Metastatic Prostate Cancer Research Articles

Influence of metastatic sites and burden on oncological outcomes in patients progressing to metastatic castration resistant prostate cancer

PurposeMetastatic castration-resistant prostate cancer (mCRPC) patients harbor reduced life expectancy after first-line treatment progression. Currently, no information is available regarding the influence of metastatic sites and osseous burden on progression-free (PFS) and overall survival (OS) of mCRPC patients.MethodsWe relied on the Frankfurt Metastatic Cancer Database of the Prostate (FRAMCAP) database to select patients progressing to mCRPC and stratified them according to lymph node vs. osseous vs. visceral metastatic sites. Moreover, we stratified osseous mCRPC patients regarding the number of metastatic lesions. Endpoints were PFS and OS in uni- and multivariable Cox regression models.ResultsOf 363 patients, 9.4% harbored M1a vs. 78% M1b vs. 12% M1c mCRPC with significantly higher PSA in M1b (9 vs. 22 vs. 8ng/ml). Rates of DeNovo (15% vs. 60% vs. 56%) were significantly lower in the M1a mCRPC group, compared to M1b and M1c (p < 0.001). In PFS analyses, a median of 12.7 vs. 10.1 vs. 15.9 months for M1a vs. M1b vs. M1c mCRPC was observed (p > 0.05). In multivariable Cox regression models, M1c mCRPC was independently at higher risk for progression (hazard ratio [HR]: 5.93, p = 0.048), relative to M1a. Regarding OS, significant differences were observed (p = 0.002), with median OS of 58 vs. 42 vs. 25 months for M1a vs. M1b vs. M1c mCRPC and corresponding HRs of 1.54 (p = 0.11) and 2.76 (p < 0.01). In multivariable models M1c mCRPC was associated with higher risk of death (HR: 3.56, p = 0.049), relative to M1a. No differences were observed after stratification according to number of bone lesions (all p ≥ 0.05).ConclusionM1c mCRPC patients are independently at higher risk for progression and death, while M1a patients harbor best cancer-control outcomes.

Prostate-Specific Antigen Stratification for Predicting Advanced Prostate Cancer Events in Men Approaching Age Limits for Recommended Screening.

Our goal was to quantify the ability of various PSA values in predicting the likelihood of developing metastatic or fatal prostate cancer in older men. We used a random sample of patients in the US Veterans Health Administration to identify 80,706 men who had received PSA testing between ages 70 to 75. Our primary end point was time to development of either metastatic prostate cancer or death from prostate cancer. We used cumulative/dynamic modeling to account for competing events (death from non-prostate cancer causes) in studying both the discriminative ability of PSA as well as for positive predictive value and negative predictive value at 3 time points. PSA demonstrated time-dependent predictive discrimination, with receiver operating characteristic area under the curve at 5, 10, and 14 years decreasing from 0.83 to 0.77 to 0.73, respectively, but without statistically significant difference when stratified by race. At PSA thresholds between 1 and 8 ng/mL, the positive predictive value of developing advanced prostate cancer was significantly greater in Black than White patients. For instance, at a PSA > 3, at 5, 10, and 14 years, White patients had 2.4%, 2.9%, and 3.7% risk of an event, whereas Black patients had 4.3%, 6.5%, and 8.3% risk. In men aged 70 to 75 deciding whether to cease PSA testing with borderline-elevated PSA values, the risk of developing metastatic or fatal prostate cancer is quantifiable and relatively low. Risk assessment in this setting must account for the higher incidence of prostate cancer in Black men.

Predictive genomic and transcriptomic analysis on endoscopic ultrasound-guided fine needle aspiration materials from primary pancreatic adenocarcinoma: a prospective multicentre study

