prostate cancer (mCRPC) has been firmly established in recent years. We analyzed the prognostic value of functional parameters such as mean standardized uptake volume (SUVmean), maximum standardized uptake volume (SUVmax), metabolic total volume (MTV; the volume of interest consisting of all spatially connected voxels within a fixed threshold of 40% of the SUVmax), and total lesion activity (TLA: the product of MTV and mean standardized uptake value) estimated with FCH-PET/CT in mCRPC patients in progression after docetaxel and treated with new antiandrogen receptor therapies, abiraterone or enzalutamide.

METHODS

We retrospectively studied 94 mCRPC patients, mean age 74 years (range 42-90), previously treated with docetaxel who were treated with either abiraterone (n = 52) or enzalutamide (n = 42). An FCH-PET/CT was performed at baseline, and patients were evaluated on a monthly basis for serological PSA response and every 3 months for radiological response. We measured MTV, SUVmean, SUVmax and TLA for each lesion and analyzed the sum of MTV (SMTV), SUVmean (SSUVmean), SUVmax (SSUVmax) and TLA (STLA) values for a maximum of 20 lesions. Univariate analysis was used to correlate these data with PFS and OS.

RESULTS

We observed a median SMTV of 130 cm³, median SSUVmax of 106.5 and a median STLA of 495,070. All of these parameters were significant for PFS and OS in univariate analysis, while only STLA was significant for PFS and OS in multivariate analysis after adjusting for lesion and age (p < 0.0001 and p = 0.001, respectively). Baseline PSA values maintained a certain reliability for OS (p = 0.034).

CONCLUSIONS

Semiquantitative parameters of FCH-PET/CT play a prognostic role in mCRCP patients treated with abiraterone or enzalutamide.

Reduction of 68Ga-PSMA renal uptake with mannitol infusion: preliminary results

PURPOSE

Urea-based prostate-specific membrane antigen (PSMA) ligands labelled with ⁶⁸Ga or ¹⁷⁷Lu are new tracers with great potential for theranostic approaches in prostate cancer. However, clinical studies have shown that the kidneys are one of the off-target organs along with the salivary and lacrimal glands. In the kidneys, PSMA is physiologically expressed in the apical epithelium of the proximal tubules, and mannitol acts as an osmotic diuretic in these tubules. We investigated the potential of mannitol to reduce renal uptake of ⁶⁸Ga-PSMA.

METHODS

Kidney uptake (SUVmax) was calculated in nine patients undergoing ⁶⁸Ga-PSMA PET/CT at baseline (b-PET/CT) and after intravenous infusion of 500 ml of 10% mannitol (m-PET/CT). Two different infusion schemes for mannitol were used: (1) 500 ml mannitol was infused over 40 min after ⁶⁸Ga-PSMA administration (A-infusion) and (2) 250 ml mannitol was infused over 15 min before and again after ⁶⁸Ga-PSMA administration (B-infusion).

RESULTS

In patients receiving the A-infusion, mean SUV_max increased by 11.9% and 7.4% in the right and left kidney, respectively. In patients receiving the B-infusion, mean SUV_max decreased by 24.3% and 22.4% in the right and left kidney, respectively.

CONCLUSION

Our preliminary findings indicate that mannitol may play a role in reducing off-target ⁶⁸Ga-PSMA renal uptake. Administration of the osmotic diuretic should be rapid and start before ⁶⁸Ga-PSMA injection. These results warrant dosimetric studies in patients treated with ¹⁷⁷Lu-PSMA to find the best scheme for mannitol administration.

Peptide receptor radionuclide therapy with (177)Lu-DOTATATE in advanced bronchial carcinoids: prognostic role of thyroid transcription factor 1 and (18)F-FDG PET

PURPOSE

Typical and atypical carcinoids (TC and AC) represent 20 - 25 % of all neuroendocrine tumours. No standard therapeutic approach is available for patients with advanced disease. The aim of this phase II study was to investigate the efficacy and safety of peptide receptor radionuclide therapy with (177)Lu-DOTATATE (Lu-PRRT) and the role of thyroid transcription factor 1 (TTF-1) and (18)F-FDG PET as prognostic factors in patients with advanced TC or AC.

