Curative-intent Metastasis-directed Therapies for Molecularly-defined Oligorecurrent Prostate Cancer: A Prospective Phase II Trial Testing the Oligometastasis Hypothesis

Four-year Prostate-specific Antigen Response Rate as a Predictive Measure in Intermediate-risk Prostate Cancer Treated With Ablative Therapies: The SPRAT Analysis

AIMS

There is a lack of early predictive measures of outcome for patients with intermediate-risk prostate cancer (PCa) treated with stereotactic body radiotherapy (SBRT). The aim of the present study was to explore 4-year prostate-specific antigen response rate (4yPSARR) as an early predictive measure.

MATERIALS AND METHODS

Individual patient data from six institutions for patients with intermediate-risk PCa treated with SBRT between 2006 and 2016 with a 4-year (42-54 months) PSA available were analysed. Cumulative incidences of biochemical failure and metastasis were calculated using Nelson-Aalen estimates and overall survival was calculated using the Kaplan-Meier method. Biochemical failure-free survival was analysed according to 4yPSARR, with groups dichotomised based on PSA <0.4 ng/ml or ≥0.4 ng/ml and compared using the Log-rank test. A multivariable competing risk analysis was carried out to predict for biochemical failure and the development of metastases.

RESULTS

Six hundred and thirty-seven patients were included, including 424 (67%) with favourable and 213 (33%) with unfavourable intermediate-risk disease. The median follow-up was 6.2 years (interquartile range 4.9-7.9). The cumulative incidence of biochemical failure and metastasis was 7 and 0.6%, respectively; overall survival at 6 years was 97%. The cumulative incidence of biochemical failure at 6 years if 4yPSARR <0.4 ng/ml was 1.7% compared with 27% if 4yPSARR ≥0.4 ng/ml (P < 0.0001). On multivariable competing risk analysis, 4yPSARR was a statistically significant predictor of biochemical failure-free survival (subdistribution hazard ratio 15.3, 95% confidence interval 7.5-31.3, P < 0.001) and metastasis-free survival (subdistribution hazard ratio 31.2, 95% confidence interval 3.1-311.6, P = 0.003).

CONCLUSION

4yPSARR is an encouraging early predictor of outcome in patients with intermediate-risk PCa treated with SBRT. Validation in prospective trials is warranted.

Toxicity and Efficacy of Local Ablative, Image-guided Radiotherapy in Gallium-68 Prostate-specific Membrane Antigen Targeted Positron Emission Tomography-staged, Castration-sensitive Oligometastatic Prostate Cancer: The OLI-P Phase 2 Clinical Trial

BACKGROUND

Local ablative radiotherapy (aRT) of oligometastatic prostate cancer (PCa) is very promising and has become a focus of current clinical research.

OBJECTIVE

We hypothesize that aRT is safe and effective in gallium-68 prostate-specific membrane antigen targeted positron emission tomography (PSMA-PET)-staged oligometastatic PCa patients.

DESIGN, SETTING, AND PARTICIPANTS

A nonrandomized, prospective, investigator-initiated phase 2 trial recruited patients with oligometastatic PCa (five or fewer lymph node or osseous metastases) after local curative therapy, without significant comorbidity and androgen deprivation therapy (ADT), at two German centers from 2014 to 2018.

INTERVENTION

All PSMA-PET-positive metastases were treated with aRT. No systemic therapy was initiated.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The primary endpoint was treatment-related toxicity (grade ≥2) 24 mo after aRT. A one-sided single-sample test of proportions was planned to test whether the endpoint occurs in <15% of the patients. Key secondary endpoints were time to progression of prostate-specific antigen (PSA) and time to ADT, which were associated with potential prognostic factors by Cox regression.

RESULTS AND LIMITATIONS

Of 72 patients, 63 received aRT (13% dropout rate). The median follow-up was 37.2 mo. No treatment-related grade ≥2 toxicity was observed 2 yr after treatment. The median time to PSA progression and time to ADT were 13.2 and 20.6 mo, respectively. Of the patients, 21.4% were free of PSA progression after 3 yr.

CONCLUSIONS

It was observed that aRT is safe, and midterm PSA progression and ADT-free time were achieved in one of five patients. Randomized clinical trials are indicated to further evaluate the option of delaying ADT in selected patients.

