A joint physics and radiobiology DREAM team vision - Towards better response prediction models to advance radiotherapy

Radiotherapy developed empirically through experience balancing tumour control and normal tissue toxicities. Early simple mathematical models formalized this practical knowledge and enabled effective cancer treatment to date. Remarkable advances in technology, computing, and experimental biology now create opportunities to incorporate this knowledge into enhanced computational models. The ESTRO DREAM (Dose Response, Experiment, Analysis, Modelling) workshop brought together experts across disciplines to pursue the vision of personalized radiotherapy for optimal outcomes through advanced modelling. The ultimate vision is leveraging quantitative models dynamically during therapy to ultimately achieve truly adaptive and biologically guided radiotherapy at the population as well as individual patient-based levels. This requires the generation of models that inform response-based adaptations, individually optimized delivery and enable biological monitoring to provide decision support to clinicians. The goal is expanding to models that can drive the realization of personalized therapy for optimal outcomes. This position paper provides their propositions that describe how innovations in biology, physics, mathematics, and data science including AI could inform models and improve predictions. It consolidates the DREAM team's consensus on scientific priorities and organizational requirements. Scientifically, it stresses the need for rigorous, multifaceted model development, comprehensive validation and clinical applicability and significance. Organizationally, it reinforces the prerequisites of interdisciplinary research and collaboration between physicians, medical physicists, radiobiologists, and computational scientists throughout model development. Solely by a shared understanding of clinical needs, biological mechanisms, and computational methods, more informed models can be created. Future research environment and support must facilitate this integrative method of operation across multiple disciplines.

EviGUIDE - a tool for evidence-based decision making in image-guided adaptive brachytherapy for cervical cancer

PURPOSE

To develop a novel decision-support system for radiation oncology that incorporates clinical, treatment and outcome data, as well as outcome models from a large clinical trial on magnetic resonance image-guided adaptive brachytherapy (MR-IGABT) for locally advanced cervical cancer (LACC).

METHODS

A system, called EviGUIDE, was developed that combines dosimetric information from the treatment planning system, patient and treatment characteristics, and established tumor control probability (TCP), and normal tissue complication probability (NTCP) models, to predict clinical outcome of radiotherapy treatment of LACC. Six Cox Proportional Hazards models based on data from 1341 patients of the EMBRACE-I study have been integrated. One TCP model for local tumor control, and five NTCP models for OAR morbidities.

RESULTS

EviGUIDE incorporates TCP-NTCP graphs to help users visualize the clinical impact of different treatment plans and provides feedback on achievable doses based on a large reference population. It enables holistic assessment of the interplay between multiple clinical endpoints and tumour and treatment variables. Retrospective analysis of 45 patients treated with MR-IGABT showed that there exists a sub-cohort of patients (20%) with increased risk factors, that could greatly benefit from the quantitative and visual feedback.

CONCLUSION

A novel digital concept was developed that can enhance clinical decision- making and facilitate personalized treatment. It serves as a proof of concept for a new generation of decision support systems in radiation oncology, which incorporate outcome models and high-quality reference data, and aids the dissemination of evidence-based knowledge about optimal treatment and serve as a blueprint for other sites in radiation oncology.

Risk Factors for Local Failure Following Chemoradiation and Magnetic Resonance Image-Guided Brachytherapy in Locally Advanced Cervical Cancer: Results From the EMBRACE-I Study

PURPOSE

To report clinical and treatment characteristics, remission and failure patterns, and risk factors for local failure (LF) from the EMBRACE-I study.

MATERIALS AND METHODS

EMBRACE-I was a prospective, observational, multicenter cohort study on magnetic resonance imaging-based image-guided adaptive brachytherapy (MR-IGABT) in locally advanced cervical cancer. Treatment consisted of external beam radiotherapy, concurrent chemotherapy, and MR-IGABT. LF was defined as progressive or recurrent disease in the cervix, uterus, parametria, pelvic wall, or vagina. Competing risk analysis was used to estimate local tumor control (LC) and Cox proportional regression models for multivariable analysis and dose-response analysis.

