Superior Prognostic Value of Cumulative Intracranial Tumor Volume Relative to Largest Intracranial Tumor Volume for Stereotactic Radiosurgery-Treated Brain Metastasis Patients

Navigating Post-Operative Outcomes: A Comprehensive Reframing of an Original Graded Prognostic Assessment in Patients with Brain Metastases

BACKGROUND

Graded Prognostic Assessment (GPA) has been proposed for various brain metastases (BMs) tailored to the primary histology and molecular profiles. However, it does not consider whether patients have been operated on or not and does not include surgical outcomes as prognostic factors. The residual tumor burden (RTB) is a strong predictor of overall survival. We validated the GPA score and introduced "volumetric GPA" in the largest cohort of operated patients and further explored the role of RTB as an additional prognostic factor.

METHODS

A total of 630 patients with BMs between 2007 and 2020 were included. The four GPA components were analyzed. The validity of the original score was assessed using Cox regression, and a modified index incorporating RTB was developed by comparing the accuracy, sensitivity, specificity, F1-score, and AUC parameters.

RESULTS

GPA categories showed an association with survival: age (p < 0.001, hazard ratio (HR) 2.9, 95% confidence interval (CI) 2.5-3.3), Karnofsky performance status (KPS) (p < 0.001, HR 1.3, 95% CI 1.2-1.5), number of BMs (p = 0.019, HR 1.4, 95% CI 1.1-1.8), and the presence of extracranial manifestation (p < 0.001, HR 3, 95% CI 1.6-2.5). The median survival for GPA 0-1 was 4 months; for GPA 1.5-2, it was 12 months; for GPA 2.5-3, it was 21 months; and for GPA 3.5-4, it was 38 months (p < 0.001). RTB was identified as an independent prognostic factor. A cut-off of 2 cm3 was used for further analysis, which showed a median survival of 6 months (95% CI 4-8) vs. 13 months (95% CI 11-14, p < 0.001) for patients with RTB > 2 cm3 and <2 cm3, respectively. RTB was added as an additional component for a modified volumetric GPA score. The survival rates with the modified GPA score were: GPA 0-1: 4 months, GPA 1.5-2: 7 months, GPA 2.5-3: 18 months, and GPA 3.5-4: 34 months. Both scores showed good stratification, with the new score showed a trend towards better discrimination in patients with more favorable prognoses.

CONCLUSION

The prognostic value of the original GPA was confirmed in our cohort of patients who underwent surgery for BM. The RTB was identified as a parameter of high prognostic significance and was incorporated into an updated "volumetric GPA". This score provides a novel tool for prognosis and clinical decision making in patients undergoing surgery. This method may be useful for stratification and patient selection for further treatment and in future clinical trials.

Artificial-intelligence-driven measurements of brain metastases' response to SRS compare favorably with current manual standards of assessment

Background

Evaluation of treatment response for brain metastases (BMs) following stereotactic radiosurgery (SRS) becomes complex as the number of treated BMs increases. This study uses artificial intelligence (AI) to track BMs after SRS and validates its output compared with manual measurements.

Methods

Patients with BMs who received at least one course of SRS and followed up with MRI scans were retrospectively identified. A tool for automated detection, segmentation, and tracking of intracranial metastases on longitudinal imaging, MEtastasis Tracking with Repeated Observations (METRO), was applied to the dataset. The longest three-dimensional (3D) diameter identified with METRO was compared with manual measurements of maximum axial BM diameter, and their correlation was analyzed. Change in size of the measured BM identified with METRO after SRS treatment was used to classify BMs as responding, or not responding, to treatment, and its accuracy was determined relative to manual measurements.

Results

From 71 patients, 176 BMs were identified and measured with METRO and manual methods. Based on a one-to-one correlation analysis, the correlation coefficient was R2 = 0.76 (P = .0001). Using modified BM response classifications of BM change in size, the longest 3D diameter data identified with METRO had a sensitivity of 0.72 and a specificity of 0.95 in identifying lesions that responded to SRS, when using manual axial diameter measurements as the ground truth.

Conclusions

Using AI to automatically measure and track BM volumes following SRS treatment, this study showed a strong correlation between AI-driven measurements and the current clinically used method: manual axial diameter measurements.

