Histology-driven hypofractionated radiation therapy schemes for early-stage lung adenocarcinoma and squamous cell carcinoma.

BACKGROUND AND PURPOSE: Histology was found to be an important prognostic factor for local tumor control probability (TCP) after stereotactic body radiotherapy (SBRT) of early-stage non-small-cell lung cancer (NSCLC). A histology-driven SBRT approach has not been explored in routine clinical practice and histology-dependent fractionation schemes remain unknown. Here, we analyzed pooled histologic TCP data as a function of biologically effective dose (BED) to determine histology-driven fractionation schemes for SBRT and hypofractionated radiotherapy of two predominant early-stage NSCLC histologic subtypes adenocarcinoma (ADC) and squamous cell carcinoma (SCC). MATERIAL AND METHODS: The least-χ2 method was used to fit the collected histologic TCP data of 8510 early-stage NSCLC patients to determine parameters for a well-developed radiobiological model per the Hypofractionated Treatment Effects in the Clinic (HyTEC) initiative. RESULTS: A fit to the histologic TCP data yielded independent radiobiological parameter sets for radiotherapy of early-stage lung ADC and SCC. TCP increases steeply with BED and reaches an asymptotic maximal plateau, allowing us to determine model-independent optimal fractionation schemes of least doses in 1-30 fractions to achieve maximal tumor control for early-stage lung ADC and SCC, e.g., 30, 44, 48, and 51 Gy for ADC, and 32, 48, 54, and 58 Gy for SCC in 1, 3, 4, and 5 fractions, respectively. CONCLUSION: We presented the first determination of histology-dependent radiobiological parameters and model-independent histology-driven optimal SBRT and hypofractionated radiation therapy schemes for early-stage lung ADC and SCC. SCC requires substantially higher radiation doses to maximize tumor control than ADC, plausibly attributed to tumor genetic diversity and microenvironment. The determined optimal SBRT schemes agree well with clinical practice for early-stage lung ADC. These proposed optimal fractionation schemes provide first insights for histology-based personalized radiotherapy of two predominant early-stage NSCLC subtypes ADC and SCC, which require further validation with large-scale histologic TCP data.

Optimal Radiation Therapy Fractionation Regimens for Early-Stage Non-Small Cell Lung Cancer.

PURPOSE: A series of radiobiological models were developed to study tumor control probability (TCP) for stereotactic body radiation therapy (SBRT) of early-stage non-small cell lung cancer (NSCLC) per the Hypofractionated Treatment Effects in the Clinic (HyTEC) working group. This study was conducted to further validate 3 representative models with the recent clinical TCP data ranging from conventional radiation therapy to SBRT of early-stage NSCLC and to determine systematic optimal fractionation regimens in 1 to 30 fractions for radiation therapy of early-stage NSCLC that were found to be model-independent. METHODS AND MATERIALS: Recent clinical 1-, 2-, 3-, and 5-year actuarial or Kaplan-Meier TCP data of 9808 patients from 56 published papers were collected for radiation therapy of 2 to 4 Gy per fraction and SBRT of early-stage NSCLC. This data set nearly triples the original HyTEC sample, which was used to further validate the HyTEC model parameters determined from a fit to the clinical TCP data. RESULTS: TCP data from the expanded data set are well described by the HyTEC models with α/ß ratios of about 20 Gy. TCP increases sharply with biologically effective dose and reaches an asymptotic maximal plateau, which allows us to determine optimal fractionation schemes for radiation therapy of early-stage NSCLC. CONCLUSIONS: The HyTEC radiobiological models with α/ß ratios of about 20 Gy determined from the fits to the clinical TCP data for SBRT of early-stage NSCLC describe the recent TCP data well for both radiation therapy of 2 to 4 Gy per fraction and SBRT dose and fractionation schemes of early-stage NSCLC. A steep dose response exists between TCP and biologically effective dose, and TCP reaches an asymptotic maximum. This feature results in model-independent optimal fractionation regimens determined whenever safe for SBRT and hypofractionated radiation therapy of early-stage NSCLC in 1 to 30 fractions to achieve asymptotic maximal tumor control, and T2 tumors require slightly higher optimal doses than T1 tumors. The proposed optimal fractionation schemes are consistent with clinical practice for SBRT of early-stage NSCLC.

