European Society of Radiotherapy and Oncology (ESTRO) strategy 2024-2026: Growth and diversification in a rapidly changing world

In 2019, the European Society of Radiotherapy and Oncology (ESTRO) published its 2030 Vision "Radiation Oncology, Optimal Health, For All, Together". However, in 2020, the global pandemic, coinciding with the Society's 40th anniversary, had long-term consequences on global behaviours and on the financial environment for scientific associations worldwide. In 2022, ESTRO conducted a survey among its members, revealing their strong appreciation for networking opportunities and the creation of high-quality interdisciplinary scientific content. In response to the survey findings and to address the evolving landscape following the COVID pandemic, ESTRO initiated a strategic review process to respond to, and refocus on, the opportunities and challenges ahead. This paper, marking a turning point in ESTRO's strategy for achieving its Vision 2030 in a post-pandemic era, describes the 2022-23 strategic review process, discussions, and consequent recommendations. The comprehensive strategic review process involved: (i) pre-meeting preparations with surveys and strategic documents; (ii) a carefully themed three-day retreat in Brussels incorporating a blend of plenary sessions, workshops focusing on ESTRO's role, value creation and capture, strategic objectives; and (iii) a post-retreat phase including qualitative analysis and development of action plans. The strategic review emphasized the need for adaptive tactics for scientific associations to remain current and productive in the face of changing global conditions. The development of key strategic goals for the years 2024-2026 focused on improving research impact, strengthening and diversifying ESTRO's educational offerings and fostering proactive and mutually beneficial partnerships. The Board approved these objectives, alongside prioritising digital innovation, financial sustainability, and community engagement for ESTRO's continued growth and development. In essence, ESTRO aims to advocate, empower, expand, and diversify its community, with the overarching goal of enhancing cancer care for patients in Europe, and beyond.

Differential Impact of Consolidative Thoracic Radiotherapy in Extensive-Stage Small Cell Lung Cancer Based on Systemic Therapy Type and Sex

PURPOSE/OBJECTIVE(S)

Consolidative thoracic radiotherapy (cTRT) has been shown in phase III RCTs to improve overall (OS) and progression-free survival (PFS) after initial chemotherapy (chemo) in extensive-stage small cell lung cancer (ES-SCLC). This benefit was particularly pronounced in women compared to men in the 2015 CREST trial (hazard ratio [HR] 0.68 vs. 1.01, respectively). However, it is unknown whether similar findings would apply after chemoimmunotherapy (chemo-IO) became standard of care first-line treatment in 2018. In this analysis, we report national practice patterns and survival outcomes of cTRT versus no cTRT following chemo or chemo-IO, stratified by sex.

MATERIALS/METHODS

Patients from the nationwide Flatiron Health de-identified electronic health record-derived database were included if they completed 4-6 cycles of first-line systemic therapy (platinum-doublet chemo or chemo-IO) for stage IV SCLC diagnosed between 2014 and 2021. Patients who progressed or started cTRT within 14 days or died within 90 days of completing systemic therapy were excluded to account for immortal time bias. We evaluated OS and PFS using multivariable Cox proportional hazards regression with receipt of cTRT as an independent covariate and last date of chemo as index date. As a sensitivity analysis to address potential selection bias, we weighted the models by the inverse probability of receiving cTRT. All OS and PFS analyses were stratified by systemic therapy type and sex.

RESULTS

A total of 1,227 patients were included (850 chemo, 377 chemo-IO). The proportion of patients who received cTRT increased from 11.7% in 2014 to 20.7% in 2017, and then decreased to 16.4% in 2021. There were no statistically significant differences in baseline characteristics between patients who did and did not receive cTRT. In adjusted analyses among women receiving chemo, cTRT was associated with superior OS (HR 0.68; 95% confidence interval [CI] 0.51-0.91) and PFS (HR 0.64; 95% CI 0.47-0.86) [Table 1]. There was a non-statistically significant trend towards improved OS (HR 0.57; 95% CI 0.32-1.02) and PFS (HR 0.59; 95% CI 0.34-1.02) among women receiving chemo-IO. No OS or PFS benefit with cTRT was observed in men receiving either chemo or chemo-IO. Findings were similar in weighted analyses.

CONCLUSION

The survival impact of cTRT may be differentially impacted by sex, with female patients appearing more likely to benefit than male patients regardless of systemic therapy type. While the underpinnings of this association need to be elucidated, stratification by sex should be considered for RCTs studying cTRT in ES-SCLC.

Preoperative Partial Breast Irradiation in Patients with Low-Risk Breast Cancer: A Systematic Review of Literature

BACKGROUND

Preoperative instead of standard postoperative partial breast irradiation (PBI) after breast-conserving surgery (BCS) has the advantage of reducing the irradiated breast volume, toxicity, and number of radiotherapy sessions and can allow tumor downstaging. In this review, we assessed tumor response and clinical outcomes after preoperative PBI.

PATIENTS AND METHODS

We conducted a systematic review of studies on preoperative PBI in patients with low-risk breast cancer using the databases Ovid Medline, Embase.com, Web of Science (Core Collection), and Scopus (PROSPERO registration CRD42022301435). References of eligible manuscripts were checked for other relevant manuscripts. The primary outcome measure was pathologic complete response (pCR).

RESULTS

A total of eight prospective and one retrospective cohort study were identified (n = 359). In up to 42% of the patients, pCR was obtained and this increased after a longer interval between radiotherapy and BCS (0.5-8 months). After a maximum median follow-up of 5.0 years, three studies on external beam radiotherapy reported low local recurrence rates (0-3%) and overall survival of 97-100%. Acute toxicity consisted mainly of grade 1 skin toxicity (0-34%) and seroma (0-31%). Late toxicity was predominantly fibrosis grade 1 (46-100%) and grade 2 (10-11%). Cosmetic outcome was good to excellent in 78-100% of the patients.

CONCLUSIONS

Preoperative PBI showed a higher pCR rate after a longer interval between radiotherapy and BCS. Mild late toxicity and good oncological and cosmetic outcomes were reported. In the ongoing ABLATIVE-2 trial, BCS is performed at a longer interval of 12 months after preoperative PBI aiming to achieve a higher pCR rate.

Prediction of pathologic complete response after single-dose MR-guided partial breast irradiation in low-risk breast cancer patients: the ABLATIVE-2 trial-a study protocol

BACKGROUND

Partial breast irradiation (PBI) is standard of care in low-risk breast cancer patients after breast-conserving surgery (BCS). Pre-operative PBI can result in tumor downstaging and more precise target definition possibly resulting in less treatment-related toxicity. This study aims to assess the pathologic complete response (pCR) rate one year after MR-guided single-dose pre-operative PBI in low-risk breast cancer patients.

METHODS

The ABLATIVE-2 trial is a multicenter prospective single-arm trial using single-dose ablative PBI in low-risk breast cancer patients. Patients ≥ 50 years with non-lobular invasive breast cancer ≤ 2 cm, grade 1 or 2, estrogen receptor-positive, HER2-negative, and tumor-negative sentinel node procedure are eligible. A total of 100 patients will be enrolled. PBI treatment planning will be performed using a radiotherapy planning CT and -MRI in treatment position. The treatment delivery will take place on a conventional or MR-guided linear accelerator. The prescribed radiotherapy dose is a single dose of 20 Gy to the tumor, and 15 Gy to the 2 cm of breast tissue surrounding the tumor. Follow-up MRIs, scheduled at baseline, 2 weeks, 3, 6, 9, and 12 months after PBI, are combined with liquid biopsies to identify biomarkers for pCR prediction. BCS will be performed 12 months after radiotherapy or after 6 months, if MRI does not show a radiologic complete response. The primary endpoint is the pCR rate after PBI. Secondary endpoints are radiologic response, toxicity, quality of life, cosmetic outcome, patient distress, oncological outcomes, and the evaluation of biomarkers in liquid biopsies and tumor tissue. Patients will be followed up to 10 years after radiation therapy.

DISCUSSION

This trial will investigate the pathological tumor response after pre-operative single-dose PBI after 12 months in patients with low-risk breast cancer. In comparison with previous trial outcomes, a longer interval between PBI and BCS of 12 months is expected to increase the pCR rate of 42% after 6-8 months. In addition, response monitoring using MRI and biomarkers will help to predict pCR. Accurate pCR prediction will allow omission of surgery in future patients.

TRIAL REGISTRATION

The trial was registered prospectively on April 28th 2022 at clinicaltrials.gov (NCT05350722).

