Application of a smart 18F-FDG-PET adaptive threshold segmentation algorithm for the biological target volume delineation in head and neck cancer.

BACKGROUND: The aim of the present study is to evaluate the reliability of a 18F-fluorodeoxyglucose (18F-FDG) PET adaptive threshold segmentation (ATS) algorithm, previously validated in a preclinical setting on several scanners, for the biological target volume (BTV) delineation of head and neck radiotherapy planning. METHODS: [18F]FDG PET ATS algorithm was studied in treatment plans of head and neck squamous cell carcinoma on a dedicated workstation (iTaRT, Tecnologie Avanzate, Turin, Italy). BTVs segmented by the present ATS algorithm (BTVATS) were compared with those manually segmented for the original radiotherapy treatment planning (BTVVIS). We performed a qualitative and quantitative volumetric analysis with a comparison tool within the ImSimQA TM software package (Oncology Systems Limited, Shrewsbury, UK). We reported figures of merit (FOMs) to convey complementary information: Dice Similarity Coefficient, Sensitivity Index, and Inclusiveness Index. RESULTS: The study was conducted on 32 treatment plans. Median BTVATS was 11 cm3 while median BTVVIS was 14 cm3. The median Dice Similarity Coefficient, Sensitivity Index, Inclusiveness Index were 0.72, 63%, 88%, respectively. Interestingly, the median volume and the median distance of the voxels that are over contoured by ATS were respectively 1 cm3 and 1 mm. CONCLUSIONS: ATS algorithm could be a smart and an independent operator tool when implemented for 18F-FDG-PET-based tumor volume delineation. Furthermore, it might be relevant in case of BTV-based dose painting.

Stereotactic radiotherapy for brain oligometastases.

Brain metastases, the most common metastases in adults, will develop in up to 40% of cancer patients, accounting for more than one-half of all intracranial tumors. They are most associated with breast and lung cancer, melanoma and, less frequently, colorectal and kidney carcinoma. Magnetic resonance imaging (MRI) is the gold standard for diagnosis. For the treatment plan, computed tomography (CT ) images are co-registered and fused with a gadolinium-enhanced T1-weighted MRI where tumor volume and organs at risk are contoured. Alternatively, plain and contrast-enhanced CT scans are co-registered. Single-fraction stereotactic radiotherapy (SRT ) is used to treat patients with good performance status and up to 4 lesions with a diameter of 30 mm or less that are distant from crucial brain function areas. Fractionated SRT (2-5 fractions) is used for larger lesions, in eloquent areas or in proximity to crucial or surgically inaccessible areas and to reduce treatment-related neurotoxicity. The single-fraction SRT dose, which depends on tumor diameter, impacts local control. Fractionated SRT may encompass different schedules. No randomized trial data compared the safety and efficacy of single and multiple fractions. Both single-fraction and fractionated SRT provide satisfactory local control rates, tolerance, a low risk of transient acute adverse events and of radiation necrosis the incidence of which correlated with the irradiated brain volume.

Prognostic role of pre-treatment magnetic resonance imaging (MRI)-based radiomic analysis in effectively cured head and neck squamous cell carcinoma (HNSCC) patients.

OBJECTIVES: To identify and validate baseline magnetic resonance imaging (b-MRI) radiomic features (RFs) as predictors of disease outcomes in effectively cured head and neck squamous cell carcinoma (HNSCC) patients. MATERIALS AND METHODS: Training set (TS) and validation set (VS) were retrieved from preexisting datasets (HETeCo and BD2Decide trials, respectively). Only patients with both pre- and post-contrast enhancement T1 and T2-weighted b-MRI and at least 2 years of follow-up (FUP) were selected. The combination of the best extracted RFs was used to classify low risk (LR) vs. high risk (HR) of disease recurrence. Sensitivity, specificity, and area under the curve (AUC) of the radiomic model were computed on both TS and VS. Overall survival (OS) and 5-year disease-free survival (DFS) Kaplan-Meier (KM) curves were compared for LR vs. HR. The radiomic-based risk class was used in a multivariate Cox model, including well-established clinical prognostic factors (TNM, sub-site, human papillomavirus [HPV]). RESULTS: In total, 57 patients of TS and 137 of VS were included. Three RFs were selected for the signature. Sensitivity of recurrence risk classifier was 0.82 and 0.77, specificity 0.78 and 0.81, AUC 0.83 and 0.78 for TS and VS, respectively. VS KM curves for LR vs. HR groups significantly differed both for 5-year DFS (p<.0001) and OS (p=.0004). A combined model of RFs plus TNM improved prognostic performance as compared to TNM alone, both for VS 5-year DFS (C-index: 0.76 vs. 0.60) and OS (C-index: 0.74 vs. 0.64). CONCLUSIONS: Radiomics of b-MRI can help to predict recurrence and survival outcomes in HNSCC.