We apply endoscopic ultrasound-guided fine needle aspiration biopsy to cytopathologically diagnose and sample nucleic acids from primary tumours regardless of the disease stage. 397 patients with proven pancreatic adenocarcinoma were included and followed up in a multicentre prospective study. DNA and mRNA were extracted from materials of primary tumours obtained by endoscopic ultrasound-guided fine needle aspiration biopsy and analysed using targeted deep sequencing and RNAseq respectively. The variant allele frequency of the KRAS mutation was used to evaluate the tumour cellularity, ranging from 15 to 20% in all cells, regardless of the tumour stage. The molecular profile of metastatic primary tumours significantly differed from other types of tumours, more frequently having TP53 mutations (p=0.0002), less frequently having RNF43 mutations, and possessing more basal-like mRNA component (p=0.001). Molecular markers associated with improved overall survival were: mutations in homologous recombination deficiency genes in patients who received first-line platinum-based chemotherapy (p=0.025) and wild-type TP53 gene in patients with locally advanced tumours who received radio-chemotherapy (p=0.01). The GemPred transcriptomic profile was associated with a significantly better overall survival in patients with locally advanced or metastatic pancreatic cancer who received a gemcitabine-based first-line treatment (p=0.019). The combination of genomic and transcriptomic analyses of primary pancreatic tumours enables us to distinguish metastatic tumours from other tumour types. Our molecular strategy may assist in predicting overall survival outcomes for platinum or gemcitabine-based chemotherapies, as well as radio-chemotherapy. Institut National Du Cancer (BCB INCa_7294), CHU of Toulouse, Inserm and Ligue Nationale Contre le Cancer (CIT program).

Multivariable models of outcomes with [177Lu]Lu-PSMA-617: analysis of the phase 3 VISION trial

[177Lu]Lu-PSMA-617 (177Lu-PSMA-617) prolonged life in patients with metastatic castration-resistant prostate cancer (mCRPC) in VISION (NCT03511664). However, distinguishing between patients likely and unlikely to respond remains a clinical challenge. We present the first multivariable models of outcomes with 177Lu-PSMA-617 built using data from VISION, a large prospective phase 3 clinical trial powered for overall survival. Adults with progressive post androgen receptor pathway inhibitor and taxane prostate-specific membrane antigen (PSMA)-positive mCRPC received 177Lu-PSMA-617 plus protocol-permitted standard of care (SoC) or SoC alone. In this post hoc analysis, multivariable Cox proportional hazards models of overall survival (OS) and radiographic progression-free survival (rPFS), and a logistic regression model of prostate-specific antigen response (≥50% decline; PSA50) were constructed and evaluated using C-index or receiver operating characteristic (ROC) analyses with bootstrapping validation. Nomograms were constructed for visualisation. Patients were randomised between June 2018 and October 2019. Data from all 551 patients in the 177Lu-PSMA-617 arm were analysed in multivariable modelling. The OS nomogram (C-index, 0.73; 95% confidence interval [CI], 0.70-0.76) included whole-body maximum standardised uptake value (SUVmax), time since diagnosis, opioid analgesic use, aspartate aminotransferase, haemoglobin, lymphocyte count, presence of PSMA-positive lesions in lymph nodes, lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and neutrophil count. The rPFS nomogram (C-index, 0.68; 0.65-0.72) included SUVmax, time since diagnosis, opioid analgesic use, lymphocyte count, presence of liver metastases by computed tomography, LDH, and ALP. The PSA50 nomogram (area under ROC curve, 0.72; 95% CI, 0.68-0.77) included SUVmax, lymphocyte count and ALP. Performances of the OS and rPFS models were maintained when they were reconstructed excluding SUVmax. These models of outcomes with 177Lu-PSMA-617 are the first built using prospective phase 3 data. They show that a combination of pretreatment laboratory, clinical, and imaging parameters, reflecting both patient and tumour status, influences outcomes. These models are important for aiding treatment selection, patient management, and clinical trial design. Novartis.

Investigating High-risk Factors, Precise Diagnosis, and Treatment of Castration- Resistant Prostate Cancer (CRPC).

