Linac-Based Radiosurgery for Patients With Brain Oligometastases From a Breast Primary, in the Trastuzumab Era-Impact of Tumor Phenotype and Prescribed SRS Dose

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.

Brain Metastases in the Setting of Stable Versus Progressing Extracranial Disease Among Patients With Metastatic Breast Cancer

INTRODUCTION

Women with metastatic breast cancer (BC) are at risk of developing brain metastases (BrM), which may result in significant morbidity and mortality. Given the emergence of systemic therapies with activity in the brain, more breast oncology clinical trials include patients with BrM, but most require extracranial disease progression for trial participation.

METHODS

We evaluated the proportion of patients with BC BrM who have intracranial disease progression in the setting of stable extracranial disease in a retrospective cohort study of 751 patients treated between 2008 and 2018 at the Sunnybrook Odette Cancer. Extracranial disease progression was defined as any progression outside of the brain within 4 weeks of a patient's local/regional treatment. Clinical/pathologic characteristics and outcomes were also abstracted from patients' medical records.

RESULTS

Of 752 patients in the cohort, 691 were included in our study. Sixty-one patients were excluded due to the presence of a second primary tumor or uncertain tissue origin of the BrM. BC subtype based on the primary tumor was known for 592 (85.6%) patients; 33.1% (n = 196) had HER2+ disease, 40% (n = 237) had HR+/HER2- disease, and 26.9% (n = 159) had triple negative BC. Extracranial disease status was available for 677 patients (98%); 41.1% (n = 284/691) had stable extracranial disease and 56.8% (n = 393/691) had extracranial disease progression within 4 weeks of treatment for BrM.

DISCUSSION

A high proportion of patients with BC BrM (41.1%) would be excluded from clinical trials due to stable extracranial disease. Efforts should be made to design trials for this patient population.

Association of Brain Metastases With Survival in Patients With Limited or Stable Extracranial Disease: A Systematic Review and Meta-analysis

IMPORTANCE

Intracranial metastatic disease (IMD) is a severe complication of cancer with profound prognostic implications. Patients with IMD in the setting of limited or stable extracranial disease (IMD-SE) may represent a unique and understudied subset of patients with IMD with superior prognosis.

OBJECTIVE

To evaluate overall survival (OS), progression-free survival (PFS), and intracranial PFS (iPFS) in patients with IMD-SE secondary to any primary cancer.

DATA SOURCES

Records were identified from MEDLINE, EMBASE, CENTRAL, and gray literature sources from inception to June 21, 2021.

STUDY SELECTION

Studies in English reporting OS, PFS, or iPFS in patients with IMD-SE (defined as IMD and ≤2 extracranial metastatic sites) and no prior second-line chemotherapy or brain-directed therapy were selected.

DATA EXTRACTION AND SYNTHESIS

Author, year of publication, type of study, type of primary cancer, and outcome measures were extracted. Random-effects meta-analyses were performed to estimate effect sizes, and subgroup meta-analysis and metaregression were conducted to measure between-study differences in February 2022.

MAIN OUTCOMES AND MEASURES

The primary end point was OS described as hazard ratios (HRs) and medians for comparative and single-group studies, respectively. Secondary end points were PFS and iPFS.

RESULTS

Overall, 68 studies (5325 patients) were included. IMD-SE was associated with longer OS (HR, 0.52; 95% CI, 0.39-0.70) and iPFS (HR, 0.63; 95% CI, 0.52-0.76) compared with IMD in the setting of progressive extracranial disease. The weighted median OS estimate for patients with IMD-SE was 17.9 months (95% CI, 16.4-22.0 months), and for patients with IMD-PE it was 8.0 months (95% CI, 7.2-12.8 months). Pooled median OS for all patients with IMD-SE was 20.9 months (95% CI, 16.35-25.98 months); for the subgroup with breast cancer it was 20.2 months (95% CI, 10.43-38.20 months), and for non-small cell lung cancer it was 27.5 months (95% CI, 18.27-49.66 months). Between-study heterogeneity for OS and iPFS were moderate (I2 = 56.5%) and low (I2 = 0%), respectively.

CONCLUSIONS AND RELEVANCE

In this systematic review and meta-analysis of patients with IMD-SE, limited systemic disease was associated with improved OS and iPFS. Future prospective trials should aim to collect granular information on the extent of extracranial disease to identify drivers of mortality and optimal treatment strategies in patients with brain metastases.