Cone-beam computed tomography-based radiomics in prostate cancer: a mono-institutional study.

PURPOSE: The purpose of the reported study was to investigate the value of cone-beam computed tomography (CBCT)-based radiomics for risk stratification and prediction of biochemical relapse in prostate cancer. METHODS: The study population consisted of 31 prostate cancer patients. Radiomics features were extracted from weekly CBCT scans performed for verifying treatment position. From the data, logistic-regression models were learned for establishing tumor stage, Gleason score, level of prostate-specific antigen, and risk stratification, and for predicting biochemical recurrence. Performance of the learned models was assessed using the area under the receiver operating characteristic curve (AUC-ROC) or the area under the precision-recall curve (AUC-PRC). RESULTS: Results suggest that the histogram-based Energy and Kurtosis features and the shape-based feature representing the standard deviation of the maximum diameter of the prostate gland during treatment are predictive of biochemical relapse and indicative of patients at high risk. CONCLUSION: Our results suggest the usefulness of CBCT-based radiomics for treatment definition in prostate cancer.

Improving radiation oncology through clinical audits: Introducing the IROCA project.

As radiotherapy practice and processes become more complex, the need to assure quality control becomes ever greater. At present, no international consensus exists with regards to the optimal quality control indicators for radiotherapy; moreover, few clinical audits have been conducted in the field of radiotherapy. The present article describes the aims and current status of the international IROCA "Improving Radiation Oncology Through Clinical Audits" project. The project has several important aims, including the selection of key quality indicators, the design and implementation of an international audit, and the harmonization of key aspects of radiotherapy processes among participating institutions. The primary aim is to improve the processes that directly impact clinical outcomes for patients. The experience gained from this initiative may serve as the basis for an internationally accepted clinical audit model for radiotherapy.

Anal cancer FDG-PET standard uptake value: correlation with tumor characteristics, treatment response and survival.

PURPOSE: The present work studies the correlation of (18) F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) standardized uptake value (SUV) with tumor characteristics, clinical response and prognosis in a series of anal canal cancer patients treated with chemo-radiotherapy. MATERIALS AND METHODS: Fifty-five patients were included in the present analysis. PET maximum SUV (SUVmax) of primary tumor was calculated for each patient. The correlation with clinical parameters, tumor response and survival data were analyzed. RESULTS: SUVmax significantly correlated with T-stage (p = 0.01) and histology (p = 0.03). Median SUVmax was higher for lesions with partial response (PR, 21/55, 38%) than for lesions with complete response (CR, 34/55, 62%) but without statistical significance (p = 0.17). The actuarial disease-free survival (DFS) and overall survival (OS) rates were 53.0 and 77.8% at 2 years and 41.3 and 58.6% at 5 years, respectively. Median SUVmax did not statistically correlate with clinical response or survival. CR and T1-T2 stage were statistically significant prognostic factors for disease-free survival (p < 0.0001 and p = 0.02, respectively) and CR was significant also for overall survival (p < 0.0001). CONCLUSIONS: Our data suggest that pre-treatment FDG-PET/CT SUVmax cannot directly predict tumor response and survival, but it is strongly associated with tumor characteristics such as primary tumor stage and histology, being the first one of the most important and validated prognostic factors for anal cancer.

Radiotherapy for vestibular schwannoma: Review of recent literature results.

BACKGROUND: The management of vestibular schwannoma is still a quite controversial issue and can include wait and see policy, surgery and radiotherapy, mainly with stereotactic technique. The purpose of this study is to review the results of recent clinical series treated by radiotherapy. MATERIALS AND METHODS: Literature search was performed by Pubmed and Scopus by using the words "vestibular schwannoma, acoustic neuroma, radiotherapy, radiosurgery". RESULTS: Management options of VS include wait and see, surgery and radiotherapy. In case of small lesions, literature data report local control rates higher than 90% after radiosurgery (SRS) similar those of surgical techniques. Recent literature reviews show favourable functional outcome by using SRS. Several literature data support the use of fractionated stereotactic radiotherapy (FSRT) in case of large inoperable lesions. CONCLUSION: Radiotherapy plays a relevant role in the treatment of VS. In small-size lesions, SRS can guarantee similar local control and potentially better function outcome compared to surgery. In case of large and irregularly shaped lesions, FSRT can be the used when surgery is not feasible.

