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

Progression-directed therapy in patients with oligoprogressive castration-resistant prostate cancer

PURPOSE

Oligoprogressive lesions are observed in a subset of patients who progress to castration-resistant prostate cancer (CRPC), while other lesions remain controlled by systemic therapy. This study evaluates the impact of progression-directed therapy (PDT) on these oligoprogressive lesions.

MATERIALS AND METHODS

This retrospective study included 40 patients diagnosed with oligoprogressive CRPC. PDT was performed for treating all progressive sites using radiotherapy. Fifteen patients received PDT using radiotherapy for all progressive sites (PDT group) while 25 had additional first-line systemic treatments (non-PDT group). In PDT group, 7 patients underwent PDT and unchanged systemic therapy (PDT-A group) and 8 patients underwent PDT with additional new line of systemic therapy on CRPC (PDT-B group). The Kaplan-Meier method was used to assess treatment outcomes.

RESULTS

The prostate specific antigen (PSA) nadir was significantly lower in PDT group compare to non-PDT group (p=0.007). A 50% PSA decline and complete PSA decline were observed in 13 patients (86.7%) and 10 patients (66.7%) of PDT group and in 18 patients (72.0%) and 11 patients (44.0%) of non-PDT group, respectively. The PSA-progression free survival of PDT-B group was significantly longer than non-PDT group. The median time to failure of first-line systemic therapy on CRPC was 30.2 months in patients in PDT group and 14.9 months in non-PDT group (p=0.014). PDT-B group showed a significantly longer time to progression than non-PDT group (p=0.025). Minimal PDT-related adverse events were observed.

CONCLUSIONS

PDT can delay progression of disease and enhance treatment efficacy with acceptable tolerability in oligoprogressive CRPC.

Study protocol and preliminary results from a mono-centric cohort within a trial testing stereotactic body radiotherapy and abiraterone (ARTO-NCT03449719)

Background

ARTO trial was designed to evaluate the difference in terms of outcomes between patients affected by oligo metastatic castrate resistant prostate cancer (mCRPC) treated with Abiraterone acetate and randomized to receive or not SBRT on all sites of disease. Here, we present a preliminary analysis conducted on patients enrolled at promoting institution.

Objective

To present a preliminary overview about population features, clinical outcomes, adverse events, quality of life and explorative translational research.

Design, setting, and participants

ARTO (NCT03449719) is a phase II trial including patients affected by oligo mCRPC, randomized to receive standard of care (GnRH agonist or antagonist plus abiraterone acetate 1000 mg and oral prednisone 10 mg daily) with or without SBRT on all metastatic sites of disease. All subjects have < 3 bone or nodal metastases. All patients are treated in I line mCRPC setting, no previous lines of treatment for mCRPC are allowed.

Outcome measurements and statistical analysis

Data about a mono-centric cohort of 42 patients enrolled are presented in the current analysis, with focus on baseline population features, PSA drop at 3 months, biochemical response, and quality of life outcomes. Descriptive statistics regarding translational research are also presented.

Results and limitation

Significant difference in terms of PSA drop at three months was not detected (p = 0.68). Biochemical response (PSA reduction > 50%) was reported in 73.7 versus 76.5% of patients in control vs SBRT arm, respectively (p = 0.84). All patients are alive. Progression occurred in 1 versus 0 patients in the control versus SBRT arm, respectively. After 3 months, an average decrease of 13 points in terms of Global Health Score was reported for the overall population. However, complete recovery was noticed at 6 months. Circulating tumor cells detection rate was 40%.

Conclusions

SBRT + Abiraterone treatment was safe and well tolerated, non-significant trend in terms of PSA drop and biochemical response at 3 months was detected in SBRT arm. Interestingly, CTCs detection in this selected cohort of oligo-mCRPC was lower if compared to historical data of unselected mCRPC patients.

Oligoprogressive castration-resistant prostate cancer treated with metastases-directed stereotactic body radiation therapy: predictive factors for patients' selection

Oligoprogression is defined as limited metastatic clone resistant to on-going systemic treatment that grows in a background of stable or responding systemic disease. Aim of the present study was to analyze oligoprogressive prostate cancer (PC) patients treated with stereotactic body radiation therapy (SBRT) during systemic treatment to identify predictive factors and improve patients' selection. We included PC patients treated with SBRT on a maximum of 3 sites of oligoprogression during systemic therapy. Endpoints were freedom from polymetastatic progression (FPP), local control (LC), distant progression free survival (DPFS), overall survival (OS), and next systemic therapy free survival (NEST-FS). Fifty-three patients were treated on 85 oligoprogressive metastases. Lymph nodes were the most common sites (56.47%), followed by bone (39.29%). Median follow-up was 24.9 months. Rates of FPP at 1- and 2-year were 80.1% and 68.9%, respectively. Median time to polymetastatic progression was 33.7 months. Disease free interval (p = 0.004), site of metastases (p = 0.011), and type of systemic therapy (p = 0.003) were significant for FPP. Switch or intensification of systemic therapy after SBRT was observed in 29 (54.72%) patients with a median NEST-FS of 15.2 months. LC at 1- and 2-year was 94.0% and 92.0%, with PSA doubling time resulted to be significantly associated (p = 0.047). Median DPFS was 8.93 months and median OS was 50.6 months. In conclusion, we confirmed the efficacy of SBRT for oligoprogression from PC, with the potential to prolong the on-going systemic therapy and interrupt the metastatic cascade.

