Development of a Visually Calculated SUVmean (HIT Score) on Screening PSMA PET/CT to Predict Treatment Response to 177Lu-PSMA Therapy: Comparison with Quantitative SUVmean and Patient Outcomes

177Lu-PSMA therapy is an effective treatment in patients with metastatic castration-resistant prostate cancer. SUVmean is a valuable screening biomarker to assess the suitability for 177Lu-PSMA therapy but requires quantitative software. This study aims to develop a simple, clinically applicable prostate-specific membrane antigen PET/CT score that encompasses the elements of SUVmean without requiring additional quantification. Methods: Datasets from ethics-approved trials of patients with metastatic castration-resistant prostate cancer after androgen receptor signaling inhibition and taxane chemotherapy (or unfit for taxane), who were treated with 177Lu-PSMA-617 and 177Lu-PSMA I&T with a pretreatment screening with 68Ga-PSMA-11 PET/CT, and clinical outcome data, including a prostate-specific antigen (PSA) 50% response rate (PSA50), PSA progression-free survival (PSA-PFS), and overall survival (OS), were included. The screening 68Ga-PSMA-11 PET/CT of all participants was analyzed both semiquantitatively and visually. Semiquantitative analysis was used to derive the SUVmean Visual analysis of the 68Ga-PSMA-11 PET/CT images involved a binary visual heterogeneity assessment (homogeneous or heterogeneous), allocating a tumor SUVmax range (<15, 15-29, 30-49, 50-79, or ≥80). A 4-category score incorporating both heterogeneity and intensity of tumors (HIT) was then developed as a combination of heterogeneity and intensity (SUVmax range). The SUVmax was less than 15 for score 1, 15-79 with heterogeneous intensity for score 2, 15-79 with homogeneous intensity for score 3, and 80 or greater for score 4. This score was evaluated according to clinical outcomes (PSA50, PSA-PFS, and OS) and compared with SUVmean Results: Data from 139 participants were analyzed. In total, 75 (54%) patients achieved a PSA50 with a median PSA-PFS of 5.5 mo (95% CI, 4.1-6.0 mo) and an OS of 13.5 mo (95% CI, 11.1-17.9 mo). SUVmean was associated with PSA50 and survival outcomes when analyzed as a continuous variable or as quartiles. The PSA50 for HIT scores 1-4 was 0%, 39%, 65%, and 76%, respectively. The HIT score was strongly related to PSA-PFS and OS (log-rank test, P < 0.001 and P = 0.002). The median PSA-PFS for HIT scores 1-4 was 1.0, 4.1, 6.0, and 8.5, respectively, and the median OS was 7.6, 12.0, 18.5, and 16.9 mo, respectively. Cohen κ between readers for the HIT score was 0.71. Conclusion: A prostate-specific membrane antigen PET/CT score incorporating HIT derived from tools on a standard PET workstation is comparable with quantitative SUVmean as a prognostic tool following 177Lu-PSMA therapy.

Circulating Tumour DNA Biomarkers Associated with Outcomes in Metastatic Prostate Cancer Treated with Lutetium-177-PSMA-617

Background

Lutetium-177-prostate-specific membrane antigen- 617 (Lu-PSMA) is an effective therapy for metastatic castration-resistant prostate cancer (mCRPC). However, treatment responses are heterogeneous despite stringent positron emission tomography (PET)-based imaging selection criteria. Molecularly based biomarkers have potential to refine patient selection and optimise outcomes.

Objective

To identify circulating tumour DNA (ctDNA) features associated with treatment outcomes for men treated with Lu-PSMA.

Design setting and participants

ctDNA from men treated with Lu-PSMA in combination with idronoxil for progressive mCRPC were analysed using an 85-gene customised sequencing assay. ctDNA fractions, molecular profiles, and the presence of alterations in aggressive-variant prostate cancer (AVPC) genes were analysed at baseline, cycle 3 and at disease progression.

Intervention

Men received Lu-PSMA with idronoxil every 6 wk for up to six cycles.

Outcome measurements and statistical analysis

Baseline and exit PSMA and fluorodeoxyglucose PET/computed tomography (CT) imaging was conducted at baseline and study exit. Single-photon emission CT (SPECT) scans were performed 24 h after Lu-PSMA. Blood samples were collected at baseline,cycle 3 and at disease progression. Cox proportional-hazards models were used to assess associations and derive hazard ratios (HRs) and confidence intervals (CIs) for associations between molecular factors, imaging features, and clinical outcomes.

Results and limitations

Sixty samples from 32 men were sequenced (32 at baseline, 24 at cycle 3, four from patients with disease progression); two samples (baseline, on-treatment) from one individual were excluded from analysis owing to poor quality of the baseline sequencing data. Alterations in AVPC genes were associated with shorter prostate-specific antigen (PSA) progression-free survival (PFS) and overall survival (OS) in univariate (HR 3.4, 95% CI 1.5-7.7; p = 0.0036; and HR 3.3, 95% CI 1.4-7.7; p = 0.0063, respectively) and multivariate analyses (HR 4.8, 95% CI 1.8-13; p = 0.0014; and HR 4.1, 95% CI 1.6-11; p = 0.004).