Review of photon and proton radiotherapy for skull base tumours.

An extremely large variety of benign and malignant tumours occur at skull base; these tumour lesions are in the proximity to structures deputed to relevant physiologic functions, limiting extensive surgical approaches to this body district. Most recent progresses of surgery and radiotherapy have allowed to improve local control with acceptable rates of side effects. Various photon radiotherapy techniques are employed, including 3-dimensional conformal radiotherapy, intensity modulated radiotherapy (IMRT), stereotactic radiotherapy (SRT) and brachytherapy that is manly limited to the treatment of primary or recurrent nasopharyngeal carcinoma. Proton beam radiotherapy is also extensively used thanks to its physical characteristics. Our review, focusing in particular on meningioma, chordoma, and chondrosarcoma, suggests that proton therapy plays a major role in the treatment of malignant tumours whereas photon therapy still plays a relevant role in the treatment of benign tumour lesions.

Stereotactic radiation therapy for skull base recurrences: Is a salvage approach still possible?

AIM: A literature review was performed to analyse the role of stereotactic radiotherapy given in a single shot or in a fractionated fashion for recurrent skull base tumours in order to ascertain if it can be a real salvage approach. BACKGROUND: The management of recurrent skull base tumours can have a curative or palliative intent and mainly includes surgery and RT. MATERIALS AND METHODS: One-thousand-ninety-one articles were found in the search databases and the most relevant of them were analysed and briefly described. RESULTS: Data on recurrences of meningioma, pituitary adenoma, craniopharyngioma, chordoma and chondrosarcoma, vestibular schwannoma, glomus jugulare tumours, olfactory neuroblastoma and recurrences from head and neck tumours invading the base of skull are reported highlighting the most relevant results in terms of local control, survival, side effects and complications. CONCLUSIONS: In conclusion, it emerges that SRS and FSRT are effective and safe radiation modalities of realize real salvage treatment for recurrent skull base tumours.

Metabolic Imaging for Radiation Therapy Treatment Planning: The Role of Hybrid PET/MR Imaging.

The use of hybrid PET/MR imaging for radiotherapy treatment planning has the potential to reduce tumor and organ displacements caused by different scan times and setup changes. Although with mixed results mainly due to single-center studies with small sample size, PET/MR imaging could provide better target delineation, especially by reducing coregistration discrepancies on computed tomography simulation scan and offering better soft tissue contrast. The main limitation to drive stronger conclusions is due to the relatively low availability of hybrid PET/MR imaging systems, mainly limited to large academic centers.

Neo-Adjuvant Treatment in Primary Resectable Pancreatic Cancer: A Systematic Review and PRISMA-Compliant Updated Metanalysis of Oncological Outcomes.

BACKGROUND: Despite advances in treatment, the prognosis of resectable pancreatic adenocarcinoma remains poor. Neoadjuvant therapy (NAT) has gained great interest in hopes of improving survival. However, the results of available studies based on different treatment approaches, such as chemotherapy and chemoradiotherapy, showed contrasting results. The aim of this systematic review and meta-analysis is to clarify the benefit of NAT compared to upfront surgery (US) in primarily resectable pancreatic adenocarcinoma. METHODS: A PRISMA literature review identified 139 studies, of which 15 were finally included in the systematic review and meta-analysis. All data from eligible articles was summarized in a systematic summary and then used for the meta-analysis. Specifically, we used HR for OS and DFS and risk estimates (odds ratios) for the R0 resection rate and the N+ rate. The risk of bias was correctly assessed according to the nature of the studies included. RESULTS: From the pooled HRs, OS for NAT patients was better, with an HR for death of 0.80 (95% CI: 0.72-0.90) at a significance level of less than 1%. In the sub-group analysis, no difference was found between patients treated with chemoradiotherapy or chemotherapy exclusively. The meta-analysis of seven studies that reported DFS for NAT resulted in a pooled HR for progression of 0.66 (95% CI: 0.56-0.79) with a significance level of less than 1%. A significantly lower risk of positive lymph nodes (OR: 0.45; 95% CI: 0.32-0.63) and an improved R0 resection rate (OR: 1.70; 95% CI: 1.23-2.36) were also found in patients treated with NAT, despite high heterogeneity. CONCLUSIONS: NAT is associated with improved survival for patients with resectable pancreatic adenocarcinoma; however, the optimal treatment strategy has yet to be defined, and further studies are required.

