Cancer Patients Undergoing Radical Radiotherapy Research Articles

Explainable deep learning-based survival prediction for non-small cell lung cancer patients undergoing radical radiotherapy

Background and purposeSurvival is frequently assessed using Cox proportional hazards (CPH) regression; however, CPH may be too simplistic as it assumes a linear relationship between covariables and the outcome. Alternative, non-linear machine learning (ML)-based approaches, such as random survival forests (RSFs) and, more recently, deep learning (DL) have been proposed; however, these techniques are largely black-box in nature, limiting explainability. We compared CPH, RSF and DL to predict overall survival (OS) of non-small cell lung cancer (NSCLC) patients receiving radiotherapy using pre-treatment covariables. We employed explainable techniques to provide insights into the contribution of each covariable on OS prediction. Materials and methodsThe dataset contained 471 stage I-IV NSCLC patients treated with radiotherapy. We built CPH, RSF and DL OS prediction models using several baseline covariable combinations. 10-fold Monte-Carlo cross-validation was employed with a split of 70%:10%:20% for training, validation and testing, respectively. We primarily evaluated performance using the concordance index (C-index) and integrated Brier score (IBS). Local interpretable model-agnostic explanation (LIME) values, adapted for use in survival analysis, were computed for each model. ResultsThe DL method exhibited a significantly improved C-index of 0.670 compared to the CPH and a significantly improved IBS of 0.121 compared to the CPH and RSF approaches. LIME values suggested that, for the DL method, the three most important covariables in OS prediction were stage, administration of chemotherapy and oesophageal mean radiation dose. ConclusionWe show that, using pre-treatment covariables, a DL approach demonstrates superior performance over CPH and RSF for OS prediction and use explainable techniques to provide transparency and interpretability.

PO-2123 Deep Learning Prediction of 2-year Survival in Lung Cancer Patients Undergoing Radical Radiotherapy

PO-2123 Deep Learning Prediction of 2-year Survival in Lung Cancer Patients Undergoing Radical Radiotherapy

Changing the Face of Head and Neck Radiotherapy

<h3>Purpose/Objective(s)</h3> Radiotherapy plays a key role in the of the management of head and neck cancer patients with approximately 80% of patients receiving RT at least once during their cancer journey. Immobilization of patients during radiotherapy treatment, is essential to ensure treatment accuracy, and requires the use of a facemask. However, masks are associated with significant treatment related distress and a phenomenon called "mask anxiety". Many patients have difficulty swallowing and breathing which makes a closed facemask even less tolerable. In order to improve patients' radiotherapy treatment experience, we piloted a "faceless" open mask in our department to investigate whether such masks could be used, to reduce patients' distress without impacting on treatment accuracy, by comparing set up data for full versus open masks. <h3>Materials/Methods</h3> Over an 18-month period, all head and neck cancer patients undergoing radical radiotherapy, with a history of anxiety or claustrophobia, were offered open masks. Once 30 patients had completed radiotherapy treatment with the open mask, we analyzed the set-up data by comparing this consecutive cohort of patients, to patients in standard closed masks treated during the same time period. Our standard institutional IGRT protocol includes daily CBCT for first 3 fractions, followed by weekly CBCT. The one-dimensional standard deviations (SD) of the systematic and random set-up errors were calculated for all three orthogonal directions (<i>x, y, z</i>). Mann-Whitney U and independent t-test were used to determine any significant differences between rotational set up data for open and closed masks. <h3>Results</h3> Sixty patients were included. Thirty patients had closed masks and thirty had open masks. The SD of the systematic error (reproducibility of treatment position) in mm was slightly less for closed mask than for the open mask in all directions (vertical 0.079 vs 0.106, lateral 0.068 vs 0.101, longitudinal 0.054 vs 0.080). The SD of the random error was less for closed than for open mask in vertical, 0.219 vs 0.225, and lateral,0.144 vs 0.174, directions. It was slightly more in the longitudinal direction (0.176 compared to 0.171). The margin requirements for the faceless mask were greater than the full mask. Margins for set-up uncertainty were 3.5, 3, and 3mm (Ant Post, Sup Inf and Right Left, respectively) for closed mask, and 4, 3, and 4mm respectively for open mask. There was no significant difference in pitch, roll and yaw between open and closed masks. <h3>Conclusion</h3> In this study, we have shown that open masks are able to maintain accuracy at levels comparable to closed masks and may be offered to patients suffering mask anxiety. However, a slightly larger PTV margin may be required. For open masks to become the standard of care for all head and neck patients, a larger randomized study should be performed. Customized head rests and real time intrafraction monitoring using 3-dimensional surface imaging could also be an advantage for this cohort of patients.

