@article{RichterExnerBratengeieretal.2019,
  author    = {Richter, Anne and Exner, Florian and Bratengeier, Klaus and Polat, B{\"u}lent and Flentje, Michael and Weick, Stefan},
  title     = {Impact of beam configuration on VMAT plan quality for Pinnacle\(^3\)Auto-Planning for head and neck cases},
  series = {Radiation Oncology},
  volume    = {14},
  journal   = {Radiation Oncology},
  doi       = {10.1186/s13014-019-1211-6},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-200301},
  pages     = {12},
  year      = {2019},
  abstract  = {Background The purpose of this study was to compare automatically generated VMAT plans to find the superior beam configurations for Pinnacle3 Auto-Planning and share "best practices". Methods VMAT plans for 20 patients with head and neck cancer were generated using Pinnacle3 Auto-Planning Module (Pinnacle3 Version 9.10) with different beam setup parameters. VMAT plans for single (V1) or double arc (V2) and partial or full gantry rotation were optimized. Beam configurations with different collimator positions were defined. Target coverage and sparing of organs at risk were evaluated based on scoring of an evaluation parameter set. Furthermore, dosimetric evaluation was performed based on the composite objective value (COV) and a new cross comparison method was applied using the COVs. Results The evaluation showed a superior plan quality for double arcs compared to one single arc or two single arcs for all cases. Plan quality was superior if a full gantry rotation was allowed during optimization for unilateral target volumes. A double arc technique with collimator setting of 15° was superior to a double arc with collimator 60° and a two single arcs with collimator setting of 15° and 345°. Conclusion The evaluation showed that double and full arcs are superior to single and partial arcs in terms of organs at risk sparing even for unilateral target volumes. The collimator position was found as an additional setup parameter, which can further improve the target coverage and sparing of organs at risk.},
  language  = {en}
}
@article{WeickBreuerRichteretal.2020,
  author    = {Weick, Stefan and Breuer, Kathrin and Richter, Anne and Exner, Florian and Str{\"o}hle, Serge-Peer and Lutyj, Paul and Tamihardja, J{\"o}rg and Veldhoen, Simon and Flentje, Michael and Polat, B{\"u}lent},
  title     = {Non-rigid image registration of 4D-MRI data for improved delineation of moving tumors},
  series = {BMC Medical Imaging},
  volume    = {20},
  journal   = {BMC Medical Imaging},
  doi       = {10.1186/s12880-020-00439-6},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229271},
  year      = {2020},
  abstract  = {Background To increase the image quality of end-expiratory and end-inspiratory phases of retrospective respiratory self-gated 4D MRI data sets using non-rigid image registration for improved target delineation of moving tumors. Methods End-expiratory and end-inspiratory phases of volunteer and patient 4D MRI data sets are used as targets for non-rigid image registration of all other phases using two different registration schemes: In the first, all phases are registered directly (dir-Reg) while next neighbors are successively registered until the target is reached in the second (nn-Reg). Resulting data sets are quantitatively compared using diaphragm and tumor sharpness and the coefficient of variation of regions of interest in the lung, liver, and heart. Qualitative assessment of the patient data regarding noise level, tumor delineation, and overall image quality was performed by blinded reading based on a 4 point Likert scale. Results The median coefficient of variation was lower for both registration schemes compared to the target. Median dir-Reg coefficient of variation of all ROIs was 5.6\% lower for expiration and 7.0\% lower for inspiration compared with nn-Reg. Statistical significant differences between the two schemes were found in all comparisons. Median