Concomitant chemo-radiotherapy for unresectable oesophageal cancer: A mono-institutional study on 40 patients.

BACKGROUND/AIM: To analyse clinical response, overall (OS) and disease free survival (DFS) and toxicity in patients with unresectable oesophageal cancer treated by concomitant chemo-radiotherapy (CRT). MATERIALS AND METHODS: Forty patients with stage IIa-IVa biopsy proven oesophageal carcinoma were treated with CRT. All patients were studied with endoscopy and CT and judged unresectable after multidisciplinary discussion. CRT consisted of 3 cycles of cisplatin 100 mg/m(2) or carboplatin 300 mg/m(2) on day 1 and 5-fluorouracil 1000 mg/m(2) as a continuous infusion of 96 h associated with concurrent 3D-conformal RT. By using 15 MeV X-rays, a total dose of 60-66 Gy was delivered with daily fractions of 1.8-2.0 Gy. RESULTS: Complete response (CR), partial response (PR) and no response (NR) were observed in 50%, 20% and 20% of cases, respectively. Of the 20 patients with CR, 15 developed loco-regional recurrent disease. OS and DFS rates at 3 and 5 years were 38%, 8%, 49% and 10%, respectively. Total radiation dose ≥60 Gy improved loco-regional control and complete response (CR vs. PR + NR; p = 0.004) influenced both DFS and loco-regional control. Grade 3 gastrointestinal and haematological acute toxicity occurred in 3/40 patients (7.5%). One patient developed grade 4 renal failure. Late toxicity was reported in 2/40 patients (5.0%), consisting of grade 3 radiation pneumonitis. CONCLUSIONS: Concomitant CRT for unresectable oesophageal cancer can result in an acceptable loco-regional control with limited toxicity. Response after treatment and total radiation dose influenced the outcome.

State of the Art in Combination Immuno/Radiotherapy for Brain Metastases: Systematic Review and Meta-Analysis.

OBJECTIVES: Common origins for brain metastases (BMs) are melanoma, lung, breast, and renal cell cancers. BMs account for a large share of morbidity and mortality caused by these cancers. The advent of new immunotherapeutic treatments has made a revolution in the treatment of cancer patients and particularly, as a new concept, if it is combined with radiotherapy, may lead to considerably longer survival. This systematic review and meta-analysis aimed to evaluate the survival rate and toxicities of such a combination in brain metastases. METHODS: To perform a systematic review of the literature until January 2021 using electronic databases such as PubMed, Cochrane Library, and Embase; the Newcastle-Ottawa Scale was used to evaluate the quality of cohort studies. For data extraction, two reviewers extracted the data blindly and independently. Hazard ratio with 95% confidence interval (CI), fixed-effect model, and inverse-variance method was calculated. The meta-analysis has been evaluated with the statistical software Stata/MP v.16 (The fastest version of Stata). RESULTS: In the first step, 494 studies were selected to review the abstracts, in the second step, the full texts of 86 studies were reviewed. Finally, 28 studies were selected consisting of 1465 patients. The addition of IT to RT in the treatment of brain metastasis from melanoma and non-small-cell lung carcinoma was associated with a 39% reduction in mortality rate and has prolonged overall survival, with an acceptable toxicity profile. The addition of IT to RT compared with RT alone has a hazard ratio of 0.39(95% CI 0.34-0.44). CONCLUSIONS: A combination of immuno/radiotherapy (IR) for the treatment of patients with BMs from melanoma and non-small-cell lung carcinoma has prolonged overall survival and reduced mortality rate, with acceptable toxicity. In terms of timing, RT seems to have the best effect on the result when performed before or simultaneously with immunotherapy.

18F-FDG PET Radiomics as Predictor of Treatment Response in Oesophageal Cancer: A Systematic Review and Meta-Analysis.