Stereotactic Radiosurgery as Treatment for Brain Metastases: An Update

Stereotactic radiosurgery (SRS) is a mainstay treatment option for brain metastasis (BM). While guidelines for SRS use have been outlined by professional societies, consideration of these guidelines should be weighed in the context of emerging literature, novel technology platforms, and contemporary treatment paradigms. Here, we review recent advances in prognostic scale development for SRS-treated BM patients and survival outcomes as a function of the number of BM and cumulative intracranial tumor volume. Focus is placed on the role of stereotactic laser thermal ablation in the management of BM that recur after SRS and the management of radiation necrosis. Neoadjuvant SRS prior to surgical resection as a means of minimizing leptomeningeal spread is also discussed.

Could intracranial tumor volume predict prognosis of patients with brain metastases from esophageal carcinoma?

PURPOSE

A previous study demonstrated that intracranial tumor volume had some correlation with gastrointestinal cancer patients' outcome. The aim of this study was to analyze patients with esophageal carcinoma (EC) and brain metastases to investigate if intracranial tumor volume would be a predictor of these patients' survival.

METHODS

A total of 52 patients with brain metastases from esophageal squamous cell carcinoma or esophageal adenocarcinoma were retrospectively reviewed. Patients without images of brain metastases in the hospital information system were eliminated.

RESULTS

The median follow-up time duration was 8.4 months (interquartile range 4.0-15.2). The median overall survival (OS) from time of brain metastases diagnosis was 8.0 months for all cases. Median OS of patients with small and large cumulative intracranial tumor volume (CITV) (<6.65 cm³ , ≥6.65 cm³ ) was 11.23 and 7.4 months, respectively. Median OS of patients with large and small largest intracranial tumor volume (LITV) (≥7.75 cm³ , <7.75 cm³ ) was 6.4 and 10.6 months, respectively. Univariate analysis demonstrated that CITV (hazard ratio [HR] 1.255, 95% confidence interval [CI] 0.673-2.342, p = 0.475) or LITV (HR 1.037, 95% CI 0.570-1.887, p = 0.904) was not significantly associated with improved OS. Multivariate analysis demonstrated that CITV and LITV were not significantly associated with improved OS.

CONCLUSION

EC patients with small intracranial tumor volume may have longer OS than those with large intracranial tumor volume, but this difference did not reach statistical difference. Future studies with a larger sample size may validate the correlation of intracranial tumor volume and patient survival.

Discovery of increased number or interval growth of brain metastases on same-day GammaKnife™ planning MRI: Predicting factors and patient outcomes

Purpose

To determine factors associated with increased risk of finding new and/or enlarged brain metastases (BM) on GammaKnife™ (GK) MRI and their impact on patient outcomes.

Results

43.9% of patients showed BM growth, 32.9% had additional brain metastases (aBM), and 18.1 % had both. Initial brain metastasis velocity (iBMV) was associated with finding aBM. Time between diagnostic MRI (dMRI) and GK MRI was associated with interval growth and each day increased this risk by 2%. Prior brain metastasectomy and greater time between either dMRI or latest extracranial RT and GK MRI predicted both aBM and BM growth. aBM and/or BM growth led to management change in 1.8% of cases and were not associated with OS or incidence of distant intracranial failure.

Conclusions

Number of metastases seen on dMRI and iBMV predicted both aBM and/or BM growth, however, these factors did not significantly affect survival or incidence of distant intracranial failure.

Volumetric burden of metastatic lesions drives outcomes in patients with extracranial oligometastatic disease

Background

We hypothesized that the total volume of metastases at initial oligometastatic (OM) presentation to stereotactic body radiation therapy (SBRT) is an important prognostic factor that can refine the definition of OM disease.

Methods

Patients with extracranial oligometastatic cancer (≤5 lesions) treated with SBRT were included in an international multi‐institutional database. Multivariable Cox and competing risks regression models were used to determine the relationship between distant progression‐free survival (DPFS), widespread progression (WSP), and overall survival (OS) with the total planning target volume (PTV) at initial OM presentation to SBRT. All models were adjusted for histology, pre‐SBRT systemic therapy, osseous‐only lesions, and number of metastases.

