Review of the diagnosis and treatment of brain metastases

The curse of blood-brain barrier and blood-tumor barrier in malignant brain tumor treatment

The blood-brain barrier (BBB) is crucial for brain homeostasis but is a major obstacle in delivering anticancer drugs to brain tumors. However, this perspective requires re-evaluation, particularly for malignant brain tumors, such as gliomas and brain metastases. In these aggressive tumors, the BBB undergoes significant alterations, leading to the formation of a more permeable blood-tumor barrier. While this increased permeability allows better drug penetration, heterogeneity in blood-tumor barrier (BTB) integrity across different tumor regions remains a challenge. Additionally, the main challenge in treating brain tumors lies not in BBB penetration but in the lack of effective drugs. Conventional chemotherapies, including temozolomide and nitrosourea agents, have shown limited efficacy, and resistance mechanisms often reduce their long-term benefits. The "BBB curse" has often been blamed for the slow progress in drug development. However, emerging evidence suggests that even larger-molecule therapies, such as antibody-drug conjugates, can successfully target brain tumors. This review aims to critically reassess the roles of the BBB and BTB in brain tumor therapy, highlighting their impact on drug delivery and evaluating the current landscape of chemotherapeutic strategies. Furthermore, it explores new approaches to overcome treatment limitations, emphasizing the need for personalized and targeted therapeutic strategies.

Prognostic Factors in Postoperative Brain Metastases Derive From Non-small Cell Lung Cancer: A Retrospective Analysis

Background

Brain metastases are crucial in cancer progression, requiring focused efforts on the screening, early detection, and treatment. However, accurate forecasting the postoperative prognosis of patients with non-small cell lung cancer brain metastasis remains a challenge. This retrospective study aims to discern the factors that influence the prognosis of such patients.

Methods

A total of 151 cases from Zhejiang Cancer Hospital were collected. Univariate analysis was conducted using Kaplan-Meier and Log-rank test, while multivariate analysis was performed using Cox proportional hazards regression model. Student's t-test and chi-square test were employed to examine the differences between the long-term survival and the short-term survival groups. Ultimately, a predictive model was constructed using R 4.2.1.

Results

Univariate analysis identified 12 factors as prognostic factors, showing statistical significance. In multivariate analysis, the primary contributing factors to survival were identified as age, chemotherapy of brain metastases, pathology, surgery of nonsmall cell lung cancer, targeted drugs, and GPA score. Comparing long-term and short-term groups, age, pathology, surgery of lung, targeted therapy, and radiotherapy of brain metastases were statistically differentiating factors. Based on multivariate analysis, we established a clinical predictive model predicting 2-year, 3-year, and 5-year survival rates.

Conclusion

Younger age, receiving chemotherapy for brain metastases, adenocarcinoma pathology, lung cancer surgery, targeted therapy, and a high GPA score are associated with longer survival. This model predicts the survival period for patients with non-small cell lung cancer brain metastasis after surgery and helps in selecting more effective treatment plans.

Development of a scoring system to predict local recurrence in brain metastases following complete resection and observation

PURPOSE

Postoperative stereotactic radiosurgery to the resection cavity in patients with brain metastases is guideline-recommended therapy. However, Japanese Clinical Oncology Group 0504 study showed that postoperative observation could be a therapeutic option in patients with completed resected brain metastases. We hereby investigated the incidence and risk factors for local recurrence after complete resection without immediate radiotherapy and developed a scoring system for its prediction.

METHODS

We included 53 patients with 54 brain metastases, who underwent complete resection between January 2016 and December 2021. We identified risk factors for local recurrence and developed a scoring system to predict it using the extracted risk factors, by assigning one point to each risk factor and calculating the total scores for each patient. We evaluated the correlation between the prognostic score and time to local recurrence.

