The role of radiosurgery in patients with brain metastasis from small cell lung carcinoma

Modern Stereotactic Radiotherapy for Brain Metastases from Lung Cancer: Current Trends and Future Perspectives Based on Integrated Translational Approaches

Brain metastases (BMs) represent the most frequent metastatic event in the course of lung cancer patients, occurring in approximately 50% of patients with non-small-cell lung cancer (NSCLC) and in up to 70% in patients with small-cell lung cancer (SCLC). Thus far, many advances have been made in the diagnostic and therapeutic procedures, allowing improvements in the prognosis of these patients. The modern approach relies on the integration of several factors, such as accurate histological and molecular profiling, comprehensive assessment of clinical parameters and precise definition of the extent of intracranial and extracranial disease involvement. The combination of these factors is pivotal to guide the multidisciplinary discussion and to offer the most appropriate treatment to these patients based on a personalized approach. Focal radiotherapy (RT), in all its modalities (radiosurgery (SRS), fractionated stereotactic radiotherapy (SRT), adjuvant stereotactic radiotherapy (aSRT)), is the cornerstone of BM management, either alone or in combination with surgery and systemic therapies. We review the modern therapeutic strategies available to treat lung cancer patients with brain involvement. This includes an accurate review of the different technical solutions which can be exploited to provide a "state-of-art" focal RT and also a detailed description of the systemic agents available as effective alternatives to SRS/SRT when a targetable molecular driver is present. In addition to the validated treatment options, we also discuss the future perspective for focal RT, based on emerging clinical reports (e.g., SRS for patients with many BMs from NSCLC or SRS for BMs from SCLC), together with a presentation of innovative and promising findings in translational research and the combination of novel targeted agents with SRS/SRT.

Evaluation of First-line Radiosurgery vs Whole-Brain Radiotherapy for Small Cell Lung Cancer Brain Metastases: The FIRE-SCLC Cohort Study

Importance

Although stereotactic radiosurgery (SRS) is preferred for limited brain metastases from most histologies, whole-brain radiotherapy (WBRT) has remained the standard of care for patients with small cell lung cancer. Data on SRS are limited.

Objective

To characterize and compare first-line SRS outcomes (without prior WBRT or prophylactic cranial irradiation) with those of first-line WBRT.

Design, Setting, and Participants

FIRE-SCLC (First-line Radiosurgery for Small-Cell Lung Cancer) was a multicenter cohort study that analyzed SRS outcomes from 28 centers and a single-arm trial and compared these data with outcomes from a first-line WBRT cohort. Data were collected from October 26, 2017, to August 15, 2019, and analyzed from August 16, 2019, to November 6, 2019.

Interventions

SRS and WBRT for small cell lung cancer brain metastases.

Main Outcomes and Measures

Overall survival, time to central nervous system progression (TTCP), and central nervous system (CNS) progression-free survival (PFS) after SRS were evaluated and compared with WBRT outcomes, with adjustment for performance status, number of brain metastases, synchronicity, age, sex, and treatment year in multivariable and propensity score-matched analyses.

Results

In total, 710 patients (median [interquartile range] age, 68.5 [62-74] years; 531 men [74.8%]) who received SRS between 1994 and 2018 were analyzed. The median overall survival was 8.5 months, the median TTCP was 8.1 months, and the median CNS PFS was 5.0 months. When stratified by the number of brain metastases treated, the median overall survival was 11.0 months (95% CI, 8.9-13.4) for 1 lesion, 8.7 months (95% CI, 7.7-10.4) for 2 to 4 lesions, 8.0 months (95% CI, 6.4-9.6) for 5 to 10 lesions, and 5.5 months (95% CI, 4.3-7.6) for 11 or more lesions. Competing risk estimates were 7.0% (95% CI, 4.9%-9.2%) for local failures at 12 months and 41.6% (95% CI, 37.6%-45.7%) for distant CNS failures at 12 months. Leptomeningeal progression (46 of 425 patients [10.8%] with available data) and neurological mortality (80 of 647 patients [12.4%] with available data) were uncommon. On propensity score-matched analyses comparing SRS with WBRT, WBRT was associated with improved TTCP (hazard ratio, 0.38; 95% CI, 0.26-0.55; P < .001), without an improvement in overall survival (median, 6.5 months [95% CI, 5.5-8.0] for SRS vs 5.2 months [95% CI, 4.4-6.7] for WBRT; P = .003) or CNS PFS (median, 4.0 months for SRS vs 3.8 months for WBRT; P = .79). Multivariable analyses comparing SRS and WBRT, including subset analyses controlling for extracranial metastases and extracranial disease control status, demonstrated similar results.