Results

In total, 961 patients were included. The median follow‐up was 24.4 months (IQR: 13.8–37.5). Total PTV had a significant effect on DPFS in the first 18 months after SBRT and was most profound in the first 6 months, when each twofold increase in total PTV conferred a 40.6% increased risk of distant progression (p < 0.001). Each twofold increase in total PTV increased the risk of WSP by 45.4% in the first 6 months (p < 0.001). Total PTV had a significant effect on OS in the first 2 years after SBRT, with each twofold PTV change increasing the risk of death by 60.7% during the first 6 months (p < 0.001) and by 34% thereafter (p < 0.001). Exploratory gross tumor volume (GTV) analysis confirmed the PTV‐based observations.

Conclusion

The total volumetric burden of metastases at initial OM presentation to SBRT is strongly and independently prognostic for the risk of distant and widespread progression and survival. We propose that this metric should drive the definition of OM disease and guide treatment decision‐making.

Individualized Nomogram for Predicting Survival in Patients with Brain Metastases After Stereotactic Radiosurgery Utilizing Driver Gene Mutations and Volumetric Surrogates

It is well-known that genomic mutational analysis plays a significant role in patients with NSCLC for personalized treatment. Given the increasing use of stereotactic radiosurgery (SRS) for brain metastases (BM), there is an emerging need for more precise assessment of survival outcomes after SRS. Patients with BM and treated by SRS were eligible in this study. The primary endpoint was overall survival (OS). Cox regression models were used to identify independent prognostic factors. A survival predictive nomogram was developed and evaluated by Concordance-index (C-index), area under the curve (AUC), and calibration curve. From January 2016 to December 2019, a total of 356 BM patients were eligible. The median OS was 17.7 months [95% confidence interval (CI) 15.5–19.9] and the actual OS at 1- and 2-years measured 63.2 and 37.6%, respectively. A nomogram for OS was developed by incorporating four independent prognostic factors: Karnofsky Performance Score, cumulative tumor volume, gene mutation status, and serum lactate dehydrogenase. The nomogram was validated in a separate cohort and demonstrated good calibration and good discriminative ability (C-index = 0.780, AUC = 0.784). The prognostic accuracy of the nomogram (0.792) was considerably enhanced when compared with classical prognostic indices, including the Graded Prognostic Assessment (0.708), recursive partitioning analysis (0.587), and the SRS (0.536). Kaplan–Meier curves showed significant differences in OS among the stratified low-, median- and high-risk groups (P < 0.001). In conclusion, we developed and validated an individualized prognostic nomogram by integrating physiological, volumetric, clinical chemistry, and molecular biological surrogates. Although this nomogram should be validated by independent external study, it has a potential to facilitate more precise risk-stratifications to guide personalized treatment for BM.

Metastatic renal cell carcinoma to the brain: optimizing patient selection for gamma knife radiosurgery

INTRODUCTION

The effects of single-fraction gamma knife radiosurgery (sf-GKRS) on patients with renal cell carcinoma (RCC) brain metastases (BM) in the era of targeted agents (TA) and immune checkpoint inhibitors (ICI) are insufficiently studied.

METHODS AND MATERIALS

Clear cell metastatic RCC patients treated with sf-GKRS due to BM in 2005-2014 at three European centres were retrospectively analysed (n = 43). Median follow-up was 56 months. Ninety-five percent had prior nephrectomy, 53% synchronous metastasis and 86% extracranial disease at first sf-GKRS. Karnofsky performance status (KPS) ranged from 60 to 100%. Outcome measures were overall survival (OS), local control (LC) and adverse radiation effects (ARE).

RESULTS

One hundred and ninety-four targets were irradiated. The median number of targets at first sf-GKRS was two. The median prescription dose was 22.0 Gy. Thirty-seven percent had repeated sf-GKRS. Eighty-eight percent received TA. LC rates at 12 and 18 months were 97% and 90%. Median OS from the first sf-GKRS was 15.7 months. Low serum albumin (HR for death 5.3), corticosteroid use pre-sf-GKRS (HR for death 5.8) and KPS < 80 (HR for death 9.1) were independently associated with worse OS. No further prognostic information was gleaned from MSKCC risk group, synchronous metastasis, age, number of BM or extracranial metastases. Other prognostic scores for BM radiosurgery, including DS-GPA, renal-GPA, LLV-SIR and CITV-SIR, again, did not add further prognostic value. ARE were seldom symptomatic and were associated with tumour volume, 10-Gy volume and pre-treatment perifocal oedema. ARE were less common among patients treated with TA within 1 month of sf-GKRS.

