Commissioning of Helium Ion Therapy and the First Patient Treatment With Active Beam Delivery.

PURPOSE: Helium ions offer intermediate physical and biological properties to the clinically used protons and carbon ions. This work presents the commissioning of the first clinical treatment planning system (TPS) for helium ion therapy with active beam delivery to prepare the first patients' treatment at the Heidelberg Ion-Beam Therapy Center (HIT). METHODS AND MATERIALS: Through collaboration between RaySearch Laboratories and HIT, absorbed and relative biological effectiveness (RBE)-weighted calculation methods were integrated for helium ion beam therapy with raster-scanned delivery in the TPS RayStation. At HIT, a modified microdosimetric kinetic biological model was chosen as reference biological model. TPS absorbed dose predictions were compared against measurements with several devices, using phantoms of different complexities, from homogeneous to heterogeneous anthropomorphic phantoms. RBE and RBE-weighted dose predictions of the TPS were verified against calculations with an independent RBE-weighted dose engine. The patient-specific quality assurance of the first treatment at HIT using helium ion beam with raster-scanned delivery is presented considering standard patient-specific measurements in a water phantom and 2 independent dose calculations with a Monte Carlo or an analytical-based engine. RESULTS: TPS predictions were consistent with dosimetric measurements and independent dose engines computations for absorbed and RBE-weighted doses. The mean difference between dose measurements to the TPS calculation was 0.2% for spread-out Bragg peaks in water. Verification of the first patient treatment TPS predictions against independent engines for both absorbed and RBE-weighted doses presents differences within 2% in the target and with a maximum deviation of 3.5% in the investigated critical regions of interest. CONCLUSIONS: Helium ion beam therapy has been successfully commissioned and introduced into clinical use. Through comprehensive validation of the absorbed and RBE-weighted dose predictions of the RayStation TPS, the first clinical TPS for helium ion therapy using raster-scanned delivery was employed to plan the first helium patient treatment at HIT.

Experimental Comparison of Fiducial Markers Used in Proton Therapy: Study of Different Imaging Modalities and Proton Fluence Perturbations Measured With CMOS Pixel Sensors.

Fiducial markers are used for image guidance to verify the correct positioning of the target for the case of tumors that can suffer interfractional motion during proton therapy. The markers should be visible on daily imaging, but at the same time, they should produce minimal streak artifacts in the CT scans for treatment planning and induce only slight dose perturbations during particle therapy. In this work, these three criteria were experimentally investigated at the Heidelberg Ion Beam Therapy Center. Several small fiducial markers with different geometries and materials (gold, platinum, and carbon-coated ZrO2) were evaluated. The streak artifacts on treatment planning CT were measured with and without iMAR correction, showing significantly smaller artifacts from markers lighter than 6 mg and a clear improvement with iMAR correction. Daily imaging as X-ray projections and in-room mobile CT were also performed. Markers heavier than 6 mg showed a better contrast in the X-ray projections, whereas on the images from the in-room mobile CT, all markers were clearly visible. In the other part of this work, fluence perturbations of proton beams were measured for the same markers by using a tracker system of several high spatial resolution CMOS pixel sensors. The measurements were performed for single-energy beams, as well as for a spread-out Bragg peak. Three-dimensional fluence distributions were computed after reconstructing all particle trajectories. These measurements clearly showed that the ZrO2 markers and the low-mass gold/platinum markers (0.35mm diameter) induce perturbations being 2-3 times lower than the heavier gold or platinum markers of 0.5mm diameter. Monte Carlo simulations, using the FLUKA code, were used to compute dose distributions and showed good agreement with the experimental data after adjusting the phase space of the simulated proton beam compared to the experimental beam.

Fluence perturbation from fiducial markers due to edge-scattering measured with pixel sensors for 12C ion beams.

