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Purpose: To develop a volume‐independent conformity metric called the Gaussian Weighted Conformity Index (GWCI) to evaluate stereotactic radiosurgery/radiotherapy (SRS/SRT) plans for small brain tumors. Methods: A signed bi‐directional local distance (BLD) between the prescription isodose line and the target contour is determined for each point along the tumor contour (positive distance represents under‐coverage). A similarity score function (SF) is derived from Gaussian function, penalizing under‐ and over‐coverage at each point by assigning standard deviations of the Gaussian function. Each point along the dose line contour is scored with this SF. The average of the similarity scores determines the GWCI. A total of 40 targets from 18 patients who received Gamma‐Knife SRS/SRT treatments were analyzed to determine appropriate penalty criteria. The resulting GWCIs for test cases already deemed clinically acceptable are presented and compared to the same cases scored with the New Conformity Index to determine the influence of tumor volumes on the two conformity indices (CIs). Results: A total of four penalty combinations were tested based on the signed BLDs from the 40 targets. A GWCI of 0.9 is proposed as a cutoff for plan acceptability. The GWCI exhibits no target volume dependency as designed. Conclusion: A limitation of current CIs, volume dependency, becomes apparent when applied to SRS/SRT plans. The GWCI appears to be a more robust index, which penalizes over‐ and under‐coverage of tumors and is not skewed by the tumor volume. [ABSTRACT FROM AUTHOR]

Objectives: Large cell neuroendocrine carcinoma (LCNEC) of the lung is a rare pulmonary tumor, having similar natural history and management strategy as small cell lung cancer. Therefore, the management of brain metastases in these patients has mirrored that of SCLC through the use of whole brain radiation therapy (WBRT). We used the National Cancer Database (NCDB) to look at predictors of stereotactic radiosurgery (SRS) and any potential differences in outcomes for patients with brain metastases from LCNEC. Material and methods: We queried the NCDB from 2004 to 2015 for patients with LCNEC of the lung with brain metastases that received brain radiation. Univariable and multivariable analyses were performed to identify factors predictive of SRS use and overall survival (OS). Propensity-adjusted Cox proportional hazard ratios for survival were used to account for indication bias. Results: Out of 9970 patients with LCNEC of the lung we identified 348 with brain metastases. Sixty-eight patients were treated with upfront SRS and 280 were treated with WBRT. Patients that were treated at an academic facility or received chemotherapy as part of upfront treatment were more likely to receive SRS. Univariable analysis revealed improved outcomes with SRS compared to WBRT, with a median OS of 11 months compared to 6 months, respectively (p =.007). Multivariable Cox regression with propensity score confirmed SRS to have improved survival (HR: 0.68, 95%CI: 0.51–0.91, p =.0093). Multivariable Cox regression with propensity score also identified younger age, receipt of chemotherapy, absence of extracranial disease and non-rural locations as additional predictors of improved OS. Conclusions: Treatment of brain metastases from LCNEC of the lung with SRS was associated with improved survival. For the appropriate patients, upfront treatment of limited brain metastases with SRS may be appropriate. [ABSTRACT FROM AUTHOR]