CONCLUSIONS

We identified albumin, corticosteroid use and KPS as independent prognostic factors for sf-GKRS of clear cell RCC BM. Studies focusing on the prognostic significance of albumin in sf-GKRS are rare. Further studies with a larger number of patients are warranted to confirm the above analytical outcome. Also, in keeping with previous studies, our data showed optimal rates of local tumour control and limited toxicity post radiosurgery, rendering GKRS the tool of choice in the management of RCC BM.

Cumulative Intracranial Tumor Volume as a Prognostic Factor in Patients with Brain Metastases Undergoing Stereotactic Radiosurgery

Approximately 25-35% of all cancer patients suffer from brain metastases (BM), and many of them-in particular, those with a limited number of intracranial tumors-are treated with stereotactic radiosurgery (SRS). Accurate prediction of survival remains a key clinical challenge in this population. Several prognostic scales have been developed to facilitate this prognostication, including the Recursive Partitioning Analysis (RPA) classification, the modified Recursive Partitioning Analysis (mRPA) subclassifications, the Basic Score for Brain Metastases (BS-BM), the Score Index for Radiosurgery (SIR), the Graded Prognostic Assessment (GPA), and the diagnosis-specific Graded Prognostic Assessment (dsGPA). However, none of these scales include consideration of the cumulative intracranial tumor volume (CITV), which is defined as the sum of all intracranial tumor volumes. Since there is mounting evidence that the CITV carries significant prognostic value in SRS-treated patients with BM, this variable should be considered during survival prognostication, along with other pertinent clinical, pathological, and molecular characteristics.

A graded prognostic model for patients surviving 3 years or more (GPM ≥ 3Ys) after stereotactic radiosurgery for brain metastasis

BACKGROUND AND PURPOSE

As more cancer patients with brain metastases (BMs) are surviving longer due to recent advancements in various treatment modalities, we developed a grading system for stereotactic radiosurgery (SRS)-treated BM patients with long survival. This is a Graded Prognostic Model for Patients Surviving 3 Years or More (GPM ≥ 3Ys).

MATERIALS AND METHODS

First, using clinical factor-survival time analysis of 3237 patients in whom gamma knife (GK) SRS was performed by the second author (test cohort), we developed the GPM ≥ 3Ys based on survival ≥3 years as the objective variable. The validity of this model was then tested using another series of 3317 patients independently undergoing GK SRS performed by the third author (verification cohort). Number of patients surviving 3 years or more were 289 (8.9%) and 348 (10.5%), respectively.

RESULTS

Using the test series, among various pre-SRS clinical factors, noted below, five were shown to be highly correlated with survival of ≥3 years. Therefore, we assigned scores for these five factors, i.e., "tumor numbers 1/2-4/≥5 (score; 6/1/0)", "female/male (5/0)", "KPS ≥80%/<80% (5/0)", "primary cancers of breast/lung/gastrointestinal tract/other (score; 1/0/3/0)", "controlled primary cancer/not (8/0)" and "existing extra-cerebral metastases/not (5/0). Patients were categorized into four grades according to the sum of scores, i.e., 0-9, 10-19, 20-29 and 30-36. Post-SRS mean survival times (MSTs) differed significantly (p < 0.0001) with no overlapping of 95% confidence intervals (CIs) among the four grades. Also, in the verification series, MSTs differed significantly (p < 0.0001) with no overlapping of 95% CI among the four grades of the GPM ≥ 3Ys system.

CONCLUSION

Although this was a retrospective study, the GPM ≥ 3Ys system was shown to be very useful to physicians selecting among more aggressive treatment modalities for patients in whom longer survival can be expected.

Role of radiation therapy in brain metastases management

The challenge of the management of brain metastases has not finished yet. Although new diagnosis-specific prognostic assessment classifications and guidelines for patients with brain metastases help to guide treatment more appropriately, and even if the development of modern technologies in imaging and radiation treatment, as well as improved new systemic therapies, allow to reduce cognitive side effects and make retreatment or multiple and combined treatment possible, several questions remain unanswered. However, tailoring the treatment to the patient and his expectations is still essential; in other words, patients with a poor prognosis should not be over-treated, and those with a favorable prognosis may not be subtracted to the best treatment option. Some ongoing trials with appropriate endpoints could better inform our choices. Finally, a case-by-case inter-disciplinary discussion remains essential.