The treatment of metastatic castration-resistant prostate cancer (mCRPC) in the actual world currently presents difficulties. In light of this, it is crucial to investigate high-risk factors for the progression of advanced prostate cancer and to identify methods for delaying the onset of CRPC. This study aimed to explore the high-risk factors that impact the progression of prostate cancer and emphasize the significance of precise diagnosis and treatment based on etiological classification in the clinical management of castration-resistant prostate cancer. A retrospective analysis was conducted on 277 newly diagnosed cases of PCa treated with endocrine therapy. A follow-up was done on prostate-specific antigen (PSA) levels and testosterone. Additionally, a prospective analysis was performed on the clinical data of 60 patients with CRPC. Following the principle of "4W1H", 30 patients were included in the precision treatment group for a second biopsy and related tests, while another 30 patients were included in the conventional treatment group. The therapeutic effect and prognosis of the two groups were observed. Distant metastasis (HR = 1.879, 95% CI: 1.311 ~ 2.694, P = 0.001), PSA nadir > 0.2 ng/mL (HR = 1.843, 95% CI: 1.338 ~ 2.540, P = 0.001), testosterone nadir > 20 ng/dL (HR = 1.403, 95% CI: 1.035 ~ 1.904, P = 0.029), and time to testosterone nadir > 6 months (HR = 1.919, 95% CI: 1.364 ~ 2.701, P = 0.001) were risk factors for the progression to CRPC. Patients in the CRPC group were treated with precision therapy and conventional therapy based on their molecular subtyping. The precision treatment group showed a significantly prolonged median PSA progression-free survival compared to the conventional treatment group (16.0 months vs. 13.0 months, P=0.025). The median radiographic progression-free survival was also significantly extended in the precision treatment group compared to the conventional treatment group (21.0 months vs. 16.0 months, P=0.042). Patients with prostate cancer diagnosed with distant metastasis at initial presentation require early intervention. Close monitoring of PSA and serum testosterone changes is necessary during the process of endocrine therapy. After entering the CRPC stage, the etiological classification precision treatment can improve the therapeutic effect and improve the prognosis of patients.

ASO Author Reflections: It Does Not Matter Whether Radical Prostatectomy is Performed in High-Risk Localized Disease or at the Oligometastatic Stage.

Radical prostatectomy (RP) alone has traditionally been considered insufficient for patients with high-risk localized prostate cancer (HRPC) owing to the frequent need for adjuvant salvage radiotherapy or androgen deprivation therapy (ADT) following surgery. Previously, systemic therapy, such as ADT, was the standard treatment for metastatic prostate cancer (PC) patients; RP was not considered viable for these patients. However, since 2015, there has been a recognition that metastatic PC patients can be categorized based on the extent of their metastases, leading to the consideration of RP for some metastatic cases. In recent years, the concept of cytoreductive RP has gained traction; studies suggest that it may improve survival rates in metastatic PC patients through mechanisms, such as tumor debulking and enhancement of the immune response. A meta-analysis of retrospective studies has shown that cytoreductive RP is associated with higher cancer-specific survival rates at 1-year, 3-year, and 5-year intervals compared with systemic therapy alone. In our study, which followed HRPC and oligometastatic PC patients for an average of 46 months, we observed biochemical recurrence in 17.8% of HRPC and 13% of oligometastatic patients, with overall survival rates of 96.4% and 87%, respectively. Although prospective or randomized studies are still lacking, current retrospective studies, including our own, suggest promising outcomes for RP in HRPC and oligometastatic patients. With the increasing prevalence of robotic surgery, improved pelvic anatomy observation, and growing surgical confidence, the realization of prospective randomized study results may not be far off.

Patient preferences for metastatic prostate cancer treatment: a discrete choice experiment

Patient preferences for metastatic prostate cancer treatment: a discrete choice experiment

177Lu-PSMA-617 for metastatic prostate cancer in India

177Lu-PSMA-617 for metastatic prostate cancer in India

MSOR11 Presentation Time: 8:50 AM: Implementation and Its Experience of Open Radiopharmaceutical Source for Metastatic Prostate Cancer Treatment in Small Radiation Oncology Clinic

MSOR11 Presentation Time: 8:50 AM: Implementation and Its Experience of Open Radiopharmaceutical Source for Metastatic Prostate Cancer Treatment in Small Radiation Oncology Clinic

Integrated single-cell transcriptomic analyses identify a novel lineage plasticity-related cancer cell type involved in prostate cancer progression