Single Ultra-High Dose Rate Proton Transmission Beam for Whole Breast FLASH-Irradiation: Quantification of FLASH-Dose and Relation with Beam Parameters

Healthy tissue-sparing effects of FLASH (≥40 Gy/s, ≥4-8 Gy/fraction) radiotherapy (RT) make it potentially useful for whole breast irradiation (WBI), since there is often a lot of normal tissue within the planning target volume (PTV). We investigated WBI plan quality and determined FLASH-dose for various machine settings using ultra-high dose rate (UHDR) proton transmission beams (TBs). While five-fraction WBI is commonplace, a potential FLASH-effect might facilitate shorter treatments, so hypothetical 2- and 1-fraction schedules were also analyzed. Using one tangential 250 MeV TB delivering 5 × 5.7 Gy, 2 × 9.74 Gy or 1 × 14.32 Gy, we evaluated: (1) spots with equal monitor units (MUs) in a uniform square grid with variable spacing; (2) spot MUs optimized with a minimum MU-threshold; and (3) splitting the optimized TB into two sub-beams: one delivering spots above an MU-threshold, i.e., at UHDRs; the other delivering the remaining spots necessary to improve plan quality. Scenarios 1-3 were planned for a test case, and scenario 3 was also planned for three other patients. Dose rates were calculated using the pencil beam scanning dose rate and the sliding-window dose rate. Various machine parameters were considered: minimum spot irradiation time (minST): 2 ms/1 ms/0.5 ms; maximum nozzle current (maxN): 200 nA/400 nA/800 nA; two gantry-current (GC) techniques: energy-layer and spot-based. For the test case (PTV = 819 cc) we found: (1) a 7 mm grid achieved the best balance between plan quality and FLASH-dose for equal-MU spots; (2) near the target boundary, lower-MU spots are necessary for homogeneity but decrease FLASH-dose; (3) the non-split beam achieved >95% FLASH for favorable (not clinically available) machine parameters (SB GC, low minST, high maxN), but <5% for clinically available settings (EB GC, minST = 2 ms, maxN = 200 nA); and (4) splitting gave better plan quality and higher FLASH-dose (~50%) for available settings. The clinical cases achieved ~50% (PTV = 1047 cc) or >95% (PTV = 477/677 cc) FLASH after splitting. A single UHDR-TB for WBI can achieve acceptable plan quality. Current machine parameters limit FLASH-dose, which can be partially overcome using beam-splitting. WBI FLASH-RT is technically feasible.

Accuracy of deformable image registration-based intra-fraction motion management in Magnetic Resonance-guided radiotherapy

Background and Purpose

Intra-fraction motion management is key in Stereotactic Ablative Radiotherapy (SABR) gated delivery. This study assessed the accuracy of automatic tumor segmentation in the delivery of MR-guided radiotherapy (MRgRT) by comparing it to manual delineations performed by experienced observers.

Materials and Methods

Twenty patients previously treated with MR-guided SABR for thoracic and abdominal tumors were included. Five observers with at least two years of experience in MRgRT manually delineated the gross tumor volume (GTV) for 20 patients on 240 frames of a cine MRI on a sagittal plane. Deformable Image Registration (DIR) based GTV contours were propagated using four different algorithms from a reference frame to subsequent frames.Geometrical analysis based on the Dice Similarity Coefficient (DSC), centroid distance and Hausdorff Distance (HDD) were performed to assess the inter-observer variability and the accuracy of automatic segmentation. A Confidence Value (CV) metric for the reliability of the tumor auto-contouring was also calculated.

Results

Inter-observer delineation variability resulted in mean DSC of 0.89, HDD of 5.8 mm and centroid distance of 1.7 mm. Tumor auto-contouring by the four DIR algorithms resulted in an excellent agreement with the manual delineations by the experienced observers. Mean DSC for each algorithm across all patients was greater than 0.90, whereas the HDD and centroid distances were below 4.0 mm and 1.5 mm, respectively. The CV showed a strong correlation with the DSC.

Conclusions

DIR-based auto-contouring in MRgRT exhibited a high level of agreement with the manual contouring performed by experts, allowing accurate gated delivery.

Deep Learning for Automated Elective Lymph Node Level Segmentation for Head and Neck Cancer Radiotherapy

Depending on the clinical situation, different combinations of lymph node (LN) levels define the elective LN target volume in head-and-neck cancer (HNC) radiotherapy. The accurate auto-contouring of individual LN levels could reduce the burden and variability of manual segmentation and be used regardless of the primary tumor location. We evaluated three deep learning approaches for the segmenting individual LN levels I−V, which were manually contoured on CT scans from 70 HNC patients. The networks were trained and evaluated using five-fold cross-validation and ensemble learning for 60 patients with (1) 3D patch-based UNets, (2) multi-view (MV) voxel classification networks and (3) sequential UNet+MV. The performances were evaluated using Dice similarity coefficients (DSC) for automated and manual segmentations for individual levels, and the planning target volumes were extrapolated from the combined levels I−V and II−IV, both for the cross-validation and for an independent test set of 10 patients. The median DSC were 0.80, 0.66 and 0.82 for UNet, MV and UNet+MV, respectively. Overall, UNet+MV significantly (p < 0.0001) outperformed other arrangements and yielded DSC = 0.87, 0.85, 0.86, 0.82, 0.77, 0.77 for the combined and individual level I−V structures, respectively. Both PTVs were also significantly (p < 0.0001) more accurate with UNet+MV, with DSC = 0.91 and 0.90, respectively. The accurate segmentation of individual LN levels I−V can be achieved using an ensemble of UNets. UNet+MV can further refine this result.

Same-day consultation, simulation and lung Stereotactic Ablative Radiotherapy delivery on a Magnetic Resonance-linac

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A same-day consultation and lung SABR workflow was introduced, and experience in 10 patients reported.

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A detailed simulation procedure and the use of real-time cine magnetic resonance imaging enabled accurate treatment delivery.

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All patients reported satisfaction with the procedure, which improved patient convenience.

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On average, at least 94.4% (5th percentile) of the GTV was always located inside the PTV during beam-on.

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System-latency for triggering a beam-off event comprised 5.3% of the delivery time.

Background and Purpose

Magnetic resonance-guided radiotherapy (MRgRT) with real-time intra-fraction tumor motion monitoring allows for high precision Stereotactic Ablative Radiotherapy (SABR). This study aimed to investigate the clinical feasibility, patient satisfaction and delivery accuracy of single-fraction MR-guided SABR in a single day (one-stop-shop, OSS).

Methods and Materials

Ten patients with small lung tumors eligible for single fraction treatments were included. The OSS procedure consisted of consultation, treatment simulation, treatment planning and delivery. Following SABR delivery, patients completed a reported experience measure (PREM) questionnaire. Prescribed doses ranged 28–34 Gy. Median GTV was 2.2 cm³ (range 1.3–22.9 cm³). A gating boundary of 3 mm, and PTV margin of 5 mm around the GTV, were used with auto-beam delivery control. Accuracy of SABR delivery was studied by analyzing delivered MR-cines reconstructed from machine log files.

Results

All 10 patients completed the OSS procedure in a single day, and all reported satisfaction with the process. Median time for the treatment planning step and the whole procedure were 2.8 h and 6.6 h, respectively. With optimization of the procedure, treatment could be completed in half a day. During beam-on, the 3 mm tracking boundary encompassed between 78.0 and 100 % of the GTV across all patients, with corresponding PTV values being 94.4–100 % (5th-95th percentiles). On average, system-latency for triggering a beam-off event comprised 5.3 % of the delivery time. Latency reduced GTV coverage by an average of −0.3 %. Duty-cycles during treatment delivery ranged from 26.1 to 64.7 %.

Conclusions

An OSS procedure with MR-guided SABR for lung cancer led to good patient satisfaction. Gated treatment delivery was highly accurate with little impact of system-latency.

Clinical adoption patterns of 0.35 Tesla MR-guided radiation therapy in Europe and Asia

Background

Magnetic resonance-guided radiotherapy (MRgRT) utilization is rapidly expanding, driven by advanced capabilities including better soft tissue imaging, continuous intrafraction target visualization, automatic triggered beam delivery, and the availability of on-table adaptive replanning. Our objective was to describe patterns of 0.35 Tesla (T)-MRgRT utilization in Europe and Asia among early adopters of this novel technology.

Methods

Anonymized administrative data from all 0.35T-MRgRT treatment systems in Europe and Asia were extracted for patients who completed treatment from 2015 to 2020. Detailed treatment information was analyzed for all MR-linear accelerators (linac) and -cobalt systems.

Results

From 2015 through the end of 2020, there were 5796 completed treatment courses delivered in 46,389 individual fractions. 23.5% of fractions were adapted. Ultra-hypofractionated (UHfx) dose schedules (1–5 fractions) were delivered for 63.5% of courses, with 57.8% of UHfx fractions adapted on-table. The most commonly treated tumor types were prostate (23.5%), liver (14.5%), lung (12.3%), pancreas (11.2%), and breast (8.0%), with increasing compound annual growth rates (CAGRs) in numbers of courses from 2015 through 2020 (pancreas: 157.1%; prostate: 120.9%; lung: 136.0%; liver: 134.2%).

Conclusions

This is the first comprehensive study reporting patterns of utilization among early adopters of a 0.35T-MRgRT system in Europe and Asia. Intrafraction MR image-guidance, advanced motion management, and increasing adoption of on-table adaptive RT have accelerated a transition to UHfx regimens. MRgRT has been predominantly used to treat tumors in the upper abdomen, pelvis and lungs, and increasingly with adaptive replanning, which is a radical departure from legacy radiotherapy practices.