Use of comprehensive genomic profiling for biomarker discovery for the management of non-small cell lung cancer brain metastases.

Background: Clinical biomarkers for brain metastases remain elusive. Increased availability of genomic profiling has brought discovery of these biomarkers to the forefront of research interests. Method: In this single institution retrospective series, 130 patients presenting with brain metastasis secondary to Non-Small Cell Lung Cancer (NSCLC) underwent comprehensive genomic profiling conducted using next generation circulating tumor deoxyribonucleic acid (DNA) (Guardant Health, Redwood City, CA). A total of 77 genetic mutation identified and correlated with nine clinical outcomes using appropriate statistical tests (general linear models, Mantel-Haenzel Chi Square test, and Cox proportional hazard regression models). For each outcome, a genetic signature composite score was created by summing the total genes wherein genes predictive of a clinically unfavorable outcome assigned a positive score, and genes with favorable clinical outcome assigned negative score. Results: Seventy-two genes appeared in at least one gene signature including: 14 genes had only unfavorable associations, 36 genes had only favorable associations, and 22 genes had mixed effects. Statistically significant associated signatures were found for the clinical endpoints of brain metastasis velocity, time to distant brain failure, lowest radiosurgery dose, extent of extracranial metastatic disease, concurrent diagnosis of brain metastasis and NSCLC, number of brain metastases at diagnosis as well as distant brain failure. Some genes were solely associated with multiple favorable or unfavorable outcomes. Conclusion: Genetic signatures were derived that showed strong associations with different clinical outcomes in NSCLC brain metastases patients. While these data remain to be validated, they may have prognostic and/or therapeutic impact in the future. Statement of translation relevance: Using Liquid biopsy in NSCLC brain metastases patients, the genetic signatures identified in this series are associated with multiple clinical outcomes particularly these ones that lead to early or more numerous metastases. These findings can be reverse-translated in laboratory studies to determine if they are part of the genetic pathway leading to brain metastasis formation.

Brain Metastasis Incidence and Patterns of Presentation After Definitive Treatment of Locally Advanced Non-Small Cell Lung Cancer: A Potential Argument for Brain Magnetic Resonance Imaging Surveillance.

Purpose: Brain metastases (BMs) are a common source of morbidity and mortality. Guidelines do not advise brain surveillance for locally advanced non-small cell lung cancer (LA-NSCLC). We describe the incidence, time to development, presentation, and management of BMs after definitive chemoradiotherapy (CRT). Methods and Materials: We reviewed records of patients with LA-NSCLC treated with CRT within the period from 2013 to 2020. Descriptive statistics were used to characterize the population and the Kaplan-Meier method was used to estimate time to BM. Fisher exact tests and Wilcoxon rank-sum tests were used to compare outcomes between symptomatic and asymptomatic patients. Results: A total of 219 patients were reviewed including 96 with squamous cell carcinoma, 88 with adenocarcinoma, and 35 with large cell/not otherwise specified (LC/NOS). Thirty-nine patients (17.8%) developed BMs: 35 (90%) symptomatic and 4 (10%) asymptomatic. The rate of BM was highest in LC/NOS (34.3%) and adenocarcinoma (23.9%). Ninety percent of BMs occurred within 2 years. All asymptomatic patients underwent stereotactic radiosurgery alone, compared with 40% of symptomatic patients (P = .04). Symptomatic patients were more likely to require hospitalization (65.7% vs 0%, P = .02), craniotomy (25.7% vs 0%, not significant), and steroids (91.4% vs 0%, P < .001). Cumulative BM volume was higher for symptomatic patients (4 vs 0.24 cm3, P < .001) as was median greatest axial dimension (2.18 vs 0.52 cm, P < .001). Conclusions: We identified a high rate of BMs, particularly in LC/NOS and adenocarcinoma histology NSCLC. The majority were symptomatic. These results provide rationale for post-CRT magnetic resonance imaging brain surveillance for patients at high risk of BM.

