Outcome of whole brain irradiation with a dose-escalated simultaneous-integrated boost in patients with multiple large and/or diffuse brain metastases: real live data and review of the literature.

BACKGROUND: We retrospectively investigate feasibility and safety of whole brain radiotherapy (WBRT) including a simultaneous-integrated boost technique (WBRT-SIB) in a cohort of patients with a very poor prognosis suffering from multiple and/or large brain metastases, unfavorable primary histology, poor performance status and/or symptomatic BMs. MATERIALS AND METHODS: Thirty-five patients with high brain tumor burden, extracranial metastases and low life-expectancy were treated with WBRT-SIB mostly with 35-42 Gy/14 fractions. All metastases were boosted in patients with up to 12 BMs. In patients with > 12 BM, large and/or small metastases in critical brain regions were boosted up to a maximum of 12 SIB volumes. RESULTS: The median number of BM was 8 (range 2-45) and the median BM diameter was 12 mm (range 4-90 mm). Fifteen (43%) patients had ≥ 10 BMs and 25 patients presented with a Karnofski index ≤ 80%. Primary tumor histology was NSCLC (n = 13), SCLC (n = 11), breast cancer (n = 7), melanoma (n = 2), other (n = 2). The median iPFS was not reached, and 12- and 18-months iPFS were 75% and 50%, respectively. Overall, seven patients had intracranial progression: two patients within the SIB and WBRT area, one patient only within the SIB region and four patients had new BMs in the WBRT volume alone. The median iPFS for non-SCLC patients was 17 months and the 12- and 18-month iPFS were 56.8% and 28.4%, respectively. There was no significant OS difference between SCLC-group and non-SCLC patients (p = 0.38). Overall, median OS was 8.7 months and 1-year OS was 25%. The treatment was generally well-tolerated with no observed cases of radionecrosis. CONCLUSION: Our WBRT-SIB approach involves a combination of whole brain radiotherapy and a simultaneous integrated boost to specific tumor volumes, and its effectiveness is compared with other treatment modalities in the literature. Further research, including prospective studies with larger patient cohorts, is necessary to validate and refine the findings.

Validation of new 2D ripple filters in proton treatments of spherical geometries and non-small cell lung carcinoma cases.

A ripple filter (RiFi) is a passive energy modulator used in scanned particle therapy to broaden the Bragg peak, thus lowering the number of accelerator energies required for homogeneous target coverage, which significantly reduces the irradiation time. As we have previously shown, a new 6 mm thick RiFi with 2D groove shapes produced with 3D printing can be used in carbon ion treatments with a similar target coverage and only a marginally worse planning conformity compared to treatments with in-use 3 mm thick RiFis of an older 1D design. Where RiFis are normally not used with protons due to larger scattering and straggling effects, this new design would be beneficial in proton therapy too. Measurements of proton Bragg curves and lateral beam profiles were carried out for different RiFi designs and thicknesses as well as for no RiFi at the Heidelberg Ionenstrahl-Therapiezentrum. Base data for proton treatment planning were generated with the Monte Carlo code SHIELD-HIT12A with and without the 2D 6 mm RiFi. Plans on spherical targets in water were calculated with TRiP98 for a systematic RiFi performance analysis and for comparisons with carbon ion plans for the same respective energy depth step sizes. Plans for 9 stage I static non small cell lung cancer patients were calculated with Eclipse 13.7.15. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Measurements confirm the functionality of the new 2D RiFi design, which reduces the beam spot size compared to 1D RiFis of the same thickness. Planning studies show that a 6 mm thick 2D RiFi could be used in proton therapy to lower the irradiation time. Although slightly worse planning conformity and dose homogeneity were found for plans with the RiFi compared to plans without, satisfactory results within the planning objective were obtained for all cases.

Design of and technical challenges involved in a framework for multicentric radiotherapy treatment planning studies.

This report introduces a framework for comparing radiotherapy treatment planning in multicentric in silico clinical trials. Quality assurance, data incompatibility, transfer and storage issues, and uniform analysis of results are discussed. The solutions that are given provide a useful guide for the set-up of future multicentric planning studies or public repositories of high quality data.

Quantification of the relative biological effectiveness for ion beam radiotherapy: direct experimental comparison of proton and carbon ion beams and a novel approach for treatment planning.

PURPOSE: To present the first direct experimental in vitro comparison of the biological effectiveness of range-equivalent protons and carbon ion beams for Chinese hamster ovary cells exposed in a three-dimensional phantom using a pencil beam scanning technique and to compare the experimental data with a novel biophysical model. METHODS AND MATERIALS: Cell survival was measured in the phantom after irradiation with two opposing fields, thus mimicking the typical patient treatment scenario. The novel biophysical model represents a substantial extension of the local effect model, previously used for treatment planning in carbon ion therapy for more than 400 patients, and potentially can be used to predict effectiveness of all ion species relevant for radiotherapy. A key feature of the new approach is the more sophisticated consideration of spatially correlated damage induced by ion irradiation. RESULTS: The experimental data obtained for Chinese hamster ovary cells clearly demonstrate that higher cell killing is achieved in the target region with carbon ions as compared with protons when the effects in the entrance channel are comparable. The model predictions demonstrate agreement with these experimental data and with data obtained with helium ions under similar conditions. Good agreement is also achieved with relative biological effectiveness values reported in the literature for other cell lines for monoenergetic proton, helium, and carbon ions. CONCLUSION: Both the experimental data and the new modeling approach are supportive of the advantages of carbon ions as compared with protons for treatment-like field configurations. Because the model predicts the effectiveness for several ion species with similar accuracy, it represents a powerful tool for further optimization and utilization of the potential of ion beams in tumor therapy.