Pilot Study of a Novel Ring Gantry-Based PET/CT Linear Accelerator in Patients with Prostate Cancer Receiving [18F]-DCFPyL for PSMA PET Imaging

PURPOSE/OBJECTIVE(S)

The RefleXion X1® system is a hybrid PET imaging-radiotherapy system that uses real-time positron emissions from a PET tracer to deliver biologically guided radiotherapy (BgRT). This study (NCT05470699) evaluated the hypothesis that the X1 PET imaging subsystem would be able to detect [18F]-DCFPyL PSMA PET signal sufficient to generate a deliverable BgRT plan in patients with prostate cancer.

MATERIALS/METHODS

Patients with prostate cancer scheduled for a diagnostic [18F]-DCFPyL PSMA PET scan as part of standard of care were eligible. Upon completion of the diagnostic PSMA PET scan, images were transferred to the radiotherapy planning system for target identification and contouring. If at least one PET avid tumor lesion was identified, the patient was then scanned on the X1 unit. BgRT planning was performed on each X1 scanned patient. The target lesion volume, activity concentration (AC) and normalized target signal (NTS) were acquired. Successful and deliverable BgRT plans required that the target AC was ≥ 5 kBq/ml and NTS ≥ 2.7.

RESULTS

Twenty-six patients underwent [18F]-DCFPyL PET scans (13 with rising PSA after surgery or radiotherapy, 6 with known metastases and 7 with newly diagnosed high-risk prostate cancer). Median (range) PSA was 3.40 (0.04-122). In 16 patients a PET avid tumor was identified and contoured for planning (4 lymph nodes, 5 bone, 6 prostate gland, and 1 prostate bed). In 13 patients the target lesion was visualized on the X1 PET scan, while in 3 patients the target lesion was too close to the bladder to be clearly visualized. BgRT planning was feasible and met standard of care published SBRT organ dose constraints in 8 patients (3 prostate gland, 3 bone, 2 lymph nodes). BgRT planning was not feasible in 8 patients due to insufficient AC, low NTS or proximity of the target lesion to the PET avid bladder. The accompanying table compares median (range) target volume, AC and NTS for feasible versus not feasible plans.

CONCLUSION

This is the first study to investigate the feasibility of using [18F]-DCFPyL PET imaging for BgRT plan generation on the X1 system in patients with prostate cancer. Lesions that are relevant to radiotherapy of prostate cancer can be visualized including lymph node and bone metastases. A dedicated BgRT workflow with PSMA PET imaging on the X1 at 60 minutes post injection will result in higher target AC and will optimize BgRT planning. PET avid lesions < 1 cm or close to the bladder may make BgRT planning challenging. [18F]-DCFPyL-guided BgRT is technically feasible using the RefleXion X1. BgRT using targeted PET radiopharmaceuticals to biologically guide external beam radiotherapy represents a promising new dimension in radiation oncology and warrants further investigation.

Dosimetric Plan Evaluation of Biology Guided Radiotherapy Using [18F]-DCFPyL PSMA Radiotracer in Patients with Prostate Cancer

PURPOSE/OBJECTIVE(S)

The X1 system represents a cutting-edge solution in radiotherapy delivery, with its capability to perform Biology Guided Radiotherapy (BgRT). The system utilizes real-time positron emission tomography (PET) signal as biological fiducials to provide tracked dose delivery and is initially available for use with [18F]-Fluorodeoxyglucose (FDG). The aim of this research study is to assess the quality of BgRT treatment plans for prostate cancer using patients' PSMA PET images obtained on the X1 system.

MATERIALS/METHODS

Sixteen patients with at least one PET-avid tumor identified on their whole-body diagnostic PSMA PET scan were selected. These patients were scanned on X1 following their diagnostic scan without additional radiotracer administration. Based on the X1 PET images, a BgRT plan was created for each patient, with the prescription dose determined by the location of treatment sites. The planning objectives of organs-at-risk (OARs) were established in accordance with the 2018 Timmerman guidelines. Target coverage objective was the dose covering 95% (D95%) of the planning target volume (PTV) to be higher than 100%. The following parameters were analyzed: PTV D95%, the minimal dose (Dmin) of gross tumor volume (GTV), plan maximum dose (Dmax), conformity index (CI), gradient index (GI), and maximum point dose (D0.03cc) to the nearest OARs. The X1 BgRT planning system also generated dose volume histogram (DVH) bounds, which model variations in BgRT delivery. The low boundary of GTV Dmin, representing the minimum GTV dose in the worst-case scenario, was recorded.