Fiducial markers are nowadays a common tool for patient positioning verification before radiotherapy treatment. These markers should be visible on x-ray projection imaging, produce low streak artifacts on CTs and induce small dose perturbations due to edge-scattering effects during the ion-beam therapy treatment. In this study, the latter effect was investigated and the perturbations created by the markers were evaluated with a new measurement method using a tracker system composed of six CMOS pixel sensors. The present method enables the determination of the particle trajectory before and after the target. The experiments have been conducted at the Marburg Ion Beam Therapy Center with carbon ion beams and the measurement concept was validated by comparison with radiochromic films. This work shows that the new method is very efficient and precise to measure the perturbations due to fiducial markers with a tracker system. Three dimensional fluence distributions of all particle trajectories were reconstructed and the maximum cold spots due to the markers and their position along the beam axis were quantified. In this study, four small commercial markers with different geometries and materials (gold and carbon-coated ZrO2) were evaluated. The gold markers showed stronger perturbations than the lower density ones. However, it is important to consider that low density and low atomic number fiducial markers are not always visible on x-ray projections.

Dosimetric validation of Monte Carlo and analytical dose engines with raster-scanning 1H, 4He, 12C, and 16O ion-beams using an anthropomorphic phantom.

With high-precision radiotherapy on the rise towards mainstream healthcare, comprehensive validation procedures are essential, especially as more sophisticated technologies emerge. In preparation for the upcoming translation of novel ions, case-/disease-specific ion-beam selection and advanced multi-particle treatment modalities at the Heidelberg Ion-beam Therapy Center (HIT), we quantify the accuracy limits in particle therapy treatment planning under complex heterogeneous conditions for the four ions (1H, 4He, 12C, 16O) using a Monte Carlo Treatment Planning platform (MCTP), an independent GPU-accelerated analytical dose engine developed in-house (FRoG) and the clinical treatment planning system (Syngo RT Planning). Attaching an anthropomorphic half-head Alderson RANDO phantom to entrance window of a dosimetric verification water tank, a cubic target spread-out Bragg peak (SOBP) was optimized using the MCTP to best resolve effects of anatomic heterogeneities on dose homogeneity. Subsequent forward calculations were executed in FRoG and Syngo. Absolute and relative dosimetry was performed in the experimental beam room using 1D and 2D array ionization chamber detectors. Mean absolute percent deviation in dose (|%Δ|) between predictions and PinPoint ionization chamber measurements were within ∼2% for all investigated ions for both MCTP and FRoG. For protons and carbon ions, |%Δ| values were ∼4% for Syngo. For the four ions, 3D-γ analysis (3%/3mm criteria) of FLUKA and FRoG presented mean passing rates of 97.0(±2.4)% and 93.6(±4.2)%. FRoG demonstrated satisfactory agreement with gold standard Monte Carlo simulation and measurement, superior to the commercial system. Our pre-clinical trial landmarks the first measurements taken in anthropomorphic settings for helium, carbon and oxygen ion-beam therapy.

Development of the open-source dose calculation and optimization toolkit matRad.

PURPOSE: We report on the development of the open-source cross-platform radiation treatment planning toolkit matRad and its comparison against validated treatment planning systems. The toolkit enables three-dimensional intensity-modulated radiation therapy treatment planning for photons, scanned protons and scanned carbon ions. METHODS: matRad is entirely written in Matlab and is freely available online. It re-implements well-established algorithms employing a modular and sequential software design to model the entire treatment planning workflow. It comprises core functionalities to import DICOM data, to calculate and optimize dose as well as a graphical user interface for visualization. matRad dose calculation algorithms (for carbon ions this also includes the computation of the relative biological effect) are compared against dose calculation results originating from clinically approved treatment planning systems. RESULTS: We observe three-dimensional γ-analysis pass rates ≥ 99.67% for all three radiation modalities utilizing a distance to agreement of 2 mm and a dose difference criterion of 2%. The computational efficiency of matRad is evaluated in a treatment planning study considering three different treatment scenarios for every radiation modality. For photons, we measure total run times of 145 s-1260 s for dose calculation and fluence optimization combined considering 4-72 beam orientations and 2608-13597 beamlets. For charged particles, we measure total run times of 63 s-993 s for dose calculation and fluence optimization combined considering 9963-45574 pencil beams. Using a CT and dose grid resolution of 0.3 cm3 requires a memory consumption of 1.59 GB-9.07 GB and 0.29 GB-17.94 GB for photons and charged particles, respectively. CONCLUSION: The dosimetric accuracy, computational performance and open-source character of matRad encourages a future application of matRad for both educational and research purposes.

