Stereotactic radiosurgery for melanoma brain metastases: dose-size response relationship in the era of immunotherapy

Stereotactic Radiosurgery Dose Reduction for Melanoma Brain Metastases Patients on Immunotherapy or Target Therapy: A Single-Center Experience

BACKGROUND AND OBJECTIVES

Better local control but higher rates of adverse radiation events (ARE) have been reported when combining American Society for Radiation Oncology (ASTRO)-guideline-suggested dose (SD) stereotactic radiosurgery (SRS) with immunotherapy or targeted therapy for melanoma brain metastases. The objective of this study is to explore the efficacy and safety of lower prescription doses compared with ASTRO guidelines for single-fraction SRS for patients with melanoma metastases who are concurrently receiving immunotherapy or targeted therapy.

METHODS

We conducted a retrospective, single-center study on 194 patients who underwent SRS between 2009 and 2022. After propensity score matching, 71 patients with 292 metastases were included in the ASTRO-SD (20-24 Gy for <2 cm, 18 Gy for ≥2 to <3 cm) group and 33 patients with 292 metastases in the reduced dose (RD, <20 Gy for <2 cm, <18 Gy for ≥2 to <3 cm) group.

RESULTS

The median diameter (5.4 vs 5.2 mm, P = .6), prescription volume (0.2 vs 0.2 cm 3 , P = .2), and radiographic follow-up (11 vs 12 months, P = .2) were similar in the 2 groups. The cumulative incidence of progressing metastases was significantly higher in the SD compared with the RD group ( P = .018). Higher prescription volumes and ASTRO-suggested radiation doses were associated with local progression in multivariable analysis. Radiographic AREs were significantly more common in the SD compared with the RD group (8.6% vs 3.1%, P = .005). BRAF and other tyrosine kinase inhibitors' concurrent use, higher prescription volumes, and ASTRO-suggested radiation doses were associated with an increased risk of radiographic ARE.

CONCLUSION

This study provides evidence that RD SRS could offer reduced toxicity rates, while maintaining high local control as compared with the current guideline-SDs for the treatment of melanoma brain metastases.

Progress in immunotherapy for brain metastatic melanoma

Melanoma is highly aggressive, with brain metastasis being a significant contributor to poor outcomes. Immunotherapy has emerged as a crucial treatment modality for melanoma, particularly for addressing brain metastases. This review explores recent developments in immunotherapy for patients with melanoma brain metastasis, with such treatments encompassing immune checkpoint inhibitors and various immunotherapy combination approaches, such as dual immunotherapy, immunotherapy combined with chemotherapy, immunotherapy combined with targeted drugs, and immunotherapy combined with radiotherapy. This article also discusses existing treatment obstacles and potential future avenues for research and clinical practice.

Delayed and Concurrent Stereotactic Radiosurgery in Immunotherapy-Naïve Melanoma Brain Metastases

Melanoma remains a formidable challenge in oncology, causing the majority of skin cancer deaths in the United States, with brain metastases contributing substantially to this mortality. This paper reviews the current therapeutic strategies for melanoma brain metastases, with a focus on delayed and concurrent stereotactic radiosurgery (SRS). While surgery and traditional chemotherapy offer limited efficacy, recent advances in immunotherapy, particularly immune checkpoint inhibitors (ICIs), have played a major role in the advancement and improved efficacy of the treatment of cancers, including brain metastases. Recent studies indicate that monotherapy with ICIs may lead to a higher median overall survival compared to historical benchmarks, potentially allowing patients to delay radiosurgery. Other studies have found that combining SRS with ICIs demonstrates promise, with results indicating improved intracranial control. Ongoing clinical trials explore novel combinations of immunotherapies and radiotherapies, aiming to optimize treatment outcomes while minimizing adverse effects. As treatment options expand, future studies will be necessary to understand the interplay between therapies and their optimal sequencing to improve patient outcomes.

The Safety and Efficacy of Concurrent Immune Checkpoint Blockade and Stereotactic Radiosurgery Therapy with Practitioner and Researcher Recommendations

BACKGROUND

Immune checkpoint inhibitors (ICIs) have shown growing promise in the treatment of brain metastases, especially combined with stereotactic radiosurgery (SRS). The combination of ICIs with SRS has been studied for efficacy as well as increasing radiation necrosis risks. In this review, we compare clinical outcomes of radiation necrosis, intracranial control, and overall survival between patients with brain metastases treated with either SRS alone or SRS-ICI combination therapy.