Magnetic resonance imaging-guided radiotherapy for intermediate- and high-risk prostate cancer: Trade-off between planning target volume margin and online plan adaption

Magnetic resonance-guided radiotherapy with daily plan adaptation for intermediate- and high-risk prostate cancer is time and labor intensive. Fifty adapted plans with 3 mm planning target volume (PTV)-margin were compared with non-adapted plans using 3 or 5 mm margins. Adequate (V95% ≥ 95%) prostate coverage was achieved in 49 fractions with 5 mm PTV without plan adaptation, however, coverage of the seminal vesicles (SV) was insufficient in 15 of 50 fractions. There was no insufficient coverage for prostate and SV using plan adaptation with 3 mm. Hence, daily adaptation is recommended to obtain adequate SV-coverage when using 3 mm PTV.

Single-fraction 34Gy lung SBRT using proton transmission beams: FLASH-dose calculations and the influence of different dose-rate methods and dose/dose-rate thresholds

Purpose

Research suggests that in addition to the dose-rate, a dose threshold is also important for the reduction in normal tissue toxicity with similar tumor control after ultrahigh dose-rate radiation therapy (UHDR-RT). In this analysis we aimed to identify factors that might limit the ability to achieve this “FLASH”-effect in a scenario attractive for UHDR-RT (high fractional beam dose, small target, few organs-at-risk): single-fraction 34 Gy lung stereotactic body radiation therapy.

Methods and Materials

Clinical volumetric-modulated arc therapy (VMAT) plans, intensity modulated proton therapy (IMPT) plans and transmission beam (TB) plans were compared for 6 small and 1 large lung lesion. The TB-plan dose-rate was calculated using 4 methods and the FLASH-percentage (percentage of dose delivered at dose-rates ≥40/100 Gy/s and ≥4/8 Gy) was determined for various variables: a minimum spot time (minST) of 0.5/2 ms, maximum nozzle current (maxN) of 200/40 0nA, and 2 gantry current (GC) techniques (energy-layer based, spot-based [SB]).

Results

Based on absolute doses 5-beam TB and VMAT-plans are similar, but TB-plans have higher rib, skin, and ipsilateral lung dose than IMPT. Dose-rate calculation methods not considering scanning achieve FLASH-percentages between ∼30% to 80%, while methods considering scanning often achieve <30%. FLASH-percentages increase for lower minST/higher maxN and when using SB GC instead of energy-layer based GC, often approaching the percentage of dose exceeding the dose-threshold. For the small lesions average beam irradiation times (including scanning) varied between 0.06 to 0.31 seconds and total irradiation times between 0.28 to 1.57 seconds, for the large lesion beam times were between 0.16 to 1.47 seconds with total irradiation times of 1.09 to 5.89 seconds.

Conclusions

In a theoretically advantageous scenario for FLASH we found that TB-plan dosimetry was similar to that of VMAT, but inferior to that of IMPT, and that decreasing minST or using SB GC increase the estimated amount of FLASH. For the appropriate machine/delivery parameters high enough dose-rates can be achieved regardless of calculation method, meaning that a possible FLASH dose-threshold will likely be the primary limiting factor.

Renal atrophy following gated delivery of stereotactic ablative radiotherapy to adrenal metastases

Stereotactic ablative radiotherapy (SABR) planning for adrenal metastases aims to minimize doses to the adjacent kidney. Renal dose constraints for SABR delivery are not well defined. In 20 patients who underwent MR-guided breath-hold SABR in five daily fractions of 8–10 Gy, ipsilateral renal volumes receiving ≥20 Gy best correlated with loss of renal volumes, with median renal volume reduction being 6% (range: 3%-11%, 10th-90th percentiles). Organ function did not deteriorate in 18 patients, who had post treatment renal function tests available. This suggests that the ipsilateral renal volume receiving 20 Gy can be used as partial organ dose constraint for SABR to targets in the upper abdomen.

Impact of daily plan adaptation on organ-at-risk normal tissue complication probability for adrenal lesions undergoing stereotactic ablative radiation therapy

INTRODUCTION

Stereotactic ablative radiotherapy (SABR) can achieve good local control for metastatic adrenal lesions. Magnetic resonance (MR)-guidance with daily on-table plan adaptation can augment the delivery of SABR with greater dose certainty. The goal of this study was to quantify the potential clinical benefit MR-guided daily-adaptive adrenal SABR using the normal tissue complication probability (NTCP) framework.

METHODS

Patients treated with adrenal MR-guided SABR at a single institution were retrospectively reviewed. Lyman-Kutcher-Burman NTCP models were used to calculate the NTCP of upper abdominal organs-at-risk (OARs) at simulation and both before and after daily on-table plan adaptation. Differences in OAR NTCPs were assessed using signed-rank tests. Potential predictors of the benefits of adaptation were assessed by linear regression.

RESULTS

Fifty-two adrenal MR-guided SABR courses were analyzed. The baseline simulation plan underestimated the absolute stomach NTCP by 10.0% on average (95% confidence interval: 4.7-15.2%, p < 0.001). Daily on-table adaptation lowered absolute NTCP by 8.7% (4.2-13.2%, p < 0.001). The most significant predictor of the benefits of adaptation was lesion laterality (p = 0.018), with left-sided lesions benefitting more (13.3% [6.3-20.4%], p < 0.001) than right-sided lesions (2.1% [-1.6-5.7%], p = 0.25). Sensitivity analyses did not change the statistical significance of the findings.

CONCLUSION

NTCP analysis revealed that patients with left adrenal tumors were more likely to benefit from MR-guided daily on-table adaptive SABR using current dose/fractionation regimens due to reductions in predicted gastric toxicity. Right-sided adrenal lesions may be considered for dose escalation due to low predicted NTCP.

Markerless Real-Time 3-Dimensional kV Tracking of Lung Tumors During Free Breathing Stereotactic Radiation Therapy

Purpose

Accurate verification of tumor position during irradiation could reduce the probability of target miss. We investigated whether a commercial gantry-mounted 2-dimensional (2D) kilo-voltage (kV) imaging system could be used for real-time 3D tumor tracking during volumetric modulated arc therapy (VMAT) lung stereotactic body radiation therapy (SBRT). Markerless tumor tracking on kV fluoroscopic images was validated using a life-like moving thorax phantom and subsequently performed on kV images continuously acquired before and during free-breathing VMAT lung SBRT.

Methods and Materials

The 3D-printed/molded phantom containing 3 lung tumors was moved in 3D in TrueBeam developer mode, using simulated regular/irregular breathing patterns. Planar kV images were acquired at 7 frames/s during 11 Gy/fraction 10 MV flattening filter free VMAT. 2D reference templates were created for each gantry angle using the planning 4D computed tomography inspiration phase. kV images and templates were matched using normalized cross correlation to determine 2D tumor position, and triangulation of 2D matched projections determined the third dimension. 3D target tracking performed on cone beam computed tomography projection data from 18 patients (20 tumors) and real-time online tracking data from 2 of the 18 patients who underwent free-breathing VMAT lung SBRT are presented.

Results

For target 1 and 2 of the phantom (upper lung and middle/medial lung, mean density –130 Hounsfield units), 3D results within 2 mm of the known position were present in 92% and 96% of the kV projections, respectively. For target 3 (inferior lung, mean density –478 Hounsfield units) this dropped to 80%. Benchmarking against the respiratory signal, 13/20 (65%) tumors (10.5 ± 11.1 cm³) were considered successfully tracked on the cone beam computed tomography data. Tracking was less successful (≤50% of the time) in 7/20 (1.2 ± 1.5 cm³). Successful online tracking during lung SBRT was demonstrated.

Conclusions

3D markerless tumor tracking on a standard linear accelerator using template matching and triangulation of free-breathing kV fluoroscopic images was possible in 65% of small lung tumors. The smallest tumors were most challenging.

Investigating the potential of deep learning for patient-specific quality assurance of salivary gland contours using EORTC-1219-DAHANCA-29 clinical trial data

INTRODUCTION

Manual quality assurance (QA) of radiotherapy contours for clinical trials is time and labor intensive and subject to inter-observer variability. Therefore, we investigated whether deep-learning (DL) can provide an automated solution to salivary gland contour QA.

MATERIAL AND METHODS

DL-models were trained to generate contours for parotid (PG) and submandibular glands (SMG). Sørensen-Dice coefficient (SDC) and Hausdorff distance (HD) were used to assess agreement between DL and clinical contours and thresholds were defined to highlight cases as potentially sub-optimal. 3 types of deliberate errors (expansion, contraction and displacement) were gradually applied to a test set, to confirm that SDC and HD were suitable QA metrics. DL-based QA was performed on 62 patients from the EORTC-1219-DAHANCA-29 trial. All highlighted contours were visually inspected.

