NTCP modelling for high-grade temporal radionecrosis in a large cohort of patients receiving pencil beam scanning proton therapy for skull base and head and neck tumors

PURPOSE/OBJECTIVES

To develop a normal tissue complication probability (NTCP) model including clinical and dosimetric parameters for high-grade temporal lobe radionecroses (TRN) after pencil beam scanning (PBS) proton therapy (PT).

MATERIALS/METHODS

Data of 299 patients with skull base and Head and Neck tumors treated with PBS PT with a total dose of ≥60 Gy_RBE from 05/2004-11/2018 were included. Patients with a ≥ grade (G) 2 TRN (CTCAE v5.0 criteria) were considered as having a high-grade TRN. Nine clinical and 27 dosimetric parameters were considered for structure-wise modelling. After elimination of strongly cross-correlated variables, logistic regression models were generated using penalized LASSO regression. Bootstrapping was performed to assess parameter selection robustness. Model performance was evaluated via cross-correlation by assessing the area under the curve of receiver operating characteristic curves (AUC-ROC) and calibration with a Hosmer-Lemeshow test statistic.

RESULTS

After a median radiological follow-up of 51.5 months (range, 4-190), 27 (9%) patients developed a ≥ G2 TRN. Eleven patients had bitemporal necrosis, resulting in 38 events in 598 temporal lobes for structure-wise analysis. During Bootstrapping analysis, the highest selection frequency was found for prescription dose (PD), followed by Age, V_40Gy[%], Hypertension (HBP) and D_1cc[Gy]. During cross validation Age*PD* D_1cc[Gy]*HBP was superior in all described test statistics. Full cohort structure wise and patient wise models were built with a maximum AUC-ROC of 0.79 (structure-wise) and 0.76 (patient-wise).

CONCLUSION

While developing a logistic regression NTCP model to predict ≥ G2 TRN, the best fit was found for the model containing Age, PD, D_1cc[Gy] and HBP as risk factors. External validation will be the next step to improve generalizability and potential introduction into clinical routine.

The dependence of interplay effects on the field scan direction in PBS proton therapy

The literature is controversial about the scan direction dependency of interplay effects in pencil beam scanning (PBS) treatment of moving targets. A directional effect is supported by many simulation studies, whereas the experimental data are mostly limited to simple geometries, not reflecting realistically clinical treatment plans. We have compared increasingly complex treatment fields, from a homogeneous single energy layer to a more modulated lung plan, under identical experimental settings, seeking evidence for differences in motion mitigation due to the selection of primary scanning direction. In total, 120 experimental samples were taken, combining two primary scan directions and three rescanning regimes with different motion scenarios. 4D dose distributions were measured in water with a moving ionisation chamber array and compared to those of a stationary delivery using 2D gamma analysis. Each plan has been verified twice for the same rescanning regime and motion scenario, changing the meandering direction in between to scan perpendicularly to, or along, the target motion. Additionally, machine log files of the lung plan, together with 4DCT data, were used to calculate the dose distribution that such deliveries would have produced in the patient. The primary meandering direction has a clear influence on measured dose distributions when considering a single energy layer. Introducing spot weight modulation and multiple energy layers however, makes the dynamic of interplay more complex and difficult to predict. Overall, gamma (3%/3 mm) differences between scanning along or orthogonal to the target motion follow a normal distribution [Formula: see text] when considering multiple motion scenarios and rescanning regimes. Nevertheless, data spread [Formula: see text] is significant enough such that, for individual experiments and set-ups, a dependency may be observed even if this is not a general result. Patient reconstructed doses follow the same trend, the two primary scan directions producing statistically insignificant differences in dose distributions in terms of conformity or homogeneity. Except for extremely simplified cases of mono-energetic and homogeneous treatment fields, the interplay effect has been found to be only marginally influenced by the choice of the primary scanning direction.

Concentration of Human Hematopoietic Stem Cells in Bone Marrow Transplantation: Results of a Multicenter Study Using Baxter CS 3000 plus Cell Separator

Preliminary BM processing to produce an enriched MNC fraction from large BM volumes improves subsequent pharmacological and/or immunological “ex vivo” treatment and cryopreservation. We detail on a multicenter study (6 Transplant Centers) performed to establish an effective and reliable protocol using a CS 3000 continuous flow separator on a large series of BM processed for autologous (96) and allogeneic (12) transplantation. The reduction in volume was 78.6+7.2% while 28.9+12.4% of the original nucleated cells were found in the final product. A mean of 84.3+13.2% of the starting MNC was yielded in a fraction containing over 81% MNC. Cloning efficiency indicated than the final graft was highly enriched in progenitor cells committed to the granulocyte/macrophage pathway (> 100%) as assessed in vitro (CFU-GM). Removal of RBC and PLT was 98.3+1.1 and 37.7+14.6%, respectively. The mean dose of MNC and CFU-GM was 0.6+0.37 x 108 and 0.96+1 x 108 recipient weight. The entire process was accomplished in 87.5+20 min. We concluded that this automated device is a simple and reproducible method for BM processing suitable as first step for further “ex vivo” automated negative and/or positive cell selections.

