Perspective paper about the joint EANM/SNMMI/ESTRO practice recommendations for the use of 2-[18F]FDG-PET/CT external beam radiation treatment planning in lung cancer

In “Joint EANM/SNMMI/ESTRO Practice Recommendations for the Use of 2-[18F]FDG-PET/CT External Beam Radiation Treatment Planning in Lung Cancer V1.0” clinical indications for PET-CT in (non-)small cell lung cancer are highlighted and selective nodal irradiation is discussed. Additionally, concepts about target definition, target delineation and treatment evaluation are reviewed.

Current practice in proton therapy delivery in adult cancer patients across Europe

BACKGROUND AND PURPOSE

Major differences exist among proton therapy (PT) centres regarding PT delivery in adult cancer patient. To obtain insight into current practice in Europe, we performed a survey among European PT centres.

MATERIALS AND METHODS

We designed electronic questionnaires for eight tumour sites, focusing on four main topics: 1) indications and patient selection methods; 2) reimbursement; 3) on-going or planned studies, 4) annual number of patients treated with PT.

RESULTS

Of 22 centres, 19 (86%) responded. In total, 4233 adult patients are currently treated across Europe annually, of which 46% consists of patients with central nervous system tumours (CNS), 15% head and neck cancer (HNC), 15% prostate, 9% breast, 5% lung, 5% gastrointestinal, 4% lymphoma, 0.3% gynaecological cancers. CNS are treated in all participating centres (n = 19) using PT, HNC in 16 centres, lymphoma in 10 centres, gastrointestinal in 10 centres, breast in 7 centres, prostate in 6 centres, lung in 6 centres, and gynaecological cancers in 3 centres. Reimbursement is provided by national health care systems for the majority of commonly treated tumour sites. Approximately 74% of centres enrol patients for prospective data registration programs. Phase II-III trials are less frequent, due to reimbursement and funding problems. Reasons for not treating certain tumour types with PT are lack of evidence (30%), reimbursement issues (29%) and/or technical limitations (20%).

CONCLUSION

Across European PT centres, CNS tumours and HNC are the most frequently treated tumour types. Most centres use indication protocols. Lack of evidence for PT and reimbursement issues are the most reported reasons for not treating specific tumour types with PT.

The impact of anatomical changes during photon or proton based radiation treatment on tumor dose in glioblastoma dose escalation trials

PURPOSE/OBJECTIVE

Most dose-escalation trials in glioblastoma patients integrate the escalated dose throughout the standard course by targeting a specific subvolume. We hypothesize that anatomical changes during irradiation may affect the dose coverage of this subvolume for both proton- and photon-based radiotherapy.

MATERIAL AND METHODS

For 24 glioblastoma patients a photon- and proton-based dose escalation treatment plan (of 75 Gy/30 fr) was simulated on the dedicated radiotherapy planning MRI obtained before treatment. The escalated dose was planned to cover the resection cavity and/or contrast enhancing lesion on the T1w post-gadolinium MRI sequence. To analyze the effect of anatomical changes during treatment, we evaluated on an additional MRI that was obtained during treatment the changes of the dose distribution on this specific high dose region.

RESULTS

The median time between the planning MRI and additional MRI was 26 days (range 16-37 days). The median time between the planning MRI and start of radiotherapy was relatively short (7 days, range 3-11 days). In 3 patients (12.5%) changes were observed which resulted in a substantial deterioration of both the photon and proton treatment plans. All these patients underwent a subtotal resection, and a decrease in dose coverage of more than 5% and 10% was observed for the photon- and proton-based treatment plans, respectively.

CONCLUSION

Our study showed that only for a limited number of patients anatomical changes during photon or proton based radiotherapy resulted in a potentially clinically relevant underdosage in the subvolume. Therefore, volume changes during treatment are unlikely to be responsible for the negative outcome of dose-escalation studies.

Role of Postoperative Radiotherapy in the Management for Resected NSCLC - Decision Criteria in Clinical Routine Pre- and Post-LungART

BACKGROUND

The role of postoperative radiation therapy (PORT) in stage III N2 NSCLC is controversial. We analyzed decision-making for PORT among European radiation oncology experts in lung cancer.

METHODS

Twenty-two experts were asked before and after presentation of the results of the LungART trial to describe their decision criteria for PORT in the management of pN+ NSCLC patients. Treatment strategies were subsequently converted into decision trees and analyzed.