Optimization of Carbon Ion Treatment Plans by Integrating Tissue Specific α/ß-Values for Patients with Non-Resectable Pancreatic Cancer.

BACKGROUND: The aim of the thesis is to improve treatment plans of carbon ion irradiation by integrating the tissues' specific [Formula: see text]-values for patients with locally advanced pancreatic cancer (LAPC). MATERIAL AND METHODS: Five patients with LAPC were included in this study. By the use of the treatment planning system Syngo RT Planning (Siemens, Erlangen, Germany) treatment plans with carbon ion beams have been created. Dose calculation was based on [Formula: see text]-values for both organs at risk (OAR) and the tumor. Twenty-five treatment plans and thirty-five forward calculations were created. With reference to the anatomy five field configurations were included. Single Beam Optimization (SBO) and Intensity Modulated Particle Therapy (IMPT) were used for optimization. The plans were analyzed with respect to both dose distributions and individual anatomy. The plans were evaluated using a customized index. RESULTS: With regard to the target, a field setup with one single posterior field achieves the highest score in our index. Field setups made up of three fields achieve good results in OAR sparing. Nevertheless, the field setup with one field is superior in complex topographic conditions. But, allocating an [Formula: see text]-value of 2 Gy to the spinal cord leads to critical high maximum doses in the spinal cord. The evaluation of dose profiles showed significant dose peaks at borders of the [Formula: see text]-gradient, especially in case of a single posterior field. CONCLUSION: Optimization with specific [Formula: see text]-values allows a more accurate view on dose distribution than previously. A field setup with one single posterior field achieves good results in case of difficult topographic conditions, but leads to high maximum doses to the spinal cord. So, field setups with multiple fields seem to be more adequate in case of LAPC, being surrounded by highly radiosensitive normal tissues.

Optimization of carbon ion and proton treatment plans using the raster-scanning technique for patients with unresectable pancreatic cancer.

BACKGROUND: The aim of the thesis is to improve radiation plans of patients with locally advanced, unresectable pancreatic cancer by using carbon ion and proton beams. PATIENTS AND METHODS: Using the treatment planning system Syngo RT Planning (Siemens, Erlangen, Germany) a total of 50 treatment plans have been created for five patients with the dose schedule 15 × 3 Gy(RBE). With reference to the anatomy, five field configurations were considered to be relevant. The plans were analyzed with respect to dose distribution and individual anatomy, and compared using a customized index. RESULTS: Within the index the three-field configurations yielded the best results, though with a high variety of score points (field setup 5, carbon ion: median 74 (range 48-101)). The maximum dose in the myelon is low (e.g. case 3, carbon ion: 21.5 Gy(RBE)). A single posterior field generally spares the organs at risk, but the maximum dose in the myelon is high (e.g. case 3, carbon ion: 32.9 Gy(RBE)). Two oblique posterior fields resulted in acceptable maximum doses in the myelon (e.g. case 3, carbon ion: 26.9 Gy(RBE)). The single-field configuration and the two oblique posterior fields had a small score dispersion (carbon ion: median 66 and 58 (range 62-72 and 40-69)). In cases with topographic proximity of the organs at risk to the target volume, the single-field configuration scored as well as the three-field configurations. CONCLUSION: In summary, the three-field configurations showed the best dose distributions. A single posterior field seems to be robust and beneficial in case of difficult topographical conditions and topographical proximity of organs at risk to the target volume. A setup with two oblique posterior fields is a reasonable compromise between three-field and single-field configurations.

Experimental verification of ion range calculation in a treatment planning system using a flat-panel detector.