Cardiopulmonary bypass technique in sheep

During the past two years at the University of Modena, 72 sheep underwent cardiopulmonary bypass (CPB) for various open-heart surgical procedures. An effective protocol for anaesthesia and CPB was developed in these animals. Routine barbiturate induction and maintenance anaesthesia with isofluorane and a pressure-regulated ventilator have minimized anaesthetic problems. The type of priming fluid used was the major factor in overcoming the problems associated with haemodilution effects, clotting insufficiency and postperfusion lung syndrome. Pump flows of 60ml.kg -1 bodyweight.min-1 seem to give adequate circulatory support during heart-lung bypass. A technical report and the pharmacological support protocols used successfully in 66 of the 72 animals during a two-year period are presented.

Commissioning and Quality Assurance of an Integrated System for Patient Positioning and Setup Verification in Particle Therapy

In an increasing number of clinical indications, radiotherapy with accelerated particles shows relevant advantages when compared with high energy X-ray irradiation. However, due to the finite range of ions, particle therapy can be severely compromised by setup errors and geometric uncertainties. The purpose of this work is to describe the commissioning and the design of the quality assurance procedures for patient positioning and setup verification systems at the Italian National Center for Oncological Hadrontherapy (CNAO). The accuracy of systems installed in CNAO and devoted to patient positioning and setup verification have been assessed using a laser tracking device. The accuracy in calibration and image based setup verification relying on in room X-ray imaging system was also quantified. Quality assurance tests to check the integration among all patient setup systems were designed, and records of daily QA tests since the start of clinical operation (2011) are presented. The overall accuracy of the patient positioning system and the patient verification system motion was proved to be below 0.5 mm under all the examined conditions, with median values below the 0.3 mm threshold. Image based registration in phantom studies exhibited sub-millimetric accuracy in setup verification at both cranial and extra-cranial sites. The calibration residuals of the OTS were found consistent with the expectations, with peak values below 0.3 mm. Quality assurance tests, daily performed before clinical operation, confirm adequate integration and sub-millimetric setup accuracy. Robotic patient positioning was successfully integrated with optical tracking and stereoscopic X-ray verification for patient setup in particle therapy. Sub-millimetric setup accuracy was achieved and consistently verified in daily clinical operation.

Commissioning of an integrated platform for time-resolved treatment delivery in scanned ion beam therapy by means of optical motion monitoring

The integrated use of optical technologies for patient monitoring is addressed in the framework of time-resolved treatment delivery for scanned ion beam therapy. A software application has been designed to provide the therapy control system (TCS) with a continuous geometrical feedback by processing the external surrogates tridimensional data, detected in real-time via optical tracking. Conventional procedures for phase-based respiratory phase detection were implemented, as well as the interface to patient specific correlation models, in order to estimate internal tumor motion from surface markers. In this paper, particular attention is dedicated to the quantification of time delays resulting from system integration and its compensation by means of polynomial interpolation in the time domain. Dedicated tests to assess the separate delay contributions due to optical signal processing, digital data transfer to the TCS and passive beam energy modulation actuation have been performed. We report the system technological commissioning activities reporting dose distribution errors in a phantom study, where the treatment of a lung lesion was simulated, with both lateral and range beam position compensation. The zero-delay systems integration with a specific active scanning delivery machine was achieved by tuning the amount of time prediction applied to lateral (14.61 ± 0.98 ms) and depth (34.1 ± 6.29 ms) beam position correction signals, featuring sub-millimeter accuracy in forward estimation. Direct optical target observation and motion phase (MPh) based tumor motion discretization strategies were tested, resulting in −0.3(2.3)% and −1.2(9.3)% median (IQR) percentual relative dose difference with respect to static irradiation, respectively. Results confirm the technical feasibility of the implemented strategy towards 4D treatment delivery, with negligible percentual dose deviations with respect to static irradiation.

Tumor tracking based on correlation models in scanned ion beam therapy: an experimental study

Accurate dose delivery to extra-cranial lesions requires tumor motion compensation. An effective compensation can be achieved by real-time tracking of the target position, either measured in fluoroscopy or estimated through correlation models as a function of external surrogate motion. In this work, we integrated two internal/external correlation models (a state space model and an artificial neural network-based model) into a custom infra-red optical tracking system (OTS). Dedicated experiments were designed and conducted at GSI (Helmholtzzentrum für Schwerionenforschung). A robotic breathing phantom was used to reproduce regular and irregular internal target motion as well as external thorax motion. The position of a set of markers placed on the phantom thorax was measured with the OTS and used by the correlation models to infer the internal target position in real-time. Finally, the estimated target position was provided as input for the dynamic steering of a carbon ion beam. Geometric results showed that the correlation models transversal (2D) targeting error was always lower than 1.3 mm (root mean square). A significant decrease of the dosimetric error with respect to the uncompensated irradiation was achieved in four out of six experiments, demonstrating that phase shifts are the most critical irregularity for external/internal correlation models.