RESULTS

Following decision criteria were identified: extracapsular nodal extension, incomplete lymph node resection, multistation lymph nodes, high nodal tumor load, poor response to induction chemotherapy, ineligibility to receive adjuvant chemotherapy, performance status, resection margin, lung function and cardiopulmonary comorbidities. The LungART results had impact on decision-making and reduced the number of recommendations for PORT. The only clear indication for PORT was a R1/2 resection. Six experts out of ten who initially recommended PORT for all R0 resected pN2 patients no longer used PORT routinely for these patients, while four still recommended PORT for all patients with pN2. Fourteen experts used PORT only for patients with risk factors, compared to eleven before the presentation of the LungART trial. Four experts stated that PORT was never recommended in R0 resected pN2 patients regardless of risk factors.

CONCLUSION

After presentation of the LungART trial results at ESMO 2020, 82% of our experts still used PORT for stage III pN2 NSCLC patients with risk factors. The recommendation for PORT decreased, especially for patients without risk factors. Cardiopulmonary comorbidities became more relevant in the decision-making for PORT.

Reduced diffusion in white matter after radiotherapy with photons and protons

BACKGROUND AND PURPOSE

Radio(chemo)therapy is standard in the adjuvant treatment of glioblastoma. Inevitably, brain tissue surrounding the target volume is also irradiated, potentially causing acute and late side-effects. Diffusion imaging has been shown to be a sensitive method to detect early changes in the cerebral white matter (WM) after radiation. The aim of this work was to assess possible changes in the mean diffusivity (MD) of WM after radio(chemo)therapy using Diffusion-weighted imaging (DWI) and to compare these effects between patients treated with proton and photon irradiation.

MATERIALS AND METHODS

70 patients with glioblastoma underwent adjuvant radio(chemo)therapy with protons (n = 20) or photons (n = 50) at the University Hospital Dresden. MRI follow-ups were performed at three-monthly intervals and in this study were evaluated until 33 months after the end of therapy. Relative white matter MD changes between baseline and all follow-up visits were calculated in different dose regions.

RESULTS

We observed a significant decrease of MD (p < 0.05) in WM regions receiving more than 20 Gy. MD reduction was progressive with dose and time after radio(chemo)therapy (maximum: -7.9 ± 1.2% after 24 months, ≥50 Gy). In patients treated with photons, significant reductions of MD in the entire WM (p < 0.05) were seen at all time points. Conversely, in proton patients, whole brain MD did not change significantly.

CONCLUSIONS

Irradiation leads to measurable MD reduction in white matter, progressing with both increasing dose and time. Treatment with protons reduces this effect most likely due to a lower total dose in the surrounding white matter. Further investigations are needed to assess whether those MD changes correlate with known radiation induced side-effects.

Optimal Allocation of Proton Therapy Slots in Combined Proton-Photon Radiation Therapy

PURPOSE

Proton therapy is a limited resource that is not available to all patients who may benefit from it. We investigated combined proton-photon treatments, in which some fractions are delivered with protons and the remaining fractions with photons, as an approach to maximize the benefit of limited proton therapy resources at a population level.

METHODS AND MATERIALS

To quantify differences in normal-tissue complication probability (NTCP) between protons and photons, we considered a cohort of 45 patients with head and neck cancer for whom intensity modulated radiation therapy and intensity modulated proton therapy plans were previously created, in combination with NTCP models for xerostomia and dysphagia considered in the Netherlands for proton patient selection. Assuming limited availability of proton slots, we developed methods to optimally assign proton fractions in combined proton-photon treatments to minimize the average NTCP on a population level. The combined treatments were compared with patient selection strategies in which patients are assigned to single-modality proton or photon treatments.

RESULTS

There is a benefit of combined proton-photon treatments compared with patient selection, owing to the nonlinearity of NTCP functions; that is, the initial proton fractions are the most beneficial, whereas additional proton fractions have a decreasing benefit when a flatter part of the NTCP curve is reached. This effect was small for the patient cohort and NTCP models considered, but it may be larger if dose-response relationships are better known. In addition, when proton slots are limited, patient selection methods face a trade-off between leaving slots unused and blocking slots for future patients who may have a larger benefit. Combined proton-photon treatments with flexible proton slot assignment provide a method to make optimal use of all available resources.

CONCLUSIONS

Combined proton-photon treatments allow for better use of limited proton therapy resources. The benefit over patient selection schemes depends on the NTCP models and the dose differences between protons and photons.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Identification of patient benefit from proton beam therapy in brain tumour patients based on dosimetric and NTCP analyses

BACKGROUND

The limited availability of proton beam therapy (PBT) requires individual treatment selection strategies, such as the model-based approach. In this study, we assessed the dosimetric benefit of PBT compared to photon therapy (XRT), analysed the corresponding changes in normal tissue complication probability (NTCP) on a variety of available models, and illustrated model-based patient selection in an in-silico study for patients with brain tumours.