Cumulative intracranial tumour volume prognostic assessment: a new predicting score index for patients with brain metastases treated by stereotactic radiosurgery

Brain metastases (BM) represent the most common intracranial malignancy in adults. Limitations of existing prognostic models reduce their predictivity and clinical applicability. The aim of this study is to validate the cumulative intracranial tumour volume prognostic assessment (CITVPA) as a new prognostic score system for patients with BM treated by Stereotactic Radiosurgery (SRS). Between January 2001 and December 2015, 1894 patients underwent Gamma Knife SRS treatment. The CITVPA model was implemented and validated as follows: the CITV cut-offs were identified thanks to a receiver-operating characteristic (ROC) curve analysis; the survival predictive factors were selected through a Cox proportional hazard model; its prognostic power was compared to RPA, SIR and GPA through the Harrel concordance index (HCI). According to the ROC curve analysis, the CITV cut-off values were set at 1.5 and 4.0 cc. Based on the multivariate analysis, the CITVPA model included: age (OR 1.010, 95% CI 1.005-1.015, p < 0.001), KPS (OR 0.960, 95% CI 0.956-0.965, p < 0.001), extracranial metastases (OR 1.287, 95% CI 1.154-1.437, p < 0.001), BM number (OR 1.193, 95% CI 1.047-1.360, p = 0.008), and CITV (OR 1.028, 95% CI 1.020-1.036, p < 0.001). A score between 0 and 1 was attributed to each prognosticator; a global CITVPA score ranging from 0 to 5 was assigned with higher results corresponding to worse outcomes. The CITVPA (HCI = 0.64) exhibited a significantly (p < 0.001) higher prognostic power compared to RPA (HCI = 0.55), SIR (HCI = 0.55) and GPA (HCI = 0.61). The CITVPA represents a reliable prognostic system for patients with BM treated by SRS. However, further prospective and multicentric studies are necessary before its applicability in clinical practice.

Current approaches to the management of brain metastases

Brain metastases are a very common manifestation of cancer that have historically been approached as a single disease entity given the uniform association with poor clinical outcomes. Fortunately, our understanding of the biology and molecular underpinnings of brain metastases has greatly improved, resulting in more sophisticated prognostic models and multiple patient-related and disease-specific treatment paradigms. In addition, the therapeutic armamentarium has expanded from whole-brain radiotherapy and surgery to include stereotactic radiosurgery, targeted therapies and immunotherapies, which are often used sequentially or in combination. Advances in neuroimaging have provided additional opportunities to accurately screen for intracranial disease at initial cancer diagnosis, target intracranial lesions with precision during treatment and help differentiate the effects of treatment from disease progression by incorporating functional imaging. Given the numerous available treatment options for patients with brain metastases, a multidisciplinary approach is strongly recommended to personalize the treatment of each patient in an effort to improve the therapeutic ratio. Given the ongoing controversies regarding the optimal sequencing of the available and expanding treatment options for patients with brain metastases, enrolment in clinical trials is essential to advance our understanding of this complex and common disease. In this Review, we describe the key features of diagnosis, risk stratification and modern paradigms in the treatment and management of patients with brain metastases and provide speculation on future research directions.

Operative and peri-operative considerations in the management of brain metastasis

The number of patients who develop metastatic brain lesions is increasing as the diagnosis and treatment of systemic cancers continues to improve, resulting in longer patient survival. The role of surgery in the management of brain metastasis (BM), particularly multiple and recurrent metastases, remains controversial and continues to evolve. However, with appropriate patient selection, outcomes after surgery are typically favorable. In addition, surgery is the only means to obtain a tissue diagnosis and is the only effective treatment modality to quickly relieve neurological complications or life-threatening symptoms related to significant mass effect, CSF obstruction, and peritumoral edema. As such, a thorough understanding of the role of surgery in patients with metastatic brain lesions, as well as the factors associated with surgical outcomes, is essential for the effective management of this unique and growing patient population.

