Hypofractionated radiation therapy with versus without immune checkpoint inhibitors in patients with brain metastases: A meta-analysis

Radiation-Induced Brain Injury: Mechanistic Insights and the Promise of Gut-Brain Axis Therapies

Radiation therapy is widely recognized as an efficacious modality for treating neoplasms located within the craniofacial region. Nevertheless, this approach is not devoid of risks, predominantly concerning potential harm to the neural structures. Adverse effects may encompass focal cerebral necrosis, cognitive function compromise, cerebrovascular pathology, spinal cord injury, and detriment to the neural fibers constituting the brachial plexus. With increasing survival rates among oncology patients, evaluating post-treatment quality of life has become crucial in assessing the benefits of radiation therapy. Consequently, it is imperative to investigate therapeutic strategies to mitigate cerebral complications from radiation exposure. Current management of radiation-induced cerebral damage involves corticosteroids and bevacizumab, with preclinical research on antioxidants and thalidomide. Despite these efforts, an optimal treatment remains elusive. Recent studies suggest the gut microbiota's involvement in neurologic pathologies. This review aims to discuss the causes and existing treatments for radiation-induced cerebral injury and explore gut microbiota modulation as a potential therapeutic strategy.

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.

The Impact of Immune Checkpoint Inhibition on the Risk of Radiation Necrosis Following Stereotactic Radiotherapy for Metastatic Brain Cancer

Purpose/objective Forty percent of cancer patients develop brain metastases (BM) and are often treated with stereotactic radiation (SRS/SRT). Checkpoint inhibitor (CI) use is suspected of increasing the risk of radiation necrosis (RN). Our aim is to determine whether treatment with CI is associated with an increased risk of RN in BM patients treated with SRS/SRT. Methods We retrospectively identified the medical records of BM patients treated with SRS/SRT between 1/2017 and 12/2021 using an institutional database. RN was defined by MRI imaging read by neuroradiologists and/or surgical pathology. V12GY of patients with and without RN was compared using the Mann-Whitney test. The chi-square test was used to see if RN was associated with CI use, histology, particular CI agent used, > 1 course SRS/SRT, SRS/SRT dose, chemotherapy, whole brain radiotherapy (WBRT), age, or sex. Results Two hundred and fifty-nine patients treated with 455 courses of SRS/SRT were analyzed. The most common primary histologies were lung 56% (N=146), breast 14% (N= 37), melanoma 9% (N=24), and renal cancer 7% (N=18). A total of 53.8% (N = no. of patients) were treated with CI. The overall rate of any RN was 21.8% (N=27) in the CI group compared to 14.8% (N=141) in the non-CI group (p=0.174). Mean V12Gy was 15.525 cc and 9.419 cc in patients with and without RN (p=0.02768). Mean number of SRS/SRT courses was 2 and 1.53 for patients with and without RN, and >1 course of SRS/SRT was a predictor of RN (p <0.01). Other features analyzed were not significant. Conclusion RN was higher in the BM patients treated with SRS/SRT receiving CI compared to non-CI patients (21.8%, N=27, versus 14.6%, N= 16), but failed to reach statistical significance. V12Gy and > 1 course of SRS/SRT was associated with RN. Caution should be taken in treating patients with SRS/SRT and CI there might be an increased risk of RN.

Whole brain radiation therapy resulting in radionecrosis: a possible link with radiosensitising chemoimmunotherapy

Radionecrosis describes a rare but serious complication of radiation therapy. In clinical practice, stereotactic radiosurgery (SRS) is increasingly used in combination with systemic therapy, including chemotherapy, immune checkpoint inhibitor and targeted therapy, either concurrently or sequentially. There is a paucity of literature regarding radionecrosis in patients receiving whole brain radiation therapy (WBRT) alone (without additional SRS) in combination with immunotherapy or targeted therapies. It is observed that certain combinations increase the overall radiosensitivity of the tumorous lesions. We present a rare case of symptomatic radionecrosis almost 1 year after WBRT in a patient with non-squamous non-small cell lung cancer on third-line chemoimmunotherapy. We discuss available research regarding factors that may lead to radionecrosis in these patients, including molecular and genetic profiles, specific drug therapy combinations and their timing or increased overall survival.

