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Evolution through six generations of Leksell Gamma Knife has made it a trusted intracranial radiosurgery system for radiation oncologists and neurosurgeons

The 5th meeting of the Asian Gamma Knife Society (ALGKS 2017), which convened at Lotte City Hotel Jeju (Jeju Island, Korea) was hosted by the Asian Leksell Gamma Knife Society and The Korean Society of Stereotactic and Functional Neurosurgery. The meeting drew more than 200 attendees from 15 mainly Asian countries and featured presentations of 135 research papers, the majority focused on the use of Leksell Gamma Knife. There are 126 Leksell Gamma Knife systems operating in the Asia-Pacific region, of which 11 are Elekta’s latest generation Leksell Gamma Knife® Icon™.

“The academic quality of the presentations was outstanding,” reports Dong Gyu Kim, MD, Professor in the Department of Neurosurgery, Seoul National University College of Medicine, and ALGKS Chairman. “I saw two main trends regarding the presentations.

First, it is clear that Gamma Knife users are determined to practice evidence-based medicine – the patient data are diligently accumulated and long-term follow-up results are well-analyzed to provide a more solid base to determine dose selection and dose planning.

“The second trend was fractionation,” he continues. “Many sites are performing hypofractionated radiosurgeries, particularly with the new Icon, which was designed to facilitate straightforward, frameless fractionation. As everyone agrees, however, we need more research on the radiobiology of high dose hypofractionation. Also – to broaden the academic base of radiosurgery – an important takeaway from the meeting was that, in addition to considering the clinical impact of shifting from single-session to multi-session radiosurgery, physicians also need to consider patient selection, dose selection and indications.”

President of the 5th ALGKS, Prof. Young Jin Lim, MD, of Kyung Hee University (Seoul) added that attendance from a record number of countries, and particularly by individuals who don’t currently use Leksell Gamma Knife, attested to the meeting’s success.

“The fifth meeting was the highest attended in ALGKS history and the invitation to non-users added more diversity,” he says. “In terms of the character of the conference, it’s clear that Gamma Knife radiosurgery is only increasing in use as an important neurosurgical tool. And in radiation oncology departments, centers are appreciating the new capability of Gamma Knife to hypofractionate in select cases. I’m hoping that – given the continued use and evolution of Gamma Knife technology – ALGKS members increase their learning and sharing through academic exchange, especially Asian users through ALGKS.

“It was very gratifying to see more surgeons from countries such as China and those from Southeast Asian countries participate in this meeting,” Prof. Lim adds. “Their attendance in ALGKS meetings will only enrich our group and make its future bright. And, by sharing academic studies and clinical experiences, the current Gamma Knife experts can help the surgeons in newly installed centers.”

Also in attendance at ALGKS 2017 were Elekta’s Dan Leksell, MD, Senior Advisor and Motohiko Kimura, Vice President, Elekta KK, who selected the following among the 135 presentations as the “most interesting abstracts:”

Biological Bases for Enhancing the Response of Tumors to SRS

Song, CW, Cho C, Dusenbery K

In their experiments and a literature review, the researchers have contributed to a better understanding of the biological mechanism of stereotactic radiosurgery (SRS) and how a concomitant drug strategy might boost the clinical efficacy of SRS.

After SRS, tumor cells die en masse due to vascular damage and deterioration of the intra-tumor environment. However, residual tumor cells can repopulate, leading to tumor relapse mediated by an increase in HIF-1α and VEGF. The researchers observed that metformin (anti-diabetes drug) and docetaxel (anti-cancer drug) can prevent the upregulation of HIF-1α and VEGF in experimental mouse tumors irradiated with 15-20 Gy. They also found that the optimal interval between the first 15 Gy and the second irradiation is three days. They concluded that the effectiveness of SRS may be substantially improved by both targeting the post-fraction increase in HIF-1α and VEGF with metformin and docetaxel and by exploiting the reoxygenation of hypoxic tumor cells.

Radiosurgery a Main Approach in Movement Disorders

Regis J, Carron R, Witjas T

The investigators sought to study bilateral Gamma Knife therapy (GKT) for the treatment of essential tremor (ET), a condition in which contralateral tremor may persist if GKT is done only unilaterally. Fifteen patients with severe ET – who had received initial GKT but also severe permanent contralateral tremor – had a second GKRS (GKT2, 130 Gy single fraction) ≥ 18 months after their first GKT.

Patients were assessed before and quarterly for at least 12 months post-GKT2, with tremor rating scale, neuropsychological and gait/balance assessments and MRI. At the one-year mark, researchers reported results for nine patients. Tremor score on the treated hand was improved by 57% and ADL was improved by 95%. Preliminary results on bilateral GKT for severe ET in select patients shows that GKT is feasible without a major risk of cognitive or balance problems.