Conclusions and Relevance

Results of this study suggest that the primary trade-offs associated with SRS without WBRT, including a shorter TTCP without a decrease in overall survival, are similar to those observed in settings in which SRS is already established.

Current Management and Progress in Radiotherapy for Small Cell Lung Cancer

Radiotherapy (RT) and chemotherapy continue to be widely utilized in small cell lung cancer (SCLC) management. In most limited stage (LS)-SCLC cases, the standard initial therapy remains concurrent chemoradiotherapy (CRT), typically with an etoposide and platinum-based regimen. Hyperfractionated twice daily (BID) RT remains the standard of care, though conventional daily (QD) RT is now a viable alternative supported by randomized evidence. In LS-SCLC patients who experienced good response to CRT, prophylactic cranial irradiation (PCI) remains the standard of care. Brain imaging, ideally with MRI, should be performed prior to PCI to screen for clinically apparent brain metastases that may require a higher dose of cranial irradiation. Platinum doublet chemotherapy alone is the historic standard initial therapy in extensive stage (ES)-SCLC. Addition of immunotherapy such as atezolizumab and durvalumab to chemotherapy is now recommended after their benefits were demonstrated in recent trials. In patients with response to chemotherapy, consolidation thoracic RT and PCI could be considered, though with caveats. Emergence of hippocampal avoidance cranial irradiation and SRS in SCLC patients may supplant whole cranial irradiation as future standards of care. Incorporation of novel systemic therapies such as immunotherapies has changed the treatment paradigm and overall outlook of patients with SCLC. This narrative review summarizes the current state, ongoing trials, and future directions of radiotherapy in management of SCLC.

Multi-institutional retrospective review of stereotactic radiosurgery for brain metastasis in patients with small cell lung cancer without prior brain-directed radiotherapy

Introduction: Patients with small cell lung cancer (SCLC) brain metastasis (BM) typically receive whole brain radiotherapy (WBRT) as data regarding upfront radiosurgery (SRS) in this setting are sparse. Methods: Patients receiving SRS for SCLC BM without prior brain radiation were identified at three U.S. institutions. Overall survival (OS), freedom from intracranial progression (FFIP), freedom from WBRT (FFWBRT), and freedom from neurologic death (FFND) were determined from time of SRS. Results: Thirty-three patients were included with a median of 2 BM (IQR 1-6). Median OS and FFIP were 6.7 and 5.8 months, respectively. Median FFIP for patients with ≤2 versus >2 BM was 7.1 versus 3.6 months, p=0.0303. Eight patients received salvage WBRT and the 6-month FFWBRT and FFND were 87.8%. and 90.1%, respectively. Conclusions: Most SCLC patients with BM who received upfront SRS avoided WBRT and neurologic death, suggesting that SRS may be an option in select patients.

Gamma Knife radiosurgery for brain metastases from small-cell lung cancer: Institutional experience over more than a decade and review of the literature

INTRODUCTION

In the present study, we reviewed the efficacy of stereotactic radiosurgery (SRS) alone or in combination with WBRT, for the treatment of patients with BM secondary to SCLC. We further identified patient and treatment specific factors that correlated with improved survival.

METHODS

Forty-one patients treated with GKRS for BM secondary to SCLC from 2004 to 2017 at the University of Virginia were identified with histopathologically proven SCLC and included in the study.

RESULTS

Following the first GKRS treatment, the median survival was 6 months (1-41 months). There was no statistical difference in overall survival and tumor control between the patients who had PCI, WBRT or upfront GKRS. The only factor associated with decreased OS after the diagnosis of BM from SCLC was active extracranial disease (P=0.045, HR=2.354).