MA06.03 Deep Learning-Based Survival Prediction for Non-Small Cell Lung Cancer Patients Undergoing Radical Radiotherapy

The use of radiotherapy as part of a multimodality treatment approach has improved outcomes for patients with non-small cell lung cancer (NSCLC), though survival rates continue to lag behind those seen for many other cancers. Survival is frequently assessed using Cox proportional hazards (CPH) regression; however, this method may be too simplistic as it assumes a linear relationship between predictors and the outcome. Deep learning (DL), which employs biologically-inspired artificial neural networks, has been proposed as an alternative method to capture the complex, non-linear associations between variables required for accurate survival prediction.

630 IMPACT OF LOW SKELETAL MUSCLE MASS AND DENSITY ON OUTCOMES OF LOCALLY ADVANCED ESOPHAGEAL CANCER PATIENTS TREATED WITH RADICAL RADIOTHERAPY

Abstract Low skeletal muscle mass and density are independent predictors of clinical outcomes in multiple gastrointestinal cancers. However, its effect on the long-term survival of locally advanced esophageal cancer patients undergoing radical radiotherapy is still unclear. Methods Patients with stage II-III esophageal cancer undergoing radical radiotherapy, enrolled in a observational cohort study, were included. Skeletal muscle mass and density were measured on CT. Patients with high and low skeletal muscle mass and density were compared regarding overall survival (OS). Results 165 patients (75.8% males, median age 63) were included, from March-2012 to September-2017. Before radiotherapy, 26.7% patients had low skeletal-muscle-mass and 23.0% patients had low skeletal-muscle-density. After radiotherapy, 40.6% patients had low skeletal-muscle-mass and 30.3% patients had low skeletal-muscle-density.The median OS of high skeletal-muscle-mass/density group was significantly higher than that of low skeletal-muscle-mass/density group before radiotherapy (28.7 vs 28.2 months, p = 0.041; 29.6 vs 16.9 months, p = 0.025). The median OS of high skeletal-muscle-mass/density group was also significantly higher than that of low skeletal-muscle-mass/density group after radiotherapy (30.3 vs 20.3 months, P = 0.012; 29.6 vs 17.2 months, p = 0.018). Conclusion Low skeletal muscle mass and density are associated with long-term outcome in patients undergoing radical radiotherapy. It is suggested that oncologists should pay more attention to the management of muscle mass and density of patients with esophageal cancer undergoing radiotherapy in order to improve their nutritional status and long-term survival.

PO-1940 Variation in bladder filling for cervical cancer patients undergoing radical radiotherapy

PO-1940 Variation in bladder filling for cervical cancer patients undergoing radical radiotherapy

Rectal spacers in patients with prostate cancer undergoing radiotherapy: A survey of UK uro-oncologists.

To understand the awareness and use of rectal spacers for prostate cancer patients undergoing radical radiotherapy in the United Kingdom. An expert-devised online questionnaire was completed by members of the British Uro-oncology Group (BUG). Sixty-three specialists completed the survey (50% of BUG members at that point in time). Only 37% had used rectal spacers, mostly for private patients or those with pre-existing bowel conditions. However, many (68%) would like to use these devices in future. More than 70% of the uro-oncologists felt that bowel toxicity was underreported, but 60% believed that the use of radiotherapy without bowel toxicity was achievable with the use of rectal spacers. The current use of rectal spacers by UK uro-oncologists for patients with localised or locally advanced prostate cancer receiving radiotherapy is low and largely restricted by resourcing issues.

Impact of low skeletal muscle mass and density on outcomes of locally advanced esophageal cancer patients treated with radical radiotherapy.

