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  • 1.
    dos Santos Matias, Lucílio
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Eduardo Mondlane University, Mozambique.
    Palmqvist, Tomas
    Wolke, Jeanette
    Nilsson, Josef
    Beskow, Catharina
    Maphossa, Alexandre M.
    Toma-Dasu, Iuliana
    Stockholm University, Faculty of Science, Department of Physics.
    Dosimetric and radiobiological evaluation of hybrid inverse planning and optimization for cervical cancer brachytherapy2015In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 35, no 11, p. 6091-6096Article in journal (Refereed)
    Abstract [en]

    Aim: To compare manual graphical optimization (GrO) with hybrid inverse planning optimization (HIPO) of cervical cancer brachytherapy treatment plans using physical and radiobiological tools. Patients and Methods: Ten patients suffering from cervical cancer, treated with pulsed brachytherapy using GrO plans, were included in the study. For each patient, four different HIPO class solutions with different dose objectives to the target and constraints to the organs at risk (OAR) produced four optimized plans, that were each compared to the corresponding GrO plan. Class solution in HIPO is a set of parameters consisting of dose constraints and penalty weights, which are used for optimization. The comparison was based on the following dosimetric parameters: conformity index (COIN), minimum dose received by 98% and 90% of the high-risk clinical target volume (represented by D98 and D90, respectively), and the minimum dose imparted to 2 cm3 (D2cm3) of the most exposed OAR i.e. bladder, sigmoid colon or rectum. The HIPO class solution which produced plans with overall better dosimetric parameters was selected and its plans were compared with manual GrO plans from a radiobiological viewpoint based on the calculated complication-free tumour control probability, P+. Results: The average COIN for the GrO and the selected HIPO plans were 0.22 and 0.30, respectively. The median COIN of the GrO and the HIPO plans were not statistically different (p>0.05, Wilcoxon test). The relative percentage difference of the averaged P+ values between the HIPO and GrO plans evaluated together with the external beam radiation therapy plans was 0.01%, 0.37% and 0.98% for the bladder, sigmoid colon and rectum, respectively. The lowest P+ value for all the plans was 98.44% for sigmoid colon. Conclusion: HIPO presented comparable results in relation to manual planning with respect to dosimetric and radiobiological parameters.

  • 2. Fowler, Jack F.
    et al.
    Toma-Dasu, Iuliana
    Stockholm University, Faculty of Science, Department of Physics. Karolinska Institutet, Sweden.
    Dasu, Alexandru
    Linköping University, Sweden.
    Is the α/β ratio for prostate tumours really low and does it vary with the level of risk at diagnosis?2013In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 33, no 3, p. 1009-1011Article in journal (Refereed)
    Abstract [en]

    Aim: To answer the questions: Is the α/β ratio (radiosensitivity to size of dose-per-fraction) really low enough to justify using a few large dose fractions instead of the traditional many small doses? Does this parameter vary with prognostic risk factors? Methods and Materials: Three large statistical overviews are critiqued, with results for 5,000, 6,000 and 14,000 patients with prostate carcinoma, respectively. Results: These major analyses agree in finding the average α/β ratio to be less than 2 Gy: 1.55, (95% confidence interval=0.46-4.52), 1.4 (0.9-2.2), and the third analysis 1.7 (1.4-2.2) by ASTRO and 1.6 (1.2-2.2) by Phoenix criteria. All agree that α/β values do not vary significantly with the low, intermediate, high and “all included” risk factors. Conclusion: The high sensitivity to dose-per-fraction is an intrinsic property of prostate carcinomas and this supports the use of hypofractionation to increase the therapeutic gain for these tumours with dose-volume modelling to reduce the risk of late complications in rectum and bladder.