RESULTS

Increasing the magnitude of all 3 types of errors resulted in progressively severe deterioration/increase in average SDC/HD. 19/124 clinical PG contours were highlighted as potentially sub-optimal, of which 5 (26%) were actually deemed clinically sub-optimal. 2/19 non-highlighted contours were false negatives (11%). 15/69 clinical SMG contours were highlighted, with 7 (47%) deemed clinically sub-optimal and 2/15 non-highlighted contours were false negatives (13%). For most incorrectly highlighted contours causes for low agreement could be identified.

CONCLUSION

Automated DL-based contour QA is feasible but some visual inspection remains essential. The substantial number of false positives were caused by sub-optimal performance of the DL-model. Improvements to the model will increase the extent of automation and reliability, facilitating the adoption of DL-based contour QA in clinical trials and routine practice.

Using Spatial Probability Maps to Highlight Potential Inaccuracies in Deep Learning-Based Contours: Facilitating Online Adaptive Radiation Therapy

PURPOSE

Contouring organs at risk remains a largely manual task, which is time consuming and prone to variation. Deep learning-based delineation (DLD) shows promise both in terms of quality and speed, but it does not yet perform perfectly. Because of that, manual checking of DLD is still recommended. There are currently no commercial tools to focus attention on the areas of greatest uncertainty within a DLD contour. Therefore, we explore the use of spatial probability maps (SPMs) to help efficiency and reproducibility of DLD checking and correction, using the salivary glands as the paradigm.

METHODS AND MATERIALS

A 3-dimensional fully convolutional network was trained with 315/264 parotid/submandibular glands. Subsequently, SPMs were created using Monte Carlo dropout (MCD). The method was boosted by placing a Gaussian distribution (GD) over the model's parameters during sampling (MCD + GD). MCD and MCD + GD were quantitatively compared and the SPMs were visually inspected.

RESULTS

The addition of the GD appears to increase the method's ability to detect uncertainty. In general, this technique demonstrated uncertainty in areas that (1) have lower contrast, (2) are less consistently contoured by clinicians, and (3) deviate from the anatomic norm.

CONCLUSIONS

We believe the integration of uncertainty information into contours made using DLD is an important step in highlighting where a contour may be less reliable. We have shown how SPMs are one way to achieve this and how they may be integrated into the online adaptive radiation therapy workflow.

Strategies to improve deep learning-based salivary gland segmentation

BACKGROUND

Deep learning-based delineation of organs-at-risk for radiotherapy purposes has been investigated to reduce the time-intensiveness and inter-/intra-observer variability associated with manual delineation. We systematically evaluated ways to improve the performance and reliability of deep learning for organ-at-risk segmentation, with the salivary glands as the paradigm. Improving deep learning performance is clinically relevant with applications ranging from the initial contouring process, to on-line adaptive radiotherapy.

METHODS

Various experiments were designed: increasing the amount of training data (1) with original images, (2) with traditional data augmentation and (3) with domain-specific data augmentation; (4) the influence of data quality was tested by comparing training/testing on clinical versus curated contours, (5) the effect of using several custom cost functions was explored, and (6) patient-specific Hounsfield unit windowing was applied during inference; lastly, (7) the effect of model ensembles was analyzed. Model performance was measured with geometric parameters and model reliability with those parameters' variance.

RESULTS

A positive effect was observed from increasing the (1) training set size, (2/3) data augmentation, (6) patient-specific Hounsfield unit windowing and (7) model ensembles. The effects of the strategies on performance diminished when the base model performance was already 'high'. The effect of combining all beneficial strategies was an increase in average Sørensen-Dice coefficient of about 4% and 3% and a decrease in standard deviation of about 1% and 1% for the submandibular and parotid gland, respectively.

CONCLUSIONS

A subset of the strategies that were investigated provided a positive effect on model performance and reliability. The clinical impact of such strategies would be an expected reduction in post-segmentation editing, which facilitates the adoption of deep learning for autonomous automated salivary gland segmentation.

Initial Impact and Operational Responses to the COVID-19 Pandemic by American Radiation Oncology Practices

PURPOSE

In February 2020, the COVID-19 pandemic reached the United States. The impact of the pandemic on the US radiation oncology field remains unknown. The American Society for Radiation Oncology surveyed US radiation oncology practice leaders to gauge initial impact and immediate operational responses to the pandemic.

METHODS AND MATERIALS

From April 16 to April 30, 2020, the American Society for Radiation Oncology surveyed US radiation oncology practice leaders by email to gauge initial impact and immediate operational responses to the COVID-19 pandemic.

RESULTS

Two hundred twenty-two (43%) of 517 leaders responded from community and academic practices (62% and 34%, respectively), hospital-based and free-standing centers (69% and 29%), and metro and rural locations (88% and 12%). Practices reported treating an average of 1086 patients per year in 2019 (range, 0-7900) with an average daily treatment volume of 70 patients (range, 5-400). All practices reported uninterrupted operation. On average, practices were treating 68% of their typical volume (range, 10%-95%), with 92% implementing planned treatment postponement for lower risk patients. An estimated revenue decrease of 20% or more was experienced by 71% of practices. Confirmed COVID-19 patient cases were treated by 39% of practices. Seventy percent experienced staff shortages. Almost all (98%) practices implemented formal operational procedures to protect patients and staff, although personal protective equipment/infection control supply shortages were reported by 78% of practices. Seventy-four percent used telemedicine for virtual follow-up surveillance, and 15% leveraged telemedicine for on-treatment assessment.

CONCLUSIONS

The clinical and financial impacts of the COVID-19 pandemic on US radiation oncology were deep and broad. Despite reported shortages in personal protective equipment, declines in revenue, and reduced patient volumes, practices adapted quickly by refining standard processes of care, implementing recommended safety measures, and employing telemedicine to facilitate treatment continuity. Patients with higher risk disease experienced uninterrupted access to care. We plan to continue regular surveying across the lifespan of the pandemic to document the geographic and temporal impact of COVID-19 on the field and its patients.

Effect of COVID-19 pandemic on practice in European radiation oncology centers

ESTRO surveyed European radiation oncology department heads to evaluate the impact of COVID-19. Telemedicine was used in 78% of the departments, and 60% reported a decline in patient volume. Use of protective measures was implemented on a large scale, but shortages of personal protective equipment were present in more than half of the departments.

Magnetic Resonance-guided Stereotactic Radiotherapy for Localized Prostate Cancer: Final Results on Patient-reported Outcomes of a Prospective Phase 2 Study

BACKGROUND

The recent introduction of magnetic resonance-guided radiation therapy (MRgRT) has allowed improved treatment planning and delivery of stereotactic body radiotherapy (SBRT) in prostate cancer (PC). The health-related quality of life (HRQoL) outcomes using this novel approach are important in shared decision making for patients.

OBJECTIVE

To report HRQoL using both patient- and clinician-reported outcomes at 1 yr following stereotactic MRgRT for patients with localized PC.

DESIGN, SETTING, AND PARTICIPANTS

A prospective phase 2 trial included 101 patients with localized PC.

INTERVENTION

All patients received 36.25Gy in five fractions of MRgRT delivered within 2 wk.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

HRQoL was prospectively assessed at baseline, at the last fraction, at 6 wk, and at 3, 6, 9, and 12 mo after treatment, by patient-reported outcome measures using European Organization for Research and Treatment of Cancer QLQ-C30 and QLQ-PR25 questionnaires, and International Prostate Symptom Score. At the same time points, clinicians reported on symptomatic adverse events (AEs). Effect sizes for changes in HRQoL were calculated with repeated measures analysis of variance.

RESULTS AND LIMITATIONS

Availability of HRQoL data exceeded 95% at all study time points. From both questionnaires and the recorded AEs, the largest treatment effects on urinary and bowel symptoms were recorded in the first 6 wk of follow-up. Thereafter, all symptoms decreased and returned to baseline values at 12 mo. No grade ≥3 toxicity was reported. No patient reported any relevant limitation due to urinary symptoms, and only 2.2% of patients reported a relevant impact on daily activities due to bowel problems at 1 yr. The majority of patients had intermediate- or high-risk PC for which androgen deprivation therapy (83.2%) was prescribed, thereby precluding study of MRgRT on sexual function. Longer follow-up is awaited in order to evaluate the oncological outcome.

CONCLUSIONS

Delivery of MRgRT for SBRT resulted in low toxicity at 1 yr.

PATIENT SUMMARY

All patients completed magnetic resonance-guided radiation therapy, which was well tolerated with only transient early urinary and bowel symptoms, which resolved 1 yr after treatment, as confirmed by patient-reported outcome measures.

Delivery of magnetic resonance-guided single-fraction stereotactic lung radiotherapy

BACKGROUND AND PURPOSE

Single-fraction stereotactic ablative radiotherapy (SABR) is an effective treatment for early-stage lung cancer, but concerns remain about the accurate delivery of SABR in a single session. We evaluated the delivery of single-fraction lung SABR using magnetic resonance (MR)-guidance.