Cancer cell plasticity is the ability of neoplastic cells to alter their identity and acquire new biological properties under microenvironmental pressures. In prostate cancer (PCa), lineage plasticity often results in therapy resistance and trans-differentiation to neuroendocrine (NE) lineage. However, identifying the cancer cells harboring lineage plasticity-related status remains challenging. Based on 13 multi-center human PCa bulk transcriptomic cohorts (samples=3314) and 9 bulk transcriptomic datasets derived from PCa experimental models, we established an integrated lineage plasticity-related gene signature, termed LPSig. Leveraging this gene signature, AUCell enrichment analysis was applied to identify the cell population with high lineage plasticity from a comprehensive single-cell RNA-sequencing (scRNA-seq) meta-atlas assembled by us, which consisted of 10 public human PCa scRNA-seq datasets (samples=93, cells=222,529). Moreover, additional scRNA-seq dataset of human PCa, multiplex immunohistochemistry staining for human PCa tissues, invitro and invivo functional experiments, as well as qPCR and Western blot analyses were employed to validate our findings. We found that LPSig could finely capture the dynamics of tumor lineage plasticity throughout the progression of PCa, accurately estimating the status of lineage plasticity. Based on LPSig, we identified a previously undefined minority population of lineage plasticity-related PCa cells (LPCs) from the human PCa scRNA-seq meta-atlas assembled by this study. Furthermore, in-depth dissection revealed pivotal roles of LPCs in trans-differentiation, tumor recurrence, and poor patient survival during PCa progression. Furthermore, we identified HMMR as a representative cell surface marker for LPCs, which was validated using additional scRNA-seq datasets and multiplexed immunohistochemistry. Moreover, HMMR was transcriptionally inhibited by androgen receptor (AR), and was required for the aggressive adenocarcinoma features and NE phenotype. Our study uncovers a novel population of lineage plasticity-related cells with low AR activity, stemness-like traits, and elevated HMMR expression, that may facilitate poor prognosis in PCa. This work was supported by National Key R&D Program of China (2022YFA0807000), National Natural Science Foundation of China (82160584), Advanced Prostate Cancer Diagnosis and Treatment Technology Innovation Team of Kunming Medical University (CXTD202216), and Reserve Talents of Young and Middle-aged Academic Leaders in Yunnan Province (202105AC160013).

Wnt5a promotes VM formation by modulating the stemness and EMT progression of prostate cancer cell.

The incidence of prostate cancer (PCa) is increasing annually, making it the leading cause of tumor-related mortality in males. The available treatment options for metastatic PCa are limited. Vasculogenic mimicry (VM), an emerging phenomenon involving aggressive tumor cells, has a significant impact on patient survival. Misregulation of Wnt5a expression is commonly observed during cancer progression. However, there is a lack of comprehensive studies investigating the effects of Wnt5a on tumor VM formation. In this study, we demonstrate that alterations in wnt5a expression, either through gain or loss, have a significant influence on the formation of VM in tumor cells mediated by cell stemness and EMT progression. Further research has demonstrated that Wnt5a regulates the formation of VM through the PI3K/JNK signaling pathway. These experimental findings offer a novel avenue for the clinical management of prostate cancer.

Long-term Survival After Metastatic Pancreatic Cancer

Long-term Survival After Metastatic Pancreatic Cancer

Outcomes for Patients with Metastatic Castration-Resistant Prostate Cancer and Liver Metastasis Receiving [177Lu]Lu-PSMA-617.