METHODS

For 92 patients treated at two PBT centres, volumetric modulated arc therapy treatment plans were retrospectively created for comparison with the clinically applied PBT plans. Several dosimetric parameters for the brain excluding tumour and margins, cerebellum, brain stem, frontal and temporal lobes, hippocampi, cochleae, chiasm, optic nerves, lacrimal glands, lenses, pituitary gland, and skin were compared between both modalities using Wilcoxon signed-rank tests. NTCP differences (ΔNTCP) were calculated for 11 models predicting brain necrosis, delayed recall, temporal lobe injury, hearing loss, tinnitus, blindness, ocular toxicity, cataract, endocrine dysfunction, alopecia, and erythema. A patient was assumed to be selected for PBT if ΔNTCP exceeded a threshold of 10 percentage points for at least one of the side-effects.

RESULTS

PBT substantially reduced the dose in almost all investigated OARs, especially in the low and intermediate dose ranges and for contralateral organs. In general, NTCP predictions were significantly lower for PBT compared to XRT, in particular in ipsilateral organs. Considering ΔNTCP of all models, 80 patients (87.0%) would have been selected for PBT in this in-silico study, mainly due to predictions of a model on delayed recall (51 patients).

CONCLUSION

In this study, substantial dose reductions for PBT were observed, mainly in contralateral organs. However, due to the sigmoidal dose response, NTCP was particularly reduced in ipsilateral organs. This underlines that physical dose-volume parameters alone may not be sufficient to describe the clinical relevance between different treatment techniques and highlights potential benefits of NTCP models. Further NTCP models for different modern treatment techniques are mandatory and existing models have to be externally validated in order to implement the model-based approach in clinical practice for cranial radiotherapy.

Overestimation of grey matter atrophy in glioblastoma patients following radio(chemo)therapy

Objective

Brain atrophy has the potential to become a biomarker for severity of radiation-induced side-effects. Particularly brain tumour patients can show great MRI signal changes over time caused by e.g. oedema, tumour progress or necrosis. The goal of this study was to investigate if such changes affect the segmentation accuracy of normal appearing brain and thus influence longitudinal volumetric measurements.

Materials and methods

T1-weighted MR images of 52 glioblastoma patients with unilateral tumours acquired before and three months after the end of radio(chemo)therapy were analysed. GM and WM volumes in the contralateral hemisphere were compared between segmenting the whole brain (full) and the contralateral hemisphere only (cl) with SPM and FSL. Relative GM and WM volumes were compared using paired t tests and correlated with the corresponding mean dose in GM and WM, respectively.

Results

Mean GM atrophy was significantly higher for full segmentation compared to cl segmentation when using SPM (mean ± std: ΔV_GM,full = − 3.1% ± 3.7%, ΔV_GM,cl = − 1.6% ± 2.7%; p < 0.001, d = 0.62). GM atrophy was significantly correlated with the mean GM dose with the SPM cl segmentation (r = − 0.4, p = 0.004), FSL full segmentation (r = − 0.4, p = 0.004) and FSL cl segmentation (r = -0.35, p = 0.012) but not with the SPM full segmentation (r = − 0.23, p = 0.1).

Conclusions

For accurate normal tissue volume measurements in brain tumour patients using SPM, abnormal tissue needs to be masked prior to segmentation, however, this is not necessary when using FSL.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10334-021-00922-3.

MR Image Changes of Normal-Appearing Brain Tissue after Radiotherapy

Simple Summary

Radiotherapy is one of the most important treatment options against cancer. Irradiation of cancerous tissue either directly destroys the cancer cells or damages them such that they cannot reproduce. One side-effect of radiotherapy is that tumor-surrounding normal tissue is inevitably also irradiated, albeit at a lower dose. The resulting long-term damage can significantly affect cognitive performance and quality of life. Many studies investigated the effect of irradiation on normal-appearing brain tissues and some of these correlated imaging findings with functional outcome. This article provides an overview of the examination of radiation-induced injuries using conventional and enhanced MRI methods and summarizes conclusions about the underlying tissue changes. Radiation-induced morphologic, microstructural, vascular, and metabolic tissue changes have been observed, in which the effect of irradiation was evident in terms of decreased perfusion and neuronal health as well as increased diffusion and atrophy.