Brain metastasis from urachal carcinoma

Background

Urachal carcinoma (UC) is a rare variant of bladder carcinoma. Only seven cases of brain metastasis from UC have been reported in the literature thus far.

Case Description

A 77-year-old female was diagnosed with a brain tumor in her left cerebellum 2 years after she underwent surgery for a primary UC in the bladder. Surgery was performed via a midline suboccipital approach and the tumor was totally removed. The excised lesion was pathologically diagnosed as a metastasis and displayed typical pathological features of urachal adenocarcinoma with abundant mucin mixed with signet ring cells. A recurrence was observed at the site of tumor removal 6 months after surgery, and then, gamma knife radiotherapy was performed to the lesion.

Conclusion

According to the five previously reported similar cases and our case, tumor removal is the treatment of choice. Routine whole brain radiotherapy is not the best treatment choice; however, local radiotherapy including conventional local radiotherapy or gamma knife radiotherapy could be implemented instead.

Prognostic grading system specifically for elderly patients with brain metastases after stereotactic radiosurgery: a 2-institution study

OBJECTIVEWith the aging of the population, increasing numbers of elderly patients with brain metastasis (BM) are undergoing stereotactic radiosurgery (SRS). Among recently reported prognostic grading indexes, only the basic score for brain metastases (BSBM) is applicable to patients 65 years or older. However, the major weakness of this system is that no BM-related factors are graded. This prompted the authors to develop a new grading system, the elderly-specific (ES)-BSBM.METHODSFor this IRB-approved, retrospective cohort study, the authors used their prospectively accumulated database comprising 3267 consecutive patients undergoing Gamma Knife SRS for BMs during the 1998-2016 period at the Mito GammaHouse. Among these 3267 patients, 1789 patients ≥ 65 years of age were studied (Yamamoto series [Y-series]). Another series of 1785 patients ≥ 65 years of age in whom Serizawa and colleagues performed Gamma Knife SRS during the same period (Serizawa series [S-series]) was used for validity testing of the ES-BSBM.RESULTSTwo factors were identified as strongly impacting longer survival after SRS by means of multivariable analysis using the Cox proportional hazard model with a stepwise selection procedure. These factors are the number of tumors (solitary vs multiple: HR 1.450, 95% CI 1.299-1.621; p < 0.0001) and cumulative tumor volume (≤ 15 cm3 vs > 15 cm3: HR 1.311, 95% CI 1.078-1.593; p = 0.0067). The new index is the addition of scores 0 and 1 for these 2 factors to the BSBM. The ES-BSBM system is based on categorization into 3 classes by adding these 2 scores to those of the original BSBM. Each ES-BSBM category has 2 possible scores. For the category ES-BSBM 4-5, the score is either 4 or 5; for ES-BSBM 2-3, the score is either 2 or 3; and for ES-BSBM 0-1, the score is either 0 or 1. In the Y-series, the median survival times (MSTs, months) after SRS were 17.5 (95% CI 15.4-19.3) in ES-BSBM 4-5, 6.9 (95% CI 6.4-7.4) in ES-BSBM 2-3, and 2.8 (95% CI 2.5-3.6) in ES-BSBM 0-1 (p < 0.0001). Also, in the S-series, MSTs were, respectively, 20.4 (95% CI 17.2-23.4), 7.9 (95% CI 7.4-8.5), and 3.2 (95% CI 2.8-3.6) (p < 0.0001). The ES-BSBM system was shown to be applicable to patients with all primary tumor types as well as to those 80 years or older.CONCLUSIONSThe authors found that the addition of the number of tumors and cumulative tumor volume as scoring factors to the BSBM system significantly improved the prognostic value of this index. The present study is strengthened by testing the ES-BSBM in a different patient group.

Cystic Formation After Stereotactic Radiosurgery of Brain Metastasis

BACKGROUND

Limited information is available on the natural history and etiology of cystic formation after stereotactic radiosurgery (SRS) for brain metastases (BM). We aimed to characterize the natural history of cyst formation after SRS of BM and analyze potential risk factors.

METHODS

We retrospectively reviewed 214 consecutive patients who underwent a total of 1106 SRSs for BM. Demographic, clinical, dosimetric, and magnetic resonance imaging MRI data were reviewed. Statistical analysis was accomplished using Student's t test, and univariate and multivariate logistic regression.