RESULTS

One thousand three hundred eighteen patients with a median follow-up of 52 months were available for this analysis. Eighty-one patients had persistent disease 3 months after end of treatment. Of those, 60 patients achieved LC at 6-9 months without further treatment, whereas 21 patients had progressive disease. In addition, 77 patients developed a local recurrence after complete remission comprising a total number of 98 LFs. LFs were located inside the MR-IGABT target volumes in 90% of patients with LF. In multivariable analysis, histology, minimal dose to 90% of high-risk clinical target volume (CTV_HR), maximum tumor dimension, CTV_HR > 45 cm³, overall treatment time, tumor necrosis on magnetic resonance imaging at diagnosis, uterine corpus infiltration at diagnosis and at MR-IGABT, and mesorectal infiltration at MR-IGABT had significant impact on LF. Dose-response analysis showed that a minimal dose to 90% of 85 Gy to the CTV_HR led to 95% (95% CI, 94 to 97) LC 3 years postintervention for squamous cell in comparison to 86% (95% CI, 81 to 90) for adeno/adenosquamous carcinoma histology.

CONCLUSION

The present study demonstrates the safety and validity of the GYN GEC-ESTRO/ICRU-89 target concept and provides large-scale evidence for dose prescription and new risk factors for LF in MR-IGABT in locally advanced cervical cancer.

Neural network-assisted automated image registration for MRI-guided adaptive brachytherapy in cervical cancer

PURPOSE

In image-guided adaptive brachytherapy (IGABT) a quantitative evaluation of the dosimetric changes between fractions due to anatomical variations, can be implemented via rigid registration of images from subsequent fractions based on the applicator as a reference structure. With available treatment planning systems (TPS), this is a manual and time-consuming process. The aim of this retrospective study was to automate this process. A neural network (NN) was trained to predict the applicator structure from MR images. The resulting segmentation was used to automatically register MR-volumes.

MATERIAL AND METHODS

DICOM images and plans of 56 patients treated for cervical cancer with high dose-rate (HDR) brachytherapy were used in the study. A 2D and a 3D NN were trained to segment applicator structures on clinical T2-weighted MRI datasets. Different rigid registration algorithms were investigated and compared. To evaluate a fully automatic registration workflow, the NN-predicted applicator segmentations (AS) were used for rigid image registration with the best performing algorithm. The DICE coefficient and mean distance error between dwell positions (MDE) were used to evaluate segmentation and registration performance.

RESULTS

The mean DICE coefficient for the predicted AS was 0.70 ± 0.07 and 0.58 ± 0.04 for the 3D NN and 2D NN, respectively. Registration algorithms achieved MDE errors from 8.1 ± 3.7 mm (worst) to 0.7 ± 0.5 mm (best), using ground-truth AS. Using the predicted AS from the 3D NN together with the best registration algorithm, an MDE of 2.7 ± 1.4 mm was achieved.

CONCLUSION

Using a combination of deep learning models and state of the art image registration techniques has been demonstrated to be a promising solution for automatic image registration in IGABT. In combination with auto-contouring of organs at risk, the auto-registration workflow from this study could become part of an online-dosimetric interfraction evaluation workflow in the future.

Good health information for people with a migration background

Background

Studies show that people with a migration background are often uncertain concerning the kinds of health services that are offered and where to turn to with which health concerns. Some factors, like fears or obstacles (e.g. deductibles), lead to the health system not being used (on time). This is particularly true for those who are socioeconomically or socially disadvantaged. The aim of the project was to get an insight into the information needs of this population group as a basis for producing and disseminating good health information in the future.

Methods

In this qualitative study co-researchers conducted guided focus groups (separated by sex) or interviews in their first languages. In total, more than 100 people from 16 different countries of origin were involved in the survey.

Results

In general, a substantial need for multilingual health information prepared in easy-to-understand language was expressed. Some health topics (e.g. the Austrian health system, mental health and available support) were mentioned by many participants. Other issues were relevant for few groups only (e.g. TCM). Gender differences can be seen in some groups but not in all. Besides acquaintances/relatives, general practitioners were named as main source of information. Indications can be derived on how health information should be prepared, designed and distributed. Besides multilingual health information, translation services are needed during appointments but also for the medical reports.