PATIENT SUMMARY

In this clinical trial, 63 patients with up to five metastases of prostate cancer without androgen deprivation therapy were included. We showed that local ablative radiotherapy is safe and that one in five patients had no recurrent prostate-specific antigen value after 3 yr. Local ablative radiotherapy might be an option to avoid systemic therapy in selected patients.

18F-DCFPyL (PSMA) PET in the Management of Men with Biochemical Failure after Primary Therapy: Initial Clinical Experience of an Academic Cancer Center

Purpose: To describe the initial experience of an academic center using ¹⁸F-DCFPyL PET in managing men with recurrent prostate cancer. Materials & Methods: This prospective, single-arm IRB-approved study included men with biochemical failure after primary therapy for prostate cancer and negative/equivocal CT and bone scintigraphy who were candidates for salvage therapy, as determined by a multidisciplinary panel of experts. ¹⁸F-DCFPyL PET was assessed for the presence and extent of recurrence: local, oligometastatic (≤4), or extensive. Post-PET management and clinical outcome, including PSA response, was documented. For patients who received PET-directed ablative therapies, response was categorized as “complete” if PSA became undetectable or “favorable” if PSA decreased ≥50%. Results: Forty-seven men with biochemical failure after radical prostatectomy (n = 29), primary radiotherapy (n = 15) or focal tumor ablation (n = 3) were included. PET was positive in (43/47) 91.5%, including local recurrence in (9/47) 19.2%; oligometastatic disease in (16/47) 34%; and extensive metastatic disease in (18/47) 38.3%. PET-directed focal ablative therapies without systemic therapy were given to (13/29) 44.8% of patients without extensive metastases on PET with a mean PSA response of 69% (median, 74.5%; range: 35–100). Favorable biochemical response was observed in (10/13) 76.9% of patients with limited recurrence on PET, and in 23.1% (3/13), there was complete response. Conclusion: ¹⁸F-DCFPyL PET was positive in >90% of patients with biochemical failure. For those with limited recurrence, PSMA PET-directed local ablative therapies resulted in favorable outcome in more than 3 in 4 patients, and in nearly a quarter of them, there was complete biochemical response.

Incorporating PSMA-Targeting Theranostics Into Personalized Prostate Cancer Treatment: a Multidisciplinary Perspective

Recent developments in prostate-specific membrane antigen (PSMA) targeted diagnostic imaging and therapeutics (theranostics) promise to advance the management of primary, biochemically recurrent, and metastatic prostate cancer. In order to maximize the clinical impact of PSMA-targeted theranostics, a coordinated approach between the clinical stakeholders involved in prostate cancer management is required. Here, we present a vision for multidisciplinary use of PSMA theranostics from the viewpoints of nuclear radiology, medical oncology, urology, and radiation oncology. We review the currently available and forthcoming PSMA-based imaging and therapeutics and examine current and potential impacts on prostate cancer management from early localized disease to advanced treatment-refractory disease. Finally, we highlight the clinical and research opportunities related to PSMA-targeted theranostics and describe the importance of multidisciplinary collaboration in this space.

Single-Center Experience of Focal Thermo-Ablative Therapy After Pelvic Radiotherapy for In-Field Prostate Cancer Oligo-Recurrence

PURPOSE

In-field prostate cancer (PCa) oligo-recurrence after pelvic radiotherapy is a challenging situation for which metastasis-directed treatments may be beneficial, but options for focal therapies are scarce.

METHODS

We retrospectively reviewed data for patients with three or less in-field oligo-recurrent nodal, bone and/or locally recurrent (prostate, seminal vesicles, or prostatic bed) PCa lesions after radiation therapy, identified with molecular imaging (PET and/or MRI) and treated by focal ablative therapy (cryotherapy or radiofrequency) at the Institut Bergonié between 2012 and 2020. Chosen endpoints were the post-procedure PSA response (partially defined as a >50% reduction, complete as a PSA <0.05 ng/ml), progression-free survival (PFS) defined as either a biochemical relapse (defined as a rise >25% of the Nadir and above 2 ng/ml), radiological relapse (on any imaging technique), decision of treatment modification (hormonotherapy initiation or line change) or death, and tolerance.