Abstract

Radiotherapy is part of the standard treatment of most primary brain tumors. Large clinical target volumes and physical characteristics of photon beams inevitably lead to irradiation of surrounding normal brain tissue. This can cause radiation-induced brain injury. In particular, late brain injury, such as cognitive dysfunction, is often irreversible and progressive over time, resulting in a significant reduction in quality of life. Since 50% of patients have survival times greater than six months, radiation-induced side effects become more relevant and need to be balanced against radiation treatment given with curative intent. To develop adequate treatment and prevention strategies, the underlying cause of radiation-induced side-effects needs to be understood. This paper provides an overview of radiation-induced changes observed in normal-appearing brains measured with conventional and advanced MRI techniques and summarizes the current findings and conclusions. Brain atrophy was observed with anatomical MRI. Changes in tissue microstructure were seen on diffusion imaging. Vascular changes were examined with perfusion-weighted imaging and susceptibility-weighted imaging. MR spectroscopy revealed decreasing N-acetyl aspartate, indicating decreased neuronal health or neuronal loss. Based on these findings, multicenter prospective studies incorporating advanced MR techniques as well as neurocognitive function tests should be designed in order to gain more evidence on radiation-induced sequelae.

Dose-escalated simultaneously integrated boost photon or proton therapy in pancreatic cancer in an in-silico study: Gastrointestinal organs remain critical

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Robustly optimized proton plans (rMFO-IMPT) with simultaneously integrated boost (SIB) were clinically applicable.

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Gastrointestinal organs reached critical dose values in rMFO-IMPT, VMAT and Tomotherapy techniques.

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rMFO-IMPT significantly reduced the low and intermediate dose to organs at risk.

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No clinically significant differences on results depending on tumor location or surgical status were observed.

Purpose

To compare the dosimetric results of an in-silico study among intensity-modulated photon (IMRT) and robustly optimized intensity-modulated proton (IMPT) treatment techniques using a dose-escalated simultaneously integrated boost (SIB) approach in locally recurrent or advanced pancreatic cancer patients.

Material and methods

For each of 15 locally advanced pancreatic cancer patients, a volumetric-modulated arc therapy (VMAT), a Tomotherapy (TOMO), and an IMPT treatment plan was optimized on free-breathing treatment planning computed tomography (CT) images. For the photon treatment plans, doses of 66 Gy and 51 Gy, both as SIB in 30 fractions, were prescribed to the gross tumor volume (GTV) and to the planning target volume (PTV), respectively. For the proton plans, a dose prescription of 66 Gy(RBE) to the GTV and of 51 Gy(RBE) to the clinical target volume (CTV) was planned. For each SIB-treatment plan, doses to the targets and OARs were evaluated and statistically compared.

Results

All treatment techniques reached the prescribed doses to the GTV and CTV or PTV. The stomach and the bowel, in particular the duodenum and the small bowel, were found to be frequently exposed to doses exceeding 50 Gy, irrespective of the treatment technique. For doses below 50 Gy, the IMPT technique was statistically significant superior to both IMRT techniques regarding decreasing dose to the OARs, e.g. volume of the bowel receiving 15 Gy (V_15Gy) was reduced for IMPT compared to VMAT (p = 0.003) and TOMO (p < 0.001).

Conclusion

With all photon and proton techniques investigated, the radiation dose to gastrointestinal OARs remained critical when treating patients with unresectable locally recurrent or advanced pancreatic cancer using a dose-escalated SIB approach.

Technical Note: ADAM PETer - An anthropomorphic, deformable and multimodality pelvis phantom with positron emission tomography extension for radiotherapy

OBJECTIVE

To develop an anthropomorphic, deformable and multimodal pelvis phantom with positron emission tomography extension for radiotherapy (ADAM PETer).

METHODS

The design of ADAM PETer was based on our previous pelvis phantom (ADAM) and extended for compatibility with PET and use in 3T magnetic resonance imaging (MRI). The formerly manually manufactured silicon organ surrogates were replaced by three-dimensional (3D) printed organ shells. Two intraprostatic lesions, four iliac lymph node metastases and two pelvic bone metastases were added to simulate prostate cancer as multifocal and metastatic disease. Radiological properties [computed tomography (CT) and 3T MRI] of cortical bone, bone marrow and adipose tissue were simulated by heavy gypsum, a mixture of Vaseline and K₂ HPO₄ and peanut oil, respectively. For soft tissues, agarose gels with varying concentrations of agarose, gadolinium (Gd) and sodium fluoride (NaF) were developed. The agarose gels were doped with patient-specific activity concentrations of a Fluorine-18 labelled compound and then filled into the 3D printed organ shells of prostate lesions, lymph node and bone metastases. The phantom was imaged at a dual energy CT and a 3T PET/MRI scanner.