The abscopal effect: inducing immunogenicity in the treatment of brain metastases secondary to lung cancer and melanoma

PURPOSE

The phenomenon of radiation therapy (RT) causing regression of targeted lesions as well as lesions outside of the radiation field is known as the abscopal effect and is thought to be mediated by immunologic causes. This phenomena has been described following whole brain radiation (WBRT) and stereotactic radiosurgery (SRS) of brain metastasis (BM) in advanced melanoma and non-small-cell lung cancer (NSCLC). We systematically reviewed the available literature to identify which radiation modality and immunotherapy (IT) combination may elicit the abscopal effect, the optimal timing of RT and IT, and potential adverse effects inherent to the combination of RT and IT.

METHODS

Using PRISMA guidelines, a search of PubMed, Medline, and Web of Science was conducted to identify studies demonstrating the abscopal effect during treatment of NSCLC or melanoma with BM.

RESULTS

598 cases of irradiated BM of melanoma or NSCLC in 18 studies met inclusion criteria. The most commonly administered ITs included PD-1 or CTLA-4 immune checkpoint inhibitors (ICI), with RT most commonly administered within 3 months of ICI. Synergy between ICI and RT was described in 16 studies including evidence of higher tumor response within and outside of the irradiated field. In the 12 papers (n = 232 patients) that reported objective response rate (ORR) in patients with BM treated with RT and concurrent systemic IT, the non-weighted mean ORR was 49.4%; in the 5 papers (n = 110 patients) that reported ORR for treatment with RT or IT alone, the non-weighted mean ORR was 27.8%. No studies found evidence of significantly increased toxicity in patients receiving RT and ICI.

CONCLUSION

The combination of RT and ICIs may enhance ICI efficacy and induce more durable responses via the abscopal effect in patients with brain metastases of melanoma or NSCLC.

Shrinkage of a pituitary metastasis of melanoma induced by pembrolizumab: a case report

BACKGROUND

Pituitary metastases are rare, often deriving from lung or breast cancer owing to the upper vena cava proximity. Pituitary metastases can manifest with signs and symptoms of pituitary tumors, consequent to mass effect (headache, visual impairment) and/or hormonal alterations (hyperprolactinemia, hypopituitarism, and diabetes insipidus). Immune checkpoint inhibitors burst immunity against tumors, significantly increasing patients' survival, but their autoimmune side effects frequently involve the skin, the gastrointestinal tract, and the endocrine glands (pituitary, thyroid, pancreas).

CASE PRESENTATION

A 77-year-old Caucasian man had undergone trans-nasal sphenoidal surgery for a nonsecreting pituitary macroadenoma in 2001, without remnant or endocrine deficits. In 2016, he was operated for a shoulder melanoma. In February 2018, imaging evaluation demonstrated metastases in lung, liver, and femur. Therefore, treatment with pembrolizumab (anti-programmed death 1) was scheduled in May 2018, but, before starting this therapy, a brain computed tomography performed for a sudden loss of consciousness detected a sellar mass of 17 × 12 mm, which extended to the pituitary stalk and compressed the optic chiasma. Focused magnetic resonance imaging confirmed the size and characteristics of the lesion, while emergency evaluation of the hormonal profile demonstrated an impairment of adrenal and thyroid function. The pituitary lesion demonstrated a remarkable shrinkage (8 × 6 mm), which was confirmed by subsequent imaging evaluations.

CONCLUSIONS

This is the first case reporting on effectiveness of immune checkpoint inhibitors in a patient with pituitary metastasis from a melanoma.

Efficacy and Safety of Combined Brain Radiotherapy and Immunotherapy in Non-Small-Cell Lung Cancer With Brain Metastases: A Systematic Review and Meta-Analysis

BACKGROUND

Immune checkpoint inhibitors (ICIs) are recommended to treat advanced non-small-cell lung cancer (NSCLC), whereas brain radiotherapy (RT) is the mainstream therapy for patients with brain metastases (BMs). This systematic review and meta-analysis investigated whether the combination of brain RT and ICIs would generate a synergistic effect without unacceptable toxicity to treat NSCLC with BMs.

METHODS

Literature searching was performed in PubMed, Embase, Web Of Science, and The Cochrane Library up to December 20, 2020. Heterogeneity, sensitivity analysis, forest plots, and publication bias were analyzed using Stata 15.0.

RESULTS

Nineteen studies were included. In the comparison of the brain RT+ICIs arm and brain RT alone arm, the pooled effect size (ES) for overall survival (OS) (hazard ratio [HR] = 0.77; 95% confidence interval [CI] 0.71-0.83; I² = 0; P < .001; n = 4) and grade 3-4 neurological adverse events (AEs) (risk ratio [RR] = 0.91; 95% CI 0.41-2.02; I² = 26.5; P = .809; n = 4) indicated that the brain RT+ICIs model had significantly better systemic efficacy and similar neurological AEs compared with brain RT alone for NSCLC. Concurrent RT+ICIs were identified as the optimal model, which achieved the best efficacy without significantly increased AEs compared with sequential RT+ICIs.