  • 3.
    Kjellsson Lindblom, Emely
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Dasu, Alexandru
    Toma-Dasu, Iuliana
    Stockholm University, Faculty of Science, Department of Physics. Karolinska Institute, Sweden.
    Hypoxia Induced by Vascular Damage at High Doses Could Compromise the Outcome of Radiotherapy2019In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 39, no 5, p. 2337-2340Article in journal (Refereed)
    Abstract [en]

    Background/Aim: This study investigated the impact of temporary vascular collapse on tumour control probability (TCP) in stereotactic body radiotherapy (SBRT), taking into account different radiosensitivities of chronically and acutely hypoxic cells. Materials and Methods: Three-dimensional tumours with heterogeneous oxygenation were simulated assuming different fractions of collapsed vessels at every treatment fraction. The modelled tumours contained a chronically hypoxic subvolume of 30-60% of the tumour diameter, and a hypoxic fraction ≤5 mm Hg of 30-50%. The rest of the tumours were well-oxygenated at the start of the simulated treatment. Results: For all simulated cases, the largest reduction in TCP from 97% to 2% was found in a tumour with a small chronically hypoxic core treated with 60 Gy in eight fractions and assuming a treatment-induced vascular collapse of 35% in the well-oxygenated region. Conclusion: The timing of SBRT fractions should be considered together with the tumour oxygenation to avoid loss of TCP in SBRT.

  • 4.
    Kjellsson Lindblom, Emely
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Hui, Susanta
    Brooks, Jamison
    Dasu, Alexandru
    Kujawski, Maciej
    Toma-Dasu, Iuliana
    Stockholm University, Faculty of Science, Department of Physics. Karolinska Institutet, Sweden.
    Radiation-induced vascular damage and the impact on the treatment outcome of stereotactic body radiotherapy2019In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 39, no 6, p. 2721-2727Article in journal (Refereed)
    Abstract [en]

    Background/Aim: The aim of this study was to investigate radiation-induced tumour vascular damage and its impact thereof on the outcome of stereotactic body radiotherapy (SBRT). Materials and Methods: Vessel densities in animal tumours before and after a single dose of 20 Gy were quantified and used as input for simulations of three-dimensional tumours with heterogeneous oxygenation. SBRT treatments of the modelled tumours in 1-8 fractions were simulated. The impact of vessel collapse on the outcome of SBRT was investigated by calculating tumour control probability (TCP) and the dose required to obtain a TCP of 50% (D50). Results: A radiation-induced increase of acute hypoxia in tumours during SBRT treatment could be simulated based on the experimental data. The D50 values for these tumours were higher than for the simulated tumours without vessel collapse. Conclusion: The vascular changes after high doses of radiation could compromise the outcome of SBRT by increasing tumour hypoxia.

  • 5.
    Lazzeroni, Marta
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Khazraei Manesh, Zohreh
    Sandström, Helena
    Stockholm University, Faculty of Science, Department of Physics.
    Barsoum, Pierre
    Toma-Dasu, Iuliana
    Stockholm University, Faculty of Science, Department of Physics.
    Impact of tumour cell infiltration on treatment outcome in Gamma Knife radiosurgery: a modelling study2019In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 39, no 4, p. 1675-1687Article in journal (Refereed)
    Abstract [en]

    Background: High-grade gliomas with a widespread infiltration beyond the lesion detectable on diagnostic images are increasingly treated with Gamma Knife™ Radiosurgery (GKRS). The aim of this study was to assess the cell infiltration impact on the GKRS outcome for invasive gliomas. Materials and Methods: Tumor cell distribution was predicted using a novel algorithm whose computations are iterated until they reach an agreement with histopathology results. Treatment plans with different combinations of dose prescription (20 Gy at 50%-20% isodose) and targets [Gross Tumour Volume (GTV), zone 1 with 100%-60% of the GTV cell density and zone 2 with 60%-0% of the GTV cell density] were evaluated using standard conformity indexes (CI) and radiobiological parameters. Results: Considerable differences in terms of tumor control probability were found between plans having similar CI but different targets. Conclusion: To account for tumor cell infiltration outside the target is of key importance in GKRS and a radiobiological evaluation should accompany well-established CI.

  • 6. Mohanty, Chitralekha
    et al.
    Zielinska-Chomej, Katarzyna
    Edgren, Margareta
    Hirayama, Ryoichi
    Murakami, Takeshi
    Lind, Bengt
    Toma-Dasu, Iuliana
    Stockholm University, Faculty of Science, Department of Physics. Karolinska Institutet, Sweden.
    Predicting the sensitivity to ion therapy based on the response to photon irradiation - experimental evidence and mathematical modelling2014In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 34, no 6, p. 2801-2806Article in journal (Refereed)
    Abstract [en]