RESULTS

The compositions of the soft tissue surrogates are the following (given as mass fractions of agarose[w%]/NaF[w%]/Gd[w%]): Muscle (4/1/0.027), prostate (1.35/4.2/0.011), prostate lesions (2.25/4.2/0.0085), lymph node and bone metastases (1.4/4.2/0.025). In all imaging modalities, the phantom simulates human contrast. Intraprostatic lesions appear hypointense as compared to the surrounding normal prostate tissue in T2-weighted MRI. The PET signal of all tumors can be localized as focal spots at their respective site. Activity concentrations of 12.0 kBq/mL (prostate lesion), 12.4 kBq/mL (lymph nodes) and 39.5 kBq/mL (bone metastases) were measured.

CONCLUSION

The ADAM PETer pelvis phantom can be used as multimodal, anthropomorphic model for CT, 3T-MRI and PET measurements. It will be central to simulate and optimize the technical workflow for the integration of PET/MRI-based radiation treatment planning of prostate cancer patients.

Proposal for the delineation of neoadjuvant target volumes in oesophageal cancer

PURPOSE

To define instructions for delineation of target volumes in the neoadjuvant setting in oesophageal cancer.

MATERIALS AND METHODS

Radiation oncologists of five European centres participated in the following consensus process: [1] revision of published (MEDLINE) and national/institutional delineation guidelines; [2] first delineation round of five cases (patient 1-5) according to national/institutional guidelines; [3] consensus meeting to discuss the results of step 1 and 2, followed by a target volume delineation proposal; [4] circulation of proposed instructions for target volume delineation and atlas for feedback; [5] second delineation round of five new cases (patient 6-10) to peer review and validate (two additional centres) the agreed delineation guidelines and atlas; [6] final consensus on the delineation guidelines depicted in an atlas. Target volumes of the delineation rounds were compared between centres by Dice similarity coefficient (DSC) and maximum/mean undirected Hausdorff distances (H_max/H_mean).

RESULTS

In the first delineation round, the consistency between centres was moderate (CTVtotal: DSC = 0.59-0.88; H_mean = 0.2-0.4 cm). Delineations in the second round were much more consistent. Lowest variability was obtained between centres participating in the consensus meeting (CTVtotal: DSC: p < 0.050 between rounds for patients 6/7/8/10; H_mean: p < 0.050 for patients 7/8/10), compared to validation centres (CTVtotal: DSC: p < 0.050 between validation and consensus meeting centres for patients 6/7/8; H_mean: p < 0.050 for patients 7/10). A proposal for delineation of target volumes and an atlas were generated.

CONCLUSION

We proposed instructions for target volume delineation and an atlas for the neoadjuvant radiation treatment in oesophageal cancer. These will enable a more uniform delineation of patients in clinical practice and clinical trials.

Toxicity of L19-Interleukin 2 Combined with Stereotactic Body Radiation Therapy: A Phase 1 Study

PURPOSE

The immunocytokine L19-IL2 delivers interleukin-2 to the tumor by exploiting the selective L19-dependent binding of extradomain B of fibronectin on tumor blood vessels. In preclinical models, L19-IL2 has been shown to enhance the local and abscopal effects of radiation therapy. The clinical safety of L19-IL2 monotherapy has been established previously. In this study, the safety and tolerability of L19-IL2 after stereotactic body radiation therapy (SBRT) was assessed.

METHODS AND MATERIALS

Patients with oligometastatic solid tumors received radical SBRT to all visible metastases. Within 1 week after SBRT, intravenous L19-IL2 using a 3 + 3 dose escalation design was administered. Safety and tolerability were analyzed as the primary endpoint using the Common Terminology Criteria for Adverse Events 4.03 scoring system, with progression-free and overall survival as secondary endpoints.

RESULTS

A total of 6 patients in 2 L19-IL2 dose levels were included. The 15 million International Units (Mio IU) dose level was well tolerated with no dose-limiting toxicity. The most frequently reported adverse events were chills, noninfectious fever, fatigue, edema, erythema, pruritus, nausea/vomiting, and cough and dyspnea. Blood analysis revealed abnormalities in liver function tests, anemia, hypoalbuminemia, and hypokalemia. At the second dose level (ie, 22.5 Mio IU), which is the recommended dose for L19-IL2 monotherapy, all 3 included patients experienced dose-limiting toxicity but recovered without sequelae. We documented 2 long-term progression-free responders, both having non-small cell lung cancer as primary tumor.

CONCLUSIONS

Based on the results of this phase 1 clinical trial, the recommended phase 2 dose for SBRT combined with L19-IL2 is 15 Mio IU. The therapeutic efficacy of this combination is currently being evaluated in the multicentric EU-funded phase 2 clinical trial, ImmunoSABR.

