Buelent Polat

Radiotherapy in adrenocortical carcinoma

Adrenocortical carcinoma (ACC) is a rare malignancy, and patients with ACC have a poor prognosis. Even after radical surgery, up to 85% of patients develop recurrent disease. Systemic treatment options still have limited efficacy. Because the role of radiotherapy is not defined well and because ACC often is considered radioresistant, the authors reviewed the available data on radiotherapy for ACC. Original articles and reviews were identified using a PubMed search strategy that included the period up to July 2008. Ten articles were identified that covered radiotherapy in a total of 129 patients with ACC (64 patients received postoperative irradiation, and 65 patients received palliative therapy for advanced disease). In addition, 26 patients were identified in the German ACC Registry who received palliative radiotherapy. Furthermore, patterns of failure after adjuvant radiotherapy were investigated, and the authors provided recommendations for patient selection, treatment planning, and treatment protocols. In an adjuvant setting, postoperative radiotherapy was able to prevent local recurrence in the majority of patients. In those with advanced disease, a response to radiotherapy was observed in 57% of patients who received palliative radiotherapy. Therefore, the authors concluded that radiotherapy may play an important role in the care of patients with ACC. Until better evidence is available, the authors recommended the following approach: Adjuvant radiotherapy to the tumor bed should be considered in patients at high risk for local recurrence (eg, incomplete/R1 resection); a total dose of >40 grays (Gy) with single fractions of 1.8 Gy to 2 Gy should be administered (including a boost volume to reach from 50 Gy to 60 Gy in individual patients); and radiotherapy in a palliative setting may be used for symptomatic metastases to bone, brain, or vena cava obstruction. With state‐of‐the‐art technology, acute and long‐term toxicities mostly were mild to moderate. However, the authors concluded that prospective investigations would be required to fully define the therapeutic potential of this important treatment option. Cancer 2009.

Dose–response relationship for radiation-induced pneumonitis after pulmonary stereotactic body radiotherapy

PURPOSE To evaluate dosimetric factors predictive for radiation-induced pneumonitis (RP) after pulmonary stereotactic body radiotherapy (SBRT). MATERIALS AND METHODS A retrospective analysis was performed based on 59 consecutive patients treated with cone-beam CT-based image-guided SBRT for primary NSCLC (n=21) or pulmonary metastases (n=54). The majority of patients were treated with radiosurgery of 26 Gy to 80% (n=29) or three fractions of 12.5 Gy to 65% (n=40). To correct for different single fraction doses, local doses were converted to 2 Gy equivalent normalized total doses (NTDs) using α/β ratio of 3 Gy for RP. Dose-volume parameters and incidences of RP ≥ grade II SWOG were fitted using NTCP models. RESULTS Eleven patients developed RP grade II. With an average MLD of 10.3±5.6 Gy to the ipsilateral lung, a significant dose-response relationship was observed: the MLD was 12.5±4.3 Gy and 9.9±5.8 Gy for patients with and without development of RP, respectively. Additionally, volumes of the lung exposed to minimum doses between 2.5 and 50 Gy (V(2.5)-V(50)) were correlated with incidences of RP with a continuous decrease of the goodness of fit for higher doses. CONCLUSIONS The MLD and V(2.5)-V(50) of the ipsilateral lung were correlated with incidences of RP after pulmonary SBRT.

Intra-fractional uncertainties in image-guided intensity-modulated radiotherapy (IMRT) of prostate cancer

