Oncological Outcomes After Hippocampus-Sparing Whole-Brain Radiotherapy in Cancer Patients With Newly Diagnosed Brain Oligometastases: A Single-Arm Prospective Observational Cohort Study in Taiwan

Trajectory of long-term neuropsychological performances and cognitive-deterioration-free survival after hippocampus-sparing whole-brain radiotherapy in cancer patients mostly with newly diagnosed brain oligometastases

Neurocognitive functions (NCFs) might change after conventional whole-brain radiotherapy (WBRT). The technique of hippocampus sparing during WBRT (HS-WBRT) may substantially preserve NCFs. Therefore, the aim of this study was to examine whether trajectories of neuropsychological performances maintained or improved after HS-WBRT. A total of 125 cancer patients underwent the HS-WBRT course. Before HS-WBRT, all participants underwent multidomain neurocognitive assessment, mainly involving executive functions and hippocampus-related memory. After radiotherapy, the above assessment was administered at regular time points to monitor longitudinal neuropsychological performances. The delta values of post-radiotherapy and baseline NCF scores showed a sustained trend, signifying cognitive maintenance rather than deterioration. This trend was observed for hippocampus-related verbal memory and frontal-lobe-related executive functions, represented by the score of Word List-immediate memory and Modified Card Sorting Test - Complete Categories, respectively. The potential predictors of longitudinal multidomain neuropsychological performances included age at enrollment, baseline NCF scores, and the assessment time (months) elapsed since enrollment, signifying the trajectory of patients' neuropsychological performances after HS-WBRT. Among longitudinal neuropsychological outcomes, there was a considerable time trend toward maintenance in verbal learning immediate memory [odds ratio, 1.112, 95% confidence interval, 1.08 - 1.15], which persisted even after adjusting for the most independent predictor (baseline NCF scores). Functional preservation of longitudinal multidomain neuropsychological performances was evident after HS-WBRT. Such neurocognitive preservation, particularly hippocampus-related memory functions, was meaningfully sustained in our patients after undergoing the standardized course of hippocampus sparing during WBRT.

Neurotoxicity-sparing radiotherapy for brain metastases in breast cancer: a narrative review

Breast cancer brain metastasis (BCBM) has a devastating impact on patient survival, cognitive function and quality of life. Radiotherapy remains the standard management of BM but may result in considerable neurotoxicity. Herein, we describe the current knowledge on methods for reducing radiation-induced cognitive dysfunction in patients with BCBM. A better understanding of the biology and molecular underpinnings of BCBM, as well as more sophisticated prognostic models and individualized treatment approaches, have appeared to enable more effective neuroprotection. The therapeutic armamentarium has expanded from surgery and whole-brain radiotherapy to stereotactic radiosurgery, targeted therapies and immunotherapies, used sequentially or in combination. Advances in neuroimaging have allowed more accurate screening for intracranial metastases, precise targeting of intracranial lesions and the differentiation of the effects of treatment from disease progression. The availability of numerous treatment options for patients with BCBM and multidisciplinary approaches have led to personalized treatment and improved therapeutic outcomes. Ongoing studies may define the optimal sequencing of available and emerging treatment options for patients with BCBM.

Region-Specific Effects of Fractionated Low-Dose Versus Single-Dose Radiation on Hippocampal Neurogenesis and Neuroinflammation

BACKGROUND

Despite technical advances in hippocampus-sparing radiotherapy, radiation-induced injury to neural stem cell compartments may affect neurocognitive functions. In pre-clinical mouse models with fractionated low-dose radiation (FLDR) and single-dose radiation (SDR), the accurate response to radiation-induced injury was analyzed in different hippocampal subregions.

METHODS

Adult and juvenile C57BL/6NCrl mice were exposed to FLDR (20 × 0.1 Gy, daily exposure from Monday to Friday for 4 weeks) or SDR (1 × 2 Gy). In addition, 72 h after the last exposure, neuroglia (astrocytes and microglia) and neuroprogenitor cells were characterized and quantified in the hippocampal cornu ammonis (CA) and dentate gyrus (DG) by immunofluorescence studies.

RESULTS

After analyzing different hippocampal subregions, it was observed that radiation responses varied between non-neurogenic CA, with no detectable inflammatory alterations, and neurogenic DG, characterized by impaired neurogenesis and subsequent neuroinflammation. Age-dependent differences in radiosensitivity appeared to depend on the varying proliferative potential of neural stem cell niches. Using the same overall dose for FLDR and SDR (2 Gy), both the cumulative dose over time and also the single dose fraction have decisive impacts on hippocampal damage.

CONCLUSION

Region-specific effects of radiation-induced hippocampal injury relies primarily on cell deaths of proliferating neuroprogenitors. Dose per fraction defines the extent of neuronal injury, and subsequently activated microglia and reactive astrocytes modulate dynamic processes of neuroinflammation. Thus, limiting both cumulative doses and dose fractions to hippocampal DG is an important issue of clinical radiotherapy to preserve neurocognitive functions.