Stereotactic radiosurgery for patients with breast cancer brain oligometastases - molecular subtypes and clinical outcomes

Background

We sought to determine the clinical outcomes of patients with breast cancer (BC) who had undergone stereotactic radiosurgery (SRS) for a limited number of brain metastases (BM) and to identify factors influencing overall survival (OS) and local control.

Materials and methods

The records of 45 patients who underwent SRS for 72 brain lesions were retrospectively evaluated. Statistics included the chi-squared test, Kaplan-Meier method, and the multivariate Cox model.

Results

The median number of treated BM was 2 (range 1-10). Median OS from BM diagnosis and post-SRS were 27.6 [95% confidence interval (CI): 14.8-40.5) and 18.5 months (95% CI: 11.1-25.8), respectively. One-year and two-year survival rates after BM diagnosis were 55% and 41%, respectively. In a univariate analysis, the Luminal-B-human-epidermal-growth-receptor-positive (HER2+) subtype had the longest median OS at 39.1 months (95% CI: 34.1-44.1, p = 0.004). In an adjusted analysis, grade 2 [hazard ratio (HR): 0.1; 95% CI: 0.1-0.6, p = 0.005), craniotomy (HR: 0.3; 95% CI: 0.1-0.7; p = 0.006), and ≥ 2 systemic therapies received (HR: 0.3; 95% CI: 0.1-0.9, p = 0.028) were associated with improved OS. One-year and two-year intracranial progression-free survival rates were 85% and 63%, respectively. Four factors for a higher risk of any intracranial recurrence remained significant in the adjusted analysis, as follows: age < 50 years (HR: 4.2; 95% CI: 1.3-36.3; p = 0.014), grade 3 (HR: 3.7; 95% CI: 1.1-13.2; p = 0.038), HER2+ (HR: 6.9; 95% CI: 1.3-36.3; p = 0.023), and whether the brain was the first metastatic site (HR: 4.7; 95% CI: 1.6-14.5; p = 0.006).

Conclusion

Intrinsic BC characteristics are important determinants for both survival and intracranial control for patients undergoing SRS for oligometastatic brain disease.

LINAC-based stereotactic radiosurgery/radiotherapy for brain metastases in patients with breast cancer

Background:

Brain metastases (BM) are common in patients with HER2-positive and triple-negative breast cancer. In this study we aim to report clinical outcomes with LINAC-based stereotactic radiosurgery/radiotherapy (SRS/SRT) for BM in patients of breast cancer.

Methods:

Clinical and dosimetric records of breast cancer patients treated for BM at our institute between May, 2015 and December, 2019 were retrospectively reviewed. Patients of previously treated or newly diagnosed breast cancer with at least a radiological diagnosis of BM; 1–4 in number, ≤3·5 cm in maximum dimension, with a Karnofsky Performance Score of ≥60 were taken up for treatment with SRS. SRT was generally considered if a tumour was >3·5 cm in diameter, near a critical or eloquent structure, or if the proximity of moderately sized tumours would lead to dose bridging in a single-fraction SRS plan. The median prescribed SRS dose was 15 Gy (range 7–24 Gy) and SRT dose was 27 Gy in 3 fractions.

Clinical assessment and MR imaging was done at 6 weeks post-SRS and then every 3 months thereafter. Intracranial progression-free survival (PFS) and overall survival (OS) were calculated using Kaplan–Meier method and subgroups were compared using log rank test.

Results:

Total, 40 tumours were treated in 31 patients. The median tumour diameter was 2·3 cm (range 1·0–4·6 cm). SRS and SRT were delivered in 27 and 4 patients, respectively. SRS/SRT was given as a boost to whole brain radiotherapy (WBRT) in four patients and as salvage for progression after WBRT in six patients. In general, nine patients underwent prior surgery. The median follow-up was 7·9 months (0·2–34 months). Twenty (64·5%) patients developed local recurrence, 10 (32·3%) patients developed distant intracranial relapse and 7 patients had both local and distant intracranial relapse. The estimated local control at 6 months and 1 year was 48 and 35%, respectively. Median intracranial progression free survival (PFS) was 3·73 months (range 0·2–25 months). Median intracranial PFS was 3·02 months in patients who received SRS alone or as boost after WBRT, while it was 4·27 months in those who received SRS as salvage after WBRT (p = 0·793). No difference in intracranial PFS was observed with or without prior surgery (p = 0·410). Median overall survival (OS) was 21·7 months (range 0·2–34 months) for the entire cohort. Patients who received prior WBRT had a poor OS (13·31 months) as compared to SRS alone (21·4 months; p = 0·699).

Conclusion:

In patients with BM after breast cancer SRS alone, WBRT + SRS and surgery + SRS had comparable PFS and OS.

