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Purpose or objective: Oligoprogression (OPD) is defined as a condition where limited progression (1-3 metastases) is observed in patients undergoing systemic cancer treatment. Local treatment of OPD might delay systemic therapy line switch, which could be beneficial in patients experiencing prolonged global disease control with novel targeted or immune therapies. In this study we investigated the impact on outcome of stereotactic body radiotherapy (SBRT) in patients with OPD from metastatic lung cancer. Materials and methods: Data from a cohort of consecutive patients treated with Cyberknife and Linacbased SBRT between June 2015 and August 2021 were collected. All extracranial metastatic sites of OPD from lung cancer were included. Dose regimens consisted of 24 in 2 fractions, 30-51 Gy in 3 fractions, 30-55 Gy in 5 fractions, 52.5 Gy in 7 fractions and 44-56 Gy in 8 fractions. Dose was expressed as Biological Effective Dose for α/β=10 (BED10). Kaplan-Meyer method was used to calculate Overall Survival (OS), Local Control (LC) and Disease Progression-free Survival (DPFS) from the start date of SBRT to event. Results: Sixty-three patients, 34 female and 29 male were included. Median age was 75 years (range 25–83). All patients received concurrent systemic treatment before the start of the SBRT: 19 chemotherapy (CT) alone (30%), 26 CT plus immunotherapy (IT) or plus Tyrosin kinase inhibitors (TKI) (41%) and 18 IT/TKI alone (29%). SBRT was delivered to lung (n=29), mediastinal node (n=9), bone (n=7), adrenal gland (n=19), other visceral metastases (1) and other node metastases (n=4). A median BED10 of 104 (range 39-151) Gy10 was delivered. After a median follow up of 20 months (range 1-48), median overall survival was median OS was 23 months (figure 1). LC was 93% at 1 year and 87% at 2 years. DPFS was 7 months. At univariate analysis, age, type of systemic treatment, metastatic site receiving SBRT and BED were not significant prognostic factors for overall survival. Conclusion: SBRT in lung cancer patients for oligoprogression resulted in a long median OS of 23 months. One-year LC was 93%. Median DPFS was 7 months, translating into continuation of effective systemic treatment as other metastases grow slowly. SBRT could be useful to postpone the change of chemotherapy and/or immunotherapy. More research is needed to select OPD patients eligible for SBRT. [ABSTRACT FROM AUTHOR]

• Re-irradiation (re-RT) of intracranial recurrent meningiomas is still matter of debate and limited by radiation tolerance of the surrounding tissue and the increased risk of side effects. • Re-RT is increasingly considered in current clinical practice, but its efficacy and safety for brain tumors are still under investigation. The optimal choice of patient selection, RT modalities and dose for re-irradiation are not well established yet. • This retrospective analysis aims at providing data about clinical outcomes, toxicities and prognostic factors in a cohort of 181 intracranial recurrent meningioma patients treated in 8 different Italian centers with different RT modalities. Re-irradiation (re-RT) for recurrent intracranial meningiomas is hindered by the limited radiation tolerance of surrounding tissue and the risk of side effects. This study aimed at assessing outcomes, toxicities and prognostic factors in a cohort of patients with recurrent meningiomas re-treated with different RT modalities. A multi-institutional database from 8 Italian centers including intracranial recurrent meningioma (RM) patients who underwent re-RT with different modalities (SRS, SRT, PT, EBRT) was collected. Biologically Equivalent Dose in 2 Gy-fractions (EQD2) and Biological Effective Dose (BED) for normal tissue and tumor were estimated for each RT course (α/β = 2 for brain tissue and α/β = 4 for meningioma). Primary outcome was second progression-free survival (s-PFS). Secondary outcomes were overall survival (OS) and treatment-related toxicity. Kaplan–Meier curves and Cox regression models were used for analysis. Between 2003 and 2021 181 patients (pts) were included. Median age at re-irradiation was 62 (range 20–89) and median Karnofsky Performance Status (KPS) was 90 (range 60–100). 78 pts were identified with WHO grade 1 disease, 65 pts had grade 2 disease and 10 pts had grade 3 disease. 28 pts who had no histologic sampling were grouped with grade 1 patients for further analysis. Seventy-five (41.4 %) patients received SRS, 63 (34.8 %) patients SRT, 31 (17.1 %) PT and 12 (6.7 %) EBRT. With a median follow-up of 4.6 years (interquartile range 1.7–6.8), 3-year s-PFS was 51.6 % and 3-year OS 72.5 %. At univariate analysis, SRT (HR 0.32, 95 % CI 0.19–0.55, p < 0.001), longer interval between the two courses of irradiation (HR 0.37, 95 % CI 0.21–0.67, p = 0.001), and higher tumor BED (HR 0.45 95 % CI 0.27–0.76, p = 0.003) were associated with longer s-PFS; in contrast, Ki67 > 5 % (HR 2.81, 95 % CI 1.48–5.34, p = 0.002) and WHO grade > 2 (HR 3.08, 95 % CI 1.80–5.28, p < 0.001) were negatively correlated with s-PFS. At multivariate analysis, SRT, time to re-RT and tumor BED maintained their statistically significant prognostic impact on s-PFS (HR 0.36, 95 % CI 0.21–0.64, p < 0.001; HR 0.38, 95 % CI 0.20–0.72, p = 0.003 and HR 0.31 95 % CI 0.13–0.76, p = 0.01, respectively). Acute and late adverse events (AEs) were reported in 38 (20.9 %) and 29 (16 %) patients. Larger tumor GTV (≥10 cc) was significantly associated with acute and late toxicity (p < 0.001 and p = 0.009, respectively). In patients with recurrent meningiomas, reirradiation is a feasible treatment option associated with acceptable toxicity profile. Prognostic factors in the decision-making process have been identified and should be incorporated in daily practice. [ABSTRACT FROM AUTHOR]