Conclusions

ctDNA alterations in AVPC genes were associated with shorter PSA PFS and OS among men treated with Lu-PSMA and intermittent idronoxil. These candidate molecular biomarkers warrant further study to determine whether they have predictive value and potential to guide synergistic combination strategies to enhance outcomes for men treated with Lu-PSMA for mCRPC.

Patient summary

Certain DNA/gene changes detected in the blood of men with advanced prostate cancer were associated with shorter benefit from lutetium PSMA, a targeted radioactive therapy. This information may be useful in determining which men may benefit most from this treatment, but additional research is needed.

The Tyr Phenomenon: A Hypocalcemic Response in High-Volume Treatment Responders to 177Lu-Prostate-Specific Membrane Antigen Therapy

177Lu-prostate-specific membrane antigen (PSMA) is an effective treatment for metastatic castration-resistant prostate cancer. Rarer treatment-related adverse events have not yet been described. Methods: We present case reviews of 2 men with a marked hypocalcemic osteosclerotic response to 177Lu-PSMA-I&T therapy. A clinical dataset of 177Lu-PSMA-I&T therapy was evaluated to estimate the incidence and clinical association with hypocalcemia. Results: Forty-one of the 127 men (32%) had a serum calcium drop, and 6 (5%) developed clinical hypocalcemia during 177Lu-PSMA therapy. The baseline total tumor volume was significantly higher in those who developed hypocalcemia (median, 3,249 cm3 [interquartile range, 1,856-3,852] vs. 465 [interquartile range 135-1,172]; P = 0.002). The mean prostate-specific antigen response in those with hypocalcemia was 78% (SD, 24%). Conclusion: Hypocalcemia may occur in response to 177Lu-PSMA-I&T, particularly with both high-volume bone metastases and a significant prostate-specific antigen response, and may be severe, requiring corticosteroids. Further evaluation of 177Lu-PSMA-induced hypocalcemia is required to better understand mechanisms, optimal treatments, and repercussions from any subsequent osteosclerotic response.

177Lu-PSMA SPECT Quantitation at 6 Weeks (Dose 2) Predicts Short Progression-Free Survival for Patients Undergoing 177Lu-PSMA-I&T Therapy

177Lu-PSMA is an effective treatment in metastatic castration-resistant prostate cancer (mCRPC). Our ability to assess response rates and adjust treatment may be improved using predictive tools. This study aimed to evaluate change in 177Lu-PSMA SPECT quantitative parameters to monitor treatment response. Methods: One hundred twenty-seven men with progressive mCRPC previously treated with androgen-signaling inhibition (99%) and chemotherapy (71%) received a median of 3 (interquartile range [IQR], 2-5) 8-GBq (IQR, 8-8.5 GBq) doses of 177Lu-PSMA-I&T. Imaging included 68Ga-PSMA-11 PET/CT (SUVmax > 15 at a single site and > 10 at all sites > 2 cm), diagnostic CT, and 177Lu SPECT/CT from vertex to mid thigh (24 h after treatment). 177Lu SPECT/CT quantitative analysis was undertaken at cycles 1 (baseline) and 2 (week 6) of treatment. Clinical and biochemical results were assessed to evaluate prostate-specific antigen (PSA) progression-free survival (PFS) and overall survival (OS). Results: A PSA reduction of more than 50% was seen in 58% (74/127). The median PSA PFS was 6.1 mo (95% CI, 5.5-6.7), and OS was 16.8 mo (95% CI, 13.5-20.1). At the time of analysis, 41% (52/127) were deceased. At baseline and week 6, 76% (96/127) had analyzable serial 177Lu SPECT/CT imaging. SPECT total tumor volume (TTV) was reduced between baseline and week 6 in 74% (71/96; median, -193; IQR, -486 to -41). Any increase in SPECT TTV between baseline and week 6 was associated with significantly shorter PSA PFS (hazard ratio, 2.5; 95% CI, 1.5-4.2; P = 0.0008) but not OS. Median PSA PFS in those with an increase in SPECT TTV was 3.7 mo (95% CI, 2.8-6.8), compared with 6.7 mo (95% CI, 5.8-10.6) in those with no increase in SPECT TTV. An increase in SPECT TTV greater than 20% was also associated with PSA PFS (hazard ratio, 1.9; 95% CI, 1.2-3.0; P = 0.008) but less significantly than any change in SPECT TTV. There was a significant difference in PSA PFS between patients with both increased PSA and SPECT TTV and patients with reduced SPECT TTV and PSA (median, 2.8 vs. 9.0 mo; P < 0.0001). Conclusion: Increasing PSMA SPECT TTV on quantitative 177Lu SPECT/CT predicts short progression-free survival and may play a future role as an imaging response biomarker, identifying when to cease or intensify 177Lu-PSMA therapy.

