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Due to its inherent technical challenges, craniospinal irradiation (CSI) entails crucial considerations regarding plan complexity and robustness. The scope of this work was to establish and validate methods suitable for the evaluation of robustness, as well as for dose verification in CSI with VMAT. Five patients previously treated with CSI were retrospectively selected. For each patient, two technically different treatment plans were generated, based on the conventional (static overlap) and staggered (dynamic overlap) configuration. These techniques served as a benchmark to evaluate the potential of a metric proposed in this work, aimed at quantifying robustness, the Overlap Robustness Index (ORI). Furthermore, they were utilized to assess the suitability of two experimental methods relying on film dosimetry, as well as on Delta4 phantom for identifying sources of uncertainties in CSI applications. In accordance with the positional error simulation performed, the staggered approach yielded a statistically significant superior ORI value compared to the conventional one. Additionally, the strong correlation observed between the positional shift induced dose distribution changes and ORI results (Spearman's r = -0.941, p-value < 0.001) demonstrated the sensitivity of ORI in detecting areas of steep dose gradients within the overlapping regions that could potentially compromise the quality of treatment. Concerning dose verification, analysis in terms of dose profiles revealed a superior dosimetric accuracy for the staggered technique relative to conventional for both film and Delta4 measurements. Film-based gamma index results showed that staggered technique outperformed the conventional for the majority of passing criteria considered, with differences in passing rates up to 8.1%. The two treatment techniques however, exhibited equivalent dose delivery accuracy for the clinically relevant passing criteria when Delta4 was employed, with passing rate differences less than 0.6%. Findings of this study revealed that ORI is suitable for quantifying robustness in CSI with VMAT, while radiochromic films appeared to be the best candidate for CSI dose verification in this work. [ABSTRACT FROM AUTHOR]

Intracranial tumors have been traditionally treated with surgery. Novel RT techniques, such as stereotactic radiosurgery (SRS), have expanded therapeutic options in this field. As the literature reports high control rates and limited toxicity after stereotactic radiosurgery for intracranial neuromas and meningiomas SRS has been established as an appealing option for both clinicians and patients. Although radiosurgery has been traditionally performed as Gamma Knife or Cyberknife surgery nowadays widely available linac-based approaches have gained popularity. In this single institution study, we present the results of linac-based stereotactic radiosurgery after a long follow up of patients treated for benign intracranial neuromas and meningiomas focusing on local control and toxicity. Thirty-four consecutive patients were treated during 2000-2004 with primary or postoperative SRS for tumors less than 3.5 cm in maximum diameter. Stereotactic radiosurgery was performed using the 6 MV beam of a non-dedicated Elekta SL-18 linear accelerator converted for radiosurgery with the attachment of an isocentric subsystem (Phillips SRS200XK). Non-coplanar arc irradiation was delivered with circular collimators ranging in diameter from 10- 30 mm. A stereotactic headring fixation was used. A treatment plan was achieved using 1-8 isocenters. Neuroma patients were treated with 11-12 Gy, while larger doses of 12-15.5 Gy were given to meningioma patients. Combining a different number, span and weight of noncoplanar arcs, as well as weight and collimator size of each isocenter used, high conformality of the treatment dose to the borders of the tumor was established. Since nervous tissue is a late responding tissue, a long follow up is required after radiosurgery for benign intracranial tumors to assess not only tumor control but also RT-related toxicity. SRS patients were followed up twice yearly for the first year and annually thereafter. Imaging studies as well as cranial nerve assessment were mandatory. Clinical follow up was obtained from the patients or their referral doctors. After twenty years 26 patients are still in follow up and high rates of local control are documented with no cases of treatment failure Tumor shrinkage was observed in 61,5% and 58% of neuroma and meningioma patients, respectively. Toxicity was minimum with no patient developing new permanent facial or trigeminal neuropathy. Overall, our study confirms the efficacy and safety of linac-based stereotactic radiosurgery after extended follow up for neuroma and meningioma patients. [ABSTRACT FROM AUTHOR]