It is well known that patients with liver metastasis from metastatic castration-resistant prostate cancer have poor or only transient responses to many forms of systemic therapy. Data on outcomes after treatment with [177Lu]Lu-PSMA-617 (LuPSMA) are scarce. The VISION trial reports a hazard ratio for overall survival (OS) in the subgroup of patients with liver metastasis without disclosing the absolute duration of survival. Using real-world clinical data, we examined this important subgroup of patients, describing prostate-specific antigen (PSA) response and OS. Methods: A single-institution database was assembled to include all patients receiving LuPSMA at Mayo Clinic in Rochester, Minnesota, for whom treatment was initiated between March 2022 and March 2023. Baseline clinicopathologic and imaging characteristics were abstracted. Patients were then categorized by presence or absence of liver metastasis on pretreatment prostate-specific membrane antigen (PSMA) PET. PSA response and OS for the 2 groups (liver metastasis vs. no liver metastasis) were compared using χ2 testing and the Kaplan-Meier method, respectively. A multivariate Cox regression analysis was performed, including established prognostic factors. Finally, those with pretreatment circulating tumor DNA as determined in an 83-gene panel were assessed for the presence of pathogenic and likely pathogenic alterations. These findings were summarized using descriptive statistics and compared between the 2 cohorts using the Fisher exact test. Results: The overall cohort consisted of 273 patients, including 43 (15.75%) with liver metastasis on pretreatment PSMA PET/CT. The median number of cycles received was 3 (range, 1-6) for patients with liver metastasis and 5 (range, 1-6) for those without hepatic involvement. The 50% or greater reduction in PSA from baseline response rate was lower for those with liver metastasis than for those without (30.23% [13/43] vs 49.77% [106/213], P = 0.019). At a median follow-up of 10 mo (interquartile range, 9-13 mo), there was a significant difference in median OS (8.35 mo vs. not reached, P < 0.001). On multivariate analysis, the presence of liver metastasis was independently associated with shorter survival (hazard ratio, 4.06; P < 0.001). Conclusion: Our data suggest that the presence of liver metastasis predicts poorer outcomes in patients receiving LuPSMA treatment. Alternative and combination approaches should be explored to maximize the antitumor activity of radiopharmaceutical therapy in the liver.

Dysphasia: metastatic prostate cancer to the leptomeninges: a case report

BackgroundLeptomeningeal metastasis occurs in 5% of patients with prostate cancer and indicates a very poor prognosis.Case presentationA 60-year-old Caucasian male patient diagnosed with metastatic castration-resistant prostate cancer with sclerotic bone metastases and soft tissue metastases underwent multiple courses of chemotherapy and hormone therapy. The diagnosis of prostate cancer is based on elevated prostate-specific antigen levels and tissue biopsy. He subsequently presented with expressive aphasia. Nonspecific, diffuse irregular dural/pachymeningeal thickening enhancement was noted on magnetic resonance imaging. Upon evaluation by neurology, electroencephalogram was negative for an epileptiform correlate. The workup included a lumbar puncture to rule out infectious etiology. The patient’s neurological status stabilized, and he was discharged home with a plan for continued therapy with abiraterone and prednisone. Due to advanced malignancy, the patient enrolled in hospice and died 3 weeks after hospital discharge.ConclusionsCentral nervous system metastasis occurs very rarely in prostate cancer. With the increase in life expectancy and advances in oncologic therapy for prostate cancer, physicians should be aware of and consider central nervous system metastasis in men aged 50 years and above.

Advancing prostate cancer detection: High-accuracy urine test distinguishes between high and low-risk cancers

Prostate cancer remains one of the leading causes of cancer-related deaths among men. The standard method for early detection involves measuring Prostate-specific antigen (PSA) levels in the blood, with elevated PSA levels prompting further diagnostic procedures, such as a prostate biopsy. While effective, biopsies can be painful and carry risks of complications such as fever and urinary tract infections. To reduce unnecessary biopsies, researchers have sought alternative diagnostic methods. In recent years, a urine test was developed for early-stage prostate cancer detection. However, this test struggled to differentiate between aggressive and slow-growing cancers, the latter of which often require minimal treatment and are managed through active surveillance. To address this limitation, scientists at Wunderkind University have significantly enhanced the urine test. By analysing the genomes of thousands of prostate cancer patients, they identified a panel of 16 genes detectable in urine that can effectively distinguish between high-risk and low-risk cancers. When applied to individuals with elevated PSA levels, this improved test demonstrated an impressive 97% accuracy in identifying advanced prostate cancer. This advancement holds great promise for reducing unnecessary biopsies and improving patient outcomes by accurately identifying those needing aggressive treatment versus those suitable for observation. This review paper will explore the development, validation, and clinical implications of this novel urine test, highlighting its potential to transform prostate cancer diagnostics and patient management.