Evaluation of 177Lu-PSMA-617 SPECT/CT Quantitation as a Response Biomarker Within a Prospective 177Lu-PSMA-617 and NOX66 Combination Trial (LuPIN)

¹⁷⁷Lu-PSMA-617 is an effective and novel treatment in metastatic castration-resistant prostate cancer (mCRPC). Our ability to assess response rates and therefore efficacy may be improved using predictive tools. This study investigated the predictive value of serial ¹⁷⁷Lu-PSMA-617 SPECT/CT (¹⁷⁷Lu SPECT) imaging in monitoring treatment response. Methods: Fifty-six men with progressive mCRPC previously treated with chemotherapy and novel androgen signaling inhibitor were enrolled into the LuPIN trial and received up to 6 doses of ¹⁷⁷Lu-PSMA-617 and a radiation sensitizer (3-(4-hydroxyphenyl)-2H-1-benzopyran-7-ol [NOX66]). ⁶⁸Ga-PSMA-11 and ¹⁸F-FDG PET/CT were performed at study entry and exit, and ¹⁷⁷Lu SPECT from vertex to mid thighs was performed 24 h after each treatment. SPECT quantitative analysis was undertaken at cycles 1 (baseline) and 3 (week 12) of treatment. Results: Thirty-two of the 56 men had analyzable serial ¹⁷⁷Lu SPECT imaging at both cycle 1 and cycle 3. In this subgroup, median prostate-specific antigen (PSA) progression-free survival (PFS) was 6.3 mo (95% CI, 5-10 mo) and median overall survival was 12.3 mo (95% CI, 12-24 mo). The PSA 50% response rate was 63% (20/32). ¹⁷⁷Lu SPECT total tumor volume (SPECT TTV) was reduced in 68% (22/32; median, -0.20 m³ [95% CI, -1.4 to -0.001]) and increased in 31% (10/32; median, 0.36 [95% CI, 0.1-1.4]). Any increase in SPECT TTV was associated with shorter PSA PFS (hazard ratio, 4.1 [95% CI, 1.5-11.2]; P = 0.006). An increase of 30% or more in SPECT TTV was also associated with a shorter PSA PFS (hazard ratio, 3.3 [95% CI, 1.3-8.6]; P =0.02). Tumoral SUV_max was reduced in 91% (29/32) and SUV_mean in 84% (27/32); neither was associated with PSA PFS or overall survival outcomes. PSA progression by week 12 was also associated with a shorter PSA PFS (hazard ratio, 26.5 [95% CI, 5.4-131]). In the patients with SPECT TTV progression at week 12, 50% (5/10) had no concurrent PSA progression (median PSA PFS, 4.5 mo [95% CI, 2.8-5.6 mo]), and 5 of 10 men had both PSA and SPECT TTV progression at week 12 (median PSA PFS, 2.8 mo [95% CI, 1.8-3.7 mo]). Conclusion: Increasing SPECT TTV on quantitative ¹⁷⁷Lu SPECT predicts a short PFS and may play a future role as an imaging response biomarker.

Patient outcomes following a response biomarker-guided approach to treatment using 177Lu-PSMA-I&T in men with metastatic castrate-resistant prostate cancer (Re-SPECT)

Background

¹⁷⁷LuPSMA is an effective treatment in metastatic castrate-resistant prostate cancer with trials adopting a standardised dose interval. Adjusting treatment intervals utilising early response biomarkers may improve patient outcomes.

Objective

This study evaluated progression-free survival (PFS) and overall survival (OS) based on treatment interval adjustment utilising ¹⁷⁷LuPSMA 24-h SPECT/CT (¹⁷⁷Lu-SPECT) and early prostate-specific antigen (PSA) response.

Design

Retrospective analysis of a clinical ¹⁷⁷Lu-PSMA-I&T treatment programme.

Methods

In all, 125 men were treated with 6-weekly ¹⁷⁷LuPSMA-I&T [median 3 cycles, interquartile range (IQR): 2-4], median dose 8.0 GBq [95% confidence interval (CI): 7.5-8.0]. Imaging screening involved ⁶⁸GaPSMA-11 PET/diagnostic CT. ¹⁷⁷Lu-SPECT/diagnostic CT was acquired following each therapy, and clinical assessments 3-weekly. Following dose 2 (week 6), a composite PSA and ¹⁷⁷Lu-SPECT/CT imaging response [partial response (PR), stable disease (SD), and progressive disease (PD)] determined ongoing management. Response group (RG) 1 (marked reduction in PSA/imaging PR) break in treatment until subsequent PSA rise, then re-treatment. RG 2 (stable or reduced PSA and/or imaging SD) 6-weekly treatments until six doses, or no longer clinically benefitting. RG 3 (rise in PSA and/or imaging PD) recommended for an alternative treatment.

Results

Overall PSA50% response rate (PSARR) was 60% (75/125), median PSA-PFS 6.1 months (95%CI: 5.5-6.7), and median OS 16.8 months (95%CI: 13.5-20.1). 35% (41/116) were classified as RG 1, 34% (39/116) RG 2, and 31% (36/116) RG 3. PSARRs by RG were 95% (38/41), 74% (29/39), and 8% (3/36); median PSA-PFS rates were 12.1 months (95%CI: 9.3-17.4), 6.1 months (95%CI: 5.8-9.0), and 2.6 months (95%CI: 1.6-3.1); and OS rates were 19.2 months (95%CI: 16.8-20.7), 13.2 months (95%CI: 12.0-18.8), and 11.2 months (95%CI: 8.7-15.6) for RG 1, 2, and 3, respectively. The median months of 'treatment holiday' for RG 1 was 6.1 months (IQR: 3.4-8.7). Nine men had received prior ¹⁷⁷LuPSMA-617 and were retreated with ¹⁷⁷LuPSMA-I&T, with a PSARR of 56% on re-treatment.