Use of radiotherapy in breast cancer patients with brain metastases: a retrospective 11-year single center study

AIM

To analyse the use of radiotherapy (RT) and factors affecting overall survival (OS) after RT in breast cancer patients with brain metastases.

METHODS

Breast cancer patients treated from 2008 to 2018 with whole brain RT (WBRT) or stereotactic radiosurgery (SRS) at a large regional cancer referral center were identified from the hospital's RT register. Clinical variables were extracted from medical records. OS was calculated from date of first RT until death or last follow up. Potential factors affecting OS were analyzed.

RESULTS

255 females with WBRT (n = 206) or SRS (n = 49) as first RT were included. An increased use of initial SRS was observed in the second half of the study period. The most common WBRT fractionation regimen was 3 Gy × 10. SRS was most often single fractions; 18 or 25 Gy between 2009 and 2016, while fractionated SRS was mostly used in 2017 and 2018. Median OS in the WBRT group was 6 months (CI 1-73) relative to 23 (CI 0-78) in the SRS group. Age, performance status, initial RT technique, extracranial disease, brain metastasis surgery, number of brain metastases and DS-GPA score had significant impact on OS. Only ECOG 0 and brain metastasis surgery were associated with superior OS in multivariate analysis.

CONCLUSION

WBRT was the most frequent primary RT. An increased use of initial SRS was observed in the second half of the study period. Only ECOG 0 and brain metastasis surgery were associated with superior OS in multivariate analysis.

Safety of radiosurgery concurrent with systemic therapy (chemotherapy, targeted therapy, and/or immunotherapy) in brain metastases: a systematic review

Stereotactic radiosurgery (SRS) is a standard option for brain metastases (BM). There is lack of consensus when patients have a systemic treatment, if a washout is necessary. The aim of this review is to analyze the toxicity of SRS when it is concurrent with chemotherapies, immunotherapy, and/or targeted therapies. From Medline and Embase databases, we searched for English literature published up to April 2020 according to the PRISMA guidelines, using for key words the list of the main systemic therapies currently in use And "radiosurgery," "SRS," "GKRS," "Gamma Knife," "toxicity," "ARE," "radiation necrosis," "safety," "brain metastases." Studies reporting safety or toxicity with SRS concurrent with systemic treatment for BM were included. Of 852 abstracts recorded, 77 were included. The main cancers were melanoma, lung, breast, and renal carcinoma. These studies cumulate 6384 patients. The median SRS dose prescription was 20 Gy [12-30] .For some, they compared a concurrent arm with a non-concurrent or a SRS-alone arm. There were no skin toxicities, no clearly increased rate of bleeding, or radiation necrosis with significant clinical impact. SRS combined with systemic therapy appears to be safe, allowing the continuation of treatment when brain SRS is considered.

Validation of Nine Different Prognostic Grading Indexes for Radiosurgery of Brain Metastases in Breast Cancer Patients and Development of an All-Encompassing Prognostic Tool

Purpose: Several prognostic indexes for overall survival (OS) after radiotherapy of brain metastases in breast cancer patients exist but are mainly validated for whole-brain radiotherapy or not specifically for breast cancer patients. To date, no such index provides information beyond mere OS.

Methods: We retrospectively analyzed 95 breast cancer patients treated with stereotactic radiosurgery for 203 brain metastases. The Kaplan–Meier method with log-rank test was used to assess OS, local control (LC), distant cranial control (DCC), and extracranial control (EC). Cox regression was applied to detect prognostic outcome factors. A point scoring system was designed to stratify patients based on outcome. Nine established prognostic indexes were analyzed using the concordance index (c-index).

Results: Two out of nine analyzed prognostic indexes for OS showed a significant c-index, the breast graded prognostic assessment (bGPA; 0.631; 95% CI, 0.514–0.748; p = 0.037) and the modified bGPA (mod-bGPA; 0.662; 95% CI, 0.547–0.777; p = 0.010). Significant results from multivariate analysis (Karnofsky Performance Score, Her2/neu receptor status, extracranial control) were used to generate a new point system: the breast cancer stereotactic radiotherapy score (bSRS), which discriminated three significantly different prognostic groups, for LC, DCC, EC, and OS, respectively. However, the c-index was only significant for OS (0.689; 95% CI, 0.577–0.802; p = 0.003).

Conclusions: The new bSRS score was superior to the bGPA and mod-bGPA scores for prognosis of OS. The bSRS is easy to use and the first tool, which might also provide outcome assessment beyond mere OS. Future studies need to validate these findings.