Lethal Prostate Cancer in Mexico: Data from the Can.Prost Mexican Registry and a Project for Early Detection

Introduction: Epidemiological data are crucial for adopting primary and secondary prevention strategies and to develop screening protocols against prostate cancer (PCa). Despite the comprehensive characterization of PCa across White and Black men, there is a lack of data from the Mexican population. This manuscript presents data from the Can.Prost registry that captures PCa trends over the past two decades in Mexico City; furthermore, we aimed to compare clinical differences and oncological outcomes before and after the promotion of early detection actions through a campaign against PCa that occurred in 2014. Methods: A retrospective observational study on newly diagnosed Mexican PCa patients was carried out at the Instituto Nacional de Cancerología (INCan) in Mexico City. During 2014 and 2015, a project for the early diagnosis of PCa (“OPUS program”) was launched in the aforementioned tertiary hospital. Starting at the age of 45 years, all men were invited for a PSA measurement and a specialist urologist consultation. All individuals with clinical or biochemical suspicion of PCa (PSA &gt; 4 ng/mL), in the context of age and prostate volume, underwent ultrasound-guided transrectal prostate biopsy. Then, patients with pathologically confirmed prostate cancer were stratified according to the year of diagnosis: Group A accounted for those diagnosed between 2000 and 2014 and Group B for those patients diagnosed in the timeframe of 2015–2021. Comparisons of PCa characteristics, treatment modalities and oncologic outcomes between Group A and B were performed. Results: Overall, we collected data from 2759 PCa patients from 2000 to 2021. The median PSA at baseline was 32 ng/mL, and 25% had a family history of PCa. Overall, 25.8% were asymptomatic and 46% had a non-metastatic presentation. After the OPUS campaign, PSA at diagnosis was significantly lower across all age groups. The incidence of PCa diagnosis in asymptomatic men was higher (31.4% vs. 19.9%) and a higher proportion of men were diagnosed with organ-confined, palpable disease (46% vs. 28%) (p &lt; 0.001). The rate of patients eligible for active/radical treatment was higher after the OPUS campaign (patients who received surgery increased from 12.78% to 32.41%; patients who underwent radiation increased from 28.38% to 49.61%). The proportion of patients diagnosed with non-clinically significant disease was negligible and remained stable across time. Conclusions: PCa in Mexican patients displays aggressive features at diagnosis, whereas the rate of non-significant disease is negligible. The introduction of early detection strategies may lead to lower symptomatic and metastatic PCa and higher opportunities for radical treatment. This emphasizes the need for public awareness and for adjustment of screening strategies to the peculiarities of the Mexican population.

PARP inhibitors in prostate cancer: clinical applications.

Despite recent advancements in the treatment of metastatic castrate-resistant prostate cancer (mCRPC), this disease remains lethal. A novel family of targeted pharmaceuticals known as poly-ADP-ribose polymerase (PARP) inhibitors has been developed to treat mCRPC patients with homologous recombination repair (HRR) gene alterations. The FDA recently approved olaparib and rucaparib for treating mCRPC patients with HRR gene alterations. Ongoing trials are investigating combination therapies involving PARP inhibitors combined with radiation, chemotherapy, immunotherapy, and androgen receptor signaling inhibitors (ARSIs) to improve the effectiveness of PARP inhibitors and broaden the range of patients who can benefit from the treatment. This review provides an overview of the development of PARP inhibitors in prostate cancer and analyzes the mechanisms underlying their resistance.

Cutaneous and Subcutaneous Prostate-Specific Membrane Antigen-Avid Lesions.

We report the case of a 62-year-old man with metastatic castration-resistant prostate cancer with subcutaneous involvement being treated with 177Lu-prostate-specific membrane antigen (PSMA). Before treatment, he was diagnosed with 2 subcutaneous nodules in the chest wall and soft tissue edema in the pubic and inguinal regions showing PSMA avidity. Biopsy and immunohistochemistry assessment confirmed cutaneous metastases from prostate cancer. He received 3 cycles of 177Lu-PSMA, resulting in a decline in PSA levels and resolution of symptoms. This case underscores the challenging diagnosis of cutaneous metastasis from prostate cancer, especially in atypical presentations. We also reviewed all causes of PSMA-avid lesions in the skin and subcutaneous tissues.