METHODS

A total of 34 consecutive patients with radiologically documented progressive disease were treated with Lu-PRRT at a therapeutic cumulative activity of 18.5 or 27.8 GBq in four or five cycles according to the patient's kidney function and bone marrow reserve. Information on TTF-1 was available in all patients. FDG PET studies prior to Lu-PRRT were available in 29 patients.

RESULTS

The median follow-up was 29 months (range 7 - 69 months). The disease control rate (DCR) in patients with TC was 80 %: 6 % complete response, 27 % partial response and 47 % stable disease. The median progression-free survival (mPFS) was 20.1 months (95 % CI 11.8 - 26.8 months). Stable disease was achieved in 47 % of patients with AC with a mPFS of 15.7 months (95 % CI 10.6 - 25.9 months). No major acute or delayed toxicity occurred in either group or with either cumulative activity. mPFS in patients with TTF-1-negative TC was 26.3 months (95 % CI 12.9 - 45.2 months), but in patients with TTF-1-positive TC mPFS was 7.2 months (4.2 - 14.0 months; p = 0.0009). FDG PET was negative in 13 patients (10 TC and 3 AC) and positive in 16 patients (4 TC and 12 AC). The mPFS in the FDG PET-negative group was 26.4 months (95 % CI 14.2 - 48.9 months) and 15.3 months (11.7 - 31.1 months) in the FDG PET-positive group.

CONCLUSION

Lu-PRRT showed antitumour activity in terms of DCR and PFS and proved safe, even in patients with a higher risk of side effects. TTF-1 would appear to be a prognostic factor. FDG PET positivity in bronchial carcinoids is a hallmark of aggressive tumour and is more frequent in patients with AC than in those with TC.

Biomarkers and Molecular Imaging as Predictors of Response to Neoadjuvant Chemoradiotherapy in Patients With Locally Advanced Rectal Cancer

Standard treatment of patients with locally advanced rectal cancer (LARC) includes neoadjuvant chemoradiotherapy (NCRT) followed by surgery. Tumor regression after NCRT varies substantially among individuals and pathological complete response is a known prognostic factor for LARC. The identification of a predictive model for response to chemoradiotherapy would help clinicians to identify patients who would probably benefit from multimodal treatment and to perform an early assessment of individual prognosis. Carcinoembryonic antigen has proven to be a good predictor of response in several clinical trials. Other widely studied predictive models in LARC include molecular biomarkers, analyzed at various levels and by different techniques, and molecular imaging, in particular magnetic resonance imaging and positron emission tomography/computed tomography. Although none of the studied markers have been approved in clinical practice, their evaluation in larger, prospective trials and in combined predictive models could be of use to define tailored therapeutic strategies.

(18)F-Fluorocholine PET/CT for early response assessment in patients with metastatic castration-resistant prostate cancer treated with enzalutamide

PURPOSE

We investigated the role of (18)F-methylcholine (FCH) PET/CT in the early evaluation of patients with metastatic castration-resistant prostate cancer (mCRPC) treated with enzalutamide.

METHODS

The study group comprised 36 patients with a median age of 72 years (range 48-90 years) who were treated with enzalutamide 160 mg once daily after at least one chemotherapeutic regimen with docetaxel. Patients were evaluated monthly for serological prostate-specific antigen (PSA) response. FCH PET/CT was performed at baseline and repeated after 3-6 weeks. Univariate and multivariate Cox regression models addressed potential predictors of progression-free survival (PFS) and overall survival (OS).

