The prognostic value of tumor necrosis in patients undergoing stereotactic radiosurgery of brain metastases

Cystic Brain Metastasis Outcomes After Gamma Knife Radiation Therapy

Purpose

The response of cystic brain metastases (BMets) to radiation therapy is poorly understood, with conflicting results regarding local control, overall survival, and treatment-related toxicity. This study aims to examine the role of Gamma Knife (GK) in managing cystic BMets.

Methods and Materials

Volumetric analysis was conducted to measure tumor and edema volume at the time of GK and follow-up magnetic resonance imaging studies. Survival was described using the Kaplan-Meier method, and the cumulative incidence of progression was described using the Aalen-Johansen estimator. We evaluated the association of 4 variables with survival using Cox regression analysis.

Results

Between 2016 and 2021, 54 patients with 83 cystic BMets were treated with GK at our institution. Lung cancer was the most common pathology (51.9%), followed by breast cancer (13.0%). The mean target volume was 2.7 cm3 (range, 0.1-39.0 cm3), and the mean edema volume was 13.9 cm3 (range, 0-165.5 cm3). The median prescription dose of single-fraction and fractionated GK was 20 Gy (range, 14-27.5 Gy). With a median follow-up of 8.9 months, the median survival time (MST) was 11.1 months, and the 1-year local control rate was 75.9%. Gamma Knife was associated with decreased tumor and edema volumes over time, although 68.5% of patients required steroids after GK. Patients whose tumors grew beyond baseline after GK received significantly more whole-brain radiation therapy (WBRT) before GK than those whose tumors declined after GK. Higher age at diagnosis of BMets and pre-GK systemic therapy were associated with worse survival, with an MST of 7.8 months in patients who received it compared with 23.3 months in those who did not.

Conclusions

Pre-GK WBRT may select for BMets with increased radioresistance. This study highlights the ability of GK to control cystic BMets with the cost of high posttreatment steroid use.

The Extent of Necrosis in Brain Metastases May Predict Subtypes of Primary Cancer and Overall Survival in Patients Receiving Craniotomy

Although necrosis is common in brain metastasis (BM), its biological and clinical significances remain unknown. We evaluated necrosis extent differences by primary cancer subtype and correlated BM necrosis to overall survival post-craniotomy. We analyzed 145 BMs of patients receiving craniotomy. Necrosis to tumor ratio (NTR) was measured. Patients were divided into two groups by NTR: BMs with sparse necrosis and with abundant necrosis. Clinical features were compared. To investigate factor relevance for BM necrosis, multivariate logistic regression, random forests, and gradient boosting machine analyses were performed. Kaplan−Meier analysis and log-rank tests were performed to evaluate the effect of BM necrosis on overall survival. Lung cancer was a more common origin for BMs with abundant necrosis (42/72, 58.33%) versus sparse necrosis (23/73, 31.51%, p < 0.01). Primary cancer subtype and tumor volume were the most relevant factors for BM necrosis (p < 0.01). BMs harboring moderately abundant necrosis showed longer survival, versus sparse or highly abundant necrosis (p = 0.04). Lung cancer BM may carry larger necrosis than BMs from other cancers. Further, moderately abundant necrosis in BM may predict a good prognosis post-craniotomy.

Local tumor progression treated with Gamma Knife radiosurgery: differences between patients with 2-4 versus 5-10 brain metastases based on an update of a multi-institutional prospective observational study (JLGK0901)

OBJECTIVE

The Japanese Leksell Gamma Knife (JLGK)0901 study proved the efficacy of Gamma Knife radiosurgery (GKRS) in patients with 5-10 brain metastases (BMs) as compared to those with 2-4, showing noninferiority in overall survival and other secondary endpoints. However, the difference in local tumor progression between patients with 2-4 and those with 5-10 BMs has not been sufficiently examined for this data set. Thus, the authors reappraised this issue, employing the updated JLGK0901 data set with detailed observation via enhanced MRI. They applied sophisticated statistical methods to analyze the data.