PurposeTo evaluate intra-fractional uncertainties during intensity-modulated radiotherapy (IMRT) of prostate cancer.Patients and MethodsDuring IMRT of 21 consecutive patients, kilovolt (kV) cone-beam computed tomography (CBCT) images were acquired prior to and immediately after treatment: a total of 252 treatment fractions with 504 CBCT studies were basis of this analysis. The prostate position in anterior-posterior (AP) direction was determined using contour matching; patient set-up based on the pelvic bony anatomy was evaluated using automatic image registration. Internal variability of the prostate position was the difference between absolute prostate and patient position errors. Intra-fractional changes of prostate position, patient position, rectal distension in AP direction and bladder volume were analyzed.ResultsWith a median treatment time of 16 min, intra-fractional drifts of the prostate were > 5 mm in 12% of all fractions and a margin of 6 mm was calculated for compensation of this uncertainty. Mobility of the prostate was independent from the bony anatomy with poor correlation between absolute prostate motion and motion of the bony anatomy (R2 = 0.24). A systematic increase of bladder filling by 41 ccm on average was observed; however, these changes did not influence the prostate position. Small variations of the prostate position occurred independently from intra-fractional changes of the rectal distension; a weak correlation between large internal prostate motion and changes of the rectal volume was observed (R2 = 0.55).ConclusionClinically significant intra-fractional changes of the prostate position were observed and margins of 6 mm were calculated for this intra-fractional uncertainty. Repeated or continuous verification of the prostate position may allow further margin reduction.ZusammenfassungZielZiel der Arbeit war die Analyse von intrafraktionellen Fehlern in der intensitätsmodulierten Strahlentherapie (IMRT) des Prostatakarzinoms.Patienten und MethodikBei 21 Patienten wurde vor und nach der IMRT-Behandlung ein Kilovolt-Cone-Beam-CT (kV CBCT) aufgenommen. Basierend auf 252 Behandlungsfraktionen und 504 CBCT-Studien wurde die Position der Prostata in anterior-posteriorer (AP) Richtung mittels manueller Konturregistrierung und die Lagerung des Patienten durch automatische Registrierung des Beckenskeletts ermittelt. Die interne Lagevariabilität der Prostata war definiert als die Differenz der Positionsfehler bezüglich Prostata und knöcherner Anatomie. Intrafraktionelle Veränderungen wurden für die Position der Prostata und des Patienten, die Füllung der Blase und die AP-Weite des Rektums bestimmt.ErgebnisseBei einer medianen Behandlungszeit von 16 min waren intrafraktionelle Veränderungen der Prostataposition in 12% der Fraktionen > 5 mm; ein Sicherheitssaum von 6 mm wurde zur Kompensation berechnet. Die Beweglichkeit der Prostata war im Wesentlichen unabhängig von dem pelvinen Knochenskelett (R2 = 0,24). Eine systematische Zunahme des Blasenvolumens um durchschnittlich 41 ccm wurde während der Behandlung gemessen; dies hatte aber keinen Einfluss auf die AP-Position der Prostata. Während kleine Bewegungen der Prostata unabhängig von Änderungen der Rektumweite waren, wurde für interne Prostatabewegungen > 5 mm eine Korrelation (R2 = 0,55) mit intrafraktionellen Änderungen der Rektumweite beobachtet.SchlussfolgerungIntrafraktionelle Änderungen der Prostataposition waren von klinisch relevantem Ausmaß und benötigen einen Sicherheitssaum von 6 mm. Die kontinuierliche oder wiederholte Verifikation der Prostataposition könnte eine weitere Verkleinerung der Sicherheitssäume ermöglichen.

Nonrigid patient setup errors in the head-and-neck region.

Purpose:To investigate the magnitude and clinical relevance of relative motion/nonrigid setup errors in the head-and-neck (H&N) region.Material and Methods:Eleven patients with tumors in the H&N region were immobilized in thermoplastic head masks. Patient positioning was verified using a kilovoltage cone-beam CT (kv CBCT) prior to 100 treatment fractions. Five different regions of interest (ROIs) were selected for automatic image registration of planning CT and verification CBCT: (1) the whole volume covering planning CT and CBCT, (2) the skull, (3) the mandible, (4) C1–C3, and (5) C4–C6. Differences were calculated describing relative motion between the ROIs.Results:The 3-D patient setup error was 3.2 mm ± 1.7 mm based on registration of the whole volume. No systematic relative motion (group mean errors < 0.5 mm and < 0.5°) between planning and treatment for any ROI was observed. Mobility was largest for the skull and the mandible relative to C4–C6 with 3-D displacements of 4.7 mm ± 2.5 mm and 4.4 mm ± 2.5 mm. Relative rotations were largest around the left-right axis (nodding) between C1–C3 and C4–C6 with maximum 11°. No time trend of relative motion was observed. Margins for compensation of relative motion ranged between 5 mm and 10 mm.Conclusion:The simplification of the patient as a rigid body was shown to result in significant errors due to relative motion in the H&N region. Margins for compensation of relative motion exceeded margins for compensation of patient positioning errors.Ziel:Untersucht wurden das Ausmaß und die klinische Relevanz nichtrigider Lagerungsfehler bei der Behandlung von Kopf-Hals-Tumoren.Material und Methodik:Elf Patienten waren für die Strahlenbehandlung von Kopf-Hals-Tumoren mittels thermoplastischer Masken immobilisiert. Bei 100 Fraktionen wurde die Patientenpositionierung mittels eines Kilovolt-Cone-Beam-CT (kv-CBCT) kontrolliert. Die automatische Registrierung von Planungs-CT und Verifikations-CBCT basierte auf fünf verschiedenen Regionen: 1. dem gesamten Volumen von Planungs-CT und Verifikations-CBCT, 2. Schädel, 3. Unterkiefer, 4. C1–C3 und 5. C4–C6. Die Unterschiede zwischen den Registrierungen beschrieben das Ausmaß der Relativbewegungen im Kopf-Hals-Bereich.Ergebnisse:Der dreidimensionale Lagerungsfehler, basierend auf Region 1 (gesamtes Volumen), betrug 3,2 mm ± 1,7 mm. Für keine der anatomischen Regionen wurde eine systematische Relativbewegung zwischen Planung und Behandlung festgestellt (< 0,5 mm und < 0,5°). Am größten war die Beweglichkeit des Schädels und des Unterkiefers relativ zur kaudalen Halswirbelsäule: 4,7 mm ± 2,5 mm und 4,4 mm ± 2,5 mm. Rotationsbewegungen waren zwischen kranialer und kaudaler Halswirbelsäule am größten: maximal 11° um die Links-rechts-Achse (Nickbewegung). Ein zeitlicher Trend der Relativbewegungen wurde nicht beobachtet. Sicherheitssäume von 5–10 mm waren zur Kompensation dieser Relativbewegungen notwendig.Schlussfolgerung:Substantielle Relativbewegungen im Kopf-Hals-Bereich widerlegen ein rigides Patientenmodell. Sicherheitssäume von 5–10 mm zur Kompensation dieser Relativbewegungen verdeutlichen die klinische Relevanz.

