A combined biological and clinical rationale for evaluating metastasis directed therapy in the management of oligometastatic prostate cancer

A Phase II Trial of Stereotactic Body Radiation Therapy and Androgen Deprivation for Oligometastases in Prostate Cancer (SBRT-SG 05)

PURPOSE

SBRT-Spanish Group-05 (ClinicalTrials.gov.Identifier: NCT02192788) is a collaborative (SBRT-SG, Grupo de Investigación Clínica en Oncología Radioterápica, and Sociedad Española de Oncología Radioterápica) prospective multicenter phase II trial testing stereotactic body radiation therapy (SBRT) and androgen deprivation therapy (ADT) in patients with oligorecurrent prostate cancer.

METHODS AND MATERIALS

Two cohorts of patients with prostate cancer in an oligorecurrent stage (hormone-sensitive in the principal cohort and castration-resistant in the exploratory cohort) were assigned to receive ADT and SBRT for at least 24 months from the time of the enrollment. Concomitant treatment with chemotherapy, abiraterone, or enzalutamide was not allowed. Oncologic outcomes were assessed in both cohorts. Toxicity was prospectively analyzed.

RESULTS

From 2014 to 2019, 81 patients with a total of 126 lesions from 14 centers met the inclusion criteria, 14 of whom were castration-resistant. With a median follow-up of 40 months (12-58 months), 3-year local recurrence-free survival was 92.5% (95% CI, 79.9%-96.3%) and 85.7% (95% CI, 48.2%-95.6%) in the principal and exploratory cohorts, respectively. In the principal cohort, biochemical relapse-free survival and metastasis progression-free survival at 1, 2, and 3 years were 91% (95% CI, 81%-95.8%), 73.7% (95% CI, 61.1%-82.8%), 50.6% (95% CI, 36.2%-63.3%), and 92% (95% CI, 83%-97%), 81% (95% CI, 70%-89%), and 67% (95% CI, 53%-77%), respectively. In the exploratory cohort, metastasis progression-free survival at 1, 2, and 3 years was 64% (95% CI, 34%-83%), 43% (95% CI, 18%-66%), and 26% (95% CI, 7%-51%), respectively. None of the patients developed grade III or higher toxicity or symptoms related to local progression, and only 2 (2.4%) patients developed grade II toxicity.

CONCLUSIONS

The combination of SBRT and ADT is safe and shows favorable clinical outcomes in patients with hormone-sensitive and castration-resistant prostate cancer. Validation studies are needed in patients with castration-resistant prostate cancer.

Node Oligorecurrence in Prostate Cancer: A Challenge

Within the oligometastatic state, oligorecurrent lymph node disease in prostate cancer represents an interesting clinical entity characterized by a relatively indolent biology that makes it unique: it can be treated radically, and its treatment is usually associated with a long period of control and excellent survival. Additionally, it is an emergent situation that we are facing more frequently mainly due to (a) the incorporation into clinical practice of the PSMA-PET that provides strikingly increased superior images in comparison to conventional imaging, with higher sensitivity and specificity; (b) the higher detection rates of bone and node disease with extremely low levels of PSA; and (c) the availability of high-precision technology in radiotherapy treatments with the incorporation of stereotaxic body radiotherapy (SBRT) or stereotaxic ablative radiotherapy (SABR) technology that allows the safe administration of high doses of radiation in a very limited number of fractions with low toxicity and excellent tolerance. This approach of new image-guided patient management is compelling for doctors and patients since it can potentially contribute to improving the clinical outcome. In this work, we discuss the available evidence, areas of debate, and potential future directions concerning the utilization of new imaging-guided SBRT for the treatment of nodal recurrence in prostate cancer.

