Gamma knife stereotactic radiosurgery in the treatment of brainstem metastases: The MD Anderson experience

Factors associated with the local control of brain metastases: a systematic search and machine learning application

BACKGROUND

Enhancing Local Control (LC) of brain metastases is pivotal for improving overall survival, which makes the prediction of local treatment failure a crucial aspect of treatment planning. Understanding the factors that influence LC of brain metastases is imperative for optimizing treatment strategies and subsequently extending overall survival. Machine learning algorithms may help to identify factors that predict outcomes.

METHODS

This paper systematically reviews these factors associated with LC to select candidate predictor features for a practical application of predictive modeling. A systematic literature search was conducted to identify studies in which the LC of brain metastases is assessed for adult patients. EMBASE, PubMed, Web-of-Science, and the Cochrane Database were searched up to December 24, 2020. All studies investigating the LC of brain metastases as one of the endpoints were included, regardless of primary tumor type or treatment type. We first grouped studies based on primary tumor types resulting in lung, breast, and melanoma groups. Studies that did not focus on a specific primary cancer type were grouped based on treatment types resulting in surgery, SRT, and whole-brain radiotherapy groups. For each group, significant factors associated with LC were identified and discussed. As a second project, we assessed the practical importance of selected features in predicting LC after Stereotactic Radiotherapy (SRT) with a Random Forest machine learning model. Accuracy and Area Under the Curve (AUC) of the Random Forest model, trained with the list of factors that were found to be associated with LC for the SRT treatment group, were reported.

RESULTS

The systematic literature search identified 6270 unique records. After screening titles and abstracts, 410 full texts were considered, and ultimately 159 studies were included for review. Most of the studies focused on the LC of the brain metastases for a specific primary tumor type or after a specific treatment type. Higher SRT radiation dose was found to be associated with better LC in lung cancer, breast cancer, and melanoma groups. Also, a higher dose was associated with better LC in the SRT group, while higher tumor volume was associated with worse LC in this group. The Random Forest model predicted the LC of brain metastases with an accuracy of 80% and an AUC of 0.84.

CONCLUSION

This paper thoroughly examines factors associated with LC in brain metastases and highlights the translational value of our findings for selecting variables to predict LC in a sample of patients who underwent SRT. The prediction model holds great promise for clinicians, offering a valuable tool to predict personalized treatment outcomes and foresee the impact of changes in treatment characteristics such as radiation dose.

Short-term predictors of stereotactic radiosurgery outcome for untreated single non-small cell lung cancer brain metastases: a restrospective cohort study

Stereotactic radiosurgery (SRS) is an option for brain metastases (BM) not eligible for surgical resection, however, predictors of SRS outcomes are poorly known. The aim of this study is to investigate predictors of SRS outcome in patients with BM secondary to non-small cell lung cancer (NSCLC). The secondary objective is to analyze the value of volumetric criteria in identifying BM progression. This retrospective cohort study included patients >18 years of age with a single untreated BM secondary to NSCLC. Demographic, clinical, and radiological data were assessed. The primary outcome was treatment failure, defined as a BM volumetric increase 12 months after SRS. The unidimensional measurement of the BM at follow-up was also assessed. One hundred thirty-five patients were included, with a median BM volume at baseline of 1.1 cm3 (IQR 0.4-2.3). Fifty-two (38.5%) patients had SRS failure at follow-up. Only right BM laterality was associated with SRS failure (p=0.039). Using the volumetric definition of SRS failure, the unidimensional criteria demonstrated a sensibility of 60.78% (46.11%-74.16%), specificity of 89.02% (80.18%-94.86%), positive LR of 5.54 (2.88-10.66) and negative LR of 0.44 (0.31-0.63). SRS demonstrated a 61.5% local control rate 12 months after treatment. Among the potential predictors of treatment outcome analyzed, only the right BM laterality had a significant association with SRS failure. The volumetric criteria were able to identify more subtle signs of BM increase than the unidimensional criteria, which may allow earlier diagnosis of disease progression and use of appropriate therapies.