MATERIALS AND METHODS

An MR-simulation was performed in 17 patients, seven of whom were found to be unsuitable, largely due to unreliable tracking of small tumors. Ten patients underwent single-fraction SABR to 34 Gy on a 0.35 T MR-linac system, with online plan adaptation. Gated breath-hold SABR was delivered using a planning target volume (PTV) margin of 5 mm, and a 3 mm gating window. Continuous MR-tracking of the gross tumor volume (GTVt) was performed in sagittal plane, with visual patient feedback provided using an in-room monitor. The real-time MR images were analyzed to determine precision and efficiency of gated delivery.

RESULTS

All but one patient completed treatment in a single session. The median total in-room procedure was 120 min, with a median SABR delivery session of 39 min. Review of 7.4 h of cine-MR imaging revealed a mean GTVt coverage by the PTV during beam-on of 99.6%. Breath-hold patterns were variable, resulting in a mean duty cycle efficiency of 51%, but GTVt coverage was not influenced due to real-time MR-guidance. On-table adaptation improved PTV coverage, but had limited impact on GTV doses.

CONCLUSIONS

Single-fraction gated SABR of lung tumors can be performed with high precision using MR-guidance. However, improvements are needed to ensure MR-tracking of small tumors, and to reduce treatment times.

A Prospective Single-Arm Phase 2 Study of Stereotactic Magnetic Resonance Guided Adaptive Radiation Therapy for Prostate Cancer: Early Toxicity Results

PURPOSE

Use of stereotactic body radiation therapy (SBRT) is increasing in patients with localized prostate cancer, but concerns about early and late gastrointestinal (GI) and genitourinary (GU) toxicity exist after moderately or extremely hypofractionated radiation therapy schemes. Magnetic resonance guided radiation therapy (MRgRT) was clinically introduced in 2014. MrgRT allows for SBRT delivery with smaller uncertainty margins and permits daily adaptive planning. A phase 2 study in patients with localized prostate cancer was performed to study early GI and GU toxicity after SBRT using MRgRT.

METHODS AND MATERIALS

One hundred one patients with clinical stage T1-3bN0M0 prostate cancer were enrolled in this prospective phase 2 study. All but 4 patients had intermediate- or high-risk prostate cancer, and 82.2% received adjuvant hormonal treatment. MRgRT was delivered in 5 fractions of 7.25 Gy to the target volume using daily plan adaptation with simultaneous relative sparing of the urethra to a dose of 6.5 Gy per fraction. Early toxicity was studied using both clinician- (Common Terminology Criteria for Adverse Events and Radiation Therapy Oncology Group) and patient-reported outcome measurements (European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-C30, Quality of Life Questionnaire PR25, and International Prostate Symptom Scoring).

RESULTS

The maximum cumulative grade ≥2 early GU and GI toxicity measured by any symptom at any study time point was 23.8% and 5.0%, respectively. No early grade 3 GI toxicity was observed. Early grade 3 GU toxicity was 0% and 5.9% according to the Common Terminology Criteria for Adverse Events and Radiation Therapy Oncology Group and scoring systems, respectively, as a result of different grading of radiation cystitis. The low incidence of early GI toxicity was confirmed by patient-reported outcome data. GU grade ≥2 toxicity peaked to 19.8% at the end of MRgRT, followed by a return to the baseline average score at 3-month follow-up.

CONCLUSIONS

This prospective study of MRgRT in patients with localized prostate cancer observed a low incidence of early GI and GU toxicity, both in clinician- and patient-reported outcome measurements.

Deep Learning-Based Delineation of Head and Neck Organs at Risk: Geometric and Dosimetric Evaluation

PURPOSE

Organ-at-risk (OAR) delineation is a key step in treatment planning but can be time consuming, resource intensive, subject to variability, and dependent on anatomical knowledge. We studied deep learning (DL) for automated delineation of multiple OARs; in addition to geometric evaluation, the dosimetric impact of using DL contours for treatment planning was investigated.

METHODS AND MATERIALS

The following OARs were delineated with DL developed in-house: both submandibular and parotid glands, larynx, cricopharynx, pharyngeal constrictor muscle (PCM), upper esophageal sphincter, brain stem, oral cavity, and esophagus. DL contours were benchmarked against the manual delineation (MD) clinical contours using the Sørensen-Dice similarity coefficient. Automated knowledge-based treatment plans were used. The mean dose to the manually delineated OAR structures was reported for the MD and DL plans.

RESULTS

DL delineation of all OARs took <10 seconds per patient. For 7 of 11 OARs, the average Sørensen-Dice similarity coefficient was good (0.78-0.83). However, performance was lower for the esophagus (0.60), brainstem (0.64), PCM (0.68), and cricopharynx (0.73), often because of variations in MD. Although the average dose was statistically significantly higher in the DL plans for the inferior PCM (1.4 Gy) and esophagus (2.2 Gy), these average differences were not clinically significant. Dose to 28 of 209 (13.4%) and 7 of 209 (3.3%) OARs was >2 Gy higher and >2 Gy lower, respectively, in the DL plans.

CONCLUSIONS

DL-based segmentation for head and neck OARs is fast; for most organs and most patients, it performs sufficiently well for treatment-planning purposes. It has the potential to increase efficiency and facilitate online adaptive radiation therapy.

Normal Tissue Complication Probability Modeling of Pulmonary Toxicity After Stereotactic and Hypofractionated Radiation Therapy for Central Lung Tumors

PURPOSE

To evaluate clinical pulmonary and radiographic bronchial toxicity after stereotactic ablative radiation therapy and hypofractionated radiation therapy for central lung tumors, and perform normal tissue complication probability modeling and multivariable analyses to identify predictors for toxicity.

METHODS AND MATERIALS

A pooled analysis was performed of patients with a central lung tumor treated using ≤12 fractions at 2 centers between 2006 and 2015. Airways were manually contoured on planning computed tomography scans, and doses were recalculated to an equivalent dose of 2 Gy per fraction with an α/β ratio of 3. Grade ≥3 (≥G3) clinical pulmonary toxicity was evaluated by 2 or more physicians. Radiographic toxicity was defined as a stenosis or an occlusion with or without atelectasis using follow-up computed tomography scans. Logistic regression analyses were used for statistical analyses.

RESULTS

A total of 585 bronchial structures were studied in 195 patients who were mainly treated using 5 or 8 fractions (60%). Median patient survival was 27.9 months (95% confidence interval 22.3-33.6 months). Clinical ≥G3 toxicity was observed in 24 patients (12%) and radiographic bronchial toxicity in 55 patients (28%), both mainly manifesting ≤12 months after treatment. All analyzed dosimetric parameters correlated with clinical and lobar bronchial radiographic toxicity, with V_130Gy,EQD having the highest odds ratio. Normal tissue complication probability modeling showed a volume dependency for the development of both clinical and radiographic toxicity. On multivariate analyses, significant predictors for ≥G3 toxicity were a planning target volume overlapping the trachea or main stem bronchus (P = .005), chronic obstructive pulmonary disease (P = .034), and the total V_130Gy,EQD (P = .012). Radiographic bronchial toxicity did not significantly correlate with clinical toxicity (P = .663).

CONCLUSIONS

We identified patient and dosimetric factors associated with clinical and radiographic toxicity after high-dose radiation therapy for central lung tumors. Additional data from prospective studies are needed to validate these findings.

The Current Role of Radiotherapy in the Treatment of Small Cell Lung Cancer

Radiotherapy has been shown to play a key role in the management of small cell lung cancer. There are well-established data in the literature for the use of concurrent chemoradiotherapy for stage I-III disease, although key questions remain over the timing of radiation, the optimal dose/fractionation and particularly once versus twice daily treatment, the use of elective nodal irradiation and drug combinations. Data for the use of thoracic radiation in stage IV disease, after chemotherapy, have recently become available and are leading to a change in practice. Prophylactic cranial irradiation has been shown to be of use in both stage I-III and stage IV disease, although uncertainties surround its use in the elderly population and the use of brain imaging before treatment. This overview will address the current available evidence and focus on areas for future research.

[Radiotherapy in Europe]

Radiotherapy plays an important part in the curing of cancer patients and is an effective treatment for tumour-related symptoms. However, in many countries the level of access to this treatment modality is unacceptably low due to shortage of infrastructure, modern apparatus and trained staff. In Europe it is mainly the Eastern European countries that are behind in the provision of and accessibility to radiotherapy. Worldwide investment to narrow the gap would put an end to these undesirable differences. In addition, these investments would deliver economic benefits, especially in low-to-middle income countries. In this article, on the basis of a number of recently published reports, we discuss the differences that exist in the geographical spread of radiotherapy departments and the availability of apparatus within Europe. In conclusion we also take a short look at the Dutch situation.

Stage I-II non-small-cell lung cancer treated using either stereotactic ablative radiotherapy (SABR) or lobectomy by video-assisted thoracoscopic surgery (VATS): outcomes of a propensity score-matched analysis

BACKGROUND

Video-assisted thoracoscopic surgery (VATS) lobectomy and stereotactic ablative radiotherapy (SABR) are both used for early-stage non-small-cell lung cancer. We carried out a propensity score-matched analysis to compare locoregional control (LRC).

