Matthias Kretschmer

[18F]fluoroethylcholine-PET/CT imaging for radiation treatment planning of recurrent and primary prostate cancer with dose escalation to PET/CT-positive lymph nodes.

BackgroundAt present there is no consensus on irradiation treatment volumes for intermediate to high-risk primary cancers or recurrent disease. Conventional imaging modalities, such as CT, MRI and transrectal ultrasound, are considered suboptimal for treatment decisions. Choline-PET/CT might be considered as the imaging modality in radiooncology to select and delineate clinical target volumes extending the prostate gland or prostate fossa. In conjunction with intensity modulated radiotherapy (IMRT) and imaged guided radiotherapy (IGRT), it might offer the opportunity of dose escalation to selected sites while avoiding unnecessary irradiation of healthy tissues.MethodsTwenty-six patients with primary (n = 7) or recurrent (n = 19) prostate cancer received Choline-PET/CT planned 3D conformal or intensity modulated radiotherapy. The median age of the patients was 65 yrs (range 45 to 78 yrs). PET/CT-scans with F18-fluoroethylcholine (FEC) were performed on a combined PET/CT-scanner equipped for radiation therapy planning.The majority of patients had intermediate to high risk prostate cancer. All patients received 3D conformal or intensity modulated and imaged guided radiotherapy with megavoltage cone beam CT. The median dose to primary tumours was 75.6 Gy and to FEC-positive recurrent lymph nodal sites 66,6 Gy. The median follow-up time was 28.8 months.ResultsThe mean SUVmax in primary cancer was 5,97 in the prostate gland and 3,2 in pelvic lymph nodes. Patients with recurrent cancer had a mean SUVmax of 4,38. Two patients had negative PET/CT scans. At 28 months the overall survival rate is 94%. Biochemical relapse free survival is 83% for primary cancer and 49% for recurrent tumours. Distant disease free survival is 100% and 75% for primary and recurrent cancer, respectively. Acute normal tissue toxicity was mild in 85% and moderate (grade 2) in 15%. No or mild late side effects were observed in the majority of patients (84%). One patient had a severe bladder shrinkage (grade 4) after a previous treatment with TUR of the prostate and seed implantation.ConclusionsFEC-PET/CT planning could be helpful in dose escalation to lymph nodal sites of prostate cancer.

Rotational IMRT techniques compared to fixed gantry IMRT and tomotherapy: multi-institutional planning study for head-and-neck cases.

BackgroundRecent developments enable to deliver rotational IMRT with standard C-arm gantry based linear accelerators. This upcoming treatment technique was benchmarked in a multi-center treatment planning study against static gantry IMRT and rotational IMRT based on a ring gantry for a complex parotid gland sparing head-and-neck technique.MethodsTreatment plans were created for 10 patients with head-and-neck tumours (oropharynx, hypopharynx, larynx) using the following treatment planning systems (TPS) for rotational IMRT: Monaco (ELEKTA VMAT solution), Eclipse (Varian RapidArc solution) and HiArt for the helical tomotherapy (Tomotherapy). Planning of static gantry IMRT was performed with KonRad, Pinnacle and Panther DAO based on step&shoot IMRT delivery and Eclipse for sliding window IMRT. The prescribed doses for the high dose PTVs were 65.1Gy or 60.9Gy and for the low dose PTVs 55.8Gy or 52.5Gy dependend on resection status. Plan evaluation was based on target coverage, conformity and homogeneity, DVHs of OARs and the volume of normal tissue receiving more than 5Gy (V5Gy). Additionally, the cumulative monitor units (MUs) and treatment times of the different technologies were compared. All evaluation parameters were averaged over all 10 patients for each technique and planning modality.ResultsDepending on IMRT technique and TPS, the mean CI values of all patients ranged from 1.17 to 2.82; and mean HI values varied from 0.05 to 0.10. The mean values of the median doses of the spared parotid were 26.5Gy for RapidArc and 23Gy for VMAT, 14.1Gy for Tomo. For fixed gantry techniques 21Gy was achieved for step&shoot+KonRad, 17.0Gy for step&shoot+Panther DAO, 23.3Gy for step&shoot+Pinnacle and 18.6Gy for sliding window.V5Gy values were lowest for the sliding window IMRT technique (3499 ccm) and largest for RapidArc (5480 ccm). The lowest mean MU value of 408 was achieved by Panther DAO, compared to 1140 for sliding window IMRT.ConclusionsAll IMRT delivery technologies with their associated TPS provide plans with satisfying target coverage while at the same time respecting the defined OAR criteria. Sliding window IMRT, RapidArc and Tomo techniques resulted in better target dose homogeneity compared to VMAT and step&shoot IMRT. Rotational IMRT based on C-arm linacs and Tomotherapy seem to be advantageous with respect to OAR sparing and treatment delivery efficiency, at the cost of higher dose delivered to normal tissues. The overall treatment plan quality using Tomo seems to be better than the other TPS technology combinations.