CONCLUSIONS

Combined ICIs and brain RT exhibited favorable efficacy and acceptable toxicity for NSCLC patients with BMs, among which, the concurrent model might be the optimal option. Our results could guide the design of future randomized controlled trials and clinical practice.

Efficacy and safety of hypofractionated stereotactic radiotherapy for brain metastases using three fractions: A single-centre retrospective study

PURPOSE

Hypofractionated stereotactic radiotherapy (HFSRT) has become a standard of care for patients with a limited number of brain metastases (BM). An increasing number of linear accelerators (LA) are able to accurately perform HFSRT including VersaHD® (Elekta®) LA. The main aim of this study was to report clinical outcomes of BM treated by HFSRT using 3×7.7Gy on 70% isodose line in terms of local control (LC).

PATIENTS AND METHODS

Between November 2016 and October 2018, all patients suffering from histologically-proven primary with one or several newly diagnosed BM treated by HFSRT were retrospectively included and evaluated. Patients who had received prior treatment by neurosurgery or cerebral radiotherapy were excluded.

RESULTS

Among 44 patients, 61 BM were treated. With a median follow-up of 31.9 months, LC rates at 6 and 12 months were 93.2% and 90.9, respectively. Single-BM was independently predictive of LC (P=0.025) and overall survival (P=0.013). Acute toxicity rates were acceptable: 65.9% of patients had grade 1 and 2 and no acute grade 3 toxicity according to the NCI-CTCAE (version 5.0). Regarding delayed toxicity, one case (2.3%) of radionecrosis was confirmed by magnetic resonance spectroscopy.

CONCLUSION

In our single-centre retrospective analysis, BM treatment by HFSRT delivered in three fractions showed a 12-month LC rate of 90.9% without major toxicities, which suggests safety and efficiency of this technique. However, longer-term follow-up and prospective studies are still needed to confirm these results.

Immune checkpoint inhibitor therapy may increase the incidence of treatment-related necrosis after stereotactic radiosurgery for brain metastases: a systematic review and meta-analysis

OBJECTIVES

To compare the incidence of treatment-related necrosis between combination SRS+ICI therapy and SRS therapy alone in patients with brain metastases from melanoma and non-small cell lung cancer (NSCLC).

METHODS

A systematic literature search of Ovid-MEDLINE and EMBASE was performed up to August 10, 2020. The difference in the pooled incidence of treatment-related necrosis after SRS+ICI or SRS alone was evaluated. The cumulative incidence of treatment-related necrosis at the specific time point after the treatment was calculated and plotted. Subgroup and meta-regression analyses were additionally performed.

RESULTS

Sixteen studies (14 on melanoma, 2 on NSCLC) were included. In NSCLC brain metastasis, the reported incidences of treatment-related necrosis in SRS+ICI and SRS alone ranged 2.9-3.4% and 0-2.9%, respectively. Meta-analysis was conducted including 14 studies on melanoma brain metastasis. The incidence of treatment-related necrosis was higher in SRS+ICI than SRS alone (16.0% vs. 6.5%; p = 0.065; OR, 2.35). The incidence showed rapid increase until 12 months after the SRS when combined with ICI therapy (14%; 95% CI, 8-22%) and its pace of increase slowed thereafter. Histopathologic diagnosis as the reference standard for treatment-related necrosis and inclusion of only symptomatic cases were the source of heterogeneity in SRS+ICI.

CONCLUSIONS

Treatment-related necrosis tended to occur 2.4 times more frequently in the setting of combination SRS+ICI therapy compared with SRS alone in melanoma brain metastasis showing high cumulative incidence within the first year. Treatment-related necrosis should be considered when SRS+ICI combination therapy is used for melanoma brain metastasis, especially in the first year.

KEY POINTS

• Treatment-related necrosis occurred 2.4 times more frequently in the setting of combination SRS+ICI therapy compared with SRS alone in melanoma brain metastasis. • Treatment-related necrosis more frequently occurred in brain metastases from melanoma than NSCLC. • Reference standard for treatment-related necrosis and inclusion of only symptomatic treatment-related necrosis were a significant source of heterogeneity, indicating varying definitions of treatment-related necrosis in the literature need to be unified.