PATIENTS AND METHODS

VATS lobectomy data from six hospitals were retrospectively accessed; SABR data were obtained from a single institution database. Patients were matched using propensity scores based on cTNM stage, age, gender, Charlson comorbidity score, lung function and performance score. Eighty-six VATS and 527 SABR patients were matched blinded to outcome (1:1 ratio, caliper distance 0.025). Locoregional failure was defined as recurrence in/adjacent to the planning target volume/surgical margins, ipsilateral hilum or mediastinum. Recurrences were either biopsy-confirmed or had to be PET-positive and reviewed by a tumor board.

RESULTS

The matched cohort consisted of 64 SABR and 64 VATS patients with the median follow-up of 30 and 16 months, respectively. Post-SABR LRC rates were superior at 1 and 3 years (96.8% and 93.3% versus 86.9% and 82.6%, respectively, P = 0.04). Distant recurrences and overall survival (OS) were not significantly different.

CONCLUSION

This retrospective analysis found a superior LRC after SABR compared with VATS lobectomy, but OS did not differ. Our findings support the need to compare both treatments in a randomized, controlled trial.

The predictive value of 3D time-of-flight MR angiography in assessment of brain arteriovenous malformation obliteration after radiosurgery

BACKGROUND AND PURPOSE

The purpose of radiosurgery of bAVMs is complete angiographic obliteration of its nidus. We assessed the diagnostic accuracy of 1.5T T2-weighted MR imaging and TOF-MRA images for detecting nidus obliteration after radiosurgery.

MATERIALS AND METHODS

The pre- and postradiosurgery MR images and DSA images from 120 patients who were radiosurgically treated for a bAVM were re-evaluated by 2 observers for patency of the nidus (preradiosurgery) and obliteration (postradiosurgery: final follow-up MR imaging), by using a 3-point scale of confidence. Consensus reading of the DSA after radiosurgery was considered the criterion standard for obliteration. Sensitivity, specificity, PPVs, and NPVs, and overall diagnostic performance by using ROC were determined.

RESULTS

Mean bAVM volume during radiosurgery was 3.4 mL (95% CI, 2.6-4.3 mL). Sixty-six patients (55%) had undergone previous endovascular embolization. The mean intervals between radiosurgery and follow-up MR imaging and for DSA, respectively, were 35.6 months (95% CI, 32.3-38.9 months) and 42.1 months (95% CI, 40.3-44.0 months). With ROC, an area under curve of 0.81-0.83 was found. PPVs of final follow-up MR-imaging for definitive obliteration varied between 0.89 [corrected] and 0.95. NPV was 0.52 [corrected] . An average false-positive rate, meaning overestimation of nidus obliteration of 0.10 [corrected] and an average false-negative rate, meaning underestimation of nidus obliteration of 0.42 [corrected] were found.

CONCLUSIONS

MRA is insufficient to diagnose obliteration in the follow-up of bAVMs after radiosurgery. A remaining nidus diameter <10 mm seems to be the major limiting factor for reliable assessment of obliteration. We highly recommend follow-up DSA for definitive diagnosis of complete obliteration.

Postoperative elective nodal irradiation for squamous cell carcinoma of the head and neck: outcome and prognostic factors for regional recurrence

BACKGROUND

This study describes the results of elective irradiation in the N0 neck and tries to identify prognostic factors for regional recurrence.

MATERIALS AND METHODS

Between 1985 and 2000, 785 cN0 or pN0 necks were treated with elective nodal irradiation in 619 head and neck squamous cell carcinoma patients.

RESULTS

Regional control at 3 years was 94% in the cN0 (nondissected) neck compared with 97% in the pN0 (dissected) neck and 90% in the ipsilateral compared with 96% in the contralateral neck (P = 0.08 and P = 0.006, respectively). Regional control in the ipsilateral cN0 neck was 78% compared with 96% in the contralateral cN0 neck. Surgical margin of the primary tumor was an additional prognostic factor in all N0 and pN0 necks.

CONCLUSIONS

Neck control rates in electively irradiated N0 necks were excellent. Regional control was worse in the cN0 neck compared with the pN0 neck and in the ipsilateral neck compared with the contralateral side. Additionally, in case of positive surgical margins of the primary tumor, elective nodal irradiation should be applied, even in case of a pN0 neck.

Prophylactic cranial irradiation in extensive disease small-cell lung cancer: short-term health-related quality of life and patient reported symptoms: results of an international Phase III randomized controlled trial by the EORTC Radiation Oncology and Lung Cancer Groups

PURPOSE

Prophylactic cranial irradiation (PCI) in patients with extensive-disease small-cell lung cancer (ED-SCLC) leads to significantly fewer symptomatic brain metastases and improved survival. Detailed effects of PCI on health-related quality of life (HRQOL) are reported here.

PATIENTS AND METHODS

Patients (age, 18 to 75 years; WHO < or = 2) with ED-SCLC, and any response to chemotherapy, were randomly assigned to either observation or PCI. Health-related quality of life (HRQOL) and patient-reported symptoms were secondary end points. The European Organisation for the Research and Treatment of Cancer core HRQOL tool (Quality of Life Questionnaire C30) and brain module (Quality of Life Questionnaire Brain Cancer Module) were used to collect self-reported patient data. Six HRQOL scales were selected as primary HRQOL end points: global health status; hair loss; fatigue; and role, cognitive and emotional functioning. Assessments were performed at random assignment, 6 weeks, 3 months, and then 3-monthly up to 1 year and 6-monthly thereafter.

RESULTS

Compliance with the HRQOL assessment was 93.7% at baseline and dropped to 60% at 6 weeks. Short-term results up to 3 months showed that there was a negative impact of PCI on selected HRQOL scales. The largest mean difference between the two arms was observed for fatigue and hair loss. The impact of PCI on global health status as well as on functioning scores was more limited. For global health status, the observed mean difference was eight points on a scale 0 to 100 at 6 weeks (P = .018) and 3 months (P = .055).

CONCLUSION

PCI should be offered to all responding ED SCLC patients. Patients should be informed of the potential adverse effects from PCI. Clinicians should be alert to these; monitor their patients; and offer appropriate support, clinical, and psychosocial care.

[Prophylactic cranial irradiation in patients with extensive disease caused by small-cell lung cancer responsive to chemotherapy: fewer symptomatic brain metastases and improved survival]

OBJECTIVE

To determine the effect of prophylactic cranial irradiation (PCI) in patients with extensive-disease small-cell lung cancer (ED-SCLC) who responded to chemotherapy.

DESIGN

Randomised, controlled clinical trial; phase III study (EORTC nr 08993-22993; www.clinicaltrials.gov, nr NCT00016211).

METHOD

Patients aged 18-75 years with a functional status according to WHO < or = 2, and with ED-SCLC and any response to chemotherapy, were randomized to observation (standard care) or PCI. The primary endpoint was time to symptomatic brain metastases. If any pre-defined, key symptom suggesting brain metastases presented, a CT or MRI scan of the brain was performed. The size of the study (143 patients per arm) was determined to detect a hazard ratio (HR) of 0.44 at 80% power with 2-sided alpha = 0.05.

RESULTS

The study accrued 286 patients. PCI decreased the risk of developing symptomatic brain metastases (HR = 0.27 (95% CI: 0.16-0.44; p < 0.001)). The cumulative incidence of developing brain metastases within 1 year was 40% in the control group (95% CI: 32-49) and 15% in the PCI group (95% CI: 8-21). PCI prolonged disease-free (HR = 0.76; 95% CI: 0.59-0.96, p = 0.02) and overall survival (HR = 0.68; 95% CI; 0.52-0.88, p = 0.003). The 1-year survival rate was 27% (95% CI: 19-36) for the PCI group versus 13% (95% CI: 8-20) for controls. Acute and late treatment toxicity was acceptable. These side effects did not significantly impact on quality of life.

CONCLUSIONS

PCI significantly reduced the incidence of symptomatic brain metastases and prolonged both disease-free and overall survival and should be part of standard care in SCLC patients who respond to chemotherapy.

Tumor-volume changes after radiosurgery for vestibular schwannoma: implications for follow-up MR imaging protocol

BACKGROUND AND PURPOSE

The outcome of radiosurgery for vestibular schwannoma (VS) is assessed by posttreatment measurement of tumor size and could be influenced by the timing and quality of the assessment. This study evaluates the volumetric changes of VS after radiosurgery and proposes a radiologic follow-up program.

MATERIALS AND METHODS

Of 142 patients with VS treated with radiosurgery, we selected patients who were followed at least 3 times during a minimum of 32 months with a T1-weighted gadolinium-enhanced high-resolution 3D MR imaging examination identical to the pretreatment MR imaging. Forty-five patients were identified with a mean follow-up of 50 months (range, 32-78 months). Pre- and posttreatment tumor volumes were calculated by using BrainSCAN software by manually contouring tumors on each MR imaging study. Volume changes of >13% were defined as events.

RESULTS

At last follow-up MR imaging, volumes were smaller in 37 (82.2%) of the 45 patients. Eleven (29.7%) of these 37 tumors showed transient swelling preceding regression, with a median time to regression of 34 months (range, 20-55 months). Seven (15.6%) of the 45 tumors had volume progression compared with the tumor on pretreatment MR imaging studies. Of these 7 tumors, 3, however, had volume regression compared with the preceding MR imaging study, and in 4, volume progression was ongoing. One tumor remained the same.