Bridging the Communication Gaps: A Prospective Single-Arm Pilot Study Testing the Feasibility of Interdisciplinary Radiotherapy Planning in Locally Advanced Lung Cancer.

RATIONALE AND OBJECTIVES: The treatment of locally advanced lung cancer (LALC) with radiotherapy (RT) can be challenging. Multidisciplinary collaboration between radiologists and radiation oncologists (ROs) may optimize RT planning, reduce uncertainty in follow-up imaging interpretation, and improve outcomes. MATERIALS AND METHODS: In this prospective clinical treatment trial (clinicaltrials.gov NCT04844736), 37 patients receiving definitive RT for LALC, six attending ROs, and three thoracic radiologists were consented and enrolled across four treatment centers. Prior to RT plan finalization, representative computed tomography (CT) slices with overlaid outlines of preliminary irradiation targets were shared with the team of radiologists. The primary endpoint was to assess feasibility of receiving feedback no later than 4 business days of RT simulation on at least 50% of plans. RESULTS: Thirty-seven patients with lung cancer were enrolled, and 35 of 37 RT plans were reviewed. Of the 35 patients reviewed, mean age was 69 years. For 27 of 37 plans (73%), feedback was received within 4 or fewer days (interquartile range 3-4 days). Thirteen of 35 cases (37%) received feedback that the delineated target potentially did not include all sites suspicious for tumor involvement. In total, changes to the RT plan were recommended for over- or undercoverage in 16 of 35 cases (46%) and implemented in all cases. Radiology review resulted in no treatment delays and substantial changes to irradiated volumes: gross tumor volume, -1.9 to +96.1%; planning target volume, -37.5 to +116.5%. CONCLUSION: Interdisciplinary collaborative RT planning using a simplified workflow was feasible, produced no treatment delays, and prompted substantial changes in RT targets.

Palliative Appropriateness Criteria: A Pragmatic Method to Evaluate the Suitability of Palliative Radiotherapy Fractionation.

Purpose: To describe a novel metric to aid clinical decision making between shorter versus longer palliative radiotherapy (PRT) regimens using objective patient factors. Materials and Methods: Patients receiving PRT at a single institution between 2014 and 2018 were reviewed. The time between PRT start and finish was calculated and divided by overall survival (in days from start of PRT) to generate the percent of remaining life (PRL). This value was compared across various clinical factors using the Kruskal-Wallis test. Factors identified with a significance level p < 0.01 were included in a novel Palliative Appropriateness Criteria Score (PACS) and were included in an online risk assessment tool to assist clinicians in patient-specific fractionation decisions. Results: Totally 1027 courses of PRT were analyzed. Median age was 64 years; Eastern Cooperative Oncology Group (ECOG) performance status was 3-4 in 22%. Primary malignancies included were lung (38%), breast (13.8%), prostate (9.3%), and other (39%). The indication for PRT was pain (61%), neurological (21%), or other (18%). Palliative regimens included 199 (19.4%) receiving single fraction, 176 (17.1%) receiving 2-5 fractions, and 652 (63.5%) receiving 10 fractions. Median follow-up was 83 days overall and 437 days for patients alive at last follow-up. Factors significantly associated with increased PRL (and included in the PACS) were male gender, ECOG 3-4, lung or "other" primary diagnosis (vs. breast or prostate), PRT indication (neurological dysfunction vs. pain/other), inpatient status, and extraosseous sites treatment. Death within 30 days was significantly associated with high-risk PACS categorization, regardless of fractionation scheme (p < 0.001). Conclusions: The PACS is a novel metric for evaluating the utility of PRT regimens to improve clinical decision making. Single fraction is associated with low PRL. When considering multifraction PRT regimens, the PACS identifies patients who may benefit from shorter courses of PRT and alternatively, low-risk patients for whom a more protracted course is reasonable. Prospective external validation is warranted.