Heavy ion-beam therapy is a highly precise radiation therapy exploiting the characteristic interaction of ions with matter. The steep dose gradient of the Bragg curve allows the irradiation of targets with high-dose and a narrow dose penumbra around the target, in contrast to photon irradiation. This, however, makes heavy ion-beam therapy very sensitive to minor changes in the range calculation of the treatment planning system, as it has a direct influence on the outcome of the treatment. Our previous study has shown that ion radiography with an amorphous silicon flat-panel detector allows the measurement of the water equivalent thickness (WET) of an imaging object with good accuracy and high spatial resolution. In this study, the developed imaging technique is used to measure the WET distribution of a patient-like phantom, and these results are compared to the WET calculation of the treatment planning system. To do so, a measured two-dimensional map of the WET of an anthropomorphic phantom was compared to WET distributions based on x-ray computed tomography images as used in the treatment planning system. It was found that the WET maps agree well in the overall shape and two-dimensional distribution of WET values. Quantitatively, the ratio of the two-dimensional WET maps shows a mean of 1.004 with a standard deviation of 0.022. Differences were found to be concentrated at high WET gradients. This could be explained by the Bragg-peak degradation, which is measured in detail by ion radiography with the flat-panel detector, but is not taken into account in the treatment planning system. Excluding pixels exhibiting significant Bragg-peak degradation, the mean value of the ratio was found to be 1.000 with a standard deviation of 0.012. Employment of the amorphous silicon flat-panel detector for WET measurements allows us to detect uncertainties of the WET determination in the treatment planning process. This makes the investigated technique a very helpful tool to study the WET determination of critical and complex phantom cases.

Evaluation of different fiducial markers for image-guided radiotherapy and particle therapy.

Modern radiotherapy (RT) techniques are widely used in the irradiation of moving organs. A crucial step in ensuring the correct position of a target structure directly before or during treatment is daily image guidance by computed tomography (CT) or X-ray radiography (image-guided radiotherapy, IGRT). Therefore, combinations of modern irradiation devices and imaging, such as on-board imaging (OBI) with X-rays, or in-room CT such as the tomotherapy system, have been developed. Moreover, combinations of linear accelerators and in-room CT-scanners have been designed. IGRT is of special interest in hypofractionated and radiosurgical treatments where high single doses are applied in the proximity of critical organs at risk. Radiographically visible markers in or in close proximity to the target structure may help to reproduce the position during RT and could therefore be used as external surrogates for motion monitoring. Criteria sought for fiducial markers are (i) visibility in the radiologic modalities involved in radiotherapeutic treatment planning and image guidance, such as CT and kilovoltage (kV) OBI), (ii) low production of imaging artifacts, and (iii) low perturbation of the therapeutic dose to the target volume. Photon interaction with interstitial markers has been shown to be not as important as in particle therapy, where interaction of the particle beam, especially with metal markers, can have a significant impact on treatment. This applies especially with a scanned ion beam. Recently we commenced patient recruitment at our institution within the PROMETHEUS trial, which evaluates a hypofractionation regime, starting with 4 x 10 Gy (RBE), for patients with hepatocellular carcinoma. The aim of this work is, therefore, to evaluate potential implantable fiducial markers for enabling precise patient and thus organ positioning in scanned ion beams. To transfer existing knowledge of marker application from photon to particle therapy, we used a range of commercially available markers of different forms and sizes, consisting of carbon and gold materials, and evaluated them for their potential use in the clinical setup with scanned ion beams at our institution. All markers were implanted in a standardized Alderson phantom and were examined using CT scans and orthogonal kV OBI in our clinical routine protocol. Impact on beam perturbation downstream of the markers in the plateau region of a spread-out Bragg peak (SOBP) was estimated by using radiographic films for clinical proton and carbon ion beams of high and low energies. All tested markers achieved good visibility in CT and kV OBI. Disturbances due to artifacts and dose perturbation were highest in the arbitrarily folded gold and the thickest gold marker, but especially low in the carbon marker. Dose perturbation was highest in the arbitrarily folded gold marker. In summary, the analyzed markers offer promising potential for identifying target structures in our treatment setup at HIT and will soon be used in clinical routine. However, a careful choice of marker, depending on the tumor localization and irradiation strategy, will need to be made.