e16047 Background: Low skeletal muscle mass and density are independent predictors of clinical outcomes in multiple gastrointestinal cancers. However, its effect on the long-term survival of locally advanced esophageal cancer patients undergoing radical radiotherapy is still unclear. Methods: Patients with stage II-III esophageal cancer undergoing radical radiotherapy, enrolled in a observational cohort study, were included. Skeletal muscle mass and density were measured on CT. Patients with high and low skeletal muscle mass and density were compared regarding overall survival (OS). Results: In total, 165 patients (75.8% males, median age 63) were included, from March 2012 to September 2017. Before radiotherapy, 26.7% patients had low skeletal muscle mass and 23.0% patients had low skeletal muscle density. After radiotherapy, 40.6% patients had low skeletal muscle mass and 30.3% patients had low skeletal muscle density.The median OS of high skeletal muscle mass and density group was significantly higher than that of low skeletal muscle mass and density group before radiotherapy (28.7 months vs 28.2 months, p = 0.041; 29.6 months vs 16.9 months, p = 0.025). The median OS of high skeletal muscle mass and density group was also significantly higher than that of low skeletal muscle mass and density group after radiotherapy (30.3 months vs 20.3 months, P = 0.012; 29.6 months vs 17.2 months, p = 0.018). Conclusions: Low skeletal muscle mass and density are associated with long-term outcome in patients undergoing radical radiotherapy. It is suggested that oncologists should pay more attention to the management of muscle mass and density of patients with esophageal cancer undergoing radiotherapy in order to improve their nutritional status and long-term survival.

Evaluation of Mediators Associated with the Inflammatory Response in Prostate Cancer Patients Undergoing Radiotherapy

A recent “hot topic” in prostate cancer radiotherapy is the observed association between acute/late rectal toxicity and the presence of abdominal surgery before radiotherapy. The exact mechanism is unclear. Our working hypothesis was that a previous surgery may influence plasma level of inflammatory molecules and this might result in enhanced radiosensitivity. We here present results on the feasibility of monitoring the expression of inflammatory molecules during radiotherapy. Plasma levels of a panel of soluble mediators associated with the inflammatory response were measured in prostate cancer patients undergoing radical radiotherapy. We measured 3 cytokines (IL-1b, IL-6, and TNF alpha), 2 chemokines (CCL2 and CXCL8), and the long pentraxin PTX3. 20 patients were enrolled in this feasibility evaluation. All patients were treated with IMRT at 78 Gy. 3/20 patients reported grade 2 acute rectal toxicity, while 4/20 were scored as grade 2 late toxicity. CCL2 was the most interesting marker showing significant increase during and after radiotherapy. CCL2 levels at radiotherapy end could be modelled using linear regression including basal CCL2, age, surgery, hypertension, and use of anticoagulants. The 4 patients with late toxicity had CCL2 values at radiotherapy end above the median value. This trial is registered with ISRCTN64979094.

A Prospective Study to Evaluate Clinical Radiation Induced Pneumonitis in Lung Cancer Patients and its Dose Response Relationship with Radiotherapy

Purpose: This study was initiated to evaluate incidence, grade and dosimetric correlation of Clinical Radiation Induced Pneumonitis (RIP) (≥ grade 2) in lung cancer patients undergoing radical radiotherapy. Methods and Materials: From August, 2012 to November, 2013, 85 lung cancer patients received curative 3D CRT. On follow up 14 patients developed symptomatic pneumonitis (≥ Grade 2 as per RTOG Toxicity criteria). They underwent CT thorax/PET-CT at 3 monthly follow-up which were co-registered with planning CT images. Changes in lung density were graded as patchy, discrete and solid consolidation and contoured. Isodose surface enveloping these contours and mean doses received were noted. Result: At a median follow up of 12.5 months, incidence of clinical ≥Grade 2 RIP was 16.5%. Inclusion of mediastinum in the target volume and higher stage of disease were found to be indicators of increased risk of ≥Grade 2 RIP. Lung volumes showing patchy/discrete consolidation decreased from 3rd to 6th month and then plateaued while solid consolidation appeared at 6 months, increased at 9 months but then decreased at 12 months. Percentage isodoses encompassing grade 2 radiological RIP were between 80-85% and mean doses were between 45-48Gy. However for grade 3/4 RIP corresponding values were 90-95% and 50-54Gy. Conclusion: Incidence of ≥Grade 2 RIP with conformal RT was 16.5%. V20 alone may not be a sufficient predictor for RIP and one should consider conformal RT planning to restrict even higher isodoses beyond the PTV.