RESULTS

BgRT plans were created for all patients, except for one where the target signal was indistinguishable from the bladder. The prescription dose was 2700 cGy or 3000 cGy in 3 fractions for lymph node lesions, 2400 cGy to 3000 cGy in 3 fractions for bone metastasis, and 4500 cGy in 5 fractions for lesions in prostate. All plans met the dose constraints for OARs as per the Timmerman guidelines. The Dmax of all plans was 129.9% ± 6.9% (mean ± standard deviation). The PTV D95% and GTV Dmin were 101.7% ± 1.0% and 111.0% ± 7.6%, respectively. The low boundary of GTV Dmin was 95.9% ± 5.8%. The CI and GI were 1.22 ± 0.11 and 9.40 ± 2.12, respectively. The D0.03cc to nearest OARs was 84.6% ± 25.4%. The estimated treatment time was 699 ± 228 seconds.

CONCLUSION

This study is a pioneering effort to evaluate the quality of BgRT plans for prostate cancer patients using the [18F]-DCFPyL PSMA radiotracer. Our results showed that all BgRT plans met the planning objectives defined in the Timmerman protocol. BgRT with [18F]-DCFPyL represents a promising treatment modality for patients with prostate cancer. Further research is needed to validate this approach, including a comprehensive assessment of the dosimetric and tracking accuracy through physical measurements.

A review of clinical effects associated with metabolic syndrome and exercise in prostate cancer patients

Androgen deprivation therapy (ADT), a primary treatment for locally advanced or metastatic prostate cancer, is associated with the adverse effects on numerous physiologic parameters, including alterations in cardiometabolic variables that overlap with components of the metabolic syndrome (MetS). As MetS is an established risk factor for cardiovascular mortality and treatment for prostate cancer has been associated with the development of MetS, interventions targeting cardiometabolic factors have been investigated in prostate cancer patients to attenuate the detrimental effects of ADT. Much support exists for exercise interventions in improving MetS variables in insulin-resistant adults, but less evidence is available in men with prostate cancer. Regular exercise, when performed at appropriate intensities and volumes, can elicit improvements in ADT-related adverse effects, including MetS, and contributes to the growing body of literature supporting the role of exercise in cancer survivorship. This review (1) discusses the biologic inter-relationship between prostate cancer, ADT and MetS, (2) evaluates the current literature in support of exercise in targeting MetS and (3) describes the physiological mechanisms by which exercise may favorably alter MetS risk factors in prostate cancer patients on ADT.

Patient experience in the treatment of metastatic castration-resistant prostate cancer: state of the science

Background:

Contemporary therapies for metastatic castration-resistant prostate cancer (mCRPC) have shown survival improvements, which do not account for patient experience and health-related quality of life (HRQoL).

Methods:

This literature review included a search of MEDLINE for randomized clinical trials enrolling ⩾50 patients with mCRPC and reporting on patient-reported outcomes (PROs) since 2010.

Results:

Nineteen of 25 publications describing seven treatment regimens (10 clinical trials and nine associated secondary analyses) met the inclusion criteria and were critically appraised. The most commonly used measures were the Functional Assessment of Cancer Therapy-Prostate (n=5 trials) and Brief Pain Inventory Short Form (n=4 trials) questionnaires. The published data indicated that HRQoL and pain status augmented the clinical efficacy data by providing a better understanding of treatment impact in mCRPC. Abiraterone acetate and prednisone, enzalutamide, radium-223 dichloride and sipuleucel-T offered varying levels of HRQoL benefit and/or pain mitigation versus their respective comparators, whereas three treatments (mitoxantrone, estramustine phosphate and docetaxel, and cabazitaxel) had no meaningful impact on HRQoL or pain. The main limitation of the data were that the PROs utilized were not developed for use in mCRPC patients and hence may not have comprehensively captured symptoms important to this population.