Efficacy and Survival after Palliative Radiotherapy for Malignant Pulmonary Obstruction.

Introduction: The purpose of this study was to determine the efficacy of palliative radiotherapy (PRT) for patients with pulmonary obstruction from advanced malignancy and identify factors associated with lung re-expansion and survival. Materials and Methods: We reviewed all patients treated with PRT for malignant pulmonary obstruction (n = 108) at our institution between 2010 and 2018. Radiographic evidence of lung re-expansion was determined through review of follow-up CT or chest X-ray. Cumulative incidence of re-expansion and overall survival (OS) were estimated using competing risk methodology. Clinical characteristics were evaluated for association with re-expansion, OS, and early mortality. Treatment time to remaining life ratio (TT:RL) was evaluated as a novel metric for palliative treatment. Results: Eighty-one percent of patients had collapse of an entire lung lobe, 46% had Eastern Cooperative Oncology Group (ECOG) performance status 3-4, and 64% were inpatient at consultation. Eighty-four patients had follow-up imaging available, and 25 (23%) of all patients had lung re-expansion at median time of 35 days. Rates of death without re-expansion were 38% and 65% at 30 and 90 days, respectively. Median OS was 56 days. Death within 30 days of PRT occurred in 38%. Inpatients and larger tumors trended toward lower rates of re-expansion. Notable factors associated with OS were re-expansion, nonlung histology, tumor size, and performance status. Median TT:RL was 0.11 and significantly higher for subgroups: ECOG 3-4 (0.19), inpatients (0.16), patients with larger tumors (0.14), those unfit for systemic therapy (0.17), and with 10-fraction PRT (0.14). Conclusion: One-fourth of patients experienced re-expansion after PRT for malignant pulmonary obstruction. Survival is poor and a significant proportion of remaining life may be spent on treatment. Careful consideration of these clinical factors is recommended when considering PRT fractionation.

Rapid Development of Clinically Symptomatic Radiation Recall Pneumonitis Immediately Following COVID-19 Vaccination.

In this report, we present the case of a 66-year-old man who received local consolidation radiotherapy to the right lung and mediastinum for oligometastatic non-small cell lung cancer (NSCLC) following partial response to upfront chemoimmunotherapy. He continued with maintenance immunotherapy and was asymptomatic for eight months after completing radiation therapy. He then developed symptoms consistent with pneumonitis within three to five days of his first administration of the coronavirus disease 2019 (COVID-19) vaccine injection. He reported that these symptoms significantly intensified within three to five days of receiving his second dose of the vaccine. The clinical time frame and radiographic evidence raised suspicion for radiation recall pneumonitis (RRP). Patients undergoing maintenance immunotherapy after prior irradiation may be at increased risk of this phenomenon that may be triggered by the administration of the COVID-19 vaccine.

Long-Term Outcomes From a Phase 2 Trial of Radiofrequency Ablation Combined With External Beam Radiation Therapy for Patients With Inoperable Non-Small Cell Lung Cancer.

PURPOSE: Long-term outcomes after external beam radiation therapy (EBRT) and radiofrequency ablation (RFA) for medically inoperable early-stage non-small cell lung cancer (NSCLC) are not well known. METHODS AND MATERIALS: Patients with medically inoperable early-stage NSCLC were enrolled in a prospective single-arm, phase 2 study between June 2007 and October 2008 and were treated with RFA followed by EBRT. Radiation was delivered using hypofractionated radiation therapy (HFRT; 70.2 Gy in 26 fractions) or stereotactic body radiation therapy (54 Gy in 3 fractions). RESULTS: Twelve patients were evaluable; 10 patients were treated with HFRT. The cumulative incidence of local progression at 5 years was 16.7% (95% confidence interval [CI], 0-37.8). Median progression-free survival was 37.8 months (95% CI, 11.1 to not reached) and median overall survival was 53.6 months (95% CI, 21.0 to not reached). There were no mortalities within 30 days after RFA and no grade ≥4 toxicity. CONCLUSIONS: The combination of RFA with EBRT appears feasible with favorable long-term local control. However, because SBRT alone has similar or better rates of control, we do not recommend routine combined RFA and EBRT.