Generation of biological hypotheses by functional imaging links tumor hypoxia to radiation induced tissue inflammation/glucose uptake in head and neck cancer

BACKGROUND AND PURPOSE

Positron emission tomography (PET) is a functional imaging modality which is able to deliver tracer specific biological information, e.g. about glucose uptake, inflammation or hypoxia of tumors. We performed a proof-of-principle study that used different tracers and expanded the analytical scope to non-tumor structures to evaluate tumor-host interactions.

MATERIALS AND METHODS

Based on a previously reported prospective imaging study on 50 patients treated with curative intent chemoradiation (CRT) for head and neck squamous cell carcinoma, PET-based hypoxia and normal tissue inflammation measured by repeat 18F-fluoromisonidazole (FMISO) PET and 18F-fluorodesoxyglucose (FDG) PET, respectively, were correlated using the Spearman correlation coefficient R. PET parameters determined before and during CRT (week 1, 2 and 5), were associated with local tumor control and overall survival.

RESULTS

Tumor hypoxia at all measured times showed an inverse correlation with mid-treatment FDG-uptake of non-tumor affected oral (sub-)mucosa with R values between -0.35 and -0.6 (all p < 0.05). Mucosal FDG-uptake and mucosal hypoxia correlated positively but weaker (R values between 0.2 and 0.45). More tumor hypoxia in FMISO-PET (week 2) and less FDG-uptake of (sub-)mucosa in FDG-PET (week 4) were significantly associated with worse LC (FMISO TBR_peak: HR = 1.72, p = 0.030; FDG SUV_mean: HR = 0.23, p = 0.025) and OS (FMISO TBR_peak: HR = 1.71, p = 0.007; FDG SUV_mean: HR = 0.30, p = 0.003). Multivariable models including both parameters showed improved performance, suggesting that these modalities still bear distinct biological information despite their strong inter-correlation.

CONCLUSION

We report first clinical evidence that tumor hypoxia is inversely correlated with increased FDG-uptake during radiation, potentially expressing inflammation. This observation merits further research and may have important implication for future research on tumor hypoxia and radio-immunology. Our study demonstrates that functional imaging can be utilized to assess complex tumor-host interactions and generate novel biological insights in vivo vero.

Role of radiotherapy in the management of brain metastases of NSCLC - Decision criteria in clinical routine

BACKGROUND

Whole brain radiotherapy (WBRT) is a common treatment option for brain metastases secondary to non-small cell lung cancer (NSCLC). Data from the QUARTZ trial suggest that WBRT can be omitted in selected patients and treated with optimal supportive care alone. Nevertheless, WBRT is still widely used to treat brain metastases secondary to NSCLC. We analysed decision criteria influencing the selection for WBRT among European radiation oncology experts.

METHODS

Twenty-two European radiation oncology experts in lung cancer as selected by the European Society for Therapeutic Radiation Oncology (ESTRO) for previous projects and by the Advisory Committee on Radiation Oncology Practice (ACROP) for lung cancer were asked to describe their strategies in the management of brain metastases of NSCLC. Treatment strategies were subsequently converted into decision trees and analysed for agreement and discrepancies.

RESULTS

Eight decision criteria (suitability for SRS, performance status, symptoms, eligibility for targeted therapy, extra-cranial tumour control, age, prognostic scores and "Zugzwang" (the compulsion to treat)) were identified. WBRT was recommended by a majority of the European experts for symptomatic patients not suitable for radiosurgery or fractionated stereotactic radiotherapy. There was also a tendency to use WBRT in the ALK/EGFR/ROS1 negative NSCLC setting.

CONCLUSION

Despite the results of the QUARTZ trial WBRT is still widely used among European radiation oncology experts.

The role of computational methods for automating and improving clinical target volume definition

Treatment planning in radiotherapy distinguishes three target volume concepts: the gross tumor volume (GTV), the clinical target volume (CTV), and the planning target volume (PTV). Over time, GTV definition and PTV margins have improved through the development of novel imaging techniques and better image guidance, respectively. CTV definition is sometimes considered the weakest element in the planning process. CTV definition is particularly complex since the extension of microscopic disease cannot be seen using currently available in-vivo imaging techniques. Instead, CTV definition has to incorporate knowledge of the patterns of tumor progression. While CTV delineation has largely been considered the domain of radiation oncologists, this paper, arising from a 2019 ESTRO Physics research workshop, discusses the contributions that medical physics and computer science can make by developing computational methods to support CTV definition. First, we overview the role of image segmentation algorithms, which may in part automate CTV delineation through segmentation of lymph node stations or normal tissues representing anatomical boundaries of microscopic tumor progression. The recent success of deep convolutional neural networks has also enabled learning entire CTV delineations from examples. Second, we discuss the use of mathematical models of tumor progression for CTV definition, using as example the application of glioma growth models to facilitate GTV-to-CTV expansion for glioblastoma that is consistent with neuroanatomy. We further consider statistical machine learning models to quantify lymphatic metastatic progression of tumors, which may eventually improve elective CTV definition. Lastly, we discuss approaches to incorporate uncertainty in CTV definition into treatment plan optimization as well as general limitations of the CTV concept in the case of infiltrating tumors without natural boundaries.