CONCLUSION

Stereotactic radiosurgery is a reasonable treatment option for patients with brain metastases of SCLC who had PCI or WBRT failure.

Strategies to Preserve Cognition in Patients With Brain Metastases: A Review

Brain metastases are common to the natural history of many advanced malignancies. Historically, whole brain radiation therapy (WBRT) has played a key role in the management of brain metastases, especially for patients with multiple lesions. However, prospective trials have demonstrated consistent neurocognitive toxicities after WBRT, and various pharmacologic and anatomic strategies designed to mitigate these toxicities have been studied in recent years. Memantine, an NMDA receptor antagonist, taken during and after WBRT improved cognitive preservation in a randomized trial over placebo. Deliberate reductions in radiation dose to the hippocampus, via hippocampal-avoidance (HA)-WBRT, resulted in improved cognition over historic controls in a phase II trial, and follow-up randomized trials are now ongoing to evaluate cognitive outcomes with HA vs. conventional brain radiation techniques. Nevertheless, some of the most promising strategies currently available to reduce the cognitive effects of brain radiation may be found in efforts to avoid or delay WBRT administration altogether. Stereotactic radiosurgery (SRS), involving focused, high-dose radiation to central nervous system (CNS) lesions with maximal sparing of normal brain parenchyma, has become the standard for limited brain metastases (classically 1–3 or 4 lesions) in the wake of multiple randomized trials demonstrating equivalent survival and improved cognition with SRS alone compared to SRS plus WBRT. Today, there is growing evidence to support SRS alone for multiple (≥4) brain metastases, with comparable survival to SRS alone in patients with fewer lesions. In patients with small-cell lung cancer, the routine use of prophylactic cranial irradiation (PCI) for extensive-stage disease has been also been challenged following the results of a randomized trial supporting an alternative strategy of MRI brain surveillance and early salvage radiation for the development of brain metastases. Moreover, new systemic agents are demonstrating increasing CNS penetration and activity, with the potential to offer greater control of widespread and microscopic brain disease that was previously only achievable with WBRT. In this review, we endeavor to put these clinical data on cognition and brain metastases into historical context and to survey the evolving landscape of strategies to improve future outcomes.

Outcomes of stereotactic radiosurgery of brain metastases from neuroendocrine tumors

Background

Stereotactic radiosurgery (SRS) is an established treatment for brain metastases, yet little is known about SRS for neuroendocrine tumors given their unique natural history.

Objective

To determine outcomes and toxicity from SRS in patients with brain metastases arising from neuroendocrine tumors.

Methods

Thirty-three patients with brain metastases from neuroendocrine tumors who underwent SRS were retrospectively reviewed. Median age was 61 years and median Karnofsky performance status was 80. Primary sites were lung (87.9%), cervix (6.1%), esophagus (3%), and prostate (3%). Ten patients (30.3%) received upfront SRS, 7 of whom had neuroendocrine tumors other than small cell lung carcinoma. Kaplan-Meier survival and Cox regression analyses were performed to determine prognostic factors for survival.

Results

With median follow-up after SRS of 5.3 months, local and distant brain recurrence developed in 5 patients (16.7%) and 20 patients (66.7%), respectively. Median overall survival (OS) after SRS was 6.9 months. Patients with progressive disease per Response Assessment in Neuro-Oncology-Brain Metastases (RANO-BM) criteria at 4 to 6 weeks after SRS had shorter median time to developing recurrence at a distant site in the brain and shorter OS than patients without progressive disease: 1.4 months and 3.3 months vs 11.4 months and 12 months, respectively (both P < .001). Toxicity was more likely in lesions of small cell histology than in lesions of other neuroendocrine tumor histology, 15.7% vs 3.3% (P = .021). No cases of grade 3 to 5 necrosis occurred.

Conclusions

SRS is an effective treatment option for patients with brain metastases from neuroendocrine tumors with excellent local control despite slightly higher toxicity rates than expected. Progressive disease at 4 to 6 weeks after SRS portends a poor prognosis.