Stereotactic body radiotherapy for synchronous early stage non-small cell lung cancer.

INTRODUCTION: In patients with non-small cell lung cancer (NSCLC) who present with multiple pulmonary nodules, it is often difficult to distinguish metastatic disease from synchronous primary lung cancers (SPLC). We sought to evaluate clinical outcomes after stereotactic body radiotherapy (SBRT) alone to synchronous primary lesions. MATERIAL AND METHODS: Patients with synchronous AJCC 8th Edition Stage IA-IIA NSCLC and treated with stereotactic body radiation therapy (SBRT) to all lesions between 2009-2018 were reviewed. SPLC was defined as patients having received two courses of SBRT within 180 days for treatment of separate early stage tumors. In total, 36 patients with 73 lesions were included. Overall survival (OS), progression-free survival (PFS), cumulative incidence of local failure (LF), and regional/distant failure (R/DF) were estimated and compared with a control cohort of solitary early stage NSCLC patients. RESULTS: Median PFS was 38.8 months (95% CI 14.3-not reached [NR]); 3-year PFS rates were 50.6% (35.6-72.1). Median OS was 45.9 months (95% CI: 35.9-NR); 3-year OS was 63.0% (47.4-83.8). Three-year cumulative incidence of LF and R/DF was 6.6% (3.7-13.9) and 35.7% (19.3-52.1), respectively. Patients with SPLC were compared to a control group (n = 272) of patients treated for a solitary early stage NSCLC. There was no statistically significant difference in PFS (p = .91) or OS (p = .43). Evaluation of the patterns of failure showed a trend for worse cumulative incidence of R/DF in SPLC patients as compared to solitary early stage NSCLC (p = .06). CONCLUSION: SBRT alone to multiple lung tumors with SPLC results in comparable PFS, OS, and LF rates to a cohort of patients treated for solitary early stage NSCLC. Those with SPLC had non-significantly higher R/DF. Patients with SPLC should be followed closely for failure and possible salvage therapy.

Impact of dose to lung outside the planning target volume on distant metastasis or progression after SBRT for early-stage non-small cell lung cancer.

Mean dose (EQD2) to 3-cm shell of lung surrounding the PTV was evaluated for association with distant metastasis and PFS after SBRT for stage I NSCLC. Dose was uniformly above previously determined threshold and metastasis was uncommon. An association between outcomes and mean EQD2 could not be confirmed or refuted.

Five- Versus Ten-Fraction Regimens of Stereotactic Body Radiation Therapy for Primary and Metastatic NSCLC.

INTRODUCTION: At our institution, stereotactic body radiotherapy (SBRT) has commonly been prescribed with 50 Gy in 5 fractions and in select cases, 50 Gy in 10 fractions. We sought to evaluate the impact of these 2 fractionation schedules on local control and survival outcomes. METHODS: We reviewed patients treated with SBRT with 50 Gy/5 fraction or 50 Gy/10 fraction for early-stage non-small cell lung cancer (NSCLC) and metastatic NSCLC. Cumulative incidence of local failure (LF) was estimated using competing risk methodology. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method only for patients with stage I disease. RESULTS: Of the 353 lesions, 300 (85%) were treated with 50 Gy in 5 fractions and 53 (15%) with 10 fractions. LFs at 3 years were 6.5% and 23.9% and Kaplan-Meier estimate of median time to LF was 17.5 months and 26.2 months, respectively. Multivariable analysis revealed increasing planning target volume (hazard ratio 1.01, P = .04) as an independent predictor of increased LF, but tumor size, ultracentral location, and 10 fractions were not. Among patients with stage I NSCLC (n = 298), overall median PFS was 35.6 months and median OS was 42.4 months. There was no difference in PFS or OS between the 2 treatment regimens for patients with stage I NSCLC. Low rates of grade 3+ toxicity were observed, with 1 patient experiencing grade 3 pneumonitis after a 5-fraction regimen of SBRT. CONCLUSION: Dose-fractionation schemes with BED10 ≥ 100 Gy provide superior local control and should be offered when meeting commonly accepted constraints. If those regimens appear unsafe, 50 Gy in 10 fractions may provide acceptable compromise between tumor control and safety with relatively durable control, and minimal negative impact on long-term survival.