Oligometastatic Prostate Cancer: Current Status and Future Challenges

In accordance with the spectrum theory of metastatic disease, an oligometastatic clinical state has been proposed as an intermediary step along the natural history of cancer with few (typically 1-3) metastatic lesions identifiable on imaging that may be amenable to metastasis-directed therapy. Effective therapy of oligometastatic disease is anticipated to impact cancer evolution by delaying progression and improving patient outcome at a minimal or acceptable cost of toxicity. There has been increasing recognition of oligometastatic disease in prostate cancer with the advent of new-generation imaging agents, most notably the recently approved PET radiotracers based on targeting prostate-specific membrane antigen. Early clinical trials with metastasis-directed therapy of oligometastases have provided evidence for delaying the employment of systematic therapy and improving outcome in selected patients. Despite these encouraging results, much needs to be investigated and learned about the underlying biology of the oligometastatic state along the evolutionary clinical course of prostate cancer, the identification of relevant imaging and nonimaging predictive and prognostic biomarkers, and the development of treatment strategies to optimize short-term and long-term patient outcome. We provide a review of the current status and the lingering challenges of this rapidly evolving clinical space in prostate cancer.

OLIGO-AIRO: a national survey on the role of radiation oncologist in the management of OLIGO-metastatic patients on the behalf of AIRO

In the last years, several evidences demonstrated the role of stereotactic body radiotherapy (SBRT) in the oligometastatic disease and the possibility to increase survival in selected patients. In 2020 the study group "biology and treatment of the oligometastatic disease" of the Italian Association of Radiotherapy and Clinical Oncology (AIRO) conducted a survey evaluating the attitude of physicians in treating the oligometastatic disease and the definition of it. An electronic questionnaire was administered online to the society members. 105 questionnaires were returned. 78% responders considered as oligometastatic a disease with ≤ 5 metastases. The majority of the responders (77%) treated > 50 patients in the last year, and 89% responders agreed in considering every oligometastatic tumor susceptible to local treatments. Regarding the clinical management of the oligometastatic disease, the majority of the responders (66%) suggested an interdisciplinary discussion. When choosing a treatment option for fit patients with a single oligometastatic focus, 52% of the responders agreed in proposing only SBRT. In the case of unfit patients with a single oligometastatic lesion the agreement was in favor of the SBRT alone (89%). In the oligoprogressive setting, 41% responders opted to continue the current systemic treatment and to add SBRT, while in the case of oligoresidual disease, 70% responders was in favor of adding SBRT and continuing the current systemic treatment. In conclusions, the survey illustrated the current agreement and prescribing attitude for oligometastatic patients in Italy. The non-homogenous agreement in some clinical scenarios suggest the need of more robust evidence.

Prognostic Risk Classification for Biochemical Relapse-Free Survival in Oligometastatic Recurrent Prostate Cancer Determined by Choline PET

BACKGROUND

Choline positron emission tomography/computed tomography (PET/CT) is a new imaging technique for the detection of oligometastatic (OM) prostate cancer. The aim of this study was to evaluate the outcomes after initial OM diagnoses; treatment, particularly metastasis-directed therapy (MDT); and determine risk groups.

PATIENTS AND METHODS

This multi-center, retrospective study included patients with hormone-sensitive biological relapse after local treatment with curative intent and with fewer than six choline PET/CT metastases. The primary endpoint was biochemical relapse-free survival (bRFS). Risk groups were based on prostate-specific antigen (PSA) ≥ 0.8 ng/mL and metastatic sites at OM cancer diagnosis.

RESULTS

Between October 2012 and December 2016, 177 patients were included, with a median follow-up of 49.02 months. The median bRFS was 39.74 months. In multivariate analyses, bone metastases and PSA ≥ 0.8 ng/mL were associated with worse bRFS. Four risk groups (I to IV; hazard ratio [HR], 5.92; 95% confidence interval [CI], 1.32-26.61) were observed, with median bRFS not reached for group I (PSA < 0.8 ng/mL; node metastasis [M1a]), a 40.00-month bRFS for group II (PSA ≥ 0.8 ng/mL; M1a), 29.97-month bRFS for group III (bone metastasis [M1b], whatever the PSA level); and 22.70-month bRFS for group IV (PSA > 0.8 ng/mL and visceral metastasis [M1c]). MDT plus androgen deprivation therapy (ADT) improved bRFS over MDT alone (48.36 vs. 34.16 months; HR, 2.12; 95% CI, 1.38-3.26), particularly for group II (HR, 2.09; 95% CI, 1.09-4.00), and reached a limit of significance for group III (HR, ;3.79 95% CI, 0.88- 16.38).