Reirradiation of recurrent breast cancer with and without concurrent chemotherapy

BackgroundTreatment options for loco-regional recurrent breast cancer after previous irradiation are limited. The efficacy of chemotherapy might be hampered because of impaired tissue perfusion in preirradiated tissue. Thus, mastectomy or local excision and reconstructive surgery are the preferred treatments. However, in recent years evidence accumulates that a second breast conserving approach with reirradiation as part of the treatment might be feasible and safe and, furthermore, reirradiation might be an option for palliation. Here we report on the experience of a single community centre in reirradiation of recurrent breast cancer.MethodsThe report is based on 29 patients treated with reirradiation. All data were prospectively collected. The median age was 63 years (range 35 to 82 yrs). The interval between initial diagnosis and diagnosis before start of reirradiation was 11.6 months to 295.5 months. The mean total dose (initial dose and reirradiation dose) was 106.2 Gy (range 80.4 to 126 Gy) and the mean BED3 Gy 168,5 Gy (range 130,6 to 201,6). The mean interval between initial radiotherapy and reirradiation was 92.9 months (range 8.7 to 290.1). Inoperable or incompletely resected patients were offered concurrent chemotherapy with either 5-FU or capecitabine. All patients received 3D-conformal radiotherapy with 1.6 to 2.5 Gy/fraction five times weekly. The treatment volume comprised all visible lesions or lesions detectable on CT/MRI/FDG-PET/CT or the tumour bed or recurrent tumour.ResultsThe local progression-free survival of all patients at one and two years was 81% and 63%. Patients who had no surgery of the recurrence (16/29) had local progression-free survival at one and two years of 72% and 25% with a median progression-free survival time of 17 months. Partial remission and good symptom relief was achieved in 56% (9/16) or complete response of symptoms and/or tumour in 44% (7/16). Patients who had no distant metastases and had at least an R1-resection had a local progression-free survival of 90% after 2 years. The disease-free survival after 2 years was 43% and the median disease-free survival time was 24 months. In four patients a second breast conserving operation was performed and the cosmetic results in all four patients are good to excellent. Acute side effects were mild to moderate with no grade 3 or 4 toxicity. Accordingly, no grade 3 or 4 late effects were observed so far. No grade 3 or 4 plexopathy was observed.ConclusionIn this heterogeneous group of patients reirradiation of locoregional recurrences of breast cancer showed low to moderate acute toxicity. In our experience, local control rates are high and palliation is good.

The impact of direct aperture optimization on plan quality and efficiency in complex head and neck IMRT

BackgroundConventional step&shoot intensity modulated radio therapy (IMRT) approaches potentially lead to treatment plans with high numbers of segments and monitor units (MU) and, therefore, could be time consuming at the linear accelerator. Direct optimization methods are able to reduce the complexity without degrading the quality of the plan. The aim of this study is the evaluation of different IMRT approaches at standardized conditions for head and neck tumors.MethodFor 27 patients with carcinomas in the head and neck region a planning study with a 2-step-IMRT system (KonRad), a direct optimization system (Panther DAO) and a mixture of both approaches (MasterPlan DSS) was created. In order to avoid different prescription doses for boost volumes a simple standardization was realized. The dose was downscaled to 50 Gy to the planning target volume (PTV) which included the primary tumor as well as the bilateral lymphatic drainage (cervical and supraclavicular). Dose restrictions for the organs at risk (OAR) were downscaled to this prescription from high dose concepts up to 72 Gy. Those limits were defined as planning objectives while reaching definable PTV coverage with a standardized field setup. The parameters were evaluated from the corresponding dose volume histogram (DVH). Special attention was paid to the efficiency of the method, measured by means of calculated MU and required segments. Statistical tests of significance were applied to quantify the differences between the evaluated systems.ResultsPTV coverage for all systems in terms of V90% and V95% fell short of the requested 100% and 95%, respectively, but were still acceptable (range: 98.7% to 99.1% and 94.2% to 94.7%). Overall for OAR sparing and the burden of healthy tissue with low doses no technique was superior for all evaluated parameters. Differences were found for the number of segments where the direct optimization systems generated less segments. Lowest average numbers of MU were 308 by Panther DAO calculated for 2 Gy fractions. Based on these findings the treatment time at the linear accelerator is the lowest for Panther DAO.ConclusionsAll IMRT approaches implemented in the different treatment planning systems (TPS) generated clinically acceptable and comparable plans. No superior system in terms of PTV coverage and OAR sparing was found. Major differences in efficiency of the method in terms of calculated MU and treatment times were found.