RESULTS

Local recurrence occurred in 37 of 54 tumors (68.5%), with a median follow-up duration of 21.0 months. The median time to local recurrence was 5.1 months. Univariate and multivariate analyses revealed that non-lung adenocarcinoma, infratentorial tumors, and no postoperative systemic therapy were identified as risk factors for local recurrence (non-lung adenocarcinoma, p = 0.035; infratentorial tumors, p = 0.044; and no postoperative systemic therapy, p = 0.0069). A score ≥ 2 showed a median time to local recurrence of 2.1 months, starkly contrasting with 30.8 months for a score ≤ 1 (p = 0.0002).

CONCLUSIONS

Non-lung adenocarcinoma, infratentorial tumors, and no postoperative systemic therapy were risk factors for local recurrence. Our scoring system can predict local recurrence, thus potentially aiding treatment decisions.

Advances in determining the gross tumor target volume for radiotherapy of brain metastases

Brain metastases (BMs) are the most prevalent intracranial malignant tumors in adults and are the leading cause of mortality attributed to malignant brain diseases. Radiotherapy (RT) plays a critical role in the treatment of BMs, with local RT techniques such as stereotactic radiosurgery (SRS)/stereotactic body radiotherapy (SBRT) showing remarkable therapeutic effectiveness. The precise determination of gross tumor target volume (GTV) is crucial for ensuring the effectiveness of SRS/SBRT. Multimodal imaging techniques such as CT, MRI, and PET are extensively used for the diagnosis of BMs and GTV determination. With the development of functional imaging and artificial intelligence (AI) technology, there are more innovative ways to determine GTV for BMs, which significantly improve the accuracy and efficiency of the determination. This article provides an overview of the progress in GTV determination for RT in BMs.

Prognostic factors associated with the transition in treatment methods for brain metastases from colorectal cancer

BACKGROUND

Treatment of brain metastases (BMs) from colorectal cancer (CRC) has transitioned with the expansion of indications for stereotactic radiotherapy. Our study aimed to assess changes in prognosis and prognostic factors associated with changes in treatment for BMs from CRC.

METHODS

We retrospectively surveyed treatments for and outcomes of BMs from CRC in 208 patients treated during 1997-2018. Patients were divided into two groups according to time of BM diagnosis, i.e., 1997-2013 ("first period") and 2014-2018 ("second period"). We compared overall survival between the periods and assessed how the transition impacted prognostic factors affecting overall survival, including the following prognostic factors such as Karnofsky performance status (KPS), volume-related factors (BM number and diameter), and BM treatment modalities as covariates.

RESULTS

Of the 208 patients, 147 were treated in the first period and 61 in the second period. Whole-brain radiotherapy use decreased from 67 to 39% in the second period, and stereotactic radiotherapy use increased from 30 to 62%. Median survival after BM diagnosis improved from 6.1 to 8.5 months (p = 0.0272). Multivariate analysis revealed KPS, control of primary tumor, stereotactic radiotherapy use, and chemotherapy history as independent prognostic factors during the entire observation period. Hazard ratios of KPS, primary tumor control, and stereotactic radiotherapy were higher in the second period, whereas prognostic impact of chemotherapy history before BM diagnosis was similar in both periods.

CONCLUSION

Overall survival of patients with BMs from CRC improved since 2014, which can be attributed to advances in chemotherapy and the more widespread use of stereotactic radiotherapy.

TME-targeted approaches of brain metastases and its clinical therapeutic evidence

The tumor microenvironment (TME), which includes both cellular and non-cellular elements, is now recognized as one of the major regulators of the development of primary tumors, the metastasis of which occurs to specific organs, and the response to therapy. Development of immunotherapy and targeted therapies have increased knowledge of cancer-related inflammation Since the blood-brain barrier (BBB) and blood-cerebrospinal fluid barrier (BCB) limit immune cells from entering from the periphery, it has long been considered an immunological refuge. Thus, tumor cells that make their way "to the brain were believed to be protected from the body's normal mechanisms of monitoring and eliminating them. In this process, the microenvironment and tumor cells at different stages interact and depend on each other to form the basis of the evolution of tumor brain metastases. This paper focuses on the pathogenesis, microenvironmental changes, and new treatment methods of different types of brain metastases. Through the systematic review and summary from macro to micro, the occurrence and development rules and key driving factors of the disease are revealed, and the clinical precision medicine of brain metastases is comprehensively promoted. Recent research has shed light on the potential of TME-targeted and potential treatments for treating Brain metastases, and we'll use that knowledge to discuss the advantages and disadvantages of these approaches.