RESULTS

At a median follow-up of 24.2 months (range 1.8-27.3 months), 34 patients were evaluable for early FCH PET/CT evaluation of response, and of these 17 showed progressive disease (PD) and 17 had stable disease or a partial response. A decrease in PSA level of more than 50% was observed in 21 patients. Early FCH PET/CT PD predicted radiological PD 3 months in advance of CT in 12 of 18 patients (66%) and was discordant with the decrease in PSA level in 13 patients. In 6 of these, biochemical PD was confirmed in 2 months. In multivariate analysis, only decrease in PSA level and FCH PET/CT were significant predictors of PFS (p = 0.0005 and p = 0.029, respectively), whereas decrease in PSA level alone was predictive of OS (p = 0.007).

CONCLUSION

This is one of the first studies to evaluate the role of FCH PET/CT as an early predictor of outcome in mCRPC patients treated with enzalutamide. Our preliminary results suggest that the combination of FCH PET/CT and decrease in PSA level could be a valid tool to predict PFS in mCRPC patients. PSA remains the single most important prognostic factor, while FCH PET/CT does not add more information on OS beyond that obtained from PSA. Further studies in larger populations are needed to confirm these data and to clarify the role of FCH PET/CT in predicting response to enzalutamide in mCRPC patients.

Early outcome prediction on 18F-fluorocholine PET/CT in metastatic castration-resistant prostate cancer patients treated with abiraterone

OBJECTIVE

We investigated the role of 18F-fluorocholine positron emission tomography/computed tomography (FCH-PET/CT) in the early evaluation of abiraterone and outcome prediction in patients with metastatic castration-resistant prostate cancer (CRPC).

PATIENT AND METHODS

Forty-three patients with metastatic CRPC progressing after docetaxel received abiraterone 1,000 mg daily with prednisone 5 mg twice daily. Patients were evaluated monthly for serological PSA response and safety. FCH-PET/CT was done at baseline and after 3 to 6 weeks. Univariate and multivariate Cox regression models addressed potential predictors of progression-free survival (PFS) and overall survival (OS).

RESULTS

Declines in PSA level of ≥50% were seen in 21 of 43 (49%) patients. Forty-two patients were evaluable for FCH-PET/CT response. FCH-PET/CT bone flare was observed in 4 of 42 (10%) evaluable patients. In univariate analysis, PSA decline and FCH-PET/CT response predicted PFS, while PSA decline and FCH-PET/CT (progression vs non progression) predicted OS. In multivariate analysis, only FCH-PET/CT (progression vs nonprogression) remained significant for PFS and OS (p = 0.022 and p = 0.027, respectively).

CONCLUSION

Early FCH-PET/CT can predict clinical outcome in CRPC beyond PSA response. These data support further studies on FCH-PET/CT for abiraterone monitoring and outcome prediction in patients with CRPC.

Early response assessment and bone flare phenomenon on 18F-fluorocholine positron emission tomography/computed tomography (FCH-PET/CT) in patients (pts) with metastatic castration-resistant prostate cancer (CRPC) treated with abiraterone acetate