sharpness in inspiration is lower compared to expiration sharpness in all cases. Registered data sets were rated better compared to the targets in all categories. Over all categories, mean expiration scores were 2.92 +/- 0.18 for the target, 3.19 +/- 0.22 for nn-Reg and 3.56 +/- 0.14 for dir-Reg and mean inspiration scores 2.25 +/- 0.12 for the target, 2.72 +/- 215 0.04 for nn-Reg and 3.78 +/- 0.04 for dir-Reg. Conclusions In this work, end-expiratory and inspiratory phases of a 4D MRI data sets are used as targets for non-rigid image registration of all other phases. It is qualitatively and quantitatively shown that image quality of the targets can be significantly enhanced leading to improved target delineation of moving tumors.},
  language  = {en}
}
@article{PolatWohllebenKosmalaetal.2022,
  author    = {Polat, B{\"u}lent and Wohlleben, Gisela and Kosmala, Rebekka and Lisowski, Dominik and Mantel, Frederick and Lewitzki, Victor and L{\"o}hr, Mario and Blum, Robert and Herud, Petra and Flentje, Michael and Monoranu, Camelia-Maria},
  title     = {Differences in stem cell marker and osteopontin expression in primary and recurrent glioblastoma},
  series = {Cancer Cell International},
  volume    = {22},
  journal   = {Cancer Cell International},
  issn      = {1475-2867},
  doi       = {10.1186/s12935-022-02510-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301240},
  year      = {2022},
  abstract  = {Background Despite of a multimodal approach, recurrences can hardly be prevented in glioblastoma. This may be in part due to so called glioma stem cells. However, there is no established marker to identify these stem cells. Methods Paired samples from glioma patients were analyzed by immunohistochemistry for expression of the following stem cell markers: CD133, Musashi, Nanog, Nestin, octamer-binding transcription factor 4 (Oct4), and sex determining region Y-box 2 (Sox2). In addition, the expression of osteopontin (OPN) was investigated. The relative number of positively stained cells was determined. By means of Kaplan-Meier analysis, a possible association with overall survival by marker expression was investigated. Results Sixty tissue samples from 30 patients (17 male, 13 female) were available for analysis. For Nestin, Musashi and OPN a significant increase was seen. There was also an increase (not significant) for CD133 and Oct4. Patients with mutated Isocitrate Dehydrogenase-1/2 (IDH-1/2) status had a reduced expression for CD133 and Nestin in their recurrent tumors. Significant correlations were seen for CD133 and Nanog between OPN in the primary and recurrent tumor and between CD133 and Nestin in recurrent tumors. By confocal imaging we could demonstrate a co-expression of CD133 and Nestin within recurrent glioma cells. Patients with high CD133 expression had a worse prognosis (22.6 vs 41.1 months, p = 0.013). A similar trend was seen for elevated Nestin levels (24.9 vs 41.1 months, p = 0.08). Conclusions Most of the evaluated markers showed an increased expression in their recurrent tumor. CD133 and Nestin were associated with survival and are candidate markers for further clinical investigation.},
  language  = {en}
}
@article{DjuzenovaFiedlerMemmeletal.2019,
  author    = {Djuzenova, Cholpon S. and Fiedler, Vanessa and Memmel, Simon and Katzer, Astrid and Sisario, Dmitri and Brosch, Philippa K. and G{\"o}hrung, Alexander and Frister, Svenja and Zimmermann, Heiko and Flentje, Michael and Sukhorukov, Vladimir L.},
  title     = {Differential effects of the Akt inhibitor MK-2206 on migration and radiation sensitivity of glioblastoma cells},
  series = {BMC Cancer},
  volume    = {19},
  journal   = {BMC Cancer},
  doi       = {10.1186/s12885-019-5517-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-200290},
  pages     = {299},
  year      = {2019},
