Impact of prophylactic cranial irradiation and hippocampal sparing on 18F-FDG brain metabolism in small cell lung cancer patients

Neuroimaging insights into lung disease-related brain changes: from structure to function

Lung diseases induce changes in brain structure and function, leading to a range of cognitive, emotional, and motor deficits. The concept of the lung-brain axis has been proposed through neuroanatomy, endocrine, and immune pathway, while a considerable number of studies also explored the existence of the lung-brain axis from a neuroimaging perspective. This survey summarizes studies exploring the relationship between lung disease and brain structure and function from neuroimaging perspective, particular in magnetic resonance imaging (MRI). We have collated existing lung diseases studies and categorized them into four types: chronic obstructive pulmonary disease (COPD), coronavirus disease 2019 (COVID-19), lung cancer and other lung diseases. The observed structural and functional changes in the brain and cognitive dysfunction induced by lung diseases are discussed. We also present distinct pattern of brain changes in various lung diseases. Neuroimaging changes in COPD are concentrated in the frontal lobes, including gray matter atrophy, white matter damage, and reduced perfusion. Patients with COVID-19 exhibit extensive microhemorrhages and neuroinflammation, brain regions functionally connected to the primary olfactory cortex show greater changes. For lung cancer patients, brain changes are mainly attributed to the neurotoxicity of radiotherapy and chemotherapy, with damage concentrated in subcortical structures, patients with cancer pain demonstrate hyperconnectivity in motor and visual networks. The survey also discusses the pathological mechanisms revealed in neuroimaging studies and clinical significance of current studies. Finally, we analyzed current limitations, mainly in terms of small sample size, non-standardized criteria, reliance on correlation analyses, lack of longitudinal studies, and absence of reliable biomarkers. We suggest future research directions should include leveraging artificial intelligence for biomarker development, conducting longitudinal and multicenter studies, and investigating the systemic effects of lung disease on the brain and neuromodulation strategies.

Current dilemma and future directions over prophylactic cranial irradiation in SCLC: a systematic review in MRI and immunotherapy era

Small cell lung cancer (SCLC) is the most malignant pathological type of lung cancer with the highest mortality, and the incidence of brain metastasis (BM) is in high frequency. So far, prophylactic cranial irradiation (PCI) has been suggested as an effective treatment for preventing brain metastasis of SCLC. PCI has long been applied to limited-stage SCLC (LS-SCLC) patients who have achieved complete remission after radiotherapy and chemotherapy as a standard treatment. However, the neurocognitive decline is a major concern surrounding PCI. New therapeutic approaches targeting PCI-induced neurotoxicity, including hippocampal protection or memantine, have been increasingly incorporated into the therapeutic interventions of PCI. Helical tomotherapy, RapidArc, and Volumetric-modulated arc therapy (VMAT) with a head-tilting baseplate are recommended for hippocampal protection. Besides, in the MRI and immunotherapy era, the significance of PCI in SCLC patients is controversial. SCLC patients with PCI should be recruited in clinical trials since this is the only way to improve the existing standard of care. This review summarizes the current therapeutic strategy and dilemma over PCI for SCLC, providing a theoretical basis for clinical decision-making and suggestions for PCI practice in clinical.

Prophylactic cranial irradiation in small cell lung cancer: an update

PURPOSE OF REVIEW

The current review presents recent updates in the seminal literature of research on prophylactic cranial irradiation (PCI) in small cell lung cancer (SCLC).

RECENT FINDINGS

Brain MRI restaging before the administration of PCI reveals a substantial proportion of brain metastasis in baseline brain metastasis free extensive-stage SCLC (ES-SCLC) and limited-stage SCLC (LS-SCLC). Posthoc analyses from the CASPIAN and IMpower133 trials revealed decreases in brain metastasis rates in ES-SCLC treated with chemoimmunotherapy relative to the brain metastasis rates in ES-SCLC treated with chemotherapy alone. A recent meta-analysis of literature published after the landmark 1999 Auperin meta-analysis confirmed the survival benefit of PCI in LS-SCLC patients. A recent study employing PET before and after PCI demonstrated that hippocampal avoidance -PCI (HA-PCI) preserved the metabolic activity of the hippocampi compared with regular PCI. Two phase III trials evaluating neurocognitive functions after HA-PCI versus PCI have yielded conflicting results. Ongoing clinical trials (MAVERICK, PRIMALung, NRG CC003, NCT04535739, NCT04829708 and NCT03514849) regarding PCI versus MRI surveillance and HA-PCI versus PCI were also discussed.

SUMMARY

Currently, the indications for PCI in SCLC are under question in the modern MRI era. Result from prospective phase III, MRI staged and MRI monitored RCTs are expected to elucidate the role of PCI in LS-SCLC and ES-SCLC. Preliminary results indicated that adding immunotherapy to chemotherapy may reduce brain metastasis rate in SCLC. Further data to this aspect are warranted to determine the role of PCI in the immuno-chemotherapy era. The future direction for PCI should be the comprehensive integration of personalized patient selection, HA-PCI utilization and potential employment of other neurocognitive preservation strategies.

Impact of Hippocampal Avoidance - Prophylactic Cranial Irradiation in Small Cell Lung Cancer Patients

BACKGROUND/AIM

Prophylactic cranial irradiation (PCI) is a well-established treatment of small cell lung cancer (SCLC) patients following response to initial chemoradiotherapy. The benefit of PCI does, however, come at the cost of cognitive decline. This has been attributed to radiation-induced toxicity at the hippocampus, a crucial anatomic area for cognition. Modern radiotherapy techniques allow dose reduction at the hippocampal region. In this review, the safety profile, effect on cognition, and changes on brain imaging modalities of hippocampal avoidance-PCI (HA-PCI) will be presented, aiming to identify a potential clinical rationale for SCLC patients.

MATERIALS AND METHODS

A systematic review of the literature was performed in Pubmed, Cochrane library databases and ClinicalTrials.gov with no past date limitations until 07/01/2022. Principles as outlined in the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement were followed.

RESULTS

Eight studies published from 2015 to 2021 were included.

CONCLUSION

HA-PCI is safe, yet its effect on neurocognition and imaging remains unclear, as studies have shown contradictory results.