Impact of Progressive Site-Directed Therapy in Oligometastatic Castration-Resistant Prostate Cancer on Subsequent Treatment Response

Simple Summary

Local treatment for oligometastatic hormone-naive prostate cancer has been shown to be effective in phase II trials. As for the efficacy of targeted therapy for oligometastatic castration-resistant prostate cancer, the results of the phase trial are not yet available, but the number of reports showing efficacy by retrospective analysis is increasing. Progressive site-directed therapy has been shown to delay the next intervention and prolong progression-free survival, but its impact on subsequent treatment efficacy and contribution to overall survival has not been reported. The purpose of this retrospective study is to evaluate the impact of progressive site-directed therapy for oligometastatic castration-resistant prostate cancer on the subsequent treatment outcomes. We found that progressive site-directed therapy was associated with better response to subsequent androgen receptor axis-targeted drugs and better overall survival. Progressive site-directed therapy for oligometastatic castration-resistant prostate cancer may improve subsequent oncological outcomes.

Abstract

The purpose of this study was to evaluate the impact of progressive site-directed therapy (PSDT) for oligometastatic castration-resistant prostate cancer (OM-CRPC) on the efficacy of subsequent androgen receptor axis-targeted (ARAT) drugs, and to demonstrate the possibility of prolonging overall survival (OS). We performed a retrospective analysis of 15 OM-CRPC patients who underwent PSDT and subsequently received first-line ARAT drugs (PSDT group) and 13 OM-CRPC patients who were treated with first-line ARAT drugs without PSDT (non-PSDT group). PSDT was performed with the intention of treating all progressing sites detected by whole-body diffusion-weighted MRI with radiotherapy. Thirteen patients (86.7%) treated with PSDT had a decrease in PSA levels, which was at least 50% in 10 (66.7%) patients. The median PSA progression-free survival (PFS) for PSDT was 7.4 months. The median PSA-PFS for ARAT was 27.2 months in patients in the PSDT group and 11.7 months in the non-PSDT group, with a significant difference between the two groups (hazard ratio [HR], 0.28; p = 0.010). The median OS was not reached in the PSDT group and was significantly longer than 44.5 months in the non-PSDT group (HR, 0.11; p = 0.014). In OM-CRPC, PSDT may improve the efficacy of subsequent ARAT and OS.

Stereotactic radiotherapy to oligoprogressive lesions detected with 68Ga-PSMA-PET/CT in castration-resistant prostate cancer patients

PURPOSE

We assessed the outcomes of stereotactic body radiotherapy (SBRT) to treat oligoprogressive castration-resistant prostate cancer (CRPC) patients with ≤5 lesions using gallium prostate-specific membrane antigen-positron emission tomography (⁶⁸Ga-PSMA-PET/CT).

METHODS

The clinical data of 67 CRPC patients with 133 lesions treated with ⁶⁸Ga-PSMA-PET/CT-based SBRT were retrospectively analyzed. All of the patients had oligoprogressive disease during androgen-deprivation therapy (ADT). The prognostic factors for overall- (OS) and progression-free survival (PFS) and the predictive factors for switching to next-line systemic treatment (NEST) and NEST-free survival (NEST-FS) were analyzed.

RESULTS

With a median follow-up of 17.5 months, the 2-year overall survival (OS) and PFS rates were 86.9% and 34.4%, respectively. The PSA response was observed in 49 patients (73.1%). Progression was observed in 37 patients (55.2%) at a median of 11.0 months following SBRT. A total of 45 patients (67.2%) remained on ADT after SBRT, and 22 patients (32.8%) had a NEST change at a median of 16.4 months after metastasis-directed treatment (MDT). Patients with a NEST change had higher post-SBRT PSA values and fewer PSA nadirs after MDT than their counterparts. In multivariate analysis, higher pre-SBRT PSA values were the only significant predictor for worse OS and NEST-FS, and no significant factor was found for PFS. No serious acute or late toxicities were observed.

CONCLUSION

This study demonstrated the feasibility of MDT using SBRT to treat oligoprogressive lesions by ⁶⁸Ga-PSMA-PET/CT in CRPC patients is efficient and well-tolerated, prolonging the effectiveness of ADT by delaying NEST.