The role of radiation therapy in the management of small cell lung cancer

Small cell lung cancer (SCLC) is a very aggressive form of lung cancer. SCLC treatment requires multidisciplinary management and timely treatment. Radiation therapy is an important part of management of all stages of SCLC, in the curative as well as in the palliative setting. The role of radiation therapy in all stages of SCLC has changed in recent years; this article describes these changes and highlights the role of radiation therapy in the management of SCLC.

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.

Management of brain metastasis with magnetic resonance imaging and stereotactic irradiation attenuated benefits of prophylactic cranial irradiation in patients with limited-stage small cell lung cancer

Background

Magnetic resonance imaging (MRI) enables a more sensitive detection of brain metastasis and stereotactic irradiation (SRI) efficiently controls brain metastasis. In limited-stage small cell lung cancer (LS-SCLC), prophylactic cranial irradiation (PCI) in patients with good responses to initial treatment is recommended based on the survival benefit shown in previous clinical trials. However, none of these trials evaluated PCI effects using the management of brain metastasis with MRI or SRI. This study aimed to determine the effects of MRI and SRI on the benefits of PCI in patients with LS-SCLC.

Methods

The clinical records of pathologically proven SCLC from January 2006 to June 2013 in facilities equipped with or had access to SRI in Japan were retrospectively reviewed. Patients with LS-SCLC and complete or good partial responses after initial treatment were included in the study and analyzed by the Kaplan-Meier method.

Results

Of 418 patients with SCLC, 124 met criteria and were divided into patients receiving PCI (PCI group; n = 29) and those without PCI (non-PCI groups; n = 95). At baseline, ratios of patients with stage III were significantly advantageous for the non-PCI group, although younger age and high ratios of complete response and MRI confirmed absence of brain metastasis were advantageous for the PCI group. Neither median survival times (25 vs. 34 months; p = 0.256) nor cumulative incidence of brain metastasis during 2 years (45.5 vs. 30.8 %; p = 0.313) significantly differed between the two groups. Moreover, these factors did not significantly differ among patients with stage III disease (25 vs. 26 months; p = 0.680, 42.3 vs. 52.3 %; p = 0.458, respectively).

Conclusion

PCI may be less beneficial in patients with LS-SCLC if the management with MRI and SRI is available.

Is stereotactic radiosurgery a rational treatment option for brain metastases from small cell lung cancer? A retrospective analysis of 70 consecutive patients

Background

Because of the high likelihood of multiple brain metastases (BM) from small cell lung cancer (SCLC), the role of focal treatment using stereotactic radiosurgery (SRS) has yet to be determined. We aimed to evaluate the efficacy and limitations of upfront and salvage SRS for patients with BM from SCLC.

Methods

This was a retrospective and observational study analyzing 70 consecutive patients with BM from SCLC who received SRS. The median age was 68 years, and the median Karnofsky performance status (KPS) was 90. Forty-six (66%) and 24 (34%) patients underwent SRS as the upfront and salvage treatment after prophylactic or therapeutic whole brain radiotherapy (WBRT), respectively. Overall survival (OS), neurological death-free survival, remote and local tumor recurrence rates were analyzed.

Results

None of our patients were lost to follow-up and the median follow-up was 7.8 months. One-and 2-year OS rates were 43% and 15%, respectively. The median OS time was 7.8 months. One-and 2-year neurological death-free survival rates were 94% and 84%, respectively. In total, 219/292 tumors (75%) in 60 patients (86 %) with sufficient radiological follow-up data were evaluated. Six-and 12-month rates of remote BM relapse were 25% and 47%, respectively. Six-and 12-month rates of local control failure were 4% and 23%, respectively. Repeat SRS, salvage WBRT and microsurgery were subsequently required in 30, 8 and one patient, respectively. Symptomatic radiation injury, treated conservatively, developed in 3 patients.

Conclusions

The present study suggested SRS to be a potentially effective and minimally invasive treatment option for BM from SCLC either alone or after failed WBRT. Although repeat salvage treatment was needed in nearly half of patients to achieve control of distant BM, such continuation of radiotherapeutic management might contribute to reducing the rate of neurological death.