METHODS

A literature search of PubMed, Scopus, Embase, Web of Science, and Cochrane was performed in May 2023 for articles comparing the safety and efficacy of SRS/ICI versus SRS-alone for treating brain metastases.

RESULTS

The search criteria identified 1961 articles, of which 48 met inclusion criteria. Combination therapy with SRS and ICI does not lead to significant increases in incidence of radiation necrosis either radiographically or symptomatically. Overall, no difference was found in intracranial control between SRS-alone and SRS-ICI combination therapy. Combination therapy is associated with increased median overall survival. Notably, some comparative studies observed decreased neurologic deaths, challenging presumptions that improved survival is due to greater systemic control. The literature supports SRS-ICI administration within 4 weeks of another for survival but remains inconclusive, requiring further study for other outcome measures.

CONCLUSIONS

Combination SRS-ICI therapy is associated with significant overall survival benefit for patients with brain metastases without significantly increasing radiation necrosis risks compared to SRS alone. Although intracranial control rates appear to be similar between the 2 groups, timing of treatment delivery may improve control rates and demands further study attention.

Low-Dose Radiosurgery for Brain Metastases in the Era of Modern Systemic Therapy

BACKGROUND AND OBJECTIVES

Dose selection for brain metastases stereotactic radiosurgery (SRS) classically has been based on tumor diameter with a reduction of dose in the settings of prior brain irradiation, larger tumor volumes, and critical brain location. However, retrospective series have shown local control rates to be suboptimal with reduced doses. We hypothesized that lower doses could be effective for specific tumor biologies with concomitant systemic therapies. This study aims to report the local control (LC) and toxicity when using low-dose SRS in the era of modern systemic therapy.

METHODS

We reviewed 102 patients with 688 tumors managed between 2014 and 2021 who had low-margin dose radiosurgery, defined as ≤14 Gy. Tumor control was correlated with demographic, clinical, and dosimetric data.

RESULTS

The main primary cancer types were lung in 48 (47.1%), breast in 31 (30.4%), melanoma in 8 (7.8%), and others in 15 patients (11.7%). The median tumor volume was 0.037cc (0.002-26.31 cm 3 ), and the median margin dose was 14 Gy (range 10-14). The local failure (LF) cumulative incidence at 1 and 2 years was 6% and 12%, respectively. On competing risk regression analysis, larger volume, melanoma histology, and margin dose were predictors of LF. The 1-year and 2-year cumulative incidence of adverse radiation effects (ARE: an adverse imaging-defined response includes increased enhancement and peritumoral edema) was 0.8% and 2%.

CONCLUSION

It is feasible to achieve acceptable LC in BMs with low-dose SRS. Volume, melanoma histology, and margin dose seem to be predictors for LF. The value of a low-dose approach may be in the management of patients with higher numbers of small or adjacent tumors with a history of whole brain radio therapy or multiple SRS sessions and in tumors in critical locations with the aim of LC and preservation of neurological function.

Stereotactic Radiation and Dual Human Epidermal Growth Factor Receptor 2 Blockade with Trastuzumab and Pertuzumab in the Treatment of Breast Cancer Brain Metastases: A Single Institution Series

(1) Background: This study aims to assess the safety and efficacy of fractionated SRT (fSRT) and pertuzumab-trastuzumab (PT) in patients with breast cancer brain metastases (BCBM). (2) Methods: Patients with HER2+ BCBM who received FSRT from 2015 to 2019 were identified. Patients were included if they were treated with fSRT within 21 days of receiving PT. All lesions were treated with LINAC-based fSRT to a total dose of 27 Gy delivered in three consecutive fractions. All patients received concurrent PT. Patients were evaluated 4-6 weeks after SRS and subsequently every 2-3 months with MRI re-imaging (3) Results: A total of 49 patients with HER2+ brain metastases were identified. Of these patients, a total of 10 patients with 32 HER2+ BCBM were treated with concurrent SRT and PT and included in the analysis. No local progression was observed. Overall response rate was 68.7%. Only one patient developed asymptomatic radionecrosis. Median time to BM occurrence was 15.6 (range: 1-40.5 months). Distant intracranial failure occurred in 4/10 patients (40.0%). Overall BCBM median survival was 33.9 months (95%CI 24.1-43.6). Mean duration of PT treatment was 27.9 months (range: 10.1-53.7 months). (4) Conclusions: In our single institution experience, fSRT and PT showed to be a safe treatment for patients with BCBM with an adequate overall response rate.