CONCLUSION

Prognostic group classifications were confirmed: PSA < 0.8 ng/mL and M1a showed a better outcome than patients with M1c and PSA ≥ 0.8 ng/mL. These results could facilitate patient selection for prospective clinical trials in OM prostate cancer.

Role of 18F-Fluciclovine and Prostate-Specific Membrane Antigen PET/CT in Guiding Management of Oligometastatic Prostate Cancer: AJR Expert Panel Narrative Review

Twenty-five years ago, oligometastatic disease was proposed as an intermediary clinical state of cancer with unique implications for therapies that may impact cancer evolution and patient outcome. Identification of limited metastases that are potentially amenable to targeted therapies fundamentally depends on the sensitivity of diagnostic tools, including new-generation imaging methods. For men with biochemical recurrence after definitive therapy of the primary prostate cancer, PET/CT using either the FDA-approved radiolabeled amino acid analogue ¹⁸F-fluciclovine or investigational radiolabeled agents targeting prostate-specific membrane antigen (PSMA) enables identification of early metastases at lower serum PSA levels than was previously feasible using conventional imaging. Evidence supports PSMA PET/CT as the most sensitive imaging modality available for identifying disease sites in oligometastatic prostate cancer. PSMA PET/CT will likely become the modality of choice after regulatory approval and will drive the development of trials of emerging metastasis-directed therapies such as stereotactic ablative body radiation and radioguided surgery. Indeed, numerous ongoing or planned clinical trials are studying advances in management of oligometastatic prostate cancer based on this heightened diagnostic capacity. In this rapidly evolving clinical environment, radiologists and nuclear medicine physicians will play major roles in facilitating clinical decision making and management of patients with oligometastatic prostate cancer.

Magnetic Resonance Imaging Based Radiomic Models of Prostate Cancer: A Narrative Review

Simple Summary

The increasing interest in implementing artificial intelligence in radiomic models has occurred alongside advancement in the tools used for computer-aided diagnosis. Such tools typically apply both statistical and machine learning methodologies to assess the various modalities used in medical image analysis. Specific to prostate cancer, the radiomics pipeline has multiple facets that are amenable to improvement. This review discusses the steps of a magnetic resonance imaging based radiomics pipeline. Present successes, existing opportunities for refinement, and the most pertinent pending steps leading to clinical validation are highlighted.

Abstract

The management of prostate cancer (PCa) is dependent on biomarkers of biological aggression. This includes an invasive biopsy to facilitate a histopathological assessment of the tumor’s grade. This review explores the technical processes of applying magnetic resonance imaging based radiomic models to the evaluation of PCa. By exploring how a deep radiomics approach further optimizes the prediction of a PCa’s grade group, it will be clear how this integration of artificial intelligence mitigates existing major technological challenges faced by a traditional radiomic model: image acquisition, small data sets, image processing, labeling/segmentation, informative features, predicting molecular features and incorporating predictive models. Other potential impacts of artificial intelligence on the personalized treatment of PCa will also be discussed. The role of deep radiomics analysis-a deep texture analysis, which extracts features from convolutional neural networks layers, will be highlighted. Existing clinical work and upcoming clinical trials will be reviewed, directing investigators to pertinent future directions in the field. For future progress to result in clinical translation, the field will likely require multi-institutional collaboration in producing prospectively populated and expertly labeled imaging libraries.

Integrating stereotactic body radiation therapy (SBRT) and systemic treatments in oligoprogressive prostate cancer: new evidence from the literature

Recent findings from literature evidenced that metastatic prostate cancer often shows heterogeneous response to therapy, with persistent sensibility to systemic treatments after biochemical, clinical, or radiographic progression. This highlights the advantage of integrated approaches in which local ablative treatments (e.g., stereotactic body radiation therapy) could prolong clinical benefit of systemic therapies beyond oligo-progression. Of course, development of predictive biomarker could be helpful in order to select patients who could much benefit from this treatment strategy. Circulating tumor cell detection and analysis could also have a crucial role in this field. A joint effort of two prospective ongoing trials (ARTO, clinical.gov identifier NCT03449719 and PRIMERA, clinical.gov identifier NCT04188275) might help to improve criteria to select patients in whom a local ablative approach might confer significant benefit. In this commentary, we summarized recent data from literature to support this thesis.