Conclusions:

Recently published randomized clinical trials of new agents for mCRPC have captured elements of the patient experience while on treatment. Further research is required to standardize methods for measuring, quantifying and reporting on HRQoL and pain in patients with mCRPC in the clinical practice setting.

Penile cancer: current therapy and future directions

Background Penile cancer (PC) is a rare cancer in western countries, but is more common in parts of the developing world. Due to its rarity and the consequent lack of randomized trials, current therapy is based on retrospective studies and small prospective trials. Design Studies of PC therapy were searched in PubMed and abstracts at major conferences. Results PC is generally an aggressive malignancy characterized by early locoregional lymph node (LN) spread and later metastases in distant sites. Given the strong predictive value of LN involvement for overall survival, evaluating regional LNs is critical. Advanced LN involvement is increasingly being treated with multimodality therapy incorporating chemotherapy and/or radiation. A single superior cisplatin-based regimen has not been defined. Further advances may occur with a better collaboration on an international scale and comprehensive understanding of tumor biology. To this end, the preventive role of circumcision and understanding of the oncogenic roles of Human Papilloma Virus-16, and smoking may yield advances. Preliminary data suggest a role for agents targeting epidermal growth factor receptor and angiogenesis. Conclusion Advances in therapy for PC will require efficient trial designs, synergistic collaboration, incentives to industry and the efforts of patient advocacy groups and venture philanthropists.

EGFR, TS, and ERCC1 expression in penile squamous cancer (PSC)

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Background: PSC is an aggressive disease with devastating consequences. While near-universal EGFR overexpression has been documented, little is known about its clinical implications, and the potential role of KRAS mutations has not been described. In other tumor types, ERCC1 and TS expression are associated with response to platinum and 5FU chemotherapy, but have not yet been evaluated in PSC.

Methods: After IRB approval, 28 PSC patients treated at LAC-USC were identified with tumor specimens available. Testing for EGFR, TS, and ERCC1 expression relative to internal standard gene was performed by real-time RT-PCR and correlated with clinical features.

Results: The median age was 45 (30-78). There were 2 Black, 1 Asian, 1 White, and 15 Hispanic men; 9 had unspecified race. T stages included 4 Tis, 6 T1, 17 T2, and 9 T3; 11 men had lymph node (LN) involvement. No KRAS mutations were identified. EGFR had the highest relative expression (median 4.65, range 1.6-44.2), followed by TS (median 1.69, range 0.49-4.69); ERCC1 overexpression was rare (median 0.54, range 0.21-1.29). Higher EGFR expression was significantly associated with poor differentiation (median 12.5 compared to 3.6 for moderate/well differentiated tumors) on continuous (p=0.03 by Mann Whitney) and cut-point analysis using >7 (two- sided p=0.03 by Fisher's exact test) but did not correlate with stage. Stage > T2 showed a trend toward higher risk of LN involvement (p=0.06 by chi square). There was no correlation between differentiation and stage, and no significant correlation for ERCC1 or TS with grade or stage.

Conclusions: EGFR overexpression is common in PSC and correlates with tumor grade but not stage, suggesting it may be important for disease progression. The absence of KRAS mutations may portend responsiveness to EGFR- targeted therapy based on experience in other tumors. Low ERCC1 as an association with platinum response will be explored in an expanded cohort.

No significant financial relationships to disclose.

Subclinical hemostatic activation and surgical volume predict peri-operative bleeding with radical prostatectomy