METHODS

This was a prospective observational study of 1194 patients harboring 1-10 BMs treated with GKRS alone. Patients were categorized into groups A (single BM, 455 cases), B (2-4 BMs, 531 cases), and C (5-10 BMs, 208 cases). Local tumor progression was defined as a 20% increase in the maximum diameter of the enhanced lesion as compared to its smallest documented maximum diameter on enhanced MRI. The authors compared cumulative incidence differences determined by competing risk analysis and also conducted propensity score matching.

RESULTS

Local tumor progression was observed in 212 patients (17.8% overall, groups A/B/C: 93/89/30 patients). Cumulative incidences of local tumor progression in groups A, B, and C were 15.2%, 10.6%, and 8.7% at 1 year after GKRS; 20.1%, 16.9%, and 13.5% at 3 years; and 21.4%, 17.4%, and not available at 5 years, respectively. There were no significant differences in local tumor progression between groups B and C. Local tumor progression was classified as tumor recurrence in 139 patients (groups A/B/C: 68/53/18 patients), radiation necrosis in 67 (24/31/12), and mixed/undetermined lesions in 6 (1/5/0). There were no significant differences in tumor recurrence or radiation necrosis between groups B and C. Multivariate analysis using the Fine-Gray proportional hazards model revealed age < 65 years, neurological symptoms, tumor volume ≥ 1 cm3, and prescription dose < 22 Gy to be significant poor prognostic factors for local tumor progression. In the subset of 558 case-matched patients (186 in each group), there were no significant differences between groups B and C in local tumor progression, nor in tumor recurrence or radiation necrosis.

CONCLUSIONS

Local tumor progression incidences did not differ between groups B and C. This study proved that tumor progression after GKRS without whole-brain radiation therapy for patients with 5-10 BMs was satisfactorily treated with the doses prescribed according to the JLGK0901 study protocol and that results were not inferior to those in patients with a single or 2-4 BMs.Clinical trial registration no.: UMIN000001812 (umin.ac.jp).

Radiomics as prognostic factor in brain metastases treated with Gamma Knife radiosurgery

PURPOSE

Gamma Knife radiosurgery (GKRS) is a non-invasive procedure for the treatment of brain metastases. This study sought to determine whether radiomic features of brain metastases derived from pre-GKRS magnetic resonance imaging (MRI) could be used in conjunction with clinical variables to predict the effectiveness of GKRS in achieving local tumor control.

METHODS

We retrospectively analyzed 161 patients with non-small cell lung cancer (576 brain metastases) who underwent GKRS for brain metastases. The database included clinical data and pre-GKRS MRI. Brain metastases were demarcated by experienced neurosurgeons, and radiomic features of each brain metastasis were extracted. Consensus clustering was used for feature selection. Cox proportional hazards models and cause-specific proportional hazards models were used to correlate clinical variables and radiomic features with local control of brain metastases after GKRS.

RESULTS

Multivariate Cox proportional hazards model revealed that higher zone percentage (hazard ratio, HR 0.712; P = .022) was independently associated with superior local tumor control. Similarly, multivariate cause-specific proportional hazards model revealed that higher zone percentage (HR 0.699; P = .014) was independently associated with superior local tumor control.

CONCLUSIONS

The zone percentage of brain metastases, a radiomic feature derived from pre-GKRS contrast-enhanced T1-weighted MRIs, was found to be an independent prognostic factor of local tumor control following GKRS in patients with non-small cell lung cancer and brain metastases. Radiomic features indicate the biological basis and characteristics of tumors and could potentially be used as surrogate biomarkers for predicting tumor prognosis following GKRS.

Assessment of an Elekta Versa HD linear accelerator for stereotactic radiosurgery with circular cone collimators

BACKGROUND

Versa HD linear accelerators (linacs) are used for stereotactic radiosurgery treatment. However, the mechanical accuracy of such systems remains a concern.

OBJECTIVE

The purpose of this study was to evaluate the accuracy of an Elekta Versa HD linac.

METHODS

We performed measurements with a ball bearing phantom to calculate the rotational isocenter radii of the linac's gantry, collimator, and table, and determine the relative locations of those isocenters. We evaluated the accuracy of the cone-beam computed tomography (CBCT) guidance with a film-embedding head phantom and circular cone-collimated radiation beams. We also performed dosimetric simulations to study the effects of the linac mechanical uncertainties on non-coplanar cone arc delivery.