Outcomes of 2-SSRS plus bevacizumab therapy strategy for brainstem metastases (BSM) over 2 cm3: a multi-center study

Despite 2-staged stereotactic radiosurgery (2-SSRS) has been reported to provide patients with improved survival and limited toxicity, 2-SSRS for brainstem metastases (BSM) larger than 2 cm3 remains challenging. We tried to find out the effectiveness and safety of 2-SSRS plus bevacizumab therapy for BSMs over 2 cm3 and prognostic factors that related to the tumor local control. Patients that received 2-SSRS plus bevacizumab therapy from four gamma knife center were retrospectively studied from Jan 2014 to December 2023. Patients' domestic characteristics and the tumor features were evaluated before and after the treatment. Cox regression model was used to find out prognostic factors for tumor local control. 53 patients with 63 lesions received the therapy. The median peri-tumor edema volume greatly reduced at the end of therapy (P < 0.01), the median tumor volume dramatically reduced (P < 0.01) and patients' KPS score improved significantly (P < 0.05) 3 months after the therapy. Patients' median OS was 12.8 months. The tumor local control rate at 3, 6, and 12 months was 98.4%, 93.4%, and 85.2%. The incidence side effects were mainly oral and nasal hemorrhage (5.7%, 3/53), and radiation necrosis (13.2%, 7/53). Patients with primary lung adenocarcinoma, therapeutic dose over 12 Gy at second-stage SRS, primary peri-tumor edema volume less than 2.3 cm³, primary tumor volume less than 3.7 cm³ would enjoy longer tumor local control. These results suggested that 2-SSRS plus bevacizumab therapy was effective and safe for BSMs over 2 cm3. However, it is important for patients with BSM to receive early diagnosis and treatment to achieve good tumor local control.

Stereotactic radiosurgery for the treatment of brainstem metastases: a multicenter retrospective study

Background

Brainstem metastases (BSM) are associated with a poor prognosis and their management represents a therapeutic challenge. BSM are often inoperable and, in absence of randomized trials, the optimal radiation treatment of BSM remains to be defined. We evaluated the efficacy and toxicity of linear accelerator (linac)-based stereotactic radiosurgery (SRS) and hypofractionated steretotactic radiotherapy (HSRT) in the treatment of BSM in a series of patients treated in different clinical centers.

Methods

We conducted a multicentric retrospective study of patients affected by 1–2 BSM from different histologies who underwent SRS/HSRT. Freedom from local progression (FLP), cancer-specific survival (CSS), overall survival (OS), and treatment-related toxicity were evaluated. In addition, predictors of treatment response and survivals were evaluated.

Results

Between 2008 and 2021, 105 consecutive patients with 111 BMS who received SRS or HSRT for 1–2 BSM were evaluated. Median follow-up time was 10 months (range 3–130). One-year FLP rate was 90.4%. At the univariate analysis, tumor volume ≤ 0.4 cc, and concurrent targeted therapy were associated with longer FLP, with combined treatment that remained a significant independent predictor [0.058, HR 0.139 (95% CI 0.0182–1.064]. Median OS and CSS were 11 months and 14.6 months, respectively. At multivariate analysis, concurrent targeted therapy administration was significantly associated with longer OS [HR 0.514 (95%CI 0.302–0.875); p = 0.01]. Neurological death occurred in 30.4% of patients, although this was due to local progression in only 3 (2.8%) patients.

Conclusion

Linac-based SRS/HSRT offers excellent local control to patients with BSM, with low treatment-related toxicity and no apparent detrimental effects on OS. When treated with ablative intent, BSM are an uncommon cause of neurological death. The present results indicates that patients with BSM should not be excluded a priori from clinical trials.