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Background: Subclinical activation of hemostasis and fibrinolysis is common in cancer and has been linked with outcome. We have previously presented (2007 Prostate Cancer Symposium) preliminary data on the relationship of laboratory markers to age and prognostic variables. We now expand our report on peri-operative (op) complication implications in early prostate cancer. Methods: With IRB approval and informed consent, blood was collected prior to open radical retropubic prostatectomy with lymph node dissection. Pre-op therapy, thrombosis, and anticoagulation were exclusion criteria. Plasma was assayed in duplicate for D-dimer, thrombin-antithrombin complex (TAT), IL-6, and IL-8. Relationships to peri-op bleeding/thrombotic events (pre-op to POD#2 hemoglobin (Hgb) drop, estimated blood loss (EBL), transfusion, post-op thrombosis) were analyzed in univariate then multivariable linear regression. Results: 153 subjects have been analyzed. Median age was 63.1 (range 35–81), pre-op PSA was 5.92 ng/mL (0.23–26.2), and 118 (77%) were clinical stage T1c. 117 (76.5%) had disease confined to the prostate; 36 had pT3 and/or lymph node involvement. Pathologic Gleason scores were 6 or less in 68 (44.4%), 7 in 71 (46.4%), and 8 or higher in 14 (9%). Median EBL was 400 mL (range 50-3000), median Hgb drop was 3.5 g/dL (-0.1–6.6), and 8 (5.2 %) required RBC transfusion. One subject experienced a DVT. On univariate analysis, pre-op TAT (p<0.001) and D-Dimer (p=0.023) levels correlated with hemoglobin drop. Platelet count, INR, and aPTT did not predict EBL nor Hgb drop. The 8 who required transfusions had lower pre-op platelet counts than those not requiring transfusion (p=0.004). Higher surgeon volume correlated with lower EBL (p<0.001) and Hgb drop (p=0.002). Multivariable linear regression showed that TAT remained significantly associated with Hgb drop (p=0.008) and surgeon volume with EBL (p<0.001) and Hgb drop (p=0.002). Conclusions: Pre-op activation of the hemostatic system is associated with less surgically related bleeding when assessed by objective measures, predicting drop in Hgb better than PT, aPTT, or platelet counts. Surgeon volume may also predict bleeding by subjective and objective measures.

No significant financial relationships to disclose.

POMB-ACE therapy for patients with international germ cell cancer collaborative group (IGCCCG) poor risk germ cell tumors (GCT): The USC experience

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Background: Patients with poor-risk GCT have low rates of cure with standard therapy, with 3 year overall survival (OS) reported at 50% (IGCCCG, JCO 1997). POMB-ACE is a rapidly alternating, dose dense chemotherapy regimen developed to improve outcomes in this population, with reported 3 year OS of 75% (Bower et al, Ann Oncol 1997). We report our experience with this regimen, including analysis of acute and long-term toxicity. Methods: Subjects with poor-risk GCT, defined by IGCCCG criteria as AFP >10,000, bHCG >50,000, LDH > 10 × ULN, non-testicular primary, or non-pulmonary visceral metastases, who were diagnosed at Los Angeles County General Hospital and USC/Norris Cancer Center between 1998 and 2005 were identified using pathology and admission records. All clinical notes and laboratory data were reviewed. Results: Of 23 poor-risk GCT patients identified, 21 received POMB-ACE; 16 were treated at the county facility. 15 patients were Hispanic. 5 had primary mediastinal tumors. 16 were stage IIIC, 4 stage IIIB, and 1 stage IIIA. The median number of cycles was 8 (range 4–12), with a median interval between treatment cycles of 14 days (range 10–39). There were no treatment-related deaths. Febrile neutropenia occurred in 5.9% of treatment cycles, grade 3/4 hematologic toxicity in 19%, and other Grade 3/4 non-hematologic toxicities in 9.8%. G-CSF support was used with 24% of cycles. Nineteen patients (90%) had a partial response, of whom 8 underwent surgery for residual disease; only 1 had residual active tumor, 4 teratoma. Marker-negative status was achieved in 5 patients (23.8%). With median follow-up of 28 months, 9 subjects have recurred (43%) and 4 have died of disease progression. The estimated 2 year disease-free survival is 54%, and 3 year OS 75%. At the end of treatment, residual neuropathy persisted in 2 patients (9.5%), renal compromise in 2 (9.5%), pulmonary toxicity in 3 (14%), and otoxicity in 1 patient (4.7%). Conclusions: In our modern North American experience, POMB-ACE is feasible to administer, even in an uninsured population. This is an effective option in poor-risk GCT patients, with 3 year OS exceeding that achieved with standard therapy. Acute toxicity is modest, however persistent adverse sequelae are common.

No significant financial relationships to disclose.