  abstract  = {Background Most tumor cells show aberrantly activated Akt which leads to increased cell survival and resistance to cancer radiotherapy. Therefore, targeting Akt can be a promising strategy for radiosensitization. Here, we explore the impact of the Akt inhibitor MK-2206 alone and in combination with the dual PI3K and mTOR inhibitor PI-103 on the radiation sensitivity of glioblastoma cells. In addition, we examine migration of drug-treated cells. Methods Using single-cell tracking and wound healing migration tests, colony-forming assay, Western blotting, flow cytometry and electrorotation we examined the effects of MK-2206 and PI-103 and/or irradiation on the migration, radiation sensitivity, expression of several marker proteins, DNA damage, cell cycle progression and the plasma membrane properties in two glioblastoma (DK-MG and SNB19) cell lines, previously shown to differ markedly in their migratory behavior and response to PI3K/mTOR inhibition. Results We found that MK-2206 strongly reduces the migration of DK-MG but only moderately reduces the migration of SNB19 cells. Surprisingly, MK-2206 did not cause radiosensitization, but even increased colony-forming ability after irradiation. Moreover, MK-2206 did not enhance the radiosensitizing effect of PI-103. The results appear to contradict the strong depletion of p-Akt in MK-2206-treated cells. Possible reasons for the radioresistance of MK-2206-treated cells could be unaltered or in case of SNB19 cells even increased levels of p-mTOR and p-S6, as compared to the reduced expression of these proteins in PI-103-treated samples. We also found that MK-2206 did not enhance IR-induced DNA damage, neither did it cause cell cycle distortion, nor apoptosis nor excessive autophagy. Conclusions Our study provides proof that MK-2206 can effectively inhibit the expression of Akt in two glioblastoma cell lines. However, due to an aberrant activation of mTOR in response to Akt inhibition in PTEN mutated cells, the therapeutic window needs to be carefully defined, or a combination of Akt and mTOR inhibitors should be considered.},
  language  = {en}
}
@article{ZimmermannRichterWeicketal.2022,
  author    = {Zimmermann, Marcus and Richter, Anne and Weick, Stefan and Exner, Florian and Mantel, Frederick and Diefenhardt, Markus and Fokas, Emmanouil and Kosmala, Rebekka and Flentje, Michael and Polat, B{\"u}lent},
  title     = {Acute toxicities of patients with locally advanced rectal cancer treated with intensified chemoradiotherapy within the CAO/ARO/AIO-12 trial: comparing conventional versus VMAT planning at a single center},
  series = {Scientific Reports},
  volume    = {12},
  journal   = {Scientific Reports},
  doi       = {10.1038/s41598-022-25647-8},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301255},
  year      = {2022},
  abstract  = {In locally advanced rectal cancer (LARC) neoadjuvant chemoradiotherapy is regarded as standard treatment. We assessed acute toxicities in patients receiving conventional 3D-conformal radiotherapy (3D-RT) and correlated them with dosimetric parameters after re-planning with volumetric modulated arc therapy (VMAT). Patients were randomized within the multicenter CAO/ARO/AIO-12 trial and received 50.4 Gy in 28 fractions and simultaneous chemotherapy with fluorouracil and oxaliplatin. Organs at risk (OAR) were contoured in a standardized approach. Acute toxicities and dose volume histogram parameters of 3D-RT plans were compared to retrospectively calculated VMAT plans. From 08/2015 to 01/2018, 35 patients with LARC were treated at one study center. Thirty-four patients were analyzed of whom 1 (3\%) was UICC stage II and 33 (97\%) patients were UICC stage III. Grade 3 acute toxicities occurred in 5 patients (15\%). Patients with acute grade 1 cystitis (n = 9) had significantly higher D\(_{mean}\) values for bladder (29.4 Gy vs. 25.2 Gy, p < 0.01) compared to patients without bladder toxicities. Acute diarrhea was associated with small bowel volume (grade 2: 870.1 ccm vs. grade 0-1: 647.3 ccm; p < 0.01) and with the irradiated volumes V5 to V50. Using VMAT planning, we could reduce mean doses and irradiated volumes for all OAR: D\(_{mean}\) bladder (21.9 Gy vs. 26.3 Gy, p < 0.01), small bowel volumes V5-V45 (p < 0.01), D\(_{mean}\) anal sphincter (34.6 Gy vs. 35.6 Gy, p < 0.01) and D\(_{mean}\) femoral heads (right 11.4 Gy vs. 25.9 Gy, left 12.5 Gy vs. 26.6 Gy, p < 0.01). Acute small bowel and bladder toxicities were dose and volume dependent. Dose and volume sparing for all OAR could be achieved through VMAT planning and might result in less acute toxicities.},