Conclusion

Personalising dosing regimens using early response biomarkers with ¹⁷⁷LuPSMA has the potential to achieve similar treatment responses to continuous dosing while allowing treatment breaks or intensification. Further evaluation of early response biomarker-guided treatment regimens in prospective trials is warranted.

Plain Language Summary

Lutetium-PSMA therapy is a new therapy for metastatic prostate cancer that is well tolerated and effective. However, not all men respond equally, with some responding very well and others progressing early. Personalising treatments require tools that can accurately measure treatment responses, preferably early in the treatment course, so adjustments to treatment can be made. Lutetium-PSMA can measure tumour sites after each therapy by taking whole body 3D images at 24 h using a small radiation wave from the treatment itself. This is called a SPECT scan. Previous work has shown that both prostate-specific antigen (PSA) response and changes in tumour volume on a SPECT scan can predict how patients will respond to treatment as early as dose 2. This study demonstrates that stratifying how men are treated based on the results of the 6-week SPECT scan and PSA response potentially allows a third of men to have break in treatment and that these men have both longer time to disease progression and OS. Men with an increase in tumour volume and increase in PSA early in treatment (6 weeks) had shorter time to disease progression and OS. Men with early biomarker disease progression were offered alternative treatments early in an attempt to allow the opportunity to allow a more effective potential therapy, if one was available. The study is an analysis of a clinical programme, and was not a prospective trial. As such, there are potential biases that could influence results. Hence, while the study is encouraging for the use of early response biomarkers to guide better treatment decisions, this must be validated in a well-designed clinical trial.

The Prognostic Value of Posttreatment 68Ga-PSMA-11 PET/CT and 18F-FDG PET/CT in Metastatic Castration-Resistant Prostate Cancer Treated with 177Lu-PSMA-617 and NOX66 in a Phase I/II Trial (LuPIN)

¹⁷⁷Lu-PSMA-617 therapy has shown high prostate-specific antigen (PSA) response rates in men with metastatic castration-resistant prostate cancer. However, early treatment resistance is common. This LuPIN substudy aimed to determine the prognostic value of posttreatment quantitative PET for PSA progression-free survival (PFS) and overall survival (OS) with ¹⁷⁷Lu-PSMA-617 therapy. Methods: Fifty-six men with progressive metastatic castration-resistant prostate cancer were enrolled in the LuPIN trial and received up to 6 doses of ¹⁷⁷Lu-PSMA-617 and a radiation sensitizer (NOX66). ⁶⁸Ga-PSMA-11 and ¹⁸F-FDG PET/CT, diagnostic CT, and bone scanning were performed at study entry and exit. Quantitative analysis tracked change in total tumor volume (TTV) and SUV. Univariable and multivariable analyses were conducted to examine the association of change in TTV (continuous and >30%), SUV_max, PSA, and radiographic progression with PSA PFS and OS. Results: All men (37/56) who underwent both screening and posttreatment molecular imaging were analyzed; 70% (26/37) had a PSA response of more than 50%. Median PSA PFS was 8.6 mo, and median OS was 22 mo. Clinical progression had occurred at trial exit in 54% (20/37). In response to treatment, a reduced PSMA SUV_max was demonstrated in 95% (35/37) and a reduced PSMA TTV in 68% (25/37). An increase in PSMA TTV by at least 30% was associated with worse OS (median, 10.2 vs. 23.6 mo; P = 0.002). Change in PSMA SUV_max was not associated with PSA PFS or OS. ¹⁸F-FDG SUV_max was reduced in 51% (18/35) and ¹⁸F-FDG TTV in 67% (22/35). An increased ¹⁸F-FDG SUV_max was associated with worse OS (median, 20.7 vs. 25.7 mo; P < 0.01). An ¹⁸F-FDG TTV increase by more than 30% was associated with a short PSA PFS (median, 3.5 vs. 8.6 mo; P < 0.001) but not OS. Both PSA and radiographic progression were associated with shorter OS (median, 14.5 vs. 25.7 mo [P < 0.001] and 12.2 vs. 23.6 mo [P = 0.002]). On multivariable analysis, only increased PSMA TTV and PSA progression remained independently prognostic of OS (hazard ratio, 5.1 [95% CI, 1.5-17.1; P = 0.008] and 3.5 [95% CI, 1.1-10.9; P = 0.03], respectively). Conclusion: Change in quantitative PSMA TTV has strong potential as a prognostic biomarker with ¹⁷⁷Lu-PSMA-617 therapy, independent of ¹⁸F-FDG PET parameters, PSA, or radiographic progression. Further research into the value of posttreatment PET as an imaging biomarker is warranted.