CONCLUSIONS

Tumor-volume measurements by standardized T1-weighted gadolinium-enhanced high-resolution 3D MR imaging follow-up protocols revealed good local control of VS after radiosurgery. The first-follow-up MR imaging at 2 years and the second at 5 years postradiosurgery differentiated transient progression from ongoing progression and may prevent unnecessary therapeutic interventions.

Radiosurgery of brain arteriovenous malformations in children

OBJECTIVE

The authors describe their experience in treating 22 children with a single brain arteriovenous malformation (bAVM) using a dedicated LINAC stereotactic radiosurgery unit.

METHODS

The findings of 22 consecutive patients < or = 18 years of age who underwent radiosurgery for a single bAVM and with at least 24 months of follow-up, or earlier proven obliteration,were reviewed. The median age at radiosurgery was 13.8 years,with a hemorrhagic presentation in 86%. Median bAVM-volume was 1.8 ml, with a median prescribed marginal dose of 19.0 Gy.

RESULTS

The crude complete obliteration-rate was 68% (n = 15) after a median follow-up of 24 months. The actuarial obliteration- rate was 45 % after two years and 64 % after three years. Patients with a radiosurgery-based AVM score < or = 1 more frequently had an excellent outcome than patients with a bAVM score > 1 (71% vs. 20%, P = 0.12), as well as an increased obliteration rate (P = 0.03) One patient died from a bAVM-related hemorrhage 27 months after radiosurgery, representing a postradiosurgery hemorrhage rate of 1.3%/year for the complete followup interval. Overall outcome was good to excellent in 68% (n = 15). Radiation-induced changes on MR imaging were seen in 36% (n = 8) after a median interval of 12.5 months, resulting in deterioration of pre-existing neurological symptoms in one patient.

CONCLUSIONS

Radiosurgery is a relatively effective, minimally invasive treatment for small bAVMs in children. The rebleeding rate is low, provided that known predilection places for bleeding had been endovascularly eliminated.Our overall results compare unfavourably to recent pediatric microsurgical series, although comparison between series remains imprecise. Nevertheless, when treatment is indicated in a child with a bAVM that is amenable to both microsurgery or radiosurgery, microsurgery should carefully be advocated over radiosurgery, because of its immediate risk reduction.

The additional value of chemotherapy to radiotherapy in locally advanced nasopharyngeal carcinoma: a meta-analysis of the published literature

PURPOSE

The purpose of this meta-analysis was to determine the additional value of neoadjuvant, concurrent, and/or adjuvant chemotherapy to radiation in the treatment of locally advanced nasopharyngeal carcinoma (NPC) with regard to the overall survival (OS) and the incidence of local-regional recurrences (LRR) and distant metastases (DM).

PATIENTS AND METHODS

To be eligible, full published studies had to deal with biopsy-proven NPC and have patients randomly assigned to receive conventional radiotherapy (66 to 70 Gy in 7 weeks) or radiotherapy combined with chemotherapy.

RESULTS

Ten randomized clinical studies were identified, including 2,450 patients. The pooled hazard ratio (HR) of death for all studies was 0.82 (95% CI, 0.71 to 0.95; P = .01) corresponding to an absolute survival benefit of 4% after 5 years. Three categories of trials were defined according to the sequence of chemotherapy, including neoadjuvant chemotherapy, at least concomitant chemoradiotherapy, and adjuvant chemotherapy. A significant interaction term (P = .02) was found among these three categories. The largest effect was found for concomitant chemotherapy, with a pooled HR of 0.48 (95% CI, 0.32 to 0.72), which corresponds to a survival benefit of 20% after 5 years. Comparable results were found for the incidence of LRR and DM.

CONCLUSION

The results of this study indicate that concomitant chemotherapy in addition to radiation is probably the most effective way to improve OS in NPC.

Radiotherapy of squamous cell carcinoma of the nasal vestibule

PURPOSE

To evaluate the results of primary radiotherapy (RT) for squamous cell carcinoma of the nasal vestibule.

METHODS AND MATERIALS

A total of 56 patients with Stage T1 and T2 tumors (Wang classification) were treated with external beam RT (EBRT) with or without a boost using endocavitary brachytherapy. Of these, 32 were treated with EBRT and an additional boost with intermediate-dose-rate brachytherapy, 15 with EBRT and a boost with high-dose-rate brachytherapy, and 9 with EBRT alone.

RESULTS

The local control rate at 2 years was 80%. Most cases could be successfully salvaged with surgery, resulting in an ultimate local control rate of 95%. No statistically significant differences were noted among the different treatment approaches. Of the 56 patients, 12% developed lymph node metastases.

CONCLUSION

Primary RT is an adequate treatment for Stage T1 and T2 squamous cell carcinoma of the nasal vestibule with excellent cosmetic results. The radiation technique used depends on the primary tumor extension and the experience of the treating radiation oncologist. In the case of N0 disease, elective treatment of the regional lymph nodes is not recommended.

The effects of irradiation on cell migration from glioblastoma multiforme biopsy spheroids

BACKGROUND

Glioblastoma multiforme (GBM) is a primary brain tumour with a very poor prognosis despite aggressive multi-modality treatment. This pre-clinical experimental study focuses on the effect of irradiation on three-dimensional glioma biopsy spheroids in vitro using an outgrowth assay to evaluate cell survival and migrational capacity of the glioma cells.

MATERIALS AND METHODS

Tumour tissue of 16 patients with high-grade glioma and two GBM cell lines were used for spheroid preparation. Outgrowth and cell density were the parameters chosen to evaluate cell cytotoxicity and migrational capacity after irradiation (20 Gy and 4 x 5 Gy).

RESULTS

Radiation inhibited outgrowth of cell line spheroids, but not of the biopsy spheroids. All biopsy and cell line spheroids showed a significantly lower cell number (95 vs. 24 cells/0.25 mm2) in the outgrowth area after irradiation.

CONCLUSION

Irradiation has a cytotoxic effect in GBM biopsy spheroids but it hardly affects cell migration. No correlation was found between patient survival and cell migration nor with cytotoxicity.

Postoperative radiotherapy in squamous cell carcinoma of the oral cavity: The importance of the overall treatment time

PURPOSE

To test the hypothesis that (1) the distinction between intermediate- and high-risk patients by clustering different prognostic factors results in a significant difference in treatment outcome and (2) a shorter interval between surgery and radiotherapy and shorter overall treatment times of radiation (OTTRT) result in higher rates of locoregional control (LRC).

METHODS AND MATERIALS

Included were patients (n = 217) with previously untreated squamous cell carcinoma of the oral cavity treated with radical surgery and postoperative radiotherapy. Patients with extranodal spread or microscopic residual disease and patients with two or more other risk factors (i.e., N2b-N3, >1 nodal level involved, perineural growth, or stage T3-T4) were classified as high-risk patients. Patients with only one other risk factor were classified as intermediate risk.

RESULTS

In the intermediate-risk group, the 3-year LRC was 87% as compared with 66% in the high-risk group (p = 0.0005). No association was found between interval and LRC. However, the OTTRT was significantly associated with LRC. The 3-year LRC was 87%, 75%, 69%, and 51% when the OTT was <6 weeks, 6-7 weeks, 7-8 weeks, and >8 weeks, respectively (p = 0.0004). The 3-year overall survival (OS) in the intermediate risk patients was 74% compared with 50% in the high-risk group (p = 0.0014). A significant association was also found between the OS and OTTRT. The OS increased from 50% when the OTTRT was >8 weeks to 74% when the OTT was <6 weeks (p = 0.006). Similar results were found with regard to the disease-free survival (DFS). In the multivariate analysis, both risk group and OTT were significantly associated with LRC, DFS, and OS. No significant interaction term was present between these two factors, which means that the OTT was of importance both for the high-risk and the intermediate-risk patients.

CONCLUSION

In the subset of patients with carcinoma of the oral cavity, the classification of high- and intermediate-risk patients by clustering a number of prognostic factors provides important prognostic information regarding LRC, DFS, and OS. The OTT was the most important prognostic factor both in the high-risk and intermediate-risk patients. Reducing the OTT to 6 weeks or less is a rather simple measure to achieve a considerable improvement of the outcome of treatment in this category of patients.

Single-fraction vs. fractionated linac-based stereotactic radiosurgery for vestibular schwannoma: a single-institution study

PURPOSE

In this single-institution trial, we investigated whether fractionated stereotactic radiation therapy is superior to single-fraction linac-based radiosurgery with respect to treatment-related toxicity and local control in patients with vestibular schwannoma.