  language  = {en}
}
@article{TamihardjaZehnerHartrampfetal.2022,
  author    = {Tamihardja, J{\"o}rg and Zehner, Leonie and Hartrampf, Philipp and Lisowski, Dominik and Kneitz, Susanne and Cirsi, Sinan and Razinskas, Gary and Flentje, Michael and Polat, B{\"u}lent},
  title     = {Salvage nodal radiotherapy as metastasis-directed therapy for oligorecurrent prostate cancer detected by positron emission tomography shows favorable outcome in long-term follow-up},
  series = {Cancers},
  volume    = {14},
  journal   = {Cancers},
  number    = {15},
  issn      = {2072-6694},
  doi       = {10.3390/cancers14153766},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-286064},
  year      = {2022},
  abstract  = {Simple Summary Patients, who suffer from oligorecurrent prostate cancer with limited nodal involvement, may be offered positron emission tomography (PET)-directed salvage nodal radiotherapy to delay disease progression. This current analysis aimed to access salvage radiotherapy for nodal oligorecurrent prostate cancer with simultaneous integrated boost to PET-involved lymph nodes as metastasis-directed therapy. A long-term oncological outcome was favorable after salvage nodal radiotherapy and severe toxicity rates were low. Androgen deprivation therapy plays a major role in recurrent prostate cancer management and demonstrates a positive influence on the rate of biochemical progression in patients receiving salvage nodal radiotherapy. The present long-term analysis may help clinicians identify patients who would benefit from salvage nodal radiotherapy and androgen deprivation therapy, as a multimodal treatment strategy for oligorecurrent prostate cancer. Abstract Background: The study aimed to access the long-term outcome of salvage nodal radiotherapy (SNRT) in oligorecurrent prostate cancer. Methods: A total of 95 consecutive patients received SNRT for pelvic and/or extrapelvic nodal recurrence after prostate-specific membrane antigen (PSMA) or choline PET from 2010 to 2021. SNRT was applied as external beam radiotherapy with simultaneous integrated boost up to a median total dose of 62.9 Gy (EQD2\(_{1.5Gy}\)) to the recurrent lymph node metastases. The outcome was analyzed by cumulative incidence functions with death as the competing risk. Fine-Gray regression analyses were performed to estimate the relative hazards of the outcome parameters. Genitourinary (GU)/gastrointestinal (GI) toxicity evaluation utilized Common Toxicity Criteria for Adverse Events (v5.0). The results are as follows: the median follow-up was 47.1 months. The five-year biochemical progression rate (95\% CI) was 50.1\% (35.7-62.9\%). Concomitant androgen deprivation therapy (ADT) was adminstered in 60.0\% of the patients. The five-year biochemical progression rate was 75.0\% (42.0-90.9\%) without ADT versus 35.3\% (19.6-51.4\%) with ADT (p = 0.003). The cumulative five-year late grade 3 GU toxicity rate was 2.1\%. No late grade 3 GI toxicity occured. Conclusions: Metastasis-directed therapy through SNRT for PET-staged oligorecurrent prostate cancer demonstrated a favorable long-term oncologic outcome. Omittance of ADT led to an increased biochemical progression.},
  language  = {en}
}
@article{TamihardjaLawrenzLutyjetal.2022,
  author    = {Tamihardja, J{\"o}rg and Lawrenz, Ingulf and Lutyj, Paul and Weick, Stefan and Guckenberger, Matthias and Polat, B{\"u}lent and Flentje, Michael},