Conclusions

When searching for health information, but also when trying to understand it, language barriers are a major obstacle. Multilingual and culture-sensitive explainer videos on selected topics are an appropriate medium for reaching a broad group of people. Low-threshold multilingual regional contact points could provide an important contribution to health equity, as a guide in the health system, providing information and translation services, and setting health promotion offers.

Key messages

• Language barriers represent a major obstacle for vulnerable population groups with migration background in all stages of the health care process.

• There is a substantial need for adequately prepared multilingual health information.

Methodology paper: a novel phantom setup for commissioning of scanned ion beam delivery and TPS

BACKGROUND

Commissioning of treatment planning systems (TPS) and beam delivery for scanned light ion beams is an important quality assurance task. This requires measurement of large sets of high quality dosimetric data in anthropomorphic phantoms to benchmark the TPS and dose delivery under realistic conditions.

METHOD

A novel measurement setup is described, which allows for an efficient collection of a large set of accurate dose data in complex phantom geometries. This setup allows dose measurements based on a set of 24 small volume ionization chambers calibrated in dose to water and mounted in a holder, which can be freely positioned in a water phantom with various phantoms mounted in front of the water tank. The phantoms can be scanned in a CT and a CT-based treatment planning can be performed for a direct benchmark of the dose calculation algorithm in various situations.

RESULTS

The system has been used for acceptance testing in scanned light ion beam therapy at Heidelberg Ion Beam Therapy Center for scanned proton and carbon ion beams. It demonstrated to be useful to collect large amounts of high quality data for comparison with the TPS calculation using various phantom geometries.

CONCLUSION

The setup is an efficient tool for commissioning and verification of treatment planning systems. It is especially suited for dynamic beam delivery, as many data points can be obtained during a single plan delivery, but can be adapted also for other dynamic therapies, like rotational IMRT.

Challenges of the Blackwood Basin, Western Australia

Growing concern about the declining state of the catchment and river led to the formation of the Blackwood Basin Group in 1992. Funded primarily by the Natural Heritage Trust and using the river as the focus, the group aims to provide leadership and support to achieve sustainable management of natural resources in the catchment. Through an Integrated Catchment Management approach, the Blackwood Basin Group has managed a range of projects to improve the community's understanding and management of the Blackwood River and its catchment. A number of research, education, demonstration and on-ground action activities relating to river management have been undertaken in partnership with community and local, state and federal government organisations. Activities include demonstrations and evaluations of riparian restoration, funding riparian restoration activities, protection of high conservation value remnant vegetation, a flood risk study, zone action planning and monitoring the condition of the river and its tributaries.

Construction of a highly bioluminescent Nitrosomonas as a probe for nitrification conditions

Cloned luciferase-encoding operons were transferred by conjugation to a natural isolate of the ammonia-oxidizing bacterial strain Nitrosomonas sp. RST41-3, thereby establishing conjugation as a tool for gene transfer into Nitrosomonas strains. Luminescence was dependent on the pH of the medium and the concentration of the substrate ammonium chloride. Moreover, the luminescence of the transconjugants was reduced immediately by micromolar concentrations of nitrapyrin and allylthiourea, which are specific inhibitors of nitrification. Our results indicate that luminescent Nitrosomonas strains may be useful as a probe to detect nitrification conditions in the natural environment as well as in sewage plants.

Use of metabolically competent human hepatoma cells for the detection of mutagens and antimutagens