Dosimetry auditing procedure with alanine dosimeters for light ion beam therapy.

BACKGROUND AND PURPOSE: In the next few years the number of facilities providing ion beam therapy with scanning beams will increase. An auditing process based on an end-to-end test (including CT imaging, planning and dose delivery) could help new ion therapy centres to validate their entire logistic chain of radiation delivery. An end-to-end procedure was designed and tested in both scanned proton and carbon ion beams, which may also serve as a dosimetric credentialing procedure for clinical trials in the future. The developed procedure is focused only on physical dose delivery and the validation of the biological dose is out of scope of the current work. MATERIALS AND METHODS: The audit procedure was based on a homogeneous phantom that mimics the dimension of a head (20 × 20 × 21 cm(3)). The phantom can be loaded either with an ionisation chamber or 20 alanine dosimeters plus 2 radiochromic EBT films. Dose verification aimed at measuring a dose of 10Gy homogeneously delivered to a virtual-target volume of 8 × 8 × 12 cm(3). In order to interpret the readout of the irradiated alanine dosimeters additional Monte Carlo simulations were performed to calculate the energy dependent detector response of the particle fluence in the alanine detector. A pilot run was performed with protons and carbon ions at the Heidelberg Ion Therapy facility (HIT). RESULTS: The mean difference of the absolute physical dose measured with the alanine dosimeters compared with the expected dose from the treatment planning system was -2.4 ± 0.9% (1σ) for protons and -2.2 ± 1.1% (1σ) for carbon ions. The measurements performed with the ionisation chamber indicate this slight underdosage with a dose difference of -1.7% for protons and -1.0% for carbon ions. The profiles measured by radiochromic films showed an acceptable homogeneity of about 3%. CONCLUSIONS: Alanine dosimeters are suitable detectors for dosimetry audits in ion beam therapy and the presented end-to-end test is feasible. If further studies show similar results, this dosimetric audit could be implemented as a credentialing procedure for clinical proton and carbon beam delivery.

Early treatment response of a rare papillary tumor of the pineal region after primary proton-beam therapy using the raster-scanning technique at HIT.

Pineocytomas are rare intracranial tumors occurring in the pineal gland region. The curative therapy of choice is gross total resection, which cannot be performed in all patients because of the frequent eloquent location of these tumors. Percutaneous fractionated radiotherapy is an alternative treatment approach that may result in high local control rates. Nevertheless, our knowledge of this tumor entity is limited and based on retrospective case series only. We present a patient with a papillary tumor of the pineal region who was treated with highly conformal proton-beam therapy at the Heidelberg Ion Therapy Center (HIT) using the raster-scanning technique.

First experiences in treatment of low-grade glioma grade I and II with proton therapy.

BACKGROUND: To retrospectively assess feasibility and toxicity of proton therapy in patients with low-grade glioma (WHO °I/II). PATIENTS AND METHODS: Proton beam therapy only administered in 19 patients (median age 29 years; 9 female, 10 male) for low-grade glioma between 2010 and 2011 was reviewed. In 6 cases proton therapy was performed due to tumor progression after biopsy, in 8 cases each due to tumor progression after (partial-) resection, and in 5 cases due to tumor progression after chemotherapy. Median total dose applied was 54 GyE (range, 48,6-54 GyE) in single fractions of median 1.8 GyE. Median clinical target volume was 99 cc (range, 6-463 cc) and treated using median 2 beams (range, 1-2). RESULTS: Proton therapy was finished as planned in all cases. At end of proton therapy, 13 patients showed focal alopecia, 6 patients reported mild fatigue, one patient with temporal tumor localization concentration deficits and speech errors and one more patient deficits in short-term memory. Four patients did not report any side effects. During follow-up, one patient presented with pseudo-progression showing worsening of general condition and brain edema 1-2 months after last irradiation and restitution after 6 months. In the present MR imaging (median follow-up 5 months; range 0-22 months) 12 patients had stable disease, 2 (1) patients partial (complete) remission, one more patient pseudo-progression (differential diagnosis: tumor progression) 4 weeks after irradiation without having had further follow-up imaging so far, and one patient tumor progression approximately 9 months after irradiation. CONCLUSION: Regarding early side effects, mild alopecia was the predominant finding. The rate of alopecia seems to be due to large treatment volumes as well as the anatomical locations of the target volumes and might be avoided by using multiple beams and the gantry in the future. Further evaluations including neuropsychological testing are in preparation.