Simple Summary: Cell killing and tumor response in cancer patients depends not only on the absorbed radiation dose but also on the dose rate and delivery time. In this study, a biodosimetry assay based on the frequency of dicentrics chromosomes scored in peripheral blood lymphocytes from prostate cancer patients and PC3 human prostate cancer cell line was used to investigate the radiobiological impact of the relative prolonged dose delivery time and/or decreased dose rate met in advanced modulated radiotherapy techniques (VMAT and IMRT) compared to conventional non-modulated (3D-CRT) in prostate patient plan irradiations. The results showed a small but statistically significant decrease in the number of dicentrics following radiation with the modulated techniques, suggesting a corresponding decrease on the radiation dose efficiency. The biodosimetry assay could be used as an alternative to the laborious conventional clonogenic assay, while both lymphocytes and cancer cell line could effectively be used for estimation of the biological absorbed dose. While rapid technological advances in radiotherapy techniques have led to a more precise delivery of radiation dose and to a decreased risk of side effects, there is still a need to evaluate the efficacy of the new techniques estimating the biological dose and to investigate the radiobiological impact of the protracted radiotherapy treatment duration. The aim of this study is to compare, at a cytogenetic level, advanced radiotherapy techniques VMAT and IMRT with the conventional 3D-CRT, using biological dosimetry. A dicentric biodosimetry assay based on the frequency of dicentrics chromosomes scored in peripheral blood lymphocytes from prostate cancer patients and PC3 human prostate cancer cell line was used. For each patient blood sample and each subpopulation of the cultured cell line, three different irradiations were performed using the 3D-CRT, IMRT, and VMAT technique. The absorbed dose was estimated with the biodosimetry method based on the induced dicentric chromosomes. The results showed a statistically significant underestimation of the biological absorbed dose of ~6% for the IMRT and VMAT compared to 3D-CRT irradiations for peripheral blood lymphocytes, whereas IMRT and VMAT results were comparable without a statistically significant difference, although slightly lower values were observed for VMAT compared to IMRT irradiation. Similar results were obtained using the PC3 cell line. The observed biological dose underestimation could be associated with the relative decreased dose rate and increase irradiation time met in modulated techniques compared to the conventional 3D-CRT irradiations. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the cytoprotective effect of subcutaneous vs. intrarectal administration of amifostine against acute radiation toxicity. Methods and materials: Patients were randomized to receive amifostine either intrarectally (Group A, n = 27) or a 500-mg flat dose subcutaneously (Group B, n = 26) before irradiation. Therapy was delivered using a four-field technique with three-dimensional conformal planning. In Group A, 1,500 mg of amifostine was administered intrarectally as an aqueous solution in 40 mL of enema. Two different toxicity scales were used: the European Organization for Research and Treatment of Cancer/Radiation Therapy Oncology Group (RTOG) rectal and urologic toxicity criteria and the Subjective-RectoSigmoid scale based on the endoscopic terminology of the World Organization for Digestive Endoscopy. Objective measurements with rectosigmoidoscopy were performed at baseline and 1¿2 days after radiotherapy completion. The area under the curve for the time course of mucositis (RTOG criteria) during irradiation represented the mucositis index. Results: Intrarectal amifostine was feasible and well tolerated without any systemic or local side effects. According to the RTOG toxicity scale, Group A had superior results with a significantly lower incidence of Grades I-II rectal radiation morbidity (11% vs. 42%, p = 0.04) but inferior results concerning urinary toxicity (48% vs. 15%, p = 0.03). The mean rectal mucositis index and Subjective-RectoSigmoid score were significantly lower in Group A (0.44 vs. 2.45 [p = 0.015] and 3.9 vs. 6.0 [p = 0.01], respectively), and the mean urinary mucositis index was lower in Group B (2.39 vs. 0.34, p < 0.028). Conclusions: Intrarectal administration of amifostine (1,500 mg) seemed to have a cytoprotective efficacy in acute radiation rectal mucositis but was inferior to subcutaneous administration in terms of urinary toxicity. Additional randomized studies are needed for definitive decisions concerning the cytoprotection of pelvic irradiated areas. [Copyright &y& Elsevier]