Adrenal SBRT: a multi-institutional review of treatment outcomes and toxicity.

The adrenal glands are a common site of metastatic disease. Definitive treatment for oligometastatic disease using ablative radiotherapy is becoming common in modern radiation oncology practice. However, most data on the treatment of adrenal metastases are limited to single institution reports. Furthermore, delivering ablative radiotherapy doses to intra-abdominal lesions can be challenging due to the proximity of the gastrointestinal tract. We report the outcomes of a multi-institutional cohort of patients treated with definitive radiotherapy for adrenal metastases, primarily using 10 fraction regimens. Retrospective review of institutional databases revealed 29 lesions in 27 patients were treated from 2005 to 2018 at two institutions. Outcome data, including local control, disease-free, and overall survival were abstracted from the medical record system. Toxicity was graded using CTCAE v5.0. Detailed radiotherapy data was abstracted from the treatment planning systems. The median dose was 50 Gy in 10 fractions. Actuarial 1 and 2 year local control was 86% and 76% respectively. The median overall and disease-free survival were 22.8 and 5.6 months respectively. There were no associations identified between local failure and GTV and PTV physical or biologic effective dose. Two patients developed late Grade 3 gastrointestinal toxicity. High dose radiotherapy to adrenal metastases is a feasible treatment with excellent local control and a reasonable safety profile. For lesions in close proximity to gastrointestinal structures, moderately hypofractionated 10 fraction regimens may be a reasonable compromise between local control and toxicity.

Bench to Bedside: Animal Models of Radiation Induced Musculoskeletal Toxicity.

Ionizing radiation is a critical aspect of current cancer therapy. While classically mature bone was thought to be relatively radio-resistant, more recent data have shown this to not be the case. Radiation therapy (RT)-induced bone loss leading to fracture is a source of substantial morbidity. The mechanisms of RT likely involve multiple pathways, including changes in angiogenesis and bone vasculature, osteoblast damage/suppression, and increased osteoclast activity. The majority of bone loss appears to occur rapidly after exposure to ionizing RT, with significant changes in cortical thickness being detectable on computed tomography (CT) within three to four months. Additionally, there is a dose-response relationship. Cortical thinning is especially notable in areas of bone that receive >40 gray (Gy). Methods to mitigate toxicity due to RT-induced bone loss is an area of active investigation. There is an accruing clinical trial investigating the use of risderonate, a bisphosphonate, to prevent rib bone loss in patients undergoing lung stereotactic body radiation therapy (SBRT). Additionally, several other promising therapeutic/preventative approaches are being explored in preclinical studies, including parathyroid hormone (PTH), amifostine, and mechanical loading of irradiated bones.

Stereotactic body radiotherapy for an isolated splenic metastasis from ovarian carcinoma.

Splenic metastases from oligometastatic ovarian carcinoma are a rare occurrence. Usual treatment for splenic metastases includes splenectomy, but some patients are either unable or unwilling to undergo surgery. Stereotactic body radiotherapy (SBRT) is an effective ablative modality for treating metastatic disease. SBRT to abdominopelvic tumors has been shown to be safe and effective for properly-selected patients and is particularly attractive in the oligometastatic setting as an alternative to radical resection. In this case study, we report a patient with an isolated splenic metastasis from ovarian carcinoma treated with 50 Gy in 10 fractions.

Limited-Stage Small Cell Lung Cancer: Is Prophylactic Cranial Irradiation Necessary?