The human hepatoma line (Hep G2) has retained the activities of various phase I and phase II enzymes which play a crucial role in the activation/detoxification of genotoxic procarcinogens and reflect the metabolism of such compounds in vivo better than experimental models with metabolically incompetent cells and exogenous activation mixtures. In the last years, methodologies have been developed which enable the detection of genotoxic effects in Hep G2 cells. Appropriate endpoints are the induction of 6-TGr mutants, of micronuclei and of comets (single cell gel electrophoresis assay). It has been demonstrated that various classes of environmental carcinogens such as nitrosamines, aflatoxins, aromatic and heterocyclic amines and polycyclic aromatic hydrocarbons can be detected in genotoxicity assays with Hep G2 cells. Furthermore, it has been shown that these assays can distinguish between structurally related carcinogens and non-carcinogens, and positive results have been obtained with rodent carcinogens (such as safrole and hexamethylphosphoramide) which give false negative results in conventional in vitro assays with rat liver homogenates. Hep G2 cells have also been used in antimutagenicity studies and can identify mechanisms not detected in conventional in vitro systems such as induction of detoxifying enzymes, inactivation of endogenously formed DNA-reactive metabolites and intracellular inhibition of activating enzymes.

Genotoxic effects of heavy metals: comparative investigation with plant bioassays

The potential use of micronucleus assays in plants for the detection of genotoxic effects of heavy-metal ions was investigated. Three different plant systems were comparatively investigated in micronucleus tests with Tradescantia pollen mother cells (Trad MCN) and micronucleus tests with meristematic root tip cells of Allium cepa and Vicia faba (Allium/ Vicia MCN). As3+, Pb2+, Cd2+, Zn2+ caused a dose-dependent increase of MCN frequencies in all three test systems. Cu2+ gave consistently negative responses in all three tests; Zn2+ caused only a moderate, statistically not significant increase of MCN frequencies in Vicia. The ranking of genotoxic potencies in all three tests was in the descending order: As3+ > Pb2+ > Cd2+ > Zn2+ Cu2+. In experiments with Tradescantia, induction of MCN was observed in a concentration range between 1 and 10 mM, whereas in tests with root tip cells, higher concentrations (10-1,000 mM) were required to show significant effects. Further increase of the exposure levels caused toxic effects (reduction of root growth), cell division delays, and a decrease of MCN frequencies. Comparisons by linear regression analyses indicated that the sensitivity of the three bioassays for heavy metals decreases in the order: Trad MCN > Vicia root MCN > Allium root MCN. In further experimental series, a soil sample which contained high concentrations of the five metals and a control soil were investigated. Aqueous soil extracts induced only weak effects in Trad MCN tests and no effects in the root tip assays, whereas cultivation of the plants in the soils resulted in a pronounced induction of MCN in the Tradescantia system and moderate effects in Vicia and Allium. In conclusion, the results of the study indicate that the Trad MCN assay detects the genotoxic effects of heavy metals and can be used for biomonitoring metal-contaminated soils.

Toxic effects of griseofulvin: disease models, mechanisms, and risk assessment

Griseofulvin (GF) has been in use for more than 30 years as a pharmaceutical drug in humans for the treatment of dermatomycoses. Animal studies give clear evidence that it causes a variety of acute and chronic toxic effects, including liver and thyroid cancer in rodents, abnormal germ cell maturation, teratogenicity, and embroyotoxicity in various species. No sufficient data from human studies are available at present to exclude a risk in humans: therefore, attempts were made to elucidate the mechanisms responsible for the toxic effects of GF and to address the question whether such effects might occur in humans undergoing GF therapy. It is well documented that GF acts as a spindle poison and its reproductive toxicity as well as the induction of numerical chromosome aberrations and of micronuclei in somatic cells possibly may result from disturbance of microtubuli formation. Likewise, a causal relationship between aneuploidy and cancer has been repeatedly postulated. However, a critical survey of the data available on aneuploidogenic chemicals revealed insufficient evidence for such an association. Conceivably, other mechanisms may be responsible for the carcinogenic effects of the drug. The induction of thyroid tumors in rats by GF is apparently a consequence of the decrease of thyroxin levels and it is unlikely that such effects occur in GF-exposed humans. The appearance of hepatocellular carcinomas (HCC) in mice on GF-supplemented diet is preceded by various biochemical and morphological changes in the liver. Among these, hepatic porphyria is prominent, it may result from inhibition of ferrochelatase and (compensatory) induction of ALA synthetase. GF-induced accumulation of porphyrins in mouse liver is followed by cell damage and necrotic and inflammatory processes. Similar changes are known from certain human porphyrias which are also associated with an increased risk for HCC. However, the porphyrogenic effect of GF therapy in humans is moderate compared with that in the mouse model, although more detailed studies should be performed in order to clarify this relationship on a quantitative basis. A further important effect of GF-feeding in mice is the formation of Mallory bodies (MBs) in hepatocytes. These cytoskeletal abnormalities occur also in humans, although under different conditions; their appearance is associated with the induction of liver disease and HCC. Chronic liver damage associated with porphyria and MB formation, enhanced cell proliferation, liver enlargement, and enzyme induction all may contribute to the hepatocarcinogenic effect of GF in mice. In conclusion, further investigation is required for adequate assessment of health risks to humans under GF therapy.