    Background/Aim: The use of ion radiation therapy is growing due to the continuously increasing positive clinical experience obtained. Therefore, there is a high interest in radio-biological experiments comparing the relative efficiency in cell killing of ions and photons as the photons are currently the main radiation modality used for cancer treatment. This comparison is particularly important since the treatment planning systems (TPSs) used at the main ion therapy centres make use of parameters describing the cellular response to photons, respectively ions, determined in vitro. It was therefore the aim of this paper to compare the effects of high LET ion radiation with low LET photons and determine whether the cellular response to low LET could predict the response to high LET irradiation. Materials and Methods: Clonogenic cell survival data of five tumor cell lines irradiated with different ion beams of similar, clinically-relevant, LET were studied in relation to the response to low LET photons. Two mathematical models were used to fit the data, the repairable-conditionally repairable damage (RCR) model and the linear quadratic (LQ) model. Results: The results indicate that the relative biological efficiency of the high LET radiation assessed with the RCR model could be predicted based only on the response to the low LET irradiation. Conclusion: The particular features of the RCR model indicate thus that tumor cells showing a large capacity for repairing the damage will have the larger benefit from radiation therapy with ions beams.

  • 7.
    Mondlane, Gracinda
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Eduardo Mondlane University, Mozambique .
    Ureba, Ana
    Stockholm University, Faculty of Science, Department of Physics.
    Gubanski, Michael
    Lind, Pehr A.
    Siegbahn, Albert
    Estimation of Risk of Normal-tissue Toxicity Following Gastric Cancer Radiotherapy with Photon- or Scanned Proton-beams2018In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 38, no 5, p. 2619-2625Article in journal (Refereed)
    Abstract [en]

    Background/Aim: Gastric cancer (GC) radiotherapy involves irradiation of large tumour volumes located in the proximities of critical structures. The advantageous dose distributions produced by scanned-proton beams could reduce the irradiated volumes of the organs at risk (OARs). However, treatment-induced side-effects may still appear. The aim of this study was to estimate the normal tissue complication probability (NTCP) following proton therapy of GC, compared to photon radiotherapy. Patients and Methods: Eight GC patients, previously treated with volumetric-modulated arc therapy (VMAT), were retrospectively planned with scanned proton beams carried out with the single-field uniform-dose (SFUD) method. A beam-specific planning target volume was used for spot positioning and a clinical target volume (CTV) based robust optimisation was performed considering setup- and range-uncertainties. The dosimetric and NTCP values obtained with the VMAT and SFUD plans were compared. Results: With SFUD, lower or similar dose-volume values were obtained for OARs, compared to VMAT. NTCP values of 0% were determined with the VMAT and SFUD plans for all OARs (p>0.05), except for the left kidney (p<0.05), for which lower toxicity was estimated with SFUD. Conclusion: The NTCP reduction, determined for the left kidney with SFUD, can be of clinical relevance for preserving renal function after radiotherapy of GC.

  • 8. Palmqvist, Tomas
    et al.
    dos S. Matias, Lucílio
    Stockholm University, Faculty of Science, Department of Physics. Eduardo Mondlane University, Mozambique.
    Langeland Marthinsen, Anne Beate
    Sundset, Marit
    Dybdahl Wanderås, Anne
    Danielsen, Signe
    Toma-Dasu, Iuliana
    Stockholm University, Faculty of Science, Department of Physics.
    Radiobiological treatment planning evaluation of inverse planning simulated annealing for cervical cancer high-dose-rate brachytherapy2015In: Anticancer Research, ISSN 0250-7005, E-ISSN 1791-7530, Vol. 35, no 2, p. 935-939Article in journal (Refereed)
    Abstract [en]

    Aim: To compare five inverse treatment plans with one conventional manually optimized plan for cervical cancer brachytherapy (BT) using radiobiological parameters combined with dosimetric and volumetric parameters.

    Materials and Methods: Five inverse treatment plans were calculated using an inverse planning simulated annealing (IPSA) algorithm for each of four fractions for 12 cervical cancer patients treated with high-dose-rate (HDR) brachytherapy. The inverse treatment plans were compared with a manually optimized plan used for the actual treatment of the patients. The comparison of the plans was performed with respect to the probability of cure without complication.

    Results: Overall, the manually optimized plan scored the best results; however, the probability of cure without complication is within an acceptable clinical range for all the plans.

    Conclusion: Although there are still considerable uncertainties in the radiobiological parameters, the radiobiological plan evaluation method presents itself as a potential complement to physical dosimetric methods.

1 - 8 of 8
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