A multi-institution evaluation of deformable image registration algorithms for automatic organ delineation in adaptive head and neck radiotherapy

BackgroundAdaptive Radiotherapy aims to identify anatomical deviations during a radiotherapy course and modify the treatment plan to maintain treatment objectives. This requires regions of interest (ROIs) to be defined using the most recent imaging data. This study investigates the clinical utility of using deformable image registration (DIR) to automatically propagate ROIs.MethodsTarget (GTV) and organ-at-risk (OAR) ROIs were non-rigidly propagated from a planning CT scan to a per-treatment CT scan for 22 patients. Propagated ROIs were quantitatively compared with expert physician-drawn ROIs on the per-treatment scan using Dice scores and mean slicewise Hausdorff distances, and center of mass distances for GTVs. The propagated ROIs were qualitatively examined by experts and scored based on their clinical utility.ResultsGood agreement between the DIR-propagated ROIs and expert-drawn ROIs was observed based on the metrics used. 94% of all ROIs generated using DIR were scored as being clinically useful, requiring minimal or no edits. However, 27% (12/44) of the GTVs required major edits.ConclusionDIR was successfully used on 22 patients to propagate target and OAR structures for ART with good anatomical agreement for OARs. It is recommended that propagated target structures be thoroughly reviewed by the treating physician.

Modulation of Carbonic Anhydrase 9 (CA9) in Human Brain Cancer

Hypoxia is a crucial factor in tumour aggressiveness and its treatment resistance, particularly in human brain cancer. Tumour resistance against radiation- and chemo- therapy is facilitated by oxygenation reduction at tumour areas. HIF-1α regulated genes are mostly responsible for this type of resistance. Among these genes, carbonic anhydrase isoform 9 (CA9) is highly overexpressed in many types of cancer especially in high grade brain cancer like GBM. CA IX contributes to tumour environment acidification by catalyzing the carbon dioxide hydration to bicarbonate and protons, leading to the acquisition of metastasic phenotypes and chemoresistance to weakly basic anticancer drugs and therefore to inadequate application of radio-therapeutic or chemotherapeutic anti-cancer treatment strategies. Inhibition of this enzymatic activity by application of specific chemical CA9 inhibitors (sulphonamide derivative compounds) or indirect inhibitors like HIF-1α inhibitors (chetomin) or molecular inhibitors like CA9-siRNA leads to reversion of these processes, leading to the CA9 functional role inhibition during tumourigenesis. Hypoxia significantly influences the tumour microenvironment behaviour via activation of genes involved in the adaptation to the hypoxic stress. It also represents an important cancer prognosis indicator and is associated with aggressive growth, malignant progression, metastasis and poor treatment response. The main objective in malignant GBM therapy is either to eradicate the tumour or to convert it into a controlled, quiescent chronic disease. Sulfonamide derivative compounds with CA9 inhibitory characteristics represent one of the optimal treatment options beside other CA9 inhibitory agents or chemical inhibitory compounds against its main regulating transcription factor which is the hypoxia induced HIF-1α when applied against human cancers with hypoxic regions like GBM, bearing potential for an effective role in human brain tumour therapeutic strategies. Glycolytic inhibitors, when added in controlled doses under hypoxia, lead to a reduced accumulation of HIF-1α and can function as indirect hypoxia regulated genes inhibitors like CA9. These may be used as alternative or in conjunction with other direct inhibitors like the sulphonamide derivate compounds, chetomin or specific siRNAs, or other different chemical compounds possessing similar functionality making them as optimal tools for optimized therapy development in cancer treatment, especially against human brain cancer. Further experimental analysis towards the tumour stage specific inhibitory CA9 characteristics determination are necessary to find the optimal therapeutic solutions among the different available modalities; whether they are direct or indirect chemical, molecular or natural inhibitors to be able to set up successful treatment approaches against the different human tumour diseases.

