Ablative Radiotherapy as a Strategy to Overcome TKI Resistance in EGFR-Mutated NSCLC

Simple Summary

Most patients with EGFR-mutated NSCLC who receive treatment with targeted therapy will eventually develop resistance, meaning the therapy will lose its efficacy. Prior studies have shown a benefit to continuing to treat patients on TKI therapy despite limited progression of one or more sites of metastatic disease in EGFR-mutated NSCLC. Based on the data reviewed here, the use of radiation therapy to sites of disease progression is both efficacious and carries a low risk for side effects, with the added benefit of allowing patients to continue on TKI therapy.

Abstract

Tyrosine kinase inhibitor (TKI) therapy is the recommended first-line treatment for metastatic non-small-cell lung cancer (NSCLC) positive for epidermal growth factor receptor (EGFR) gene mutation. However, most individuals treated with TKI therapy for EGFR-mutant NSCLC will develop tumor resistance to TKI therapy. Therapeutic strategies to overcome TKI resistance are the topic of several ongoing clinical trials. One potential strategy, which has been explored in numerous trials, is the treatment of progressive sites of disease with stereotactic body radiation treatment (SBRT) or stereotactic radiosurgery (SRS). We sought to review the literature pertaining to the use of local ablative radiation therapy in the setting of acquired resistance to TKI therapy and to discuss stereotactic radiation therapy as a strategy to overcome TKI resistance.

Quality of Life and Role of Palliative and Supportive Care for Patients With Brain Metastases and Caregivers: A Review

Brain metastases (BM) are the most commonly diagnosed secondary brain lesions in adults, influencing these patients' symptoms and treatment courses. With improvements in oncologic treatments, patients with BM are now living longer with their advanced cancers, and issues pertaining to quality of life become more pressing. The American Society of Clinical Oncology has recommended early implementation of palliative care for cancer patients, though incorporation and implementation of palliative and other supportive services in the setting of true multidisciplinary care requires additional attention and research for patients with intracranial metastases. We review the physical, cognitive, and psychosocial challenges patients with BM and their caregivers face during their cancer course as well as the current published research on quality of life metrics relating to this patient population and the diverse roles specialty palliative care, rehabilitation services, and other healthcare providers play in a comprehensive multidisciplinary care model.

Central Nervous System Metastases

The proportion of patients developing central nervous system (CNS) metastasis is increasing. Most are identified once symptomatic. Surgical resection is indicated for solitary or symptomatic brain metastases, separation surgery for compressive radioresistant spinal metastases, and instrumentation for unstable spinal lesions. Surgical biopsies are performed when histological diagnoses are required. Stereotactic radiosurgery is an option for limited small brain metastases and radioresistant spinal metastases. Whole-brain radiotherapy is reserved for extensive brain metastases and leptomeningeal disease with approaches to reduce cognitive side effects. Radiosensitive and inoperable spinal metastases typically receive external beam radiotherapy. Systemic therapy is increasingly being utilized for CNS metastases.

Integrated treatment of brain metastases

PURPOSE OF REVIEW

Optimal treatment of brain metastases has been limited to local treatment with few systemic options. Increasing use of systemic targeted therapies, chemotherapy and immunotherapy and combination of local and systemic treatments has resulted in plethora of publications. We review the existing evidence for individual treatments and new evidence for the integration of systemic and combination of local treatments.

RECENT FINDINGS

Encouraging efficacy of systemic therapies supports combination of systemic and local treatment albeit with little randomized trial data. Efficacy particularly of targeted agents provides an opportunity to delay local treatments including radiosurgery and whole brain radiotherapy. Randomized trials testing the integration of surgery, radiotherapy and radiosurgery are reviewed with emphasis on patient relevant endpoints to guide the clinician in the choice and sequence of treatments and integrating systemic and local therapies.

SUMMARY

There is increasing tendency to use focused radiation for single and oligometastases with or without surgery and decline in whole brain radiotherapy which is limited to multiple metastases in tumours without effective systemic options. Systemic therapies have promising intracranial efficacy and the sequence and combination with localized radiation is awaiting trials. Changes in practice with a move to primary systemic treatment for brain metastases without radiation, should be undertaken with caution and close monitoring.

Region-specific reduction of parvalbumin neurons and behavioral changes in adult mice following single exposure to cranial irradiation

PURPOSE

Ionizing irradiation has several long-term effects including progressive cognitive impairment. Cognitive deterioration generally appears to be caused by abnormalities in the hippocampal dentate gyrus, with abnormal function of parvalbumin-expressing interneurons (PV neurons) in the cerebral cortex. PV neurons are vulnerable to oxidative stress, which can be caused by ionizing irradiation. We speculated that selective impairment of specific brain regions due to ionizing irradiation may alter the degree of cognitive impairment.

METHODS

We irradiated mature mouse brains with 20 Gy-ionizing irradiation. Subsequently, we analyzed behavioral abnormalities and changes in the number of PV neurons.

RESULTS

PV neuron density was significantly lower in some cortical regions of irradiated mice than in control mice. Within 1 week of irradiation, both body weight and temperature of irradiated mice decreased. In the forced swim test, irradiated mice spent significantly less time immobile than did control mice. However, irradiated mice did not display any abnormalities in the elevated plus maze test, Y-maze test, tail suspension test, and social interaction test between 3 to 6 days after irradiation.

CONCLUSIONS

These results suggest that high-dose irradiation is less likely to cause brain dysfunction in the subacute phase. Moreover, the vulnerability of PV neurons appears to be brain-region specific.