64Cu-SAR-Bombesin PET-CT imaging in the staging of ER+/PR+/HER2- metastatic breast cancer: Safety, dosimetry, and feasibility in a phase I trial

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Background: Breast cancers are most frequently oestrogen receptor (ER) and progesterone receptor (PR) positive and 18F-Fluorodeoxyglucose PET-CT (FDG) used in conventional staging of breast cancer has lower sensitivity for these subtypes. Gastrin releasing peptide receptors (GRPR) are a potential alternative diagnostic and theranostic target for ER+/PR+ breast cancers due to their overexpression of GRPR. This phase 1 study aims to assess the safety and potential of the novel radiotracer 64Cu-Sarcophagine(SAR)-Bombesin (BBN) in the re-staging of recurrent metastatic ER+/PR+/human epidermal growth factor 2 negative (HER2-) breast cancer. Methods: Patients with confirmed recurrent or primary metastatic ER+/PR+/HER2- breast cancer undergoing staging prior to a new treatment underwent 64Cu-SAR-BBN PET-CT with imaging at 1, 3 and 24 hours post-injection. Bloods and vital signs were acquired for patients at baseline, 1, 3 and 24 hours post-injection timepoints, and electrocardiogram (ECG) performed 1 hour pre and 1 hour post injection. Blood tracer-clearance and dosimetry was performed. GRPR receptor status was assessed in 4/7 patients from metastatic-site biopsy samples. Staging of the patients was assessed by conventional imaging (FDG, bone scan and diagnostic CT) within 3 weeks of 64Cu-SAR-BBN imaging. All PET scans were assessed visually, and quantitatively using MIM Software. Results: 9 patients were enrolled. 7/9 patients underwent all imaging modalities, while 2/9 did not undergo BBN imaging. 1/7 patient who underwent all imaging had de- novo metastatic ER+/PR+/Her 2- breast cancer and 6/7 recurrent metastatic disease. 2/7 had lobular subtype. There were no adverse events reported, and ECG, vitals and haematological, biochemical and coagulation markers remained unchanged. All 7 patients were positive on conventional imaging, while 6/7 were positive on FDG. BBN was positive in 5/7 patients. Both BBN negative patients had disease identified on FDG. Conversely, 1 patient was BBN positive but FDG negative. 4/7 patients were BBN positive and FDG positive. In these 4 patients, mean SUVmax was higher for BBN than FDG (15 vs. 12). In classical lobular subtype (2/7), BBN was highly avid compared to FDG (SUV max 20 vs 11, and 20 vs <3) and with a higher tumor volume compared to FDG (2034 vs 504, and 634 mL vs FDG negative). Conclusions: 64Cu-SAR-Bombesin is a novel tracer which appears safe and may have a diagnostic and theranostic role in patients with metastatic ER+/PR+/HER2- breast cancer, particularly lobular subtype. Further evaluation appears warranted.

Quantifying molecular imaging patterns of treatment response or progression using a novel traffic light workflow within a prospective phase I/II trial of 177LuPSMA-617 and NOX66 (LuPIN)

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Background: 177Lutetium PSMA-617 (LuPSMA) is an effective therapy for metastatic castrate-resistant prostate cancer (mCRPC). However, treatment resistance may occur. We developed a quantitative workflow for serial PSMA PET/CT to optimise predictive and prognostic imaging biomarker capability for progression free (PFS) and overall survival (OS). Methods: 56 men with mCRPC previously treated with taxane chemotherapy and androgen signaling inhibitor were enrolled, receiving up to 6 doses of LuPSMA and a radiation sensitizer idronoxil (NOX66). 68Ga-PSMA-11 PET/CT was performed at study entry and exit. Traffic Light (TL) quantification workflow was developed to track changes in both tumour volume and intensity at a total body and lesional level. Lesions were classified as responding in green (>30% decline in volume), stable in yellow (<30% change in volume/intensity), progressive in red (>30% increase in volume/intensity, or new). Overall response pattern was categorised as responding ( green/yellow), low volume red (<50% progressive disease) or high volume red (>50% progressive disease). TL workflow results were correlated with PFS and OS. Results: 37/56 men underwent both entry and exit imaging. The median PSA decline was 77% (IQR 34-92%), and 70% (26/37) achieved PSA response >50%. PSA progression occurred in 54% (20/37) at exit imaging. Median PFS was 8.6 months (95%CI 5.6-11.6) and median OS 22 months (95% CI 18.6-25.6). 95% (35/37) had reduction in PSMA SUVmax (-26.1 (IQR +11.7 to -89.4)) and SUVmean (-3.3 (+2.9 to -14.2)). PSMA total tumor volume reduced in 68% (25/37) (median -0.64 liters (range +1.44 to -1.1)). On TL workflow, 24% (9/37) had responding/stable disease ( green/ yellow), 76% (28/37) had progressive disease ( red) of whom 41% (15/37) had low volume progression and 35% (13/37) high volume progression. Men with high volume progression had worse OS compared to responders (HR 0.18 (0.05-0.59), p 0.005), and low volume progression (HR 0.30 (0.11-0.80), p 0.02). 68% (19/28) had progression on both TL workflow and PSA, while 32% (9/28) had progression on TL workflow without PSA progression. In multivariable analysis, TL workflow and PSA progression at time of exit scans were independent predictors of OS (Table). Conclusions: This study demonstrates the feasibility of characterizing lesional response on molecular imaging with a quantification TL workflow. TL workflow response independently correlated with survival outcomes, indicating serial PSMA PET has prognostic biomarker potential. Clinical trial information: ACTRN12618001073291.[Table: see text]

177Lutetium PSMA-617 and idronoxil (NOX66) in men with end-stage metastatic castrate-resistant prostate cancer (LuPIN): Patient outcomes and predictors of treatment response of a Phase I/II trial