RESULTS

The mechanical uncertainty of the linac gantry rotation was 0.78 mm in radius, whereas that of the collimator and the table was <0.1 mm and 0.33 mm, respectively. The axes of rotation of the collimator and the table were coinciding with and 0.13 mm away from the gantry isocenter, respectively. Experiments with test plans demonstrated the limited dosimetric consequences on the circular arc delivery given the aforementioned mechanical uncertainties. End-to-end measurements determined that the uncertainty of the CBCT guidance was≤1 mm in each direction with respect to the reference CT image.

CONCLUSIONS

In arc delivery, the mechanical uncertainties associated with the gantry and the table do not require remarkable increases in geometric margins. If large enough, the residual setup errors following CBCT guidance will dominate the overall dosimetric consequence. Therefore, the Versa HD linac is a valid system for stereotactic radiosurgery using non-coplanar arc delivery.

No patient left behind: The promise of immune priming with epigenetic agents

Checkpoint inhibitors, monoclonal antibodies that inhibit PD-1 or CTLA-4, have revolutionized the treatment of multiple cancers. Despite the enthusiasm for the clinical successes of checkpoint inhibitors, and immunotherapy, in general, only a minority of patients with specific tumor types actually benefit from treatment. Emerging evidence implicates epigenetic alterations as a mechanism of clinical resistance to immunotherapy. This review presents evidence for that association, summarizes the epi-based mechanisms by which tumors evade immunogenic cell death, discusses epigenetic modulation as a component of an integrated strategy to boost anticancer T cell effector function in relation to a tumor immunosuppression cycle and, finally, makes the case that the success of this no-patient-left-behind strategy critically depends on the toxicity profile of the epigenetic agent(s).

Advancing Clostridia to Clinical Trial: Past Lessons and Recent Progress

Most solid cancers contain regions of necrotic tissue. The extent of necrosis is associated with poor survival, most likely because it reflects aggressive tumour outgrowth and inflammation. Intravenously injected spores of anaerobic bacteria from the genus Clostridium infiltrate and selectively germinate in these necrotic regions, providing cancer-specific colonisation. The specificity of this system was first demonstrated over 60 years ago and evidence of colonisation has been confirmed in multiple tumour models. The use of "armed" clostridia, such as in Clostridium Directed Enzyme Prodrug Therapy (CDEPT), may help to overcome some of the described deficiencies of using wild-type clostridia for treatment of cancer, such as tumour regrowth from a well-vascularised outer rim of viable cells. Successful preclinical evaluation of a transferable gene that metabolises both clinical stage positron emission tomography (PET) imaging agents (for whole body vector visualisation) as well as chemotherapy prodrugs (for conditional enhancement of efficacy) would be a valuable early step towards the prospect of "armed" clostridia entering clinical evaluation. The ability to target the immunosuppressive hypoxic tumour microenvironment using CDEPT may offer potential for synergy with recently developed immunotherapy strategies. Ultimately, clostridia may be most efficacious when combined with conventional therapies, such as radiotherapy, that sterilise viable aerobic tumour cells.

G Protein Coupled Receptor Kinase 3 Regulates Breast Cancer Migration, Invasion, and Metastasis

Triple negative breast cancer (TNBC) is a heterogeneous disease that has a poor prognosis and limited treatment options. Chemokine receptor interactions are important modulators of breast cancer metastasis; however, it is now recognized that quantitative surface expression of one important chemokine receptor, CXCR4, may not directly correlate with metastasis and that its functional activity in breast cancer may better inform tumor pathogenicity. G protein coupled receptor kinase 3 (GRK3) is a negative regulator of CXCR4 activity, and we show that GRK expression correlates with tumorigenicity, molecular subtype, and metastatic potential in human tumor microarray analysis. Using established human breast cancer cell lines and an immunocompetent in vivo mouse model, we further demonstrate that alterations in GRK3 expression levels in tumor cells directly affect migration and invasion in vitro and the establishment of distant metastasis in vivo. The effects of GRK3 modulation appear to be specific to chemokine-mediated migration behaviors without influencing tumor cell proliferation or survival. These data demonstrate that GRK3 dysregulation may play an important part in TNBC metastasis.