The best treatment strategy for oesophageal cancer patients achieving a complete clinical response after neoadjuvant chemoradiation is a burning topic. The available diagnostic tools, such as 18F-FDG PET/CT performed routinely, cannot accurately evaluate the presence or absence of the residual tumour. The emerging field of radiomics may encounter the critical challenge of personalised treatment. Radiomics is based on medical image analysis, executed by extracting information from many image features; it has been shown to provide valuable information for predicting treatment responses in oesophageal cancer. This systematic review with a meta-analysis aims to provide current evidence of 18F-FDG PET-based radiomics in predicting response treatments following neoadjuvant chemoradiotherapy in oesophageal cancer. A comprehensive literature review identified 1160 studies, of which five were finally included in the study. Our findings provided that pooled Area Under the Curve (AUC) of the five selected studies was relatively high at 0.821 (95% CI: 0.737-0.904) and not influenced by the sample size of the studies. Radiomics models exhibited a good performance in predicting pathological complete responses (pCRs). This review further strengthens the great potential of 18F-FDG PET-based radiomics to predict pCRs in oesophageal cancer patients who underwent neoadjuvant chemoradiotherapy. Additionally, our review imparts additional support to prospective studies on 18F-FDG PET radiomics for a tailored treatment strategy of oesophageal cancer patients. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/, identifier CRD42021274636.

The Role of Interstitial Brachytherapy for Breast Cancer Treatment: An Overview of Indications, Applications, and Technical Notes.

Breast cancer represents the second leading cause of cancer-related death in the female population, despite continuing advances in treatment options that have significantly accelerated in recent years. Conservative treatments have radically changed the concept of healing, also focusing on the psychological aspect of oncological treatments. In this scenario, radiotherapy plays a key role. Brachytherapy is an extremely versatile radiation technique that can be used in various settings for breast cancer treatment. Although it is invasive, technically complex, and requires a long learning curve, the dosimetric advantages and sparing of organs at risk are unequivocal. Literature data support muticatheter interstitial brachytherapy as the only method with strong scientific evidence to perform partial breast irradiation and reirradiation after previous conservative surgery and external beam radiotherapy, with longer follow-up than new, emerging radiation techniques, whose effectiveness is proven by over 20 years of experience. The aim of our work is to provide a comprehensive view of the use of interstitial brachytherapy to perform breast lumpectomy boost, breast-conserving accelerated partial breast irradiation, and salvage reirradiation for ipsilateral breast recurrence, with particular focus on the implant description, limits, and advantages of the technique.

A Pilot, Prospective, Observational Study to Investigate the Value of NGS in Liquid Biopsies to Predict Tumor Response After Neoadjuvant Chemo-Radiotherapy in Patients With Locally Advanced Rectal Cancer: The LiBReCa Study.

Introduction: Circulating tumor DNA (ctDNA) correlates with the response to therapy in different types of cancer. However, in patients with locally advanced rectal cancer (LARC), little is known about how ctDNA levels change with neoadjuvant chemoradiation (Na-ChRT) and how they correlate with treatment response. This work aimed to explore the value of serial liquid biopsies in monitoring response after Na-ChRT with the hypothesis that this could become a reliable biomarker to identify patients with a complete response, candidates for non-operative management. Materials and Methods: Twenty-five consecutive LARC patients undergoing long-term Na-ChRT therapy were included. Applying next-generation sequencing (NGS), we characterized DNA extracted from formalin-fixed paraffin embedded diagnostic biopsy and resection tissue and plasma ctDNA collected at the following time points: the first and last days of radiotherapy (T0, Tend), at 4 (T4), 7 (T7) weeks after radiotherapy, on the day of surgery (Top), and 3-7 days after surgery (Tpost-op). On the day of surgery, a mesenteric vein sample was also collected (TIMV). The relationship between the ctDNA at those time-points and the tumor regression grade (TRG) of the surgical specimen was statistically explored. Results: We found no association between the disappearance of ctDNA mutations in plasma samples and pathological complete response (TRG1) as ctDNA was undetectable in the majority of patients from Tend on. However, we observed that the poor (TRG 4) response to Na-ChRT was significantly associated with a positive liquid biopsy at the Top. Conclusions: ctDNA evaluation by NGS technology may identify LARC patients with poor response to Na-ChRT. In contrast, this technique does not seem useful for identifying patients prone to developing a complete response.