Brainstem metastases treated with Gamma Knife stereotactic radiosurgery: the Indiana University Health experience

Brainstem metastases offer a unique challenge in cancer treatment, yet stereotactic radiosurgery (SRS) has proven to be an effective modality in treating these tumors. This report discusses the clinical outcomes of patients with brainstem metastases treated at Indiana University with Gamma Knife (GK) radiosurgery from 2008 to 2016. 19 brainstem metastases from 14 patients who had follow-up brain imaging were identified. Median tumor volume was 0.04 cc (range: 0.01–2.0 cc). Median prescribed dose was 17.5 Gy to the 50% isodose line (range: 14–22 Gy). Median survival after GK SRS treatment to brainstem lesion was 17.2 months (range: 2.8–45.6 months). The experience at Indiana University confirms the safety and efficacy of range of GK SRS prescription doses (14–22 Gy) to brainstem metastases.

Radiosurgery for brainstem metastases with and without whole brain radiotherapy: clinical series and literature review

OBJECTIVE

The objective of this study was to investigate outcomes for patients with brainstem metastases treated with stereotactic radiosurgery (SRS).

METHODS

Patients with brainstem metastases treated with SRS between April 2006 and June 2012 were identified from a prospective database. Patient and treatment-related factors were recorded. Kaplan-Meier analysis was used to calculate survival and freedom from local and distant brain progression. Univariate and multivariate Cox regression was used to identify factors important for overall survival.

RESULTS

In total, 44 patients received SRS for 48 brainstem metastases of whom 33 (75 %) also received whole brain radiotherapy (WBRT): 23 patients (52 %) WBRT prior to SRS, 6 (13.6 %) WBRT concurrently with SRS and 4 (9.0 %) WBRT after SRS. Eight patients received a second course of WBRT at further progression. Median target volume was 1.33 cc (range 0.04-12.17) and median prescribed marginal dose was 15 Gy (range 10-22). There were four cases of local failure, and 6-month and 1-year freedom from local failure was 84.6 and 76.9 %, respectively. Median overall survival (OS) was 5.4 months. There were four cases of radionecrosis, 2 (4.8 %) of which were symptomatic. The absence of external beam brain radiotherapy (predominantly WBRT) showed a trend towards improved OS on univariate analysis. Neither local nor distant brain failure significantly impacted OS.

CONCLUSION

This retrospective series of patients treated with SRS for brainstem metastases, largely in combination with at least one course of WBRT, demonstrates that this approach is safe and results in good local control. In this cohort, no variables significantly impacted OS, including intracranial control.

Brainstem metastases treated with stereotactic radiosurgery: safety, efficacy, and dose response

The safety and efficacy of stereotactic radiosurgery (SRS) in the brainstem is questioned by some over concern of violating historical brainstem SRS dose tolerance. Our purpose was to report on the clinical outcomes of patients treated at our institution with radiosurgery for brainstem metastases. Patients with metastatic tumors within or directly abutting the brainstem from 1992 to 2014 were analyzed. Patient and tumor characteristics, SRS parameters, and toxicity were recorded and analyzed for associations with local control and survival. Multivariate statistical analysis was performed using Cox proportional hazards modeling. One-hundred and eighty-nine (189) brainstem metastases from 161 patients were included in our analysis. Whole brain irradiation was administered prior to SRS in 52 % of patients. The median margin dose was 18 Gy prescribed to the 50 % isodose line. Median imaging follow up was 5.4 months and median survival was 5.5 months after SRS. At last follow up, local control was achieved in 87.3 % of brainstem lesions treated. There were 3 recorded events of grade 3-5 toxicity (1.8 %). On multivariate analysis, a margin dose ≥16 Gy was associated with improved local control (p = 0.049) and greater KPS score was associated with improved overall survival following SRS (p = 0.024). Patients with brainstem metastases who have limited intracranial disease and/or who have received whole brain irradiation should be considered for SRS. Margin doses of at least 16 Gy are associated with superior local control, and serious radiation toxicity in SRS for brainstem metastasis appears rare.