Objective : The effectiveness of gamma knife radiosurgery (GKR) in the treatment of brain metastases is well established. The aim of this study was to evaluate the efficacy and safety of maximizing the radiation dose in GKR and the factors influencing tumor control in cases of small and medium-sized brain metastases from non-small cell lung cancer (NSCLC). Methods : We analyzed 230 metastatic brain tumors less than 5 mL in volume in 146 patients with NSCLC who underwent GKR. The patients had no previous radiation therapy for brain metastases. The pathologies of the tumors were adenocarcinoma (n=207), squamous cell carcinoma (n=18), and others (n=5). The radiation doses were classified as 18, 20, 22, and 24 Gy, and based on the tumor volume, the tumors were categorized as follows : small-sized (less than 1 mL) and medium-sized (1-3 and 3-5 mL). The progression-free survival (PFS) of the individual 230 tumors and 146 brain metastases was evaluated after GKR depending on the pathology, Eastern Cooperative Oncology Group (ECOG) performance score (PS), tumor volume, radiation dose, and anti-cancer regimens. The radiotoxicity after GKR was also evaluated. Results : After GKR, the restricted mean PFS of individual 230 tumors at 24 months was 15.6 months (14.0-17.1). In small-sized tumors, as the dose of radiation increased, the tumor control rates tended to increase (p=0.072). In medium-sized tumors, there was no statistically difference in PFS with an increase of radiation dose (p=0.783). On univariate analyses, a statistically significant increase in PFS was associated with adenocarcinomas (p=0.001), tumors with ECOG PS 0 (p=0.005), small-sized tumors (p=0.003), radiation dose of 24 Gy (p=0.014), synchronous lesions (p=0.002), and targeted therapy (p=0.004). On multivariate analyses, an improved PFS was seen with targeted therapy (hazard ratio, 0.356; 95% confidence interval, 0.150-0.842; p=0.019). After GKR, the restricted mean PFS of brain at 24 months was 9.8 months (8.5-11.1) in 146 patients, and the pattern of recurrence was mostly distant within the brain (66.4%). The small and medium-sized tumors treated with GKR showed radiotoxicitiy in five out of 230 tumors (2.2%), which were controlled with medical treatment. Conclusion :The small-sized tumors were effectively controlled without symptomatic radiation necrosis as the radiation dose was increased up to 24 Gy. The medium-sized tumors showed potential for symptomatic radiation necrosis without signifcant tumor control rate, when greater than 18 Gy. GKR combined targeted therapy improved the tumor control of GKR-treated tumors.

The paper provides a comprehensive overview of the growth and development of Hwasun Neurosurgery at Chonnam National University Hwasun Hospital over the past 18 years. As the first brain tumor center in Korea when it was established in April 2004, Hwasun Neurosurgery has since become one of the leading institutions in brain tumor education and research in the country. Its impressive clinical and basic research capabilities, dedication to professional education, and numerous academic achievements have all contributed to its reputation as a top-tier institution. We hope this will become a useful guide for other brain tumor centers or educational institutions by sharing the story of Hwasun Neurosurgery.

There has been controversy over whether to radiologically follow up or use local treatment for asymptomatic small-sized brain metastases from primary lung cancer. For brain tumors without local treatment, we evaluated potential factors related to the brain progression and whether systemic therapy controlled the tumor. We analyzed 96 patients with asymptomatic small-sized metastatic brain tumors from lung cancer. These underwent a radiologic follow-up every 2 or 3 months without local treatment of brain metastases. The pathologies of the tumors were adenocarcinoma (n = 74), squamous cell carcinoma (n = 11), and small cell carcinoma (n = 11). The primary lung cancer was treated with cytotoxic chemotherapy (n = 57) and targeted therapy (n = 39). Patients who received targeted therapy were divided into first generation (n = 23) and second or third generation (n = 16). The progression-free survival (PFS) of brain metastases and the overall survival (OS) of patients were analyzed depending on the age, tumor pathology, number, and location of brain metastases, the extent of other organ metastases, and chemotherapy regimens. The median PFS of brain metastases was 7.4 months (range, 1.1–48.3). Targeted therapy showed statistically significant PFS improvement compared to cytotoxic chemotherapy (p = 0.020). Especially, on univariate and multivariate analyses, the PFS in the second or third generation targeted therapy was more significantly improved compared to cytotoxic chemotherapy (hazard ratio 0.229; 95% confidence interval, 0.082–0.640; p = 0.005). The median OS of patients was 13.7 months (range, 2.0–65.0). Univariate and multivariate analyses revealed that the OS of patients was related to other organ metastases except for the brain (p = 0.010 and 0.020, respectively). Three out of 52 patients with brain recurrence showed leptomeningeal dissemination, while the recurrence patterns of brain metastases were mostly local and/or distant metastases (94.2%). Of the 52 patients who relapsed, 25 patients received local brain treatment. There was brain-related mortality in two patients (2.0%). The intracranial anti-tumor effect was superior to cytotoxic chemotherapy in the treatment of asymptomatic small-sized brain metastases with targeted therapy. Consequently, it becomes possible to determine the optimal timing for local brain treatment while conducting radiological follow-up for these tumors, which do not appear to increase brain-related mortality. Furthermore, this approach has the potential to reduce the number of cases requiring brain local treatment.

Arachnoid cysts are usually asymptomatic and discovered incidentally. However, cysts may occasionally rupture because of minor head trauma. We describe the radiologic follow-up of 5 patients with ruptured arachnoid cysts featuring spontaneous resolution, subdural hygroma formation, and cystic and subdural hemorrhage. From January 2004 through July 2020, 5 patients (1.3%) with ruptured arachnoid cysts were evaluated out of 388 patients with arachnoid cysts encountered at our institution at that time. The 5 patients were all male, and they ranged in age from 6–17 years (median, 12 years). The median duration of radiologic follow-up was 3.5 years (range, 2.3–10.1 years). All of the ruptured arachnoid cysts were overlying the temporal lobe with Galassi type II. The median cyst diameter was 4.9 cm (range, 4.4–8.9 cm). Four patients had a history of recent minor head trauma. There were no particular neurologic symptoms in their past medical history in all patients. In the follow-up, two patients’ cysts resolved spontaneously without hemorrhage. One patient’s cyst resolved post-burr-hole drainage for chronic subdural hemorrhage. Another patient, whose cyst led to a hemorrhage and chronic subdural hemorrhage, recovered following a craniotomy, hematoma removal, and cyst fenestration. Another patient, presenting with hygroma, cystic hemorrhage, and chronic subdural hemorrhage, was treated with burr-hole drainage. Three patients recovered postoperatively. Arachnoid cysts rarely rupture, and surgical intervention is required for some cases associated with hemorrhage. Postoperatively, all patients had good outcomes without complications in this series.