  1. The Use of Gamma Knife Radiosurgery in the Eye-conserving Therapy of Uveal and Epibulbar Melanoma with and without Tumor Resection

Sinyavskiy O, Troyanovsky R, Ivanov P, et. al

Researchers analyzed the use of Gamma Knife radiosurgery (GKRS) in the eye-conserving therapy of uveal (UM) and epibulbar melanoma (EM) with and without tumor resection.

In 46 patients, 46 eyes with UM and one patient with a large EM were treated with GKRS (70-80 Gy). Thirty patients with large tumors on macula-on secondary retinal detachment (MOSRD) had tumor resection after GKRS. In these patients, the height of the tumor was typically > 6 mm. In 16 patients without MORSD – who received GKRS only – the tumor height was < 6 mm generally. In the one EM patient, investigators performed laser resection post-GKRS. The follow up period was 12-54 months.

The results showed that all eyes were saved with visual acuity > 0.1 in 16 patients (53%) in the group with tumor resection and > 0.3 in 10 (62.5%) patients with GKRS only. Local tumor recurrence was found in one case (2.1%). Thirty-one patients (66%) had signs of neuroretinopathy, however injections of angiogenic inhibitors were effective in treating the disease.

The researchers concluded that GKRS with or without tumor resection is a highly effective method for treating UM and EM, with a 100% eye-preserving rate with positive functional results in 55.3% and with a 95.8% four-year survival rate.

More than 10 Years Survival Following Gamma Knife Surgery in Patients with Multiple Brain Metastases

Sun I, Karlsson B, Yamamoto M, et al.

Investigators hypothesized that cure may be possible for patients with multiple brain metastases (MBM) due to improved management of malignant disease in recent years, including the use of Gamma Knife surgery (GKS). The researchers obtained and analyzed data regarding 1,972 patients treated with GKS in the participating centers for MBM > 10 years ago.

The results showed that the 10-year survival rate was 1.5% based on K-M plot. Nineteen patients survived > 10 years post-GKS, 12 had NSCLC, two had malignant melanoma, one SCLC, one uterine, one testicular and one choriocarcinoma. All but one were still alive at the time of this study. The patients were treated with GKS 51 times for a total of 144 brain mets. Despite this, 13 had a KPS of 100, two of 90, one of 80 and one of 70 at the time of the latest follow up. None of the patients developed radiation-induced white matter changes, but six patients developed radiation-induced cysts and a few others had other minor symptoms. The incidence of 10-year survival was related to young patient age, female gender, controlled primary disease and KPS. Survival was unrelated to primary tumor location (lung or not), number of brain mets and synchronous presentation.

This is the largest series of patients with MBM surviving > 10 years and demonstrates that cure is possible for selected patients with MBM, the researchers concluded.

Radiosurgery for Obsessive Compulsive Disorder

Regis J, Spatola G, Martinez R

The researchers retrospectively reviewed the cases of 10 patients who had been treated for severe OCD refractory to pharmacological and psychiatric treatments. Radiosurgical capsulotomy with Leksell Gamma Knife was performed using two 4 mm isocenters targeted at the mid-putaminal point of the anterior limb of the capsule. A maximum dose of 120 Gy was prescribed for each side. Obsessive compulsive symptoms were determined by the Y-BOCS, the Beck Depression Inventory (BDI) and State-Trait Anxiety Inventory (STAI).

Before Gamma Knife radiosurgery, the median T-BOCS score was 34.5, with a median obsession score of 18 and compulsion score of 17. Seven of the 10 patients (3 non-responders) achieved a full response at their last follow-up. Evaluation of Y-BOCS, BDI, STAI-T, STAI-S and other tests showed statistically significant improvement at the last follow-up after Gamma Knife radiosurgery. Neurological examinations were normal in all patients at each visit. At last follow-up, none of the patients experienced any significant adverse neuropsychological effects or personality changes.

The researchers concluded that Gamma Knife radiosurgery is effective and well tolerated with a maximum dose of 120 Gy; it reduces both obsessions and compulsions, improves quality of life and diminishes depression and anxiety.

Prof. Kim receives Takakura Award

At the meeting, it was announced that ALGKS Chairman Prof. Gong Gyu Kim of Seoul National University Hospital was the first recipient of the Takakura Award. Prof. Kim was given the award in recognition of his longtime dedication and contribution to the Asian community with Leksell Gamma Knife. The Takakura Award is named after Prof. Kintomo Takakura, the pioneer of Gamma Knife in Japan (Tokyo University, 1990).

2019 ALGKS meeting to convene at Furukawa Seiryo Hospital

The 2019 ALGKS meeting will be held at Furukawa Seiryo Hospital, home of the Jiro Suzuki Memorial Gamma House. Hidefumi Jyokura, MD, Vice President and Director at the Gamma House will serve as host.