RESULTS

The median patient age was 61 years (range, 19-91 years), and the median duration of follow-up was 424 days (range, 91-2934 days). Eleven cases of cyst formation (0.9% of 1106 treated lesions) were identified at SRS-treated BM sites among 9 patients (2 patients developed cysts at independent sites). The median interval between first SRS and first evidence of cyst was 218 days. Seven of the 9 patients (78%) sustained progressive cyst expansion and neurologic decline requiring steroid treatment. Four of these 7 patients (57%) experienced continued neurologic decline and needed surgical fenestration. On univariate analysis, receipt of >4 rounds of SRS was the sole variable associated with an increased risk of cyst formation (odds ratio, 16.58; P = 0.001). This association remained robust after adjusting for duration of follow-up (odds ratio, 13.59; P = 0.003).

CONCLUSIONS

In our experience with 1106 SRS-treated cases of BM, cyst formation was a rare phenomenon. However, 1 in 3 patients who underwent >4 rounds of SRS sustained cyst formation. A high proportion (78%) of SRS-associated cysts progressively expanded and required medical or surgical treatment.

The growing importance of lesion volume as a prognostic factor in patients with multiple brain metastases treated with stereotactic radiosurgery

Stereotactic Radiosurgery (SRS) is considered standard of care for patients with 1–3 brain metastases (BM). Recent observational studies have shown equivalent OS in patients with 5+ BM compared to those with 2–4, suggesting SRS alone may be appropriate in these patients. We aim to review outcomes of patients treated with SRS with 2–4 versus 5+ BM. This analysis included consecutive patients from 1994 to 2015 treated with SRS. Of 1017 patients, we excluded patients with a single BM and patients without adequate survival data, resulting in 391 patients. All risk factors were entered into univariate analysis using Cox proportional hazards model, and significant factors were entered into multivariate analysis (MVA). We additionally analyzed outcomes after excluding patients with prior surgery or whole‐brain radiotherapy (WBRT). Median follow‐up was 7.1 months. Median KPS was 90, mean age was 59, and most common histologies were melanoma and lung. Median tumor volume was 3.41 cc. Patients with 2–4 BM had a median OS of 8.1 months compared to 6.2 months for those with 5+ BM (P = 0.0136). On MVA, tumor volume, KPS, and histology remained significant for OS, whereas lesion number did not. Similar results were found when excluding patients with prior surgery or WBRT. Rather than lesion number, the strongest prognostic factors for patients undergoing SRS were tumor volume >10 cc, KPS, and histology. BM number may therefore not be the most important criterion for candidacy for SRS. Patients with 5 or more BM should be considered for SRS.

Improving the Prognostic Value of Disease-Specific Graded Prognostic Assessment Model for Renal Cell Carcinoma by Incorporation of Cumulative Intracranial Tumor Volume

BACKGROUND

We tested the prognostic value of cumulative intracranial tumor volume (CITV) in the context of a disease-specific Graded Prognostic Assessment (ds-GPA) model for renal cell carcinoma (RCC) patients with brain metastasis (BM) treated with stereotactic radiosurgery (SRS).

METHODS

Patient and tumor characteristics were collected from RCC cohorts with new BM who underwent SRS. Univariable and multivariable logistic regression model was used to test the prognostic value of CITV, Karnofsky Performance Score (KPS), and the number of BM. Net reclassification index (NRI) and integrated discrimination improvement (IDI) were used to assess whether CITV improved the prognostic utility of RCC ds-GPA.

RESULTS

In univariable logistic regression models, CITV, KPS, and the number of BM were independently associated with RCC patient survival. In a multivariable Cox proportional hazard model, the association between CITV and survival remained robust after controlling for KPS and the number of BM (P = 0.042). The incorporation of the CITV into the RCC ds-GPA model (consisting of KPS and number of BM) improved prognostic accuracy with NRI >0 of 0.3156 (95% confidence interval [CI], 0.0883-0.5428; P = 0.0065) and IDI of 0.0151 (95% CI, 0.0036-0.0277; P = 0.0183). These findings were validated in an independent cohort of 107 SRS-treated RCC BM patients.

CONCLUSION

CITV is an important prognostic variable in SRS-treated RCC patients with BM. The prognostic value of the ds-GPA scale for RCC brain metastasis was enhanced by the incorporation of CITV.