Treatment of pediatric patients and young adults with particle therapy at the Heidelberg Ion Therapy Center (HIT): establishment of workflow and initial clinical data.

BACKGROUND: To report on establishment of workflow and clinical results of particle therapy at the Heidelberg Ion Therapy Center. MATERIALS AND METHODS: We treated 36 pediatric patients (aged 21 or younger) with particle therapy at HIT. Median age was 12 years (range 2-21 years), five patients (14%) were younger than 5 years of age. Indications included pilocytic astrocytoma, parameningeal and orbital rhabdomyosarcoma, skull base and cervical chordoma, osteosarcoma and adenoid-cystic carcinoma (ACC), as well as one patient with an angiofibroma of the nasopharynx. For the treatment of small children, an anesthesia unit at HIT was established in cooperation with the Department of Anesthesiology. RESULTS: Treatment concepts depended on tumor type, staging, age of the patient, as well as availability of specific study protocols. In all patients, particle radiotherapy was well tolerated and no interruptions due to toxicity had to be undertaken. During follow-up, only mild toxicites were observed. Only one patient died of tumor progression: Carbon ion radiotherapy was performed as an individual treatment approach in a child with a skull base recurrence of the previously irradiated rhabdomyosarcoma. Besides this patient, tumor recurrence was observed in two additional patients. CONCLUSION: Clinical protocols have been generated to evaluate the real potential of particle therapy, also with respect to carbon ions in distinct pediatric patient populations. The strong cooperation between the pediatric department and the department of radiation oncology enable an interdisciplinary treatment and stream-lined workflow and acceptance of the treatment for the patients and their parents.

Comparison of intensity modulated radiotherapy (IMRT) with intensity modulated particle therapy (IMPT) using fixed beams or an ion gantry for the treatment of patients with skull base meningiomas.

BACKGROUND: To examine the potential improvement in treatment planning for patients with skull base meningioma using IMRT compared to carbon ion or proton beams with and without a gantry. METHODS: Five patients originally treated with photon IMRT were selected for the study. Ion beams were chosen using a horizontal beam or an ion gantry. Intensity controlled raster scanning and the intensity modulated particle therapy mode were used for plan optimization. The evaluation included analysis of dose-volume histograms of the target volumes and organs at risk. RESULTS: In comparison with carbon and proton beams only with horizontal beams, carbon ion treatment plans could spare the OARs more and concentrated on the target volumes more than proton and photon IMRT treatment plans. Using only a horizontal fixed beam, satisfactory plans could be achieved for skull base tumors. CONCLUSION: The results of the case studies showed that using IMPT has the potential to overcome the lack of a gantry for skull base tumors. Carbon ion plans offered slightly better dose distributions than proton plans, but the differences were not clinically significant with established dose prescription concepts.

Raster-scanned carbon ion therapy for malignant salivary gland tumors: acute toxicity and initial treatment response.

BACKGROUND AND PURPOSE: To investigate toxicity and efficacy in high-risk malignant salivary gland tumors (MSGT) of the head and neck. Local control in R2-resected adenoid cystic carcinoma was already improved with a combination of IMRT and carbon ion boost at only mild side-effects, hence this treatment was also offered to patients with MSGT and microscopic residual disease (R1) or perineural spread (Pn+). METHODS: From November 2009, all patients with MSGT treated with carbon ion therapy were evaluated. Acute side effects were scored according to CTCAE v.4.03. Tumor response was assessed according to RECIST where applicable. RESULTS: 103 patients were treated from 11/2009 to 03/2011, median follow-up is 6 months. 60 pts received treatment following R2 resections or as definitive radiation, 43 patients received adjuvant radiation for R1 and/or Pn+. 16 patients received carbon ion treatment for re-irradiation. Median total dose was 73.2 GyE (23.9 GyE carbon ions + 49,9 Gy IMRT) for primary treatment and 44.9 GyE carbon ions for re-irradiation. All treatments were completed as planned and generally well tolerated with no > CTC°III toxicity. Rates of CTC°III toxicity (mucositis and dysphagia) were 8.7% with side-effects almost completely resolved at first follow-up.47 patients showed good treatment responses (CR/PR) according to RECIST. CONCLUSION: Acute toxicity remains low in IMRT with carbon ion boost also in R1-resected patients and patients undergoing re-irradiation. R2-resected patients showed high rates of treatment response, though follow-up is too short to assess long-term disease control.