Discovery and Validation of Predictive Biomarkers of Survival for Non-small Cell Lung Cancer Patients Undergoing Radical Radiotherapy: Two Proteins With Predictive Value

Lung cancer is the most frequent cause of cancer-related death world-wide. Radiotherapy alone or in conjunction with chemotherapy is the standard treatment for locally advanced non-small cell lung cancer (NSCLC). Currently there is no predictive marker with clinical utility to guide treatment decisions in NSCLC patients undergoing radiotherapy. Identification of such markers would allow treatment options to be considered for more effective therapy. To enable the identification of appropriate protein biomarkers, plasma samples were collected from patients with non-small cell lung cancer before and during radiotherapy for longitudinal comparison following a protocol that carries sufficient power for effective discovery proteomics. Plasma samples from patients pre- and during radiotherapy who had survived >18mo were compared to the same time points from patients who survived <14mo using an 8 channel isobaric tagging tandem mass spectrometry discovery proteomics platform. Over 650 proteins were detected and relatively quantified. Proteins which showed a change during radiotherapy were selected for validation using an orthogonal antibody-based approach. Two of these proteins were verified in a separate patient cohort: values of CRP and LRG1 combined gave a highly significant indication of extended survival post one week of radiotherapy treatment.

Competing risk: An illustration with aspiration pneumonia in head and neck cancer patients undergoing radical radiotherapy: A biostatistician's perspective.

Interest in survival analysis is to look and capture the information about the occurrence of events, i.e., death. In human life different types of events may happen at the same time. Sometimes, few events completely interrupt or make subtle changes on the occurrence of an event of interest. The method to capture information about the specific event of interest along with other events is known as competing risk modeling. This paper is dedicated to explore the application of competing risk model in oncology practice. It is aimed in near future that more and more survival analysis will be performed through application of competing risk modeling instead of traditional survival analysis to generate robust statistical inference.

Training programme impact on thermoplastic immobilization for head and neck radiation therapy

PurposeTo determine whether uniform guidelines and training in the stabilization and formation of thermoplastic shells can improve the reproducibility of set-up for Head and Neck cancer patients. Methods and materialsImage based measurements of the planning and treatment positions for 35 head and neck cancer patients undergoing radical radiotherapy were analysed to provide a baseline of the reproducibility of thermoplastic immobilization. Radiation therapists (RT) were surveyed to establish a perception of their confidence in thermoplastic procedures. An evidence based staff training programme was created and implemented. Set-up reproduction and staff perception were reviewed to measure the impact of the training programme. ResultsThe mean (SD) 3D vectors of anatomical displacement, measured on the patient images, improved from 4.64 (2.03) for the baseline group compared to 3.02 (1.65) following training (p < 0.01). The proportion of 3D displacements of patient data exceeding 5 mm 3D vector was decreased from 37.1% to 5.7% (p < 0.001) and the 3 mm vector from 85.7% to 42.9% (p < 0.001). The post-training survey scores demonstrated improved confidence in reproducibility of set-up for head and neck patients. ConclusionThe Thermoplastic Shells Training Program has been found to improve the treatment reproducibility for head and neck radiation therapy patients. Uniform guidelines have increased RT confidence in thermoplastic procedures.

Hyperpolarized 3 He pulmonary functional magnetic resonance imaging prior to radiation therapy

Radiation-induced lung injury (RILI) is the primary dose-limiting toxicity for radiation therapy of the lung, and although the effects of radiation dose on RILI development have been well characterized, the influence of chronic obstructive pulmonary disease (COPD) on the development of RILI and other outcomes is not well understood. The purpose of this small pilot study was to evaluate the relationship between hyperpolarized (3)He magnetic resonance imaging (MRI) measurements of COPD with RILI and 12-month survival in lung cancer patients undergoing radical radiotherapy and to evaluate the feasibility of pulmonary functional MRI as an image guidance∕planning tool for radiation therapy. Fifteen non-small cell and small cell lung cancer patients underwent pulmonary function tests, x-ray computed tomography (CT), and hyperpolarized (3)He MRI prior to radical radiation therapy (≥60 Gy). Conventional thoracic (1)H and hyperpolarized (3)He MRI were acquired to generate ventilation defect percent and the apparent diffusion coefficient for the ipsilateral and contralateral lungs independently. CT was acquired postradiation therapy and qualitatively evaluated for radiological evidence of RILI and 12-month survival was reported. Hyperpolarized (3)He MRI measurements of COPD classified 10∕15 subjects with contralateral lung COPD (CLC), and five subjects without COPD [contralateral lung normal (CLN)]. Of the 10 subjects with CLC, only four had a previous clinical diagnosis of COPD. CT images were acquired postradiation therapy for 13 subjects, and for eight (62%) of these there was qualitative evidence of RILI, including 5∕9 CLC and 3∕4 CLN subjects. The one-year survival was 2∕10 for CLC and 3∕5 for CLN subjects. In this small pilot study, we report the use of (3)He MRI to stratify lung cancer patients based on MRI evidence of COPD and showed that comorbid COPD was present in the majority of lung cancer subjects stratified for radiation therapy. Lung cancer patients with imaging evidence of COPD did not have an increased incidence of RILI compared to patients without COPD. However, preliminary data presented here indicated that one-year survival in COPD subjects was lower than expected based on previously published survival rates, which may have implications for radiation therapy in lung cancer patients with comorbid COPD.