¹⁷⁷Lu-PSMA-617 is an effective therapy for metastatic castration-resistant prostate cancer (mCRPC). However, treatment resistance occurs frequently, and combination therapies may improve outcomes. We report the final safety and efficacy results of a phase I/II study combining ¹⁷⁷Lu-PSMA-617 with idronoxil (NOX66), a radiosensitizer, and examine potential clinical, blood-based, and imaging biomarkers. Methods: Fifty-six men with progressive mCRPC previously treated with taxane chemotherapy and novel androgen signaling inhibitor (ASI) were enrolled. Patients received up to 6 doses of ¹⁷⁷Lu-PSMA-617 (7.5 GBq) on day 1 in combination with a NOX66 suppository on days 1–10 of each 6-wk cycle. Cohort 1 (n = 8) received 400 mg of NOX66, cohort 2 (n = 24) received 800 mg, and cohort 3 (n = 24) received 1,200 mg. ⁶⁸Ga-PSMA and ¹⁸F-FDG PET/CT were performed at study entry, and semiquantitative imaging analysis was undertaken. Blood samples were collected for analysis of blood-based biomarkers, including androgen receptor splice variant 7 expression. The primary outcomes were safety and tolerability; secondary outcomes included efficacy, pain scores, and xerostomia. Regression analyses were performed to explore the prognostic value of baseline clinical, blood-based, and imaging parameters. Results: Fifty-six of the 100 men screened were enrolled (56%), with a screening failure rate of 26% (26/100) for PET imaging criteria. All men had received prior treatment with ASI and docetaxel, and 95% (53/56) had received cabazitaxel. Ninety-six percent (54/56) of patients received at least 2 cycles of combination NOX66 and ¹⁷⁷Lu-PSMA-617, and 46% (26/56) completed 6 cycles. Common adverse events were anemia, fatigue, and xerostomia. Anal irritation attributable to NOX66 occurred in 38%. Forty-eight of 56 had a reduction in prostate-specific antigen (PSA) level (86%; 95% CI, 74%–94%); 34 of 56 (61%; 95% CI, 47%–74%) had a PSA reduction of at least 50%. Median PSA progression-free survival was 7.5 mo (95% CI, 5.9–9 mo), and median overall survival was 19.7 mo (95% CI, 9.5–30 mo). A higher PSMA SUV_mean correlated with treatment response, whereas a higher PSMA tumor volume and prior treatment with ASI for less than 12 mo were associated with worse overall survival. Conclusion: NOX66 with ¹⁷⁷Lu-PSMA-617 is a safe and feasible strategy in men being treated with third-line therapy and beyond for mCRPC. PSMA SUV_mean, PSMA-avid tumor volume, and duration of treatment with ASI were independently associated with outcome.

Final results of a phase I/II prospective dose escalation trial evaluating safety and efficacy of combination 177Lu PSMA 617 and NOX66 in men with end-stage metastatic castration-resistant prostate cancer (LuPIN trial)

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Background: 177LuPSMA – 617 is a promising therapy for metastatic castrate-resistant prostate cancer (mCRPC). However, treatment resistance occurs frequently and synergistic combination therapy may improve outcomes. We combined 177LuPSMA – 617 with idronoxil (NOX66), an inhibitor of external NADH oxidase type 2 with radio-sensitizing properties. We present the final safety and efficacy results. Methods: Men with progressive mCRPC after androgen signalling inhibition (ASI) and taxane chemotherapy were enrolled. Key inclusion criteria were: PSMA PET/CT intensity SUV max > 15 with no discordant disease on FDG PET/CT, haemoglobin > 100g/L, platelets > 100x109/L and eGFR > 40mls/min. Enrolled patients received up to six doses of 177 Lu-PSMA 617 (7.5Gbq) day 1 every 6 weeks in combination with NOX66 days 1-10 each cycle. Cohort 1 (n = 8) received 400mg NOX66. Following safety reviews the doses were escalated in cohorts 2 (n = 24) and 3 (n = 24) to 800mg and 1200mg of NOX66, respectively. Blood samples were prospectively collected for androgen receptor splice variant 7 (ARV7) expression. PSMA and FDG PET/CT were performed at study entry and on progression. The primary outcomes were safety and tolerability; the secondary outcomes evaluated were efficacy, pain scores, and quality of life. Results: Of the 56 men enrolled, all had received prior treatment with ASI and docetaxel, and 95% (53/56) had prior cabazitaxel. 96% (54/56) patients received ≥2 cycles and 46% (26/56) completed six cycles of treatment. Adverse events are summarized in the table below. PSA responses were as follows: 86% (48/56) had any PSA reduction and 61% (34/56) had > 50% PSA reduction. 84% (47/56) have had PSA progression to date with median follow up 18.9 months (95% CI 11.9-25.8). Median PSA PFS was 7.5 months (95% CI 6.0-9.0). 55% (31/56) have died and median overall survival was 19.7 months (95% CI 10.7-28.7). 34/56 men had baseline pain scores ≥3, of whom 53% (18/34) had significant reduction in pain indicators. There was no correlation between quantitative PET results and either PSA > 50% response, PSA PFS or OS. Conclusions: The combination of 177 Lu-PSMA 617 + NOX66 appears safe and efficacious in men with heavily pre-treated mCRPC. Exploratory analysis of ARV7 expression and quantitative PET imaging markers of treatment response and resistance is in progress. Clinical trial information: ACTRN12618001073291. [Table: see text]

Phase I/II Trial of the Combination of 177Lutetium Prostate specific Membrane Antigen 617 and Idronoxil (NOX66) in Men with End-stage Metastatic Castration-resistant Prostate Cancer (LuPIN)

BACKGROUND

Trials of lutetium prostate specific membrane antigen (PSMA) in men with metastatic castration-resistant prostate cancer (mCRPC) have demonstrated good safety and efficacy, but combination strategies may improve outcomes. Idronoxil is a synthetic flavonoid derivative with radiosensitising properties.

