Rationale for Involved Field Stereotactic Body Radiation Therapy-Enhanced Intermittent Androgen Deprivation Therapy in Hormone-Sensitive Nodal Oligo-Recurrent Prostate Cancer Following Prostate Stereotactic Body Radiation Therapy

Stereotactic Body Radiotherapy for Lymph-Nodal Oligometastatic Prostate Cancer: A Multicenter Retrospective Experience

Background: The favorable role of SBRT for lymph-nodal oligometastases from prostate cancer has been reported by several retrospective and prospective experiences, suggesting a more indolent natural history of disease when compared to patients with bone oligometastases. This retrospective multicenter study evaluates the outcomes of a cohort of patients treated with stereotactic body radiotherapy for lymph-nodal oligometastases. Methods: Inclusion criteria were up to five lymph-nodal oligometastases detected either with Choline-PET or PSMA-PET in patients naïve for ADT or already ongoing with systemic therapy and at least 6 Gy per fraction for SBRT. Only patients with exclusive lymph-nodal disease were included. The primary endpoint of the study was LC; a toxicity assessment was retrospectively performed following CTCAE v4.0. Results: A total of 100 lymph-nodal oligometastases in 69 patients have been treated with SBRT between April 2015 and November 2022. The median age was 73 years (range, 60-85). Oligometastatic disease was mainly detected with Choline-PET in 47 cases, while the remaining were diagnosed using PSMA-PET, with most of the patients treated to a single lymph-nodal metastasis (48/69 cases), two in 14 cases, and three in the remaining cases. The median PSA prior to SBRT was 1.35 ng/mL (range, 0.3-23.7 ng/mL). Patients received SBRT with a median total dose of 35 Gy (range, 30-40 Gy) in a median number of 5 (range, 3-6) fractions. With a median follow-up of 16 months (range, 7-59 months), our LC rates were 95.8% and 86.3% at 1 and 2 years. DPFS rates were 90.4% and 53.4%, respectively, at 1 and 2 years, with nine patients developing a sequential oligometastatic disease treated with a second course of SBRT. Polymetastatic disease-free survival (PMFS) at 1 and 2 years was 98% and 96%. Six patients needed ADT after SBRT for a median time of ADT-free survival of 15 months (range, 6-22 months). The median OS was 16 months (range, 7-59) with 1- and 2-year rates of both 98%. In multivariate analysis, higher LC rates and the use of PSMA-PET were related to improved DPFS rates, and OS was significantly related to a lower incidence of distant progression. No G3 or higher adverse events were reported. Conclusions: In our experience, lymph-nodal SBRT for oligometastatic prostate cancer is a safe and effective option for ADT delay with no severe toxicity.

Stereotactic radiotherapy of nodal oligometastases from prostate cancer: a prisma-compliant systematic review

Androgen deprivation therapy (ADT) is the standard treatment of metastatic prostate cancer (PCa). However, metastases-directed therapies can delay the initiation or switch of systemic treatments and allow local control (LC) and prolonged progression-free survival (PFS), particularly in patients with lymph nodes (LN) oligometastases. We performed a systematic review on stereotactic body radiotherapy (SBRT) in this setting. Papers reporting LC and/or PFS were selected. Data on ADT-free survival, overall survival, and toxicity were also collected from the selected studies. Fifteen studies were eligible (414 patients), 14 of them were retrospective analyses. A high heterogeneity was observed in terms of patient selection and treatment. In one study SBRT was delivered as a single 20 Gy fraction, while in the others the median total dose ranged between 24 and 40 Gy delivered in 3-6 fractions. LC and PFS were reported in 15 and 12 papers, respectively. LC was reported as a crude percentage in 13 studies, with 100% rate in seven and 63.2-98.0% in six reports. Five studies reported actuarial LC (2-year LC: 70.0-100%). PFS was reported as a crude rate in 11 studies (range 27.3-68.8%). Actuarial 2-year PFS was reported in four studies (range 30.0-50.0%). SBRT tolerability was excellent, with only two patients with grade 3 acute toxicity and two patients with grade 3 late toxicity. SBRT for LN oligorecurrences from PCa in safe and provides optimal LC. However, the long-term effect on PFS and OS is still unclear as well as which patients are the best candidate for this approach.

Radiotherapy in oligometastatic prostate cancer-a pattern of care survey among members of the German Society for Radiation Oncology (DEGRO)

Purpose

Due to improved imaging, oligometastatic prostate cancer (OMPC) is diagnosed more frequently. Growing evidence shows that patients with a limited number of metastases benefit from primary-directed radiotherapy (PDT) as well as from metastasis-directed radiotherapy (MDT). This survey investigates the current treatment practice for OMPC among German-speaking radiation oncologists.

Methods

Members of the German Society for Radiation Oncology (Deutsche Gesellschaft für Radioonkologie [DEGRO]) were surveyed regarding their current treatment practice via an anonymous online questionnaire sent by email. The survey included six general items and 14 specific items regarding treatment characteristics. Questionnaires with at least 50% of questions completed were considered for further analysis.

Results

A total of 204 responses were received (15% response rate), 167 were considered for further analysis. Most respondents stated to be specialized in treating prostate cancer patients and to treat 10–30 patients with OMPC per annum; 97% considered PSMA-PET/CT necessary to define oligometastatic disease. Opinions differed regarding the use of systemic therapies: 63% of the respondents aimed to defer systemic therapy using radiotherapy in OMPC, whereas 37% considered systemic therapy necessary. In the setting of synchronous OMPC, 97% recommended PDT with or without a combination of MDT and/or systemic therapy. For metachronous nodal or bone oligometastatic recurrence, 98 and 99%, respectively, would opt for MDT. The majority would combine MDT with systemic therapy in patients with metachronous oligorecurrence. Respondents recommended normofractionation, hypofractionation, and SBRT for lymph node metastases in 49, 27, and 24%, respectively. No consensus existed regarding the field size for MDT of lymph node metastases. Most respondents preferred > 5 fractions for treatment of bone metastases.

Conclusion

Local radiotherapy for PDT and MDT is routinely used among respondents of this survey, representing 12% of all German-speaking radiation oncologists. The timing of systemic therapy, fractionation schedules, and field sizes are handled differently and remain an area of active investigation.