Cerebral ischemia induced by compression tests during transcranial Doppler sonography

Compression tests performed during transcranial Doppler sonography are intended for support in identifying vessels and measuring collateral circulation within the circle of Willis. The resulting information is thought to be valuable in patients with extracranial carotid stenoses, especially for planning carotid and extra-/intracranial bypass surgery. In a retrospective analysis of a series of 380 cases, two patients with symptomatic carotid artery stenoses suffered three compression-induced focal cerebral ischemias. In two instances, these ischemias started under compression. The resulting deficits were reversible. One patient developed an additional and persisting motor deficit whose onset was delayed. The diagnostic benefit of compression tests is not established nor its risk well defined. They should not be used routinely.

[Diagnosis and prognosis of carotid artery stenosis]

The diagnosis of a carotid stenosis inevitably includes a neurological examination as well as CCT or MRI of the brain. Typical neurological and neuropsychological symptoms and signs as well as syndromes are described according to the vascular supply areas of the brain. CCT as well as MRI may identify cerebral infarction or other diseases and additionally give some information with regard to the underlying etiology or pathogenesis of an infarct. Satisfactory non-invasive demonstration of the carotid and vertebral arteries including their intracranial branches can be achieved by the use of sonographic methods (Dopplersonography, B-mode imaging, Duplex and colour-coded systems). Additionally, transcranial Dopplersonography is mandatory in most instances. Cerebral angiography is only justified preoperatively or for a disease which cannot be diagnosed reliably by other means, eg. cerebral venous thrombosis. The prognosis of a carotid stenosis depends not only on the degree of luminal narrowing and the shape of the stenosis but also on the clinical status of the patient (asymptomatic or symptomatic carotid stenosis, accompanying coronary artery disease etc.). Prophylactic treatment implies therapy of risk factors as well as antiaggregation, anticoagulation and carotid endarterectomy in selected cases.

Noninvasive assessment of CO2-induced cerebral vasomotor response in normal individuals and patients with internal carotid artery occlusions

To evaluate the CO2-induced vasomotor reactivity of the cerebral vasculature, relative changes of blood flow velocity within the middle cerebral artery were measured by transcranial Doppler ultrasonography during normocapnia and various degrees of hypercapnia and hypocapnia. We studied 40 normal individuals and 40 patients with unilateral and 15 patients with bilateral internal carotid artery occlusions. When blood flow velocity changes as percent of normocapnic values were plotted against end-tidal CO2 volume percent, a biasymptotic curve (a tangent-hyperbolic function) gave the best fit of the scattergram. The distance between the upper and lower asymptotes was defined as cerebral vasomotor reactivity. In the normal individuals, mean +/- SD vasomotor reactivity was 85.63 +/- 15.96%. In patients with internal carotid artery occlusions, vasomotor reactivity was significantly lower than normal on both the occluded (mean 45.2%, median 50.4%; p less than 0.0001) and the nonoccluded (mean +/- SD 67.7 + 13.3%, p less than 0.01) sides in the unilateral group and on both sides (mean +/- SD 36.6 +/- 15.9% and 44.9 +/- 24.6%, p less than 0.0001) in the bilateral group. The difference between vasomotor reactivity for symptomatic and asymptomatic unilateral occlusions was also highly significant (mean 37.6% and 62.9%, p less than 0.006). Vasomotor reactivity was also significantly lower in patients with low-flow infarctions on computed tomography than in patients with normal scans (mean +/- SD 36.7 +/- 25% and 60.2 +/- 16.9%, p less than 0.008). A striking association of low-flow infarctions, ischemic ophthalmopathy, and hypostatic transient ischemic attacks was found with vasomotor reactivities of less than 34% or even paradoxical reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