Absence of GAPDH regulation in tumor-cells of different origin under hypoxic conditions in - vitro.

BackgroundGene expression studies related to cancer diagnosis and treatment are important. In order to conduct such experiment accurately, absolutely reliable housekeeping genes are essential to normalize cancer related gene expression. The most important characteristics of such genes are their presence in all cells and their expression levels remain relatively constant under different experimental conditions. However, no single gene of this group of genes manifests always stable expression levels under all experimental conditions. Incorrect choice of housekeeping genes leads to interpretation errors of experimental results including evaluation and quantification of pathological gene expression. Here, we examined (a) the degree of GAPDH expression regulation in Hep-1-6 mouse hepatoma and Hep-3-B and HepG2 human hepatocellular carcinoma cell lines as well as in human lung adenocarcinoma epithelial cell line (A-549) in addition to both HT-29, and HCT-116 colon cancer cell lines, under hypoxic conditions in vitro in comparison to other housekeeping genes like β-actin, serving as experimental loading controls, (b) the potential use of GAPDH as a target for tumor therapeutic approaches was comparatively examined in vitro on both protein and mRNA level, by western blot and semi quantitative RT-PCR, respectively.FindingsNo hypoxia-induced regulatory effect on GAPDH expression was observed in the cell lines studied in vitro that were; Hep-1-6 mouse hepatoma and Hep-3-B and HepG2 human hepatocellular carcinoma cell lines, Human lung adenocarcinoma epithelial cell line (A-549), both colon cancer cell lines HT-29, and HCT-116.ConclusionAs it is the case for human hepatocellular carcinoma, mouse hepatoma, human colon cancer, and human lung adenocarcinoma, GAPDH represents an optimal choice of a housekeeping gene and/(or) loading control to determine the expression of hypoxia induced genes in tumors of different origin. The results confirm our previous findings in human glioblastoma that this gene is not an attractive target for tumor therapeutic approaches because of the lack of GAPDH regulation under hypoxia.

Egr-1 is not upregulated in response to hypoxic and oxygenation conditions in human glioblastoma in vitro

The early growth response factor 1 (Egr-1) gene (also known as krox24, NGFI-A, TIS8 or zif268) belongs to a family of immediate early response genes. This family of proteins contains a conserved zinc finger DNA-binding domain and can bind to a GC-rich sequence in the promoter region of target genes. Egr-1 expression is rapidly and transiently activated in many different cell types during development. In adult tissues, a variety of signals, including serum, growth factors, cytokines and hormones, stimulate Egr-1 expression. In several studies, it was demonstrated that the transcription factor Egr-1 is regulated by hypoxia, and it is hypothesized that Egr-1 is responsible for the hypoxia-induced regulation of the N-Myc downregulated gene 1 (NDRG1) in human tumor cells. In the present study, Egr-1 regulation was examined in the human glioblastoma cell lines U373, U251, GaMG and U87-MG under extreme hypoxic aeration conditions (0.1% O2) for 1, 6 and 24 h, 24-h extreme hypoxia with reoxygenation for 24 and 48 h, respectively, as well as oxygenated conditions (21% O2 and 5% CO2) in vitro. Protein and mRNA levels were detected in the lysates by Western blotting and RT-PCR, respectively. Egr-1 expression under hypoxic conditions was compared with the well-known and characterized hypoxia-induced gene regulator hypoxia-inducible factor-1α (HIF-1α) in parallel experimental sets. Cells incubated for 24 h with 100 µM desferroxamine served as a positive control for hypoxia, and β-tubulin and β-actin were used as loading controls. The experimental data indicate that Egr-1 was not upregulated under extreme hypoxic conditions (0.1% O2) or by reoxygenation after hypoxia in different glioblastoma cells in vitro. In conclusion, the regulation of Egr-1 in reaction to hypoxic development, at both the protein and mRNA levels, is not a general phenomenon. In contrast to previously published data, no Egr-1 regulatory events were observed in glioblastoma under hypoxic conditions in vitro. We suggest that Egr-1 regulation in human tumors in reaction to hypoxia could be a cell-specific post-translational event. Therefore, at least in glioblastoma, HIF-1α can be considered a major regulator of NDRG1 under hypoxic conditions. Further extensive analysis of tumor cells from different origins under similar physiological conditions is necessary to increase our knowledge of the conditions and functional role of Egr-1 in the regulation of hypoxia-induced gene expression.