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Background: In this prospective study, in patients with CRPC previously treated with docetaxel, we evaluated prostate specific antigen (PSA) and FCH-PET/CT for early response assessment to abiraterone acetate, and assessed frequency of early FCH-PET/CT discordant with PSA and clinical response. Methods: Twenty nine metastatic CRPC pts progressing after docetaxel chemotherapy received abiraterone acetate 1,000 mg daily with prednisone 5 mg twice daily in continuous 28-day cycles. Patients were evaluated monthly for serological PSA response and safety. FCH-PET/CT was repeated after 4-6 weeks and a CT scan was done after 3 months of abiraterone acetate. FCH-PET/CT bone flare was defined as the combination, after 3 months of therapy, of an interpreting radiologist’s report indicating progressive disease (PD) in context of a ≥50% decline in PSA, no PD at 3-month CT scan, with FCH-PET/CT improvement or stability 2-3 months later. Results: Three of 29 patients treated with abiraterone acetate did not perform the follow-up FCH-PET/CT due to rapidly PD with a decline in performance status. Of the remaining 26 patients, 4 are still undergoing early response evaluation. Twenty two pts, median age was 71 yrs (range, 57-86 yrs) were evaluable for this analysis. A ≥50% PSA decline was observed in 15/22 (68%) evaluable pts. Undetectable PSA levels (≤0.1 ng/mL) occurred in one case. Early FCH PET/CT response assessment was as follows: complete response (n=2, 9%), partial response (n=7, 32%), stable disease (n=3, 14%), PD (n=10, 45%), but in 4 of 10 pts with PD a bone flare phenomenon on FCH PET/CT was observed. PSA decline ≥50% and FCH PET/CT response correlated in 19 of 22 pts (86%). Conclusions: Discordant findings between serologic PSA response and increases in early FCH-PET/CT bone lesion intensity are reported here for the first time in CRPC. Further investigation is needed to clarify the confounding effect of FCH-PET/CT bone flare on patient management and interpretation of results.

PET/CT imaging in different types of lung cancer: an overview

Lung cancer (LC) still represents one of the most common tumours in both women and men. PET/CT is a whole-body non-invasive imaging procedure that has been increasingly used for the assessment of LC patients. In particular, PET/CT added value to CT is mainly related to a more accurate staging of nodal and metastatic sites and to the evaluation of the response to therapy. Although the most common PET tracer for LC evaluation is 18F-FDG, new tracers have been proposed for the evaluation of lung neuroendocrine tumours (68Ga-DOTA-peptides, 18F-DOPA) and for the assessment of central nervous system metastasis (11C-methionine). This review focuses on the main clinical applications and accuracy of PET/CT for the detection of non-small cells lung cancer (NSCLC), broncho-alveolar carcinoma (BAC), small cells lung cancer (SCLC), lung neuroendocrine tumours (NET) and solitary pulmonary nodules (SPN).

PET/CT and radiotherapy in gynecological cancer

Molecular imaging, in particular, positron emission tomography (PET), has brought an additional dimension to management of patients with cancer and to radiation therapy planning. The combination of PET and computed tomography (CT) in a single system (PET/CT) to form an inherently fused anatomical and functional dataset has provided an imaging modality which could be used as the prime tool in the delineation of tumour volumes and the preparation of patient treatment plans, especially when integrated with virtual simulation. PET imaging (typically using ¹⁸F-FDG) can provide data on metabolically active tumour volumes. These functional data have the potential to modify treatment volumes and to guide treatment delivery to cells with particular metabolic characteristics. Depending on its sensitivity and specificity, ¹⁸F-FDG PET has been shown to influence the selection of target volumes also in gynecological cancer. The potential of such data from PET was recognized at an early stage and was integrated into the radiotherapy treatment for some gynecological malignancies. In particular ¹⁸F-FDG PET has been demonstrated to be useful in patients with cervical cancer candidate to radiotherapy; preliminary data suggest a potential use also in patients with endometrial cancer, uterine sarcoma and ovarian cancer. This paper reviews the state of the art of the integration of PET and PET/CT applications in radiotherapy, and the use of ¹⁸F-FDG PET in disease staging, patient selection, treatment planning and treatment evaluation in gynaecological malignancies, in particular in patients with cervical cancer, endometrial cancer, uterine sarcoma and ovarian cancer.

[Use of the pancreolauryl test in the diagnosis of exocrine pancreatic insufficiency. Preliminary results]

The Pancreolauryl Test (PLT), a tubeless test used to study exocrine pancreatic function, was performed in 18 patients (8 healthy controls and 10 patients with suspected chronic pancreatitis) to evaluate its sensitivity and clinical applicability. The sensitivity rate of PLT was 75%, the specificity 85.7%, the predictive value of a positive test 60% and of a negative test 92.3%. The PLT proved to be a non invasive, easy to perform test; besides it was acceptable to the patients, without collateral effects.