[Laser trabeculoplasty in glaucoma chronicum simplex. Results of a prospective, clinical study]

Between 1984 and 1986, 104 patients with open-angle glaucoma of various etiologies were treated by laser trabeculoplasty (LTP) in a prospective clinical study. In order to ensure that the group of patients studied was homogeneous, only the 85 consecutive patients (85 eyes) with primary open-angle glaucoma were included, using a specially designed software program. The number of patients with pseudoexfoliation glaucoma, aphakic glaucoma, and congenital glaucoma was too small to allow statistical comparison with those who had chronic open-angle glaucoma. Criteria for success were defined as follows: no progression of disk cupping or visual field defects, mean intraocular pressure below 24 mm Hg as calculated by a day profile, and no increase in medication. These conditions were satisfied by 76% of the patients after six months and by 64% after 12 months. Initially, coagulations were performed over 180 degrees in the inferior circumference. If this did not suffice, the upper 180 degrees were also coagulated. If LTP is to be effective, thorough coagulation with tender blanching effects is mandatory. Average preoperative pressure values of over 22 mm Hg and a postoperative pressure increase of between 5 and 14 mm Hg are favorable prognostic signs. None of the parameters age, sex, duration, intensity of glaucomatous disease, or preoperative medication had any influence on the efficacy of LTP. In 14 of the 45 patients in whom only one eye was treated a simultaneous decrease in pressure was also observed in the untreated eye. The side effects of LTP bear no relation to its benefits, so that LTP is very suitable as a therapy between medication and surgery. Careful follow-ups of the patients are necessary because of possible increases in intraocular pressure in the course of time.

[The so-called "ocular histoplasmosis syndrome"]

The authors describe seven patients presenting with ophthalmoscopic findings typical of "presumed ocular histoplasmosis syndrome." However, no humoral antibodies could be demonstrated. Moreover, the results of skin tests were all negative even after "boostering." Hence, the diagnosis of ocular histoplasmosis had to be ruled out. Tests for listeriosis, lues, leptospirosis, ornithosis, Toxocara canis, toxoplasmosis, Larva migrans, and Candida albicans were also negative. There are evidently other, so far unknown, agents which lead to an ophthalmoscopic picture that mimics ocular histoplasmosis with its typical "punched-out lesions" and central hemorrhagic chorioretinopathy. One of these agents may be Epstein-Barr virus, because two of six patients had increased antibody levels of Epstein-Barr nuclear antigen and early antigen, indicating an active or persistent state of viral infection.

Cardiac tamponade in medical patients: treatment and prognosis in the echocardiographic era

Experience was reviewed in the management of pericardial tamponade in 36 patients with emphasis on factors governing short and long-term survival. Malignant pericardial effusion was the most common etiology and accounted for pericardial tamponade in 14 of the 36 patients (39%). Of the 36 patients, three received medical therapy alone, 18 were treated by one or more needle pericardiocentesis, pericardial drains were inserted in six patients, and thoracotomy was performed in nine. Needle pericardiocentesis was attempted as the initial therapy in all but two patients and was initially successful in relieving tamponade in 30 patients. Twenty-four patients died during a follow-up of from 1 day to 6 years. Delay in diagnosing tamponade was frequent and accounted for three deaths. Two more patients died from recurrent tamponade following initial relief. Eighteen patients died primarily from complications related to their basic illness, though recurrent pericardial effusion was a contributory factor in five. One patient died following pericardiectomy. The remaining 12 patients are well and free of pericardial disease. Short-term survival in pericardial tamponade is mostly dependent upon early diagnosis and relief of tamponade. Long-term survival depends upon the prognosis of the primary illness, irrespective of the mode of treatment used.

Spontaneous in vitro neoplastic transformation of adult human prostatic epithelium

The possible significance of spontaneous transformation of epithelium from a benign prostatic adenoma containing glandular hyperplasia is discussed.