2D and 3D convolutional neural networks for outcome modelling of locally advanced head and neck squamous cell carcinoma

For treatment individualisation of patients with locally advanced head and neck squamous cell carcinoma (HNSCC) treated with primary radiochemotherapy, we explored the capabilities of different deep learning approaches for predicting loco-regional tumour control (LRC) from treatment-planning computed tomography images. Based on multicentre cohorts for exploration (206 patients) and independent validation (85 patients), multiple deep learning strategies including training of 3D- and 2D-convolutional neural networks (CNN) from scratch, transfer learning and extraction of deep autoencoder features were assessed and compared to a clinical model. Analyses were based on Cox proportional hazards regression and model performances were assessed by the concordance index (C-index) and the model's ability to stratify patients based on predicted hazards of LRC. Among all models, an ensemble of 3D-CNNs achieved the best performance (C-index 0.31) with a significant association to LRC on the independent validation cohort. It performed better than the clinical model including the tumour volume (C-index 0.39). Significant differences in LRC were observed between patient groups at low or high risk of tumour recurrence as predicted by the model ([Formula: see text]). This 3D-CNN ensemble will be further evaluated in a currently ongoing prospective validation study once follow-up is complete.

National societies' needs as assessed by the ESTRO National Societies Committee survey: A European perspective

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A survey to assess the National Societies needs has been developed.

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64 out of 89 National societies from 32 European countries completed the questionnaire.

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The highest priority is Optimal patient care to cure cancer & reduce treatment-related toxicity.

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High need for more consensus guidelines, exchange of best practices and high quality accredited education.

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Networking between National Societies and ESTRO will be further reinforced.

Purpose

To determine how ESTRO can collaborate with Radiation Oncology National Societies (NS) according to its mission and values, and to define the new roadmap to strengthen the NS network role in the forthcoming years.

Materials and methods

The ESTRO NS committee launched a survey addressed to all European National Societies, available online from June 5th to October 30th 2018. Questions were divided into three main sections: (1) general information about NS; (2) relevant activities (to understand the landscape of each NS context of action); (3) relevant needs (to understand how ESTRO can support the NS). Eighty-nine European NS were invited to participate. Respondents were asked to rank ESTRO milestones in order of importance, indicating the level of priority to their society.

Results

A total of 58 out of 89 NS (65.2%) from 31 European countries completed the questionnaire. The majority of NS ranked “Optimal patient care to cure cancer and to reduce treatment-related toxicity” as the highest level of priority. This aligns well with the ESTRO vision 2030 “Optimal health for all together.” NS also indicated a high need for more consensus guidelines and exchange of best practices, access to high quality accredited education, implementation of the ESTRO School Core Curriculum at the national level, and defining quality indicators and standard in Radiation Oncology, improved communication and increased channelling of information.

Conclusion

The results of this survey will be used to strengthen the relations between ESTRO and European NS to promote and develop initiatives to improve cancer care.

Dose dependent cerebellar atrophy in glioma patients after radio(chemo)therapy

BACKGROUND AND PURPOSE

Radiotherapy is a standard treatment option for high-grade gliomas. Brain atrophy has previously been associated with radiotherapy. The goal of this study was to investigate dose dependent cerebellar atrophy using prospective, longitudinal MR data from adult glioma patients who received radiotherapy.

MATERIALS AND METHODS

Cerebellar volumes were measured using T1-weighted MR images from 91 glioma patients before radiotherapy (N = 91) and from longitudinal follow-ups acquired in three monthly intervals (N = 349). Relative cerebellar volumes were calculated as ratios to the corresponding baseline values. Univariate mixed effects models were used to determine factors that were significantly associated with relative cerebellar volumes. These factors were subsequently included as fixed effects in a final multivariate linear mixed effects model.

RESULTS

In multivariate analysis, cerebellar volume decreased significantly as a function of time (p < 0.001), time × dose (p < 0.001) and patient age (p = 0.007). Considering a 55 year patient receiving a mean cerebellar dose of 0 Gy (10 Gy), the linear mixed effects model predicts a relative cerebellar volume loss of 0.4% (2.0%) after 1 year and 0.7% (3.6%) after 2 years. Compared to patients treated with photons, the cerebellar dose was significantly lower in patients treated with proton therapy (p < 0.001, r = 0.62).

