Time to reconsider prophylactic cranial irradiation in extensive-stage small-cell lung cancer?

Real-world outcomes of prophylactic cranial irradiation utilization and efficacy for patients with extensive-stage small cell lung cancer treated with consolidative thoracic radiotherapy

Background

The role of prophylactic cranial irradiation (PCI) is not well-defined in extensive-stage SCLC (ES-SCLC), with conflicting results from randomized trials and a lack of relevant data for patients who received consolidative thoracic radiotherapy (CTRT). We sought to evaluate the impact of PCI on the outcomes of ES-SCLC patients who were all treated with CTRT.

Methods

A retrospective analysis of ES-SCLC patients without brain metastases who were all treated with CTRT between 2013-2021 at our institution was conducted. Overall survival (OS) and incidence of brain failure (BFR) were estimated using Kaplan-Meier estimation and cumulative incidence function. Multivariable Cox or Fine-Gray's proportional hazard regression analysis (MVA) were performed to determine association between PCI and OS.

Results

47 patients met inclusion criteria and were theoretically eligible for PCI, 27 (57.4 %) received PCI and CTRT while 20 (42.6 %) received CTRT alone. Baseline characteristics were similar except for age, where patients receiving PCI were younger (median age 62) compared to patients who did not receive PCI (median age 72). Median OS with PCI was 19.2 months, compared to 10.8 months without PCI (P = 0.0334). This improved OS remained apparent in patients who received post-chemotherapy MRI restaging (P = 0.0245). BFR was reduced with PCI (HR = 0.22 [0.09-0.52], P = 0.0004). On MVA, PCI was significantly and independently associated with improved OS (HR = 0.39 [0.19-0.80], P = 0.01) and reduced BFR (HR = 0.20 [0.09-0.44], P = < 0.001).

Conclusion

This real-world study found PCI was independently associated with improved OS and reduced BFR in ES-SCLC patients treated with CTRT compared to patients treated with CTRT not receiving PCI, including after post-chemotherapy brain MRI. The role of PCI with CTRT should be evaluated in prospective studies.

Prophylactic Cranial Irradiation for Extensive-Stage Small-Cell Lung Cancer: A Controversial Area

Small-cell lung cancer (SCLC) is a highly aggressive malignant tumor that is prone to lead to the development of brain metastases (BM). The application of prophylactic cranial irradiation (PCI) has been regarded as an important technological advance made in cancer therapy to reduce the occurrence of BM and improve patient survival. The benefits of PCI in the treatment of limited-stage SCLC have been confirmed. However, there has been continuous controversy about the indications and advantages of PCI for extensive-stage SCLC (ES-SCLC) because of the conflicting results from two prospective trials. In this review, we aimed to discuss the relevant controversy and progress made in the clinical application of PCI in ES-SCLC.

Prophylactic cranial irradiation or MRI surveillance for extensive stage small cell lung cancer

The treatment paradigm for extensive stage small cell lung cancer (ES-SCLC) is evolving. Prophylactic cranial irradiation (PCI) has long been considered a component of standard treatment in patients with extensive stage disease who respond to chemotherapy. However, in the modern era of magnetic resonance imaging, the role of PCI has become an area of controversy following conflicting level I evidence. Due to conflicting data and toxicity concerns, the routine use of PCI has declined. Recent improvements in systemic disease control with the use of immunotherapy and reductions in the toxicity attributable to PCI with hippocampal avoidance and memantine have reignited the discussion. As such, we present here a narrative review of PCI with a focus on historical milestones, randomized data, risk mitigation and future directions.

Prophylactic cranial irradiation in stage IV small cell lung cancer: Selection of patients amongst European IASLC and ESTRO experts

BACKGROUND

Due to conflicting results between major trials the role of prophylactic cranial irradiation (PCI) in stage IV small cell lung cancer (SCLC) is controversial.

METHODS

We obtained a list of 13 European experts from both the European Society for Therapeutic Radiation Oncology (ESTRO) and the International Association for the Study of Lung Cancer (IASLC). The strategies in decision making for PCI in stage IV SCLC were collected. Decision trees were created representing these strategies. Analysis of consensus was performed with the objective consensus methodology.

RESULTS

The factors associated with the recommendation for the use of PCI included the fitness of the patient, young age and good response to chemotherapy. PCI was recommended by the majority of experts for non-elderly fit patients who had at least a partial response (PR) to chemotherapy (for complete remission (CR) 85% of radiation oncologists and 69% of medical oncologists, for PR: 85% of radiation oncologists and 54% of medical oncologists). For patients with stable disease after chemotherapy, PCI was recommended by 6 out of 13 (46%) radiation oncologists and only 3 out of 13 medical oncologists (23%). For elderly fit patients with CR, a majority recommended PCI (62%) and no consensus was reached for patients with PR.