METHODS AND MATERIALS

All 129 vestibular schwannoma patients treated between 1992 and June 2000 at our linac-based radiosurgery facility were analyzed with respect to treatment schedule. Dentate patients were prospectively selected for a fractionated schedule of 5 x 4 Gy and later on 5 x 5 Gy at the 80% isodose in 1 week with a relocatable stereotactic frame. Edentate patients were prospectively selected for a nonfractionated treatment of 1 x 10 Gy and later on 1 x 12.5 Gy at 80% isodose with an invasive stereotactic frame. Both MRI and CT scans were made in all 129 patients within 1 week before treatment. All patients were followed yearly with MRI and physical examination.

RESULTS

A fractionated schedule was given to 80 patients and a single fraction to 49 patients. Mean follow-up time was 33 months (range: 12-107 months). There was no statistically significant difference between the single-fraction group and the fractionated group with respect to mean tumor diameter (2.6 vs. 2.5 cm) or mean follow-up time (both 33 months). Only mean age (63 years vs. 49 years) was statistically significantly different (p = 0.001). Outcome differences between the single-fraction treatment group and the fractionated treatment group with respect to 5-year local control probability (100% vs. 94%), 5-year facial nerve preservation probability (93% vs. 97%), and 5-year hearing preservation probability (75% vs. 61%) were not statistically significant. The difference in 5-year trigeminal nerve preservation (92% vs. 98%) reached statistical significance (p = 0.048).

CONCLUSION

Linac-based single-fraction radiosurgery seems to be as good as linac-based fractionated stereotactic radiation therapy in vestibular schwannoma patients, except for a small difference in trigeminal nerve preservation rate in favor of a fractionated schedule.

Changes in the ornithine cycle following ionising radiation cause a cytotoxic conditioning of the culture medium of H35 hepatoma cells

Cultured H35 hepatoma cells release a cytotoxic factor in response to irradiation with X-rays. When the conditioned medium from irradiated cells is given to nonirradiated cells, growth is inhibited and followed by cell death, possibly apoptosis, Analysis of the conditioned medium reveals a dramatic change in the ornithine (urea) cycle components after the irradiation. A strong decrease in medium arginine is accompanied with parallel increases in ornithine, citrulline and ammonia. The high level of ammonia appears to be largely responsible for the observed cytotoxicity. The development of hyperammonia by irradiated cells and the related toxicity depend on the radiation dose and the number of cells seeded thereafter for the medium conditioning. Development of cytotoxicity by irradiated cells is completely prevented with the arginase inhibitor L-norvaline, in arginine-deficient medium or when citrulline replaces arginine. These preventive measures result in subtoxic ammonia levels.

Effect of radiotherapy and other treatment-related factors on mid-term to long-term cognitive sequelae in low-grade gliomas: a comparative study

BACKGROUND

Because survival benefits of treatment with radiotherapy are questionable and such treatment can cause substantial damage to the brain over time, the optimum management strategy for low-grade gliomas remains controversial. We aimed to identify the specific effects of radiotherapy on objective and self-reported cognitive function, and on cognitive deterioration over time, in patients with low-grade gliomas treated with early radiotherapy.

METHODS

195 patients with low-grade glioma (of whom 104 had received radiotherapy 1-22 years previously) were compared with 100 low-grade haematological patients and 195 healthy controls. Our analyses aimed to differentiate between the effects of the tumour (eg, disease duration, lateralisation) and treatment effects (neurosurgery, radiotherapy, antiepileptic drugs) on cognitive function and on relative risk of cognitive disability.

FINDINGS

Low-grade glioma patients had lower ability in all cognitive domains than did low-grade haematological patients, and did even less well by comparison with healthy controls. Use of radiotherapy was associated with poorer cognitive function; however, cognitive disability in the memory domain was found only in radiotherapy patients who received fraction doses exceeding 2 Gy. Antiepileptic drug use was strongly associated with disability in attentional and executive function.

INTERPRETATION

Our findings suggest that the tumour itself has the most deleterious effect on cognitive function and that radiotherapy mainly results in additional long-term cognitive disability when high fraction doses are used. Additionally, the effects of other medical factors, especially antiepileptic drug use, on cognitive function in glioma patients deserve attention.

Radiosensitivity and TP 53, EGFR amplification and LOH10 analysis of primary glioma cell cultures

AIM

Determination of in-vitro radiosensitivity and genetic alterations of cell cultures derived from human glioma biopsy tissue and established glioma cell lines.

MATERIAL AND METHODS

Fresh brain tumor specimens of six patients were processed to early passage cell cultures. In addition the cell lines D 384 and Gli 6 were used. Cell cultures were irradiated with doses from 2 to 10 Gy. Following irradiation, cell survival was determined by clonogenic assay and survival curves were generated. The surviving fractions after 2 Gy (SF2) and 4 Gy (SF4) were used as radiosensitivity parameters. Genetic analysis included determination of the mutational and loss of heterozygosity (LOH) status of TP 53 (exons 5-8), the LOH 10- and epidermal growth factor receptor gene (EGFR) amplification status.

RESULTS

The SF2 and SF4 values ranged from 0.54 to 0.88 (mean: 0.70) and from 0.13 to 0.52 (mean: 0.32), respectively. Genetic alterations were found in the Gli 6 cell line and in two primary cell cultures. The genetic profile of Gli 6 showed LOH but no TP 53 mutation, complete LOH 10 and no EGFR amplification. The VU 15 cell culture showed TP 53 mutation but no LOH 10 or EGFR amplification, while VU 24 showed incomplete LOH 10, EGFR amplification and no TP 53 mutation. In the other four cell cultures and D 384 cell line no genetic alterations were diagnosed. Histopathological classification of glioblastoma multiforme and/or genetic alterations resulted in lower radiosensitivity.

CONCLUSION

In this small series of early passage glioma cell cultures low radiosensitivity and alterations in cell regulatory genes were seen. Further testing of biological behavior in larger series of patient-derived material is ongoing.

Radiotherapy-induced cerebral abnormalities in patients with low-grade glioma

Abnormalities on CT or MRI and neuropsychological performance in patients with low-grade glioma, with (n = 23) or without (n = 16) prior cerebral radiotherapy, were evaluated. Cerebral atrophy was observed in 14 of 23 patients (61%) treated with prior radiotherapy, and in 1 of 16 patients (6%) without prior radiotherapy. White matter abnormalities were observed in six patients, all of whom were treated with prior radiotherapy. These radiologic cerebral abnormalities correlated with cognitive performance.

Gemcitabine-radiotherapy in patients with locally advanced pancreatic cancer

A feasibility study was performed to assess the toxicity and efficacy of a combination of gemcitabine-radiotherapy in patients with locally advanced pancreatic cancer (LAPC). 24 patients (15 females and 9 males) with measurable LAPC were included; the median age of the patients was 63 years (range 39-74 years). The performance status ranged from 0 to 2. Gemcitabine was administered at a dose of 300 mg/m(2), concurrent with radiotherapy, three fractions of 8 Gy, on days 1, 8 and 15. When compliance allowed, gemcitabine alone was continued thereafter, at 1000 mg/m(2), weekly times 3, every 4 weeks, depending on the response and toxicity. All patients were evaluable for toxicity and response. The objective response rate was 29.2% (1 complete remission+6 partial remissions); 12 patients had stable disease. However, 2 of the radiological partial remissions were shown to be complete remissions by pathology assessment. Median duration of response was 3 months (range 1-35+months). Median time to progression was 7 months (range 2-37+months). Median survival was 10 months (range 3-37+months). Dose reduction or omission of gemcitabine was necessary in 10 patients. Non-haematological toxicity consisted of 87.5% nausea and vomiting grade I-II, diarrhoea 54%, ulceration in stomach and duodenum 37.5% (20.8% ulceration with bleeding); 1 patient developed a fistula between the duodenum and aorta, 5 months after treatment. Anaemia grade III-IV was observed in 8.3% of the patients. Neutropenia grade III-IV was observed in 8.3%, thrombocytopenia grades III-IV in 16.7%. In 1 patient who underwent resection postchemoradiation, no viable tumour cells were found. In addition, in the patient who suddenly died of a fistula between the duodenum and aorta, no viable tumour cells were detectable at autopsy. Although the toxicity of this treatment was occasionally severe, the response and survival are encouraging and warrant further studies of this combination.

Radiosensitizing effect of carbogen breathing during pulsed irradiation of the rat R1H tumor

The objective of the present study was to investigate the radiosensitizing effect of carbogen breathing during pulsed x-ray irradiation in an experimental tumor model. Rat R1H rhabdomyosarcoma tumors were irradiated with 36 Gy total dose in 1 Gy high dose rate pulses, either hourly repeated, or in an 'office hours' protocol with irradiation-free overnight intervals. With the hourly, pulsed irradiation scheme, tumor growth delay (TGD) was significantly increased from 24.4+/-0.7 days in air-breathing animals to 29.0+/-0.9 days in animals breathing carbogen during irradiation. With irradiation during office hours, the TGD was shortened, and carbogen was less effective. The data show that carbogen acts as a radiosensitizer when applied during pulsed irradiation. Translation of the experimental data to clinical practice indicates that hyperoxygenation of the tumor during pulsed dose rate (PDR) or high dose rate (HDR) brachytherapy might enhance the tumor response of patients.