Change in major amputation rate in a center dedicated to diabetic foot care during the 1980s: prognostic determinants for major amputation

From 1990 to 1993, 115 diabetic patients were consecutively hospitalized in our diabetologic unit for foot ulcer and 27 (23.5%) major amputations were carried out. The major amputation rate of this series of cases was compared with that occurring in diabetic subjects taken into our hospital for foot ulcer in two previous periods: 1979-1981 (17 major amputations in 42 inpatients or 40.5%) and 1986-1989 (26 major amputations in 78 inpatients or 33.3%). The comparison shows a progressive reduction in major amputation rate [Odds ratio 0.66, 95% confidence interval (CI) 0.46-0.96]. Univariate and multivariate analysis, carried out in the population of the 1990-1993 period, in order to detect the independent factors associated with major amputation show the following prognostic determinants of major amputation: Wagner grade (odds ratio 7.69, CI 1.58-37.53), prior stroke (odds ratio 35.05, CI 3.14-390.53), prior major amputation (odds ratio 3.49, CI 1.26-9.38), transcutaneous oxygen level (odds ratio 1.06, CI 1.01-1.12), and ankle-brachial blood pressure index (odds ratio 4.35, CI 1.58-12.05), while an independent protective role was attributed to hyperbaric oxygen treatment (odds ratio 0.15, CI 0.03-0.64). In accordance with other studies, we, therefore, conclude that a comprehensive protocol as well as a multidisciplinary approach in a dedicated center can assure a decrease in major amputation rate. The parameters of limb perfusion were the modifiable prognostic determinants most strongly predictive for amputation.

[Analysis of the routine control colposcopic findings, of the preventive gynecological oncology service]

Ten-thousand-fifty-one colposcopic examinations recorded using uniform and standardized criteria from 1983 to 1988 are analysed. The results confirm the validity of the protocol used. It is emphasized that the main problem concerning the prevention of cervical cancer still lies in putting high-risk patients in touch with the health services.

Early alteration of bioprosthetic cardiac valves in sheep: influence of the immunological status

Ten Pericarbon valve bioprostheses were examined after being implanted in tricuspid position in two different groups of animals: group I sheep with increased immunoglobulins, plasma levels, and eosinophilis count of more than 10%, due to parasitic infection, and group II sheep without any parasitic infection, i.e. with normal blood data. The explanted valve follow up was between 60-95 hours in both groups. Microscopic observation of group I valves revealed a massive blood cell (lymphocytes, eosinophilis and large mononuclear cells) infiltration especially around the natural pericardial blood vessels in the region of flexion and attachment. The epipericardial surface was covered by fibrin sheath, and immunofluorescence studies showed a strongly positive reaction for immunoglobulins (IgG and IgE) on leaflet surfaces and lamellar stratification into the fibrosa. Microcalcifications were detected around pericardial blood vessels in the same zones where infiltrated blood cells were found. In group II valves cell infiltration was absent with no signs of calcification and immunofluorescence was negative. Our data suggest that immunoglobulins adherence followed by blood cell infiltration may be one of the early causes of tissue leaflet degeneration and there is a parallel trend between plasma immunoglobulin levels and the early tissue alteration. Our data show that the experimental model for testing bioprostheses in sheep is influenced by the pre-immunological status and it is important to control it before surgery.

Experimental right ventricular outflow tract reconstruction with a composite Mitrathane monocusp patch: preliminary results

Twenty large white pigs underwent normothermic right ventricular bypass, pulmonary artery valve excision and right ventricular outflow tract (RVOT) reconstruction using a synthetic material (Mitrathane). The animals were divided in two groups (ten for each group) for the RVOT reconstruction model: Group I with a composite monocusp patch (with a new design geometrically related to pulmonary artery circumference) and Group II without a valve mechanism. Four early postoperative deaths occurred in Group I (unrelated to monocusp patch function) and seven in Group II (due to acute right ventricular failure). Follow up of the six animals of Group I was 600-630 (average 617.5) days and of the three Group II animals was 95-110 (average 101.6) days. In Group I haemodynamic studies showed no significant difference from preoperative values at 5 months while at 20 months there was a moderate valve insufficiency in all animals. In Group II severe right ventricular insufficiency was present in all animals and spontaneous death occurred after about 3 months. In Group I angiographic studies disclosed no evidence of graft calcification or stenosis while in Group II there was a moderate pulmonary trunk dilatation. Post mortem examination showed no signs of degeneration in any graft. Microscopic studies of both groups revealed an acellular layer of fibrin on the external surface and fibrous deposit on the inner part of the suture with the right ventricle. In Group I there were leukocyte and histocyte infiltration of the grafts. In these experiments our synthetic monocusp model showed good function and durability in comparison to a RVOT reconstruction without a valve mechanism.