Upfront stereotactic radiosurgery in patients with brain metastases from small cell lung cancer: retrospective analysis of 41 patients

BACKGROUND

Although the efficacy of prophylactic or therapeutic whole brain radiotherapy (WBRT) for brain metastases (BM) from small cell lung cancer (SCLC) is well established, the role of stereotactic radiosurgery (SRS) has yet to be determined. In the present retrospective analysis, we investigated whether upfront SRS might be an effective treatment option for patients with BM from SCLC.

METHODS

We analyzed 41 consecutive patients with a limited number of BM (≤ 10) from SCLC who received SRS as the initial treatment. No prophylactic and therapeutic WBRT was given prior to SRS. The median patient age was 69 years and the median Karnofsky performance status (KPS) score was 90. Repeat SRS was given for new distant lesions detected on follow-up neuroradiological imaging, as necessary. Overall survival, neurological death, and local and distant BM recurrence rates were analyzed. The survival results were tested with three prognostic scoring systems validated for SCLC: Diagnosis-specific graded prognostic assessment (DS-GPA), Radiation therapy oncology group -recursive partitioning analysis and Rades's survival score.

RESULTS

One- and 2-year overall survival rates were 44% and 17%, respectively. The median survival time was 8.1 months. Survival results replicated the DS-GPA (P = 0.022) and Rades's survival score (P = 0.034). On multivariate analysis, patients with high KPS (hazard ratio (HR): 0.308, P = 0.009) and post-SRS chemotherapy (HR: 0.324, P = 0.016) had better overall survival. In total, 95/121 tumors (79%) in 34 patients (83%) with sufficient radiological follow-up data were evaluated. Six- and 12-month rates of local control failure were 0% and 14%, respectively. Six- and 12-month distant BM rates were 22% and 44%, respectively. Repeat SRS, salvage WBRT and microsurgery were subsequently required in 18, 7 and one patient, respectively. Symptomatic radiation injury developed in two patients and both were treated conservatively.

CONCLUSIONS

Our survival analyses with the validated prognostic grading systems suggested upfront SRS for limited BM from SCLC to be a potential treatment option, with patient survival being slightly more than eight months after SRS. Although SRS provided durable local tumor control, repeat treatment was needed in nearly half of patients to achieve control of distant BM.

Local recurrence and survival following stereotactic radiosurgery for brain metastases from small cell lung cancer

PURPOSE

Stereotactic radiosurgery (SRS) represents a treatment option for patients with brain metastases from small cell lung cancer (SCLC) following prior cranial radiation. Inferior local control has been described. We reviewed our failure patterns following SRS treatment to evaluate this concern.

METHODS AND MATERIALS

Individuals with SCLC who received SRS for brain metastases from 2004 to 2011 were identified. Central nervous system (CNS) disease was detected and followed by gadolinium-enhanced, high-resolution magnetic resonance (MR) imaging. SRS dose was prescribed to the tumor periphery. Local recurrence was defined by increasing lesion size or enhancement, MR-spectroscopy, and perfusion changes consistent with recurrent disease or pathologic confirmation. Any new enhancing lesion not identified on the SRS planning scan was considered a regional failure. Overall survival (OS) and CNS control were evaluated using the Kaplan-Meier method. Factors predicted to influence outcome were tested by univariate log-rank analysis and Cox regression.

RESULTS

Fifteen males and 25 females (median age of 61 years [range, 36-79]) of which 39 received prior brain irradiation were identified. In all, 132 lesions (3.3 per patient) between 0.4 and 4.7 cm received a median dose of 16 Gy (12-22 Gy). Thirteen metastases (10%) ultimately recurred locally with 6- and 12-month control rates of 81% and 69%, respectively. Only 1 of 110 metastases <2 cm recurred. Local failure was more likely for size >2 cm (P < .001) and dose <16 Gy (P < .001). The median OS was 6.5 months, and the time to regional CNS recurrence was 5.2 months. For patients with single brain metastases, both OS (P = .037) and regional CNS recurrence (P = .003) were improved. CNS control (P = .001), and survival (P = .057), were also longer for patients with controlled systemic disease.

CONCLUSIONS

Local control following SRS for SCLC metastases is achievable for lesions <2 cm. For metastases >2 cm, local failure is more common than expected. Patients with controlled systemic disease and limited CNS involvement would benefit most from aggressive treatment.