CONCLUSION

Cerebellar volume decreased significantly and irreversibly after radiotherapy as function of time and mean cerebellar dose. Further work is now needed to correlate these results with cognitive function and motor performance.

Investigation of inter-fraction target motion variations in the context of pencil beam scanned proton therapy in non-small cell lung cancer patients

Purpose

For locally advanced‐stage non‐small cell lung cancer (NSCLC), inter‐fraction target motion variations during the whole time span of a fractionated treatment course are assessed in a large and representative patient cohort. The primary objective is to develop a suitable motion monitoring strategy for pencil beam scanning proton therapy (PBS‐PT) treatments of NSCLC patients during free breathing.

Methods

Weekly 4D computed tomography (4DCT; 41 patients) and daily 4D cone beam computed tomography (4DCBCT; 10 of 41 patients) scans were analyzed for a fully fractionated treatment course. Gross tumor volumes (GTVs) were contoured and the 3D displacement vectors of the centroid positions were compared for all scans. Furthermore, motion amplitude variations in different lung segments were statistically analyzed. The dosimetric impact of target motion variations and target motion assessment was investigated in exemplary patient cases.

Results

The median observed centroid motion was 3.4 mm (range: 0.2–12.4 mm) with an average variation of 2.2 mm (range: 0.1–8.8 mm). Ten of 32 patients (31.3%) with an initial motion <5 mm increased beyond a 5‐mm motion amplitude during the treatment course. Motion observed in the 4DCBCT scans deviated on average 1.5 mm (range: 0.0–6.0 mm) from the motion observed in the 4DCTs. Larger motion variations for one example patient compromised treatment plan robustness while no dosimetric influence was seen due to motion assessment biases in another example case.

Conclusions

Target motion variations were investigated during the course of radiotherapy for NSCLC patients. Patients with initial GTV motion amplitudes of < 2 mm can be assumed to be stable in motion during the treatment course. For treatments of NSCLC patients who exhibit motion amplitudes of > 2 mm, 4DCBCT should be considered for motion monitoring due to substantial motion variations observed.

Evaluation of response using FDG-PET/CT and diffusion weighted MRI after radiochemotherapy of pancreatic cancer: a non-randomized, monocentric phase II clinical trial-PaCa-DD-041 (Eudra-CT 2009-011968-11)

Background

Pancreatic cancer is a devastating disease with a 5-year survival rate of 20–25%. As approximately only 20% of patients diagnosed with pancreatic cancer are initially staged as resectable, it is necessary to evaluate new therapeutic approaches. Hence, neoadjuvant (radio)chemotherapy is a promising therapeutic option, especially in patients with a borderline resectable tumor. The aim of this non-randomized, monocentric, prospective, phase II clinical study was to assess the prognostic value of functional imaging techniques, i.e., [¹⁸F]2-fluoro-2-deoxy-d-glucose positron emission tomography/computed tomography (FDG-PET/CT) and diffusion weighted magnetic resonance imaging (DW-MRI), prior to and during neoadjuvant radiochemotherapy.

Methods

Patients with histologically proven resectable, borderline resectable or unresectable non-metastatic pancreatic adenocarcinoma received induction chemotherapy followed by neoadjuvant radiochemotherapy. Patients underwent FDG-PET/CT and DW-MRI including T1- and T2-weighted sequences prior to and after neoadjuvant chemotherapy as well as following induction radiochemotherapy. The primary endpoint was the evaluation of the response as quantified by the standardized uptake value (SUV) measured with FDG-PET. Response to treatment was evaluated by FDG-PET and DW-MRI during and after the neoadjuvant course. Morphologic staging was performed using contrast-enhanced CT and contrast-enhanced MRI to decide inclusion of patients and resectability after neoadjuvant therapy. In those patients undergoing subsequent surgery, imaging findings were correlated with those of the pathologic resection specimen.

Results

A total of 25 patients were enrolled in the study. The response rate measured by FDG-PET was 85% with a statistically significant decrease of the maximal SUV (SUV_max) during therapy (p < 0.001). Using the mean apparent diffusion coefficient (ADC), response was not detectable with DW-MRI. After neoadjuvant treatment 16 patients underwent surgery. In 12 (48%) patients tumor resection could be performed. The median overall survival of all patients was 25 months (range: 7–38 months).

Conclusion

Based on these limited patient numbers, it was possible to show that this trial design is feasible and that the neoadjuvant therapy regime was well tolerated. FDG-PET/CT may be a reliable method to evaluate response to the combined therapy. In contrast, when evaluating the response using mean ADC, DW-MRI did not show conclusive results.

Electronic supplementary material

The online version of this article (10.1007/s00066-020-01654-4) contains supplementary material, which is available to authorized users.