  title     = {Propensity score-matched analysis comparing dose-escalated intensity-modulated radiation therapy versus external beam radiation therapy plus high-dose-rate brachytherapy for localized prostate cancer},
  series = {Strahlentherapie und Onkologie},
  volume    = {198},
  journal   = {Strahlentherapie und Onkologie},
  number    = {8},
  doi       = {10.1007/s00066-022-01953-y},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-325055},
  pages     = {735-743},
  year      = {2022},
  abstract  = {Purpose Dose-escalated external beam radiation therapy (EBRT) and EBRT + high-dose-rate brachytherapy (HDR-BT) boost are guideline-recommended treatment options for localized prostate cancer. The purpose of this study was to compare long-term outcome and toxicity of dose-escalated EBRT versus EBRT + HDR-BT boost. Methods From 2002 to 2019, 744 consecutive patients received either EBRT or EBRT + HDR-BT boost, of whom 516 patients were propensity score matched. Median follow-up was 95.3 months. Cone beam CT image-guided EBRT consisted of 33 fractions of intensity-modulated radiation therapy with simultaneous integrated boost up to 76.23 Gy (D\(_{Mean}\)). Combined treatment was delivered as 46 Gy (D\(_{Mean}\)) EBRT, followed by two fractions HDR-BT boost with 9 Gy (D\(_{90\\%}\)). Propensity score matching was applied before analysis of the primary endpoint, estimated 10-year biochemical relapse-free survival (bRFS), and the secondary endpoints metastasis-free survival (MFS) and overall survival (OS). Prognostic parameters were analyzed by Cox proportional hazard modelling. Genitourinary (GU)/gastrointestinal (GI) toxicity evaluation used the Common Toxicity Criteria for Adverse Events (v5.0). Results The estimated 10-year bRFS was 82.0\% vs. 76.4\% (p = 0.075) for EBRT alone versus combined treatment, respectively. The estimated 10-year MFS was 82.9\% vs. 87.0\% (p = 0.195) and the 10-year OS was 65.7\% vs. 68.9\% (p = 0.303), respectively. Cumulative 5‑year late GU ≥ grade 2 toxicities were seen in 23.6\% vs. 19.2\% (p = 0.086) and 5‑year late GI ≥ grade 2 toxicities in 11.1\% vs. 5.0\% of the patients (p = 0.002); cumulative 5‑year late grade 3 GU toxicity occurred in 4.2\% vs. 3.6\% (p = 0.401) and GI toxicity in 1.0\% vs. 0.3\% (p = 0.249), respectively. Conclusion Both treatment groups showed excellent long-term outcomes with low rates of severe toxicity.},
  language  = {en}
}
@article{GrabenbauerFlentje2022,
  author    = {Grabenbauer, Felix and Flentje, Michael},
  title     = {Salvage-Bestrahlung der Prostataloge: Mitbestrahlung der regionalen LK und Bedeutung der ADT},
  series = {Strahlentherapie und Onkologie},
  volume    = {198},
  journal   = {Strahlentherapie und Onkologie},
  number    = {12},
  doi       = {10.1007/s00066-022-02001-5},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-325047},
  pages     = {1119-1121},
  year      = {2022},
  abstract  = {No abstract available.},
  language  = {de}
}
@article{LisowskiLutyjAbazarietal.2023,
  author    = {Lisowski, Dominik and Lutyj, Paul and Abazari, Arya and Weick, Stefan and Traub, Jan and Polat, B{\"u}lent and Flentje, Michael and Kraft, Johannes},
  title     = {Impact of Radiotherapy on Malfunctions and Battery Life of Cardiac Implantable Electronic Devices in Cancer Patients},
  series = {Cancers},
  volume    = {15},
  journal   = {Cancers},
  number    = {19},
  issn      = {2072-6694},
  doi       = {10.3390/cancers15194830},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-358008},
  year      = {2023},