Enhancing Effects of Olaparib by Alpha- and Beta-Emitting Radionuclides, X-Rays, and Ultraviolet A Light in Combination with Ortho-IodoHoechst in a Prostate Cancer Cell Model

Background: New therapeutic strategies for metastatic castration-resistant prostate cancer (mCRPC) have been developed in the past to achieve the best response rates. Most recently, the use of combination therapies has been explored to optimize patient outcomes. Poly(ADP-ribose) polymerase inhibitors (PARPi) may help to treat mCRPC more effectively. Objectives: This study aimed to determine whether the combination of a PARPi with different radiation qualities results in different levels of radiosensitization of PC-3 cells. Methods: The radiosensitizing potential of Olaparib in combination with 177Lu, 223Ra, X-rays and photodynamic therapy (PDT) using the UVA light-activated photosensitizer ortho-iodoHoechst33258 (oIH) was evaluated by determining the clonogenic survival, DNA damage and cell cycle analysis. Results: Here, we show that this combination strategy differentially sensitized PC-3 cells to different radiation qualities. The combination of 177Lu with Olaparib increased the numbers of persistent double-strand breaks (DSBs) by a factor of 3.3 and cell death in PC-3 cells. Overall, the β-emitter 177Lu indicated a higher radiosensitization efficacy compared to 223Ra, with X-rays corresponding to dose modification factors (DMF) of 1.77, 1.17 and 1.16 respectively. Even in the case of the α-emitter 223Ra, the effects were much less pronounced than for 177Lu. PARPi also showed a slight potentiation of the cytotoxic effects both in co-treatment with X-rays and with PDT. Conclusions: The results of our study indicate a potential role for Olaparib in further optimizing the PSMA radioligand therapy (PRLT) outcomes. However, further evaluation of the combination of PARPi with PRLT is needed to gain more insights into improving the benefit to patients suffering from mCRPC.

FAP and PSMA Expression by Immunohistochemistry and PET Imaging in Castration-Resistant Prostate Cancer: A Translational Pilot Study.

Prostate-specific membrane antigen (PSMA) is a theranostic target for metastatic prostate cancer (PCa). However, castration-resistant PCa (CRPC) may lose PSMA expression after systemic therapy. Fibroblast activation protein (FAP), expressed by carcinoma-associated fibroblasts in various cancer types, including PCa, has the potential to be an alternative target. In this study, we evaluated FAP expression in CRPC to assess its potential, using PSMA as a comparison. Methods: FAP expression was assessed using immunohistochemistry in 116 CRPC tumors: 78 adenocarcinomas, 11 small cell carcinomas, and 27 anaplastic carcinomas. Correlation analysis between manual scoring and automated scoring was performed on 54 whole-slide sections of metastatic CRPC. Paired FAP and PSMA stains were assessed in tissue microarray cores of CRPC (n = 62), consisting of locally advanced CRPC (n = 9) and metastatic CRPC (n = 53). FAP and PSMA positivity was defined by an immunohistochemistry score of at least 10. To explore the correlation of PSMA and FAP inhibitor (FAPi) PET imaging and immunohistochemistry, a preliminary analysis of 4 patients included in a [68Ga]-FAPi-46 imaging trial (NCT04457232) was conducted. Results: Manual and automated scoring of FAP yielded results with strong correlations. Overall, FAP expression in CRPC was notably lower than PSMA expression (median immunoscores, 14 vs. 72; P < 0.001). Different histologic subtypes of CRPC demonstrated distinct levels of PSMA expression, whereas their FAP expression levels were comparable. Among the 19 PSMA-negative tumors, 11 (58%) exhibited FAP positivity. FAP expression levels in lymph node metastases were significantly lower than those in nonnodal metastases (P = 0.021). Liver metastases showed significant enrichment of tumors with strong FAP expression compared with nonliver lesions (P = 0.016). In the 4 clinical trial patients, the biopsied metastatic lesions showed lower uptake on FAPi PET than on PSMA PET (median SUVmax, 9.6 vs. 14.5), consistent with FAP expression that was lower than PSMA expression in the corresponding tumor biopsy samples (median immunoscores, 30 vs. 160). Conclusion: Because of the low FAP expression levels in CRPC, the utility of FAPi PET imaging may be limited. Although FAPi PET imaging may be further tested in PSMA-negative CRPC, such as small cell carcinoma, other molecular imaging modalities should be evaluated as alternative choices.