RESULTS

Forty-three patients were included. Diagnostic imaging was mostly 18F-Choline positron emission tomography/computerized tomography (PET/CT) (75.0%), prostate specific membrane antigen (PSMA) PET/CT (9.1%) or a combination of pelvic magnetic resonance imaging (MRI), CT, and 99 mTc-bone scintigraphy (11.4%). PSA response was observed in 41.9% patients (partial in 30.3%, complete in 11.6%). In the hormone-sensitive exclusive focal ablation group (n = 31), partial and complete PSA responses were 32.3 and 12.9% respectively. Early local control (absence of visible residual active target) on the post-procedure imaging was achieved with 87.5% success. After a median follow-up of 30 months (IQR 13.3-56.8), the median PFS was 9 months overall (95% CI, 6-17), and 17 months (95% CI, 11-NA) for PSA responders. Complications occurred in 11.4% patients, with only one grade IIIb Dindo-Clavien event (uretral stenosis requiring endoscopic uretrotomy).

CONCLUSION

In PCa patients showing in-field oligo-recurrence after pelvic radiotherapy, focal ablative treatment is a feasible option, possibly delaying a systemic treatment initiation or modification. These invasive strategies should preferably be performed in expert centers and discussed along other available focal strategies in multi-disciplinary meetings.

Better survival of patients with oligo- compared with polymetastatic cancers: a systematic review and meta-analysis of 173 studies

Background: The modern concept of oligometastatic (OM) state has been initially developed to describe patients with a low burden of disease and with a potential for cure with local ablative treatments. We systematically assessed the risk of death and relapse of oligometastatic (OM) cancers compared to cancers with more diffuse metastatic spread, through a meta-analysis of published data.  Methods: PubMed, the Cochrane Library, and EMBASE were searched for studies reporting prognosis of patients with OM solid tumors. Risk of death and relapse were extracted and pooled to provide an adjusted hazard ratio with a 95% confidence interval (HR 95%CI).  The primary outcome of the study refers to overall mortality in OM vs. polymetastatic (PM) patients.  Results. Mortality and relapse associated with OM state in patients with cancer were evaluated among 104,234 participants (n=173 studies). Progression-free survival was better in patients with OM disease (hazard ratio [HR] = 0.62, 95% CI 0.57-0.68; P <.001; n=69 studies). Also, OM cancers were associated with a better overall survival (OS) (HR = 0.65, 95% CI 0.62-0.68; P<.01; n=161 studies). In colorectal (CRC), breast, non-small cell lung cancer (NSCLC) and renal cell carcinoma (RCC) the reduction in the risk of death for OM patients were 35, 38, 30 and 42%, respectively. Biliary tract and cervical cancer do not significantly better in OM stage likely for paucity of data. Conclusions. Patients with OM cancers have a significantly better prognosis than those with more widespread stage IV tumors. In OM cancer patients a personalized approach should be pursued.

Better survival of patients with oligo- compared with polymetastatic cancers: a systematic review and meta-analysis of 173 studies

Background: The modern concept of oligometastatic (OM) state has been initially developed to describe patients with a low burden of disease and with a potential for cure with local ablative treatments. We systematically assessed the risk of death and relapse of oligometastatic (OM) cancers compared to cancers with more diffuse metastatic spread, through a meta-analysis of published data.  Methods: PubMed, the Cochrane Library, and EMBASE were searched for studies reporting prognosis of patients with OM solid tumors. Risk of death and relapse were extracted and pooled to provide an adjusted hazard ratio with a 95% confidence interval (HR 95%CI).  The primary outcome of the study refers to overall mortality in OM vs. polymetastatic (PM) patients.  Results. Mortality and relapse associated with OM state in patients with cancer were evaluated among 104,234 participants (n=173 studies). Progression-free survival was better in patients with OM disease (hazard ratio [HR] = 0.62, 95% CI 0.57-0.68; P <.001; n=69 studies). Also, OM cancers were associated with a better overall survival (OS) (HR = 0.65, 95% CI 0.62-0.68; P<.01; n=161 studies). In colorectal (CRC), breast, non-small cell lung cancer (NSCLC) and renal cell carcinoma (RCC) the reduction in the risk of death for OM patients were 35, 38, 30 and 42%, respectively. Biliary tract and cervical cancer do not significantly better in OM stage likely for paucity of data. Conclusions. Patients with OM cancers have a significantly better prognosis than those with more widespread stage IV tumors. In OM cancer patients a personalized approach should be pursued.