  abstract  = {Purpose: This study analyses a large number of cancer patients with CIEDs for device malfunction and premature battery depletion by device interrogation after each radiotherapy fraction and compares different guidelines in regard to patient safety. Methods: From 2007 to 2022, a cohort of 255 patients was analyzed for CIED malfunctions via immediate device interrogation after every RT fraction. Results: Out of 324 series of radiotherapy treatments, with a total number of 5742 CIED interrogations, nine device malfunctions (2.8\%) occurred. Switching into back-up/safety mode and software errors occurred four times each. Once, automatic read-out could not be performed. The median prescribed cumulative dose at planning target volume (PTV) associated with CIED malfunction was 45.0 Gy (IQR 36.0-64.0 Gy), with a median dose per fraction of 2.31 Gy (IQR 2.0-3.0 Gy). The median maximum dose at the CIED at time of malfunction was 0.3 Gy (IQR 0.0-1.3 Gy). No correlation between CIED malfunction and maximum photon energy (p = 0.07), maximum dose at the CIED (p = 0.59) nor treatment localization (p = 0.41) could be detected. After excluding the nine malfunctions, premature battery depletion was only observed three times (1.2\%). Depending on the national guidelines, 1-9 CIED malfunctions in this study would have been detected on the day of occurrence and in none of the cases would patient safety have been compromised. Conclusion: Radiation-induced malfunctions of CIEDs and premature battery depletion are rare. If recommendations of national safety guidelines are followed, only a portion of the malfunctions would be detected directly after occurrence. Nevertheless, patient safety would not be compromised.},
  language  = {en}
}
@article{PinkawaAebersoldBoehmeretal.2021,
  author    = {Pinkawa, Michael and Aebersold, Daniel M. and B{\"o}hmer, Dirk and Flentje, Michael and Ghadjar, Pirus and Schmidt-Hegemann, Nina-Sophie and H{\"o}cht, Stefan and H{\"o}lscher, Tobias and M{\"u}ller, Arndt-Christian and Niehoff, Peter and Sedlmayer, Felix and Wolf, Frank and Zamboglou, Constantinos and Zips, Daniel and Wiegel, Thomas},
  title     = {Radiotherapy in nodal oligorecurrent prostate cancer},
  series = {Strahlentherapie und Onkologie},
  volume    = {197},
  journal   = {Strahlentherapie und Onkologie},
  number    = {7},
  issn      = {0179-7158},
  doi       = {10.1007/s00066-021-01778-1},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-307763},
  pages     = {575-580},
  year      = {2021},
  abstract  = {Objective The current article encompasses a literature review and recommendations for radiotherapy in nodal oligorecurrent prostate cancer. Materials and methods A literature review focused on studies comparing metastasis-directed stereotactic ablative radiotherapy (SABR) vs. external elective nodal radiotherapy (ENRT) and studies analyzing recurrence patterns after local nodal treatment was performed. The DEGRO Prostate Cancer Expert Panel discussed the results and developed treatment recommendations. Results Metastasis-directed radiotherapy results in high local control (often > 90\% within a follow-up of 1-2 years) and can be used to improve progression-free survival or defer androgen deprivation therapy (ADT) according to prospective randomized phase II data. Distant progression after involved-node SABR only occurs within a few months in the majority of patients. ENRT improves metastases-free survival rates with increased toxicity in comparison to SABR according to retrospective comparative studies. The majority of nodal recurrences after initial local treatment of pelvic nodal metastasis are detected within the true pelvis and common iliac vessels. Conclusion ENRT with or without a boost should be preferred to SABR in pelvic nodal recurrences. In oligometastatic prostate cancer with distant (extrapelvic) nodal recurrences, SABR alone can be performed in selected cases. Application of additional systemic treatments should be based on current guidelines, with ADT as first-line treatment for hormone-sensitive prostate cancer. Only in carefully selected patients can radiotherapy be initially used without additional ADT outside of the current standard recommendations. Results of (randomized) prospective studies are needed for definitive recommendations.},
  language  = {en}
}