OBJECTIVE

To evaluate the safety and activity of ¹⁷⁷Lu PSMA 617 (LuPSMA-617) in combination with idronoxil suppositories (NOX66) in patients with end-stage mCRPC.

DESIGN, SETTING, AND PARTICIPANTS

Thirty-two men with progressive mCRPC previously treated with taxane-based chemotherapy (91% treated with both docetaxel and cabazitaxel) and abiraterone and/or enzalutamide were enrolled in this phase I dose escalation study with phase II dose expansion.

INTERVENTION

Screening with ⁶⁸Ga PSMA and ¹⁸F-fludeoxyglucose positron emission tomography (PET)/computed tomography (CT) was performed. Men received up to six cycles of LuPSMA-617 (7.5 GBq) on day 1, with escalating doses of NOX66 on days 1-10 of a 6-wk cycle. Cohort 1 (n = 8) received 400 mg and cohort 2 (n = 24) 800 mg of NOX66.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Adverse events (AEs), pain inventory scores, prostate-specific antigen (PSA) response, progression-free survival, and overall survival were evaluated.

RESULTS AND LIMITATIONS

Fifty-six men were screened and 32 (57%) were enrolled with a screen failure rate of 21% for PET imaging criteria. Dosing was as follows: 97% (31/32) received two or more doses and 47% (15/32) completed six doses. Common AEs included xerostomia, fatigue, and anaemia. Anal irritation attributable to NOX66 occurred in 28%. PSA responses were as follows: 91% (29/32) had any PSA response (median -74%; 95% confidence interval [CI] 76-97) and 62.5% (20/32) had a PSA fall of >50% (95% CI 45-77). The median PSA progression-free survival was 6.1 mo (95% CI 2.8-9.2) and median overall survival was 17.1 mo (95% CI 6.5-27.1).

CONCLUSIONS

NOX66 with LuPSMA-617 is a safe and feasible therapeutic strategy in men treated with third-line therapy and beyond for mCRPC.

PATIENT SUMMARY

Addition of NOX66 to ¹⁷⁷Lu prostate-specific membrane antigen 617 is safe, and further studies are needed to assess its potential to augment the anticancer effects of LuPSMA-617.

Updated results of a phase I/II prospective dose escalation trial evaluating safety and efficacy of combination 177Lu PSMA 617 and idronoxil in men with mCRPC post androgen signalling inhibition and taxane chemotherapy (LuPIN trial)

5557

Background: There is no established standard of care post cabazitaxel in men with mCRPC. Ongoing trials in 177LuPSMA-617 have demonstrated good efficacy and safety, but synergistic combinations may further improve treatment responses. Idronoxil (NOX66) inhibits external NADH oxidase type 2 with downstream pro-apoptotic actions including radio-sensitization. Herein we present updated results and an additional cohort of a prospective single arm phase I/II dose escalation/expansion trial of LuPSMA-617 and NOX66 in mCRPC. Methods: Men with progressive mCRPC post androgen signalling inhibition (ASI) and 2 lines of taxane chemotherapy were considered eligible. Key inclusion criteria included PSMA PET/CT intensity SUV max > 15 with no discordant disease on FDG PET/CT, Hb >10, Platelets >100 and GFR >40mls/min. Enrolled patients received up to 6 doses of 177 Lu-PSMA 617 (7.5Gbq) day 1 every 6 weeks in combination with NOX66 days 1-10 each cycle. Cohort 1 (n=8) received 400mg NOX66. Cohorts 2 and 3 subsequently received 800mg and 1200mg of NOX66, respectively, following safety reviews. Data regarding safety, efficacy, pain scores, and QOL were collected. Results: 32 men were enrolled in cohorts 1&2 (November 2017 – June 2019) and 24 in cohort 3 (August 2019-February 2020). To date there have been no dose-limiting toxicities. Data for cohort 3 are immature. For cohorts 1 & 2: 31/32 men received ≥2 cycles, with 12/32 (47%) completing 6 cycles. Any PSA response was seen in 84% (27/32), with a PSA response > 50% in 62.5% (20/32). Median PSA PFS is 6.1 months Of men with increased baseline pain scores ≥3 (24/32), 50% (12/24) had a clinically significant reduction in pain indicators. Adverse events are summarized below. Updated results for cohorts 1 and 2 and preliminary results of cohort 3 will be presented. Conclusions: Combination LuPSMA-617 + NOX 66 appears safe and efficacious in men with heavily pre-treated end stage mCRPC. Clinical trial information: ACTRN12618001073291 .