Re-irradiation with scanned charged particle beams in recurrent tumours of the head and neck: acute toxicity and feasibility.

BACKGROUND: Treatment of surgically unresectable recurrence in the head and neck region remains a therapeutic problem with the only curative option being a second course of radiation with a tumouricidal dose. We report initial toxicity and efficacy of charged particle therapy in this situation. METHODS: Treatment-related side-effects of patients treated with charged particle beams for recurrent tumours of the head and neck were prospectively collected and patient data was retrospectively analysed with regard to toxicity and efficacy of the treatment according to CTCAE v. 4.03 and RECIST. RESULTS: Treatment was tolerated well without any severe acute toxicity. In non-chordoma/chondrosarcoma patients, overall response rate was 53.3% at 8 weeks post RT. 4/5 chordoma/chondrosarcoma patients showed no signs of further tumour progression. CONCLUSION: Initial experience of re-irradiation with scanned particle beams in recurrent tumours of the head and neck seems feasible and encouraging. Further follow-up is needed to investigate potential late effects.

Carbon ion therapy for advanced sinonasal malignancies: feasibility and acute toxicity.

PURPOSE: To evaluate feasibility and toxicity of carbon ion therapy for treatment of sinonasal malignancies. First site of treatment failure in malignant tumours of the paranasal sinuses and nasal cavity is mostly in-field, local control hence calls for dose escalation which has so far been hampered by accompanying acute and late toxicity. Raster-scanned carbon ion therapy offers the advantage of sharp dose gradients promising increased dose application without increase of side-effects. METHODS: Twenty-nine patients with various sinonasal malignancies were treated from 11/2009 to 08/2010. Accompanying toxicity was evaluated according to CTCAE v.4.0. Tumor response was assessed according to RECIST. RESULTS: Seventeen patients received treatment as definitive RT, 9 for local relapse, 2 for re-irradiation. All patients had T4 tumours (median CTV1 129.5 cc, CTV2 395.8 cc), mostly originating from the maxillary sinus. Median dose was 73 GyE mostly in mixed beam technique as IMRT plus carbon ion boost. Median follow-up was 5.1 months [range: 2.4-10.1 months]. There were 7 cases with grade 3 toxicity (mucositis, dysphagia) but no other higher grade acute reactions; 6 patients developed grade 2 conjunctivits, no case of early visual impairment. Apart from alterations of taste, all symptoms had resolved at 8 weeks post RT. Overall radiological response rate was 50% (CR and PR). CONCLUSION: Carbon ion therapy is feasible; despite high doses, acute reactions were not increased and generally resolved within 8 weeks post radiotherapy. Treatment response is encouraging though follow-up is too short to estimate control rates or evaluate potential late effects. Controlled trials are warranted.

Carbon ion therapy for ameloblastic carcinoma.

Ameloblastic carcinomas are rare odontogenic tumors. Treatment usually consists of surgical resection and sometimes adjuvant radiation. We report the case of a 71 year-old male patient undergoing carbon ion therapy for extensive local relapse of ameloblastic carcinoma. Treatment outcome was favourable with a complete remission at 6 weeks post completion of radiotherapy while RT-treatment itself was tolerated well with only mild side effects. High dose radiation hence is a potential alternative for patients unfit or unwilling to undergo extensive surgery or in cases when only a subtotal resection is planned or the resection is mutilating.