An exploratory analysis of MR-guided fractionated stereotactic radiotherapy in patients with brain metastases

Purpose

To assess the feasibility and potential benefits of online adaptive MR-guided fractionated stereotatic radiotherapy (FSRT) in patients with brain metastases (BMs).

Methods and materials

Twenty-eight consecutive patients with BMs were treated with FSRT of 30 Gy in 5 fractions on the 1.5 T MR-Linac. The FSRT fractions employed daily MR scans and the contours were utilized to create each adapted plan. The brain lesions and perilesional edema were delineated on MR images of pre-treatment simulation (Fx0) and all fractions (Fx1, Fx2, Fx3, Fx4 and Fx5) to evaluate the inter-fractional changes. These changes were quantified using absolute/relative volume, Dice similarity coefficient (DSC) and Hausdorff distance (HD) metrics. Planning target volume (PTV) coverage and organ at risk (OAR) constraints were used to compare non-adaptive and adaptive plans.

Results

A total of 28 patients with 88 lesions were evaluated, and 23 patients (23/28, 82.1%) had primary lung adenocarcinoma. Significant tumor volume reduction had been found during FSRT compared to Fx0 for all 88 lesions (median -0.75%, -5.33%, -9.32%, -17.96% and -27.73% at Fx1, Fx2, Fx3, Fx4 and Fx5, p < 0.05). There were 47 (47/88, 53.4%) lesions being accompanied by perilesional edema and the inter-fractional changes were significantly different compared to those without perilesional edema (p < 0.001). Patients with multiple lesions (13/28, 46.4%) had more significant inter-fractional tumor changes than those with single lesion (15/28, 53.6%), including tumor volume reduction and anatomical shift (p < 0.001). PTV coverage of non-adaptive plans was below the prescribed coverage in 26/140 fractions (19%), with 12 (9%) failing by more than 10%. All 140 adaptive fractions met prescribed target coverage. The adaptive plans also had lower dose to whole brain than non-adaptive plans (p < 0.001).

Conclusions

Significant inter-fractional tumor changes could be found during FSRT in patients with BMs treated on the 1.5 T MR-Linac. Daily MR-guided re-optimization of treatment plans showed dosimetric benefit in patients with perilesional edema or multiple lesions.

Recent Update on Neurosurgical Management of Brain Metastasis

Brain metastasis (BM), classified as a secondary brain tumor, is the most common malignant central nervous system tumor whose median overall survival is approximately 6 months. However, the survival rate of patients with BMs has increased with recent advancements in immunotherapy and targeted therapy. This means that clinicians should take a more active position in the treatment paradigm that passively treats BMs. Because patients with BM are treated in a variety of clinical settings, treatment planning requires a more sophisticated decision-making process than that for other primary malignancies. Therefore, an accurate prognostic prediction is essential, for which a graded prognostic assessment that reflects next-generation sequencing can be helpful. It is also essential to understand the indications for various treatment modalities, such as surgical resection, stereotactic radiosurgery, and whole-brain radiotherapy and consider their advantages and disadvantages when choosing a treatment plan. Surgical resection serves a limited auxiliary function in BM, but it can be an essential therapeutic approach for increasing the survival rate of specific patients; therefore, this must be thoroughly recognized during the treatment process. The ultimate goal of surgical resection is maximal safe resection; to this end, neuronavigation, intraoperative neuro-electrophysiologic assessment including evoked potential, and the use of fluorescent materials could be helpful. In this review, we summarize the considerations for neurosurgical treatment in a rapidly changing treatment environment.