Multidisciplinary approach in the treatment of malignant paraganglioma of the glomus vagale: a case report.

Malignant paraganglioma of the glomus vagale is a rare tumor entity originating from paraganglia or glomus cells. It typically affects middle age. It differs from benign paraganglioma because of its rapid growth and more aggressive clinical behavior. We report the case of a 40-year-old man presenting with a 5 cm lesion in the upper right cervical region detected by computed tomography (CT) and magnetic resonance imaging (MRI), which also showed enlargement of ipsilateral spinal and jugulodigastric lymph nodes with contrast enhancement. Clinical manifestations at diagnosis included a partial neurological deficit involving the right cranial nerves X, XI and XII. Tumor vascularization was assessed by digital angiography. The tumor mass was entirely removed by a right cervical approach with en-bloc resection with the regional lymph nodes. Histopathological examination showed a paraganglioma with cellular pleomorphism, necrotic microfoci, perineural infiltration and angiogenesis. Massive metastases in two of three jugulodigastric and one spinal lymph nodes on the right side were also detected. Postoperative workup included MRI, positron emission tomography (PET)/CT, meta-iodine-benzyl-guanidine (MIBG) scan, liver ultrasound and chest radiography. Subsequently, the patient underwent conformal radiotherapy with concomitant cisplatin administration. At the last clinical and radiological follow-up examination 5 years after completion of treatment, the patient was free of tumor recurrence. The integrated treatment by surgery and chemoradiation was feasible and effective in the management of this rare case of malignant paraganglioma of the glomus vagale. Multicenter studies should be done to increase the knowledge of tumor presentation and natural history and to analyze the possible treatment options.

Detection of setup uncertainties with 3D surface registration system for conformal radiotherapy of breast cancer.

AIM: To investigate the clinical application of a technique for patient set-up verification in breast cancer radiotherapy based on a 3D surface image registration system. BACKGROUND: Accurate and reproducible patient set-up is a prerequisite to correctly deliver fractionated radiotherapy. Various approaches are available to verify and correct patient setup for 3D image acquisition in a radiation treatment room. MATERIALS AND METHODS: The study analyzed the setup reproducibility of 15 patients affected by breast cancer and candidates for conformal radiotherapy by using the AlignRT system (VisionRT, London, UK). At the initial setup, electronic portal imaging device (EPID) images were compared with Digitally Reconstructed Radiographs (DRRs) and a reference three-dimensional (3D) surface image was obtained by AlignRT. Surface images were acquired prior to every subsequent setup procedure. The systematic and random errors along longitudinal and vertical directions were measured and compared for the two systems. RESULTS: The procedure for surface registration, image acquisition and comparison with the reference image took less than 1 min on average. The T test for systematic error showed no significant difference between the 2 verification systems along the longitudinal (p = 0.69) and vertical (p = 0.67) axes. The T-test for random error showed a significant difference between the 2 systems along the vertical axis (p = 0.05). CONCLUSION: AlignRT is fast, simple, non-invasive and seems to be reliable in detecting patient setup errors. Our results suggest that it could be used to assess the setup reproducibility for breast cancer patients.

Results of the IROCA international clinical audit in prostate cancer radiotherapy at six comprehensive cancer centres.

To assess adherence to standard clinical practice for the diagnosis and treatment of patients undergoing prostate cancer (PCa) radiotherapy in four European countries using clinical audits as part of the international IROCA project. Multi-institutional, retrospective cohort study of 240 randomly-selected patients treated for PCa (n = 40/centre) in the year 2015 at six European hospitals. Clinical indicators applicable to general and PCa-specific radiotherapy processes were evaluated. All data were obtained directly from medical records. The audits were performed in the year 2017. Adherence to clinical protocols and practices was satisfactory, but with substantial inter-centre variability in numerous variables, as follows: staging MRI (range 27.5-87.5% of cases); presentation to multidisciplinary tumour board (2.5-100%); time elapsed between initial visit to the radiation oncology department and treatment initiation (42-102.5 days); number of treatment interruptions ≥ 1 day (7.5-97.5%). The most common deviation from standard clinical practice was inconsistent data registration, mainly failure to report data related to diagnosis, treatment, and/or adverse events. This clinical audit detected substantial inter-centre variability in adherence to standard clinical practice, most notably inconsistent record keeping. These findings confirm the value of performing clinical audits to detect deviations from standard clinical practices and procedures.