Results of a phase I/II prospective dose-escalation trial evaluating safety and efficacy of combination 177LuPSMA-617 and NOX66 in men with mCRPC post androgen signalling inhibition and two lines of taxane chemotherapy (LuPIN trial)

120

Background: Despite treatment advances, metastatic castrate resistant prostate cancer (mCRPC) remains a lethal disease. Trials in 177LuPSMA-617 have demonstrated good efficacy and safety, but synergistic combinations may further improve treatment responses. NOX66 inhibits external NADH oxidase type 2 with downstream pro-apoptotic actions including radio-sensitization. We present results of a prospective open label single arm phase 1/2 dose escalation/expansion trial of 177LuPSMA-617 and NOX66 in mCRPC. Methods: Men with progressive mCRPC post androgen signalling inhibition (ASI) and taxane chemotherapy were eligible. Inclusion criteria included PSMA PET/CT intensity > SUV max 15, with no discordant disease on FDG PET/CT, Hb > 100 g/L, Platelets > 90 x 106/L and GFR > 40 mL/min. Protocol allowed up to 6 doses of 177 Lu-PSMA 617 (7.5Gbq) on day 1 with NOX66 (suppository) given day 1-10 at 6-weekly intervals; the first 8 men received 400mg NOX66. After safety review, dose was escalated to 800mg. Data regarding safety, efficacy, pain scores, and QOL were collected. Results: 32/43 (26% imaging screen failures) screened men were enrolled (November 2017 – June 2019), of whom 100% had prior docetaxel and ASI, and 94% (30/32) cabazitaxel. All men received ≥ 2 cycles, with 12/32 completing 6 cycles, and 16/32 2 - 5 cycles, while 4/32 remain on treatment. Any PSA response was seen in 84% (27/32), with a PSA response > 50% in 62.5% (20/32). Median PSA PFS was 6.5 months (95%CI 3.54-9.3). To date, 72% (23/32) of patients have progressed. 34% (11/32) men have died with median OS not reached. 50% (12/24) of men with baseline pain scores ≥3 (24/32) had significant reduction in pain. Adverse events are summarized below. Conclusions: Combination 177LuPSMA-617 with NOX66 appears safe and efficacious in men with heavily pre-treated mCRPC. Clinical trial information: ACTRN12618001073291. [Table: see text]

Expression of cancer stem cell markers is prognostic in metastatic gastroesophageal adenocarcinoma

Gastroesophageal adenocarcinoma is a common and highly lethal malignancy. Cancer stem cells (CSCs) have a key role in the development and progression of metastatic disease. While expression of CSC markers CD44, CD133 and aldehyde dehydrogenase 1 (ALDH1) in locoregional gastroesophageal cancer is known to be associated with poorer clinical outcomes, the significance of CSC marker expression in distal metastatic disease is unknown. We investigated the clinicopathological and prognostic associations of the CSC markers, CD44, CD133, and ALDH1, on metastatic deposits from gastroesophageal adenocarcinomas, and evaluated the association of CSC expression with urokinase-type plasminogen activator receptor (uPAR) expression. Of the 36 patients included in the study, 16 (44%) were positive for CD44, 13 (36%) were positive for CD133, and 26 (72%) were positive for ALDH1. CD44 expression was significantly associated with poorer overall survival (OS) in univariate [hazard ratio (HR) 2.9, 95% confidence interval (CI) 1.3-6.9, p=0.008] and multivariate analyses (HR 2.5, 95%CI 1.1-6.2, p=0.04). ALDH1 expression was significantly associated with poorer OS in univariate (HR 2.4, 95% CI 1.01-5.7, p=0.04) analysis but was not significant in multivariate analysis. Both CD44 and ALDH1 expression were significantly associated with uPAR expression. We found no association between CD133 expression and OS. CD44 expression on metastatic disease from gastroesophageal adenocarcinomas is an independent prognostic marker associated with poorer OS. These results expand current evidence to support the role of CSCs as biomarkers in metastatic gastroesophageal cancer.

Expression of growth differentiation factor 6 in the human developing fetal spine retreats from vertebral ossifying regions and is restricted to cartilaginous tissues

During embryogenesis vertebral segmentation is initiated by sclerotomal cell migration and condensation around the notochord, forming anlagen of vertebral bodies and intervertebral discs. The factors that govern the segmentation are not clear. Previous research demonstrated that mutations in growth differentiation factor 6 resulted in congenital vertebral fusion, suggesting this factor plays a role in development of vertebral column. In this study, we detected expression and localization of growth differentiation factor 6 in human fetal spinal column, especially in the period of early ossification of vertebrae and the developing intervertebral discs. The extracellular matrix proteins were also examined. Results showed that high levels of growth differentiation factor 6 were expressed in the nucleus pulposus of intervertebral discs and the hypertrophic chondrocytes adjacent to the ossification centre in vertebral bodies, where strong expression of proteoglycan and collagens was also detected. As fetal age increased, the expression of growth differentiation factor 6 was decreased correspondingly with the progress of ossification in vertebral bodies and restricted to cartilaginous regions. This expression pattern and the genetic link to vertebral fusion suggest that growth differentiation factor 6 may play an important role in suppression of ossification to ensure proper vertebral segmentation during spinal development.