PURPOSE: Prophylactic cranial irradiation (PCI) reduces the incidence of brain metastases in patients with limited stage small cell lung cancer (LS-SCLC). However, PCI is associated with neurotoxicity. Previous studies have not consistently used pretreatment magnetic resonance imaging. Modern imaging improvements continue to enhance early metastasis detection, potentially decreasing the utility of PCI. We sought to determine whether PCI was associated with improved outcomes in LS-SCLC patients with modern imaging. METHODS AND MATERIALS: We identified LS-SCLC patients with no intracranial disease who were treated between 2007 and 2018. Kaplan-Meier estimates of overall survival (OS) and progression-free survival (PFS) were calculated and multivariate Cox proportional hazards models were generated. The cumulative incidence of brain metastases was estimated using competing risks methodology. RESULTS: Ninety-two patients were identified without intracranial disease at initial staging, 39 of whom received PCI. Median follow-up was 56.7 months. The median OS for the cohort was 35.5 months (95% CI, 25.8-49.3), and median PFS was 19.1 months (95% CI, 12.3-30.5). Median OS with PCI versus observation was 37.9 months (95% CI, 31.8-not reached) versus 30.5 months (95% CI, 14.6-56.1; P = .07), whereas median PFS was 26.3 months (95% CI 19.1-not reached) versus 12.3 months (95% CI, 8.5-30.5; P = .02), respectively. Overall, at 2 years, the cumulative incidence of brain metastases was 10% with PCI and 29% without; this increased to 32% and 29% by 4 years (P = .66). In those patients who had negative magnetic resonance imaging of the brain after completing initial treatment, the 1-year cumulative incidence of brain metastasis was not significantly different at 8% versus 11% (P = .46) respectively. Both PCI and treatment response were independent predictors for PFS on multivariate analysis. Stratified by disease response, patients with a complete response did not benefit from PCI (P = .50), whereas those with partial response or stable disease experienced improved PFS (P = .01). CONCLUSIONS: Overall, PCI was associated with improved PFS and reduced early incidence of brain metastases. Patients achieving a complete response to initial therapy did not experience a PFS benefit with PCI. This may indicate that subsets of LS-SCLC patients can potentially be spared from PCI in the era of modern imaging.

Initial SRS for Patients With 5 to 15 Brain Metastases: Results of a Multi-Institutional Experience.

PURPOSE: Several studies evaluating stereotactic radiosurgery (SRS) for patients with >4 brain metastases (BM) demonstrated similar outcomes after treatment of 1, 2 to 4, and 5 to 15 BM; others found clinically significant survival decrements in the latter group. In this review of 8 academic centers, we compared outcomes of patients undergoing initial SRS for 1, 2 to 4, and 5 to 15 BM. METHODS AND MATERIALS: A total of 2089 patients treated with initial SRS for BM were included. Overall survival (OS) was estimated using the Kaplan-Meier method and compared using the log-rank test. Patient and disease characteristics were evaluated for association with OS and cumulative incidence of distant brain failure (DBF) using stepwise multivariable Cox proportional hazards and competing risk regression modeling. RESULTS: In this series, 989 (47%) patients had 1 metastasis, 882 (42%) had 2 to 4 metastases, and 212 (10%) had 5 to 15 metastases treated. Median OS for the 1, 2 to 4, and 5 to 15 BM groups was 14.6, 9.5, and 7.5 months, respectively (log-rank P < .01). Univariate and multivariable analyses revealed no difference in survival between 2 to 4 and 5 to 15 BM. DBF at 1 year was 30%, 41%, and 50%, respectively (Gray's P < .01). Two-year cumulative incidence of salvage SRS decreased with increasing number of BM (1: 21% vs 2-4: 19% vs 5-15: 13%; P < .01), but no difference in salvage whole brain radiation therapy was observed (1: 12% vs 2-4: 15% vs 5-15: 16%, P = .10). At the time of DBF, median brain metastasis velocity was 3.9, 6.1, and 11.7 new metastases per year in the 1, 2 to 4, and 5 to 15 BM groups, respectively (P < .01). CONCLUSIONS: Patients treated with initial SRS for 5 to 15 BM experienced survival similar to that in patients with 2 to 4 BM. Lower rates of salvage SRS were observed in the 5 to 15 BM group, with no difference in rates of salvage whole brain radiation therapy.