BACKGROUND The Gamma Knife (GK) Icon (Elekta AB) uses a cone-beam computed tomography (CBCT) scanner and an infrared camera system to support the delivery of frameless stereotactic radiosurgery (SRS). There are limited data on patients treated with frameless GK radiosurgery (GKRS). OBJECTIVE To describe the early experience, process, technical details, and short-term outcomes with frameless GKRS at our institution. METHODS We reviewed our patient selection and described the workflow in detail, including image acquisition, treatment planning, mask-based immobilization, stereotactic CBCT localization, registration, treatment, and intrafraction monitoring. Because of the short interval of follow-up, we provide crude rates of local control. RESULTS Data from 100 patients are reported. Median age is 67 yr old. 56 patients were treated definitively, 21 postoperatively, and 23 had salvage GKRS for recurrence after surgery. Forty-two patients had brain metastases, 26 meningiomas, 16 vestibular schwannomas, 9 high-grade gliomas, and 7 other histologies. Median doses to metastases were 20 Gy in 1 fraction (range: 14-21), 24 Gy in 3 fractions (range: 19.5-27), and 25 Gy in 5 fractions (range: 25-30 Gy). Thirteen patients underwent repeat SRS to the same area. Median treatment time was 17.7 min (range: 5.8-61.7). We found an improvement in our workflow and a greater number of patients eligible for GKRS because of the ability to fractionate treatments. CONCLUSION We report a large cohort of consecutive patients treated with frameless GKRS. We look forward to studies with longer follow-up to provide valuable data on clinical outcomes and to further our understanding of the radiobiology of hypofractionation in the brain.

Ex vivo CD34+ selected T-cell depletion (TCD) has been developed as a strategy to reduce the incidence of graft-versus-host disease (GVHD) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Clinical characteristics, treatment responses, and outcomes of patients developing acute (a-) and chronic (c-) GVHD after TCD allo-HSCT have not been well established. We evaluated 241 consecutive patients (median age 57 years) with acute leukemia (n = 191, 79%) or myelodysplastic syndrome (MDS) (n = 50, 21%) undergoing CD34+ selected TCD allo-HSCT without post-HCST immunosuppression in a single institution. Cumulative incidences of grade II–IV and III–IV aGVHD at 180 days were 16% (95% CI:12–21) and 5% (95% CI:3–9), respectively. The skin was the most frequent organ involved, followed by the GI tract. Patients were treated with topical corticosteroids, poorly absorbed corticosteroids (Budesonide), and/or systemic corticosteroids. The overall day 28 treatment response was high at 82%. Cumulative incidence of any cGVHD at 3 years was 5% (95% CI:3–9), with a median time of onset of 256 days (range 95–1645). The 3-year transplant-related mortality, relapse, overall survival and disease-free survival were 24% (95%CI: 18–30), 22% (95% CI:17–27), 57% (95% CI:50–64) and 54% (95% CI:47–61), respectively. The 1-year and 3-years probability of cGVHD-free/relapse-free survival (CRFS) were 65% (95% CI:59–71) and 52% (95% CI:45–59), respectively. Our findings support the use of ex vivo CD34+ selected TCD allograft as a calcineurin inhibitor-free intervention for the prevention of GVHD in patients with acute leukemia and MDS.

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