The impact of flattening-filter-free beam technology on 3D conformal RT

BackgroundThe removal of the flattening filter (FF) leads to non-uniform fluence distribution with a considerable increase in dose rate. It is possible to adapt FFF beams (flattening-filter-free) in 3D conformal radiation therapy (3D CRT) by using field in field techniques (FiF). The aim of this retrospective study is to clarify whether the quality of 3D CRT plans is influenced by the use of FFF beams.MethodThis study includes a total of 52 CT studies of RT locations that occur frequently in clinical practice. Dose volume targets were provided for the PTV of breast (n=13), neurocranium (n=11), lung (n=7), bone metastasis (n=10) and prostate (n=11) in line with ICRU report 50/62. 3D CRT planning was carried out using FiF methods. Two clinically utilized photon energies are used for a Siemens ARTISTE linear accelerator in FFF mode at 7MVFFF and 11MVFFF as well as in FF mode at 6MVFF and 10MVFF. The plan quality in relation to the PTV coverage, OAR (organs at risk) and low dose burden as well as the 2D dosimetric verification is compared with FF plans.ResultsNo significant differences were found between FFF and FF plans in the mean dose for the PTV of breast, lung, spine metastasis and prostate. The low dose parameters V5Gy and V10Gy display significant differences for FFF and FF plans in some subgroups. The DVH analysis of the OAR revealed some significant differences. Significantly more fields (1.9 – 4.5) were necessary in the use of FFF beams for each location (p<0.0001) in order to achieve PTV coverage. All the tested groups displayed significant increases (1.3 – 2.2 times) in the average number of necessary MU with the use of FFF beams (p<0.001).ConclusionsThis study has shown that the exclusive use of a linear accelerator in FFF mode is feasible in 3D CRT. It was possible to realize RT plans in comparable quality in typical cases of clinical radiotherapy. The 2D dosimetric validation of the modulated fields verified the dose calculation and thus the correct reproduction of the characteristic FFF parameters in the planning system that was used.

Time for standardization of SBRT planning through large scale clinical data and guideline-based approaches

Christos Moustakis1,2 · Oliver Blanck3,4 · Fatemeh Ebrahimi1,5 · Mark ka heng Chan3 · Iris Ernst2 · Thomas Krieger6 · Marciana-Nona Duma7 · Markus Oechsner7 · Ute Ganswindt8 · Christian Heinz8 · Horst Alheit9 · Hilbert Blank9 · Ursula Nestle10 · Rolf Wiehle10 · Christine Kornhuber11 · Christian Ostheimer11 · Cordula Petersen12 · Gerhard Pollul13 · Wolfgang Baus14 · Georg Altenstein14 · Eric Beckers15 · Katrin Jurianz15 · Florian Sterzing16 · Matthias Kretschmer17 · Heinrich Seegenschmiedt18 · Torsten Maass18 · Stefan Droege19 · Ulrich Wolf20 · Juergen Schoeffler21 · Uwe Haverkamp1,2 · Hans Eich1,2 · Matthias Guckenberger22

Erratum to: Incidental dose to coronary arteries is higher in prone than in supine whole breast irradiation

Florian Würschmidt1, Solveigh Stoltenberg2, Matthias Kretschmer1 and Cordula Petersen3 1Department of Radiotherapy and Radiooncology, Radiologische Allianz, Hamburg, Germany 2Department of Radiation Oncology, Klinikum rechts der Isar, TU München, Munich, Germany 3Center for Oncology, Department of Radiotherapy and Radio-Oncology, UKE, Hamburg, Germany We apologize for any inconvenience caused.