CONCLUSION

European radiation and medical oncologists specializing in lung cancer recommend PCI in selected patients and restrict its use primarily to fit, non-elderly patients who responded to chemotherapy.

Prophylactic cranial irradiation in small-cell lung cancer: update on patient selection, efficacy and outcomes

Over 10% of small-cell lung cancer (SCLC) patients have brain metastases (BM) at initial diagnosis; more than 50% will develop BM within 2 years. BM are detected in up to 80% of all patients at autopsy. After primary treatment, prophylactic cranial irradiation (PCI) has been established as standard of care in SCLC patients responding to initial therapy. Based on level I evidence, PCI significantly decreases the risk of intracranial relapse and shows a modest survival benefit after 3 years. However, the role of PCI in defined patient subgroups such as resected SCLC, elderly and extensive stage patients with access to magnetic resonance imaging surveillance and stereotactic radiotherapy is yet to be fully clarified. Furthermore, strategies to effective prevention of neurocognitive decline after PCI remain unclear. All these factors significantly impact treatment decision making and should be evaluated in prospective settings. New concepts such as hippocampal avoidance and drug neuroprotection prevent chronic neurocognitive effects reducing treatment-related side effects of PCI. The aim of this review is to present a summary and update of the latest evidence for patient selection, efficacy and outcome of PCI.

Prophylactic Cranial Irradiation for Limited-Stage Small-Cell Lung Cancer: Survey of US Radiation Oncologists on Current Practice Patterns

PURPOSE

Prophylactic cranial irradiation (PCI) in patients with limited-stage small-cell lung cancer (LS-SCLC) is considered the standard of care. Meta-analysis of 7 clinical trials indicates a survival benefit to PCI, but all of these trials were conducted in the pre-magnetic resonance imaging (MRI) era. Therefore, routine brain imaging with MRI before PCI-as recommended by National Comprehensive Cancer Network guidelines-is not directly supported by the evidence. Current US practice patterns for patients with LS-SCLC are unknown.

MATERIALS AND METHODS

We surveyed practicing US radiation oncologists via an institutional review board-approved online questionnaire. Questions covered demographic information and treatment recommendations for LS-SCLC.

RESULTS

We received 309 responses from US radiation oncologists. Ninety-eight percent recommended PCI for patients with LS-SCLC, 96% obtained brain MRI before PCI, 33% obtained serial brain imaging with MRI after PCI to detect new metastases, and 35% recommended memantine for patients undergoing PCI. Recommending memantine was associated with fewer years of practice (P < .001), fewer lung cancer patients treated per year (P = .045), and fewer LS-SCLC patients treated per year (P = .024).

CONCLUSION

Almost all responding radiation oncologists recommended PCI and pre-PCI brain MRI for LS-SCLC patients with disease responsive to initial therapy. Only a third of respondents followed these patients with serial brain MRI. Approximately one third provided memantine therapy to try to limit neurocognitive effects of PCI. Further research is warranted to determine the best treatment for patients with LS-SCLC. This survey can inform the development of future trials that depend on participation from radiation oncologists.

Prophylactic Cranial Irradiation (PCI) versus Active MRI Surveillance for Small Cell Lung Cancer: The Case for Equipoise

Prophylactic cranial irradiation (PCI) for SCLC offers a consistent reduction in the incidence of brain metastases at the cost of measurable toxicity to neurocognitive function and quality of life, in the setting of characteristic pathologic changes to the brain. The sequelae of PCI have historically been justified by the perception of an overall survival advantage specific to SCLC. This rationale has now been challenged by a randomized trial in extensive-stage SCLC demonstrating equivalent progression-free survival and a trend toward improved overall survival with PCI omission in the context of modern magnetic resonance imaging (MRI) staging and surveillance. In this article, we critically examine the randomized trials of PCI in extensive-stage SCLC and discuss their implications on the historical data supporting PCI for limited-stage SCLC from the pre-MRI era. Further, we review the toxicity of moderate doses of radiation to the entire brain that underlie the growing interest in active MRI surveillance and PCI omission. Finally, the evidence supporting prospective investigation of radiosurgery for limited brain metastases in SCLC is reviewed. Overall, our aim is to provide an evidence-based assessment of the debate over PCI versus active MRI surveillance and to highlight the need for contemporary trials evaluating optimal central nervous system management in SCLC.