Late rectal bleeding after 3D-CRT for prostate cancer: development of a neural-network-based predictive model

The aim of this study was to develop a model exploiting artificial neural networks (ANNs) to correlate dosimetric and clinical variables with late rectal bleeding in prostate cancer patients undergoing radical radiotherapy and to compare the ANN results with those of a standard logistic regression (LR) analysis. 718 men included in the AIROPROS 0102 trial were analyzed. This multicenter protocol was characterized by the prospective evaluation of rectal toxicity, with a minimum follow-up of 36 months. Radiotherapy doses were between 70 and 80 Gy. Information was recorded for comorbidity, previous abdominal surgery, use of drugs and hormonal therapy. For each patient, a rectal dose–volume histogram (DVH) of the whole treatment was recorded and the equivalent uniform dose (EUD) evaluated as an effective descriptor of the whole DVH. Late rectal bleeding of grade ≥ 2 was considered to define positive events in this study (52 of 718 patients). The overall population was split into training and verification sets, both of which were involved in model instruction, and a test set, used to evaluate the predictive power of the model with independent data. Fourfold cross-validation was also used to provide realistic results for the full dataset. The LR was performed on the same data. Five variables were selected to predict late rectal bleeding: EUD, abdominal surgery, presence of hemorrhoids, use of anticoagulants and androgen deprivation. Following a receiver operating characteristic analysis of the independent test set, the areas under the curves (AUCs) were 0.704 and 0.655 for ANN and LR, respectively. When evaluated with cross-validation, the AUC was 0.714 for ANN and 0.636 for LR, which differed at a significance level of p = 0.03. When a practical discrimination threshold was selected, ANN could classify data with sensitivity and specificity both equal to 68.0%, whereas these values were 61.5% for LR. These data provide reasonable evidence that results obtained with ANNs are superior to those achieved with LR when predicting late radiotherapy-related rectal bleeding. The future introduction of patient-related personal characteristics, such as gene expression profiles, might improve the predictive power of statistical classifiers. More refined morphological aspects of the dose distribution, such as dose surface mapping, might also enhance the overall performance of ANN-based predictive models.

Sexual Dysfunction and Depression in Cancer Patients Receiving Radiotherapy: A Prospective Study

Purpose/Objective(s): Quality of life (QoL) is regarded as an important issue in oncology. QoL is composed of many parameters, including sexuality. The term “sexual dysfunction” describes health problems that interfere with sexual intercourse and reproduction, in turn affecting sexuality. Cancer diagnosis and treatments often cause physical and psychological disruptions to sexual health. The main objective of this study was to delineate the rates and clinical course of sexual function (SF) and depression in cancer patients undergoing radical radiotherapy (RT). Materials/Methods: The evaluation included the completion of patients’ self-reported questionnaires. Forty-eight male and 90 female RT-naive patients with breast cancer or pelvic tumors completed the Female Sexual Function Index (FSFI), the International Index of Erectile Function (IIEF) and the Hamilton Depression Scale (HDS) prior to (Phase 1), at the end (Phase 2) and 12 months post-RT (Phase 3). Results: Out of the 174 patients initially assessed, 138 agreed to participate in the study. The majority of patients (93.8% of males and 80% of females) experienced intense sexual dysfunction. At presentation, males reported severe erectile dysfunction (ED) that was significantly associated with age. However, only in sexual desire (SD), was the difference between baseline and Phase 3 significant. Although the incidence of severe ED in all three study phases was impressive, it remained stable over time (severe ED: 79.2% Phase 1 82.2% Phase 3). For all women, an improvement was observed in all parameters of the FSFI over the course of the study. FSFI total scores at Phase 3 were higher compared to Phase 1 and 2 (p<0.05). Females who underwent pelvic RT scored lower than those who underwent breast RT. The differences were significant at all three study phases (p<0.001). As to the primary site, the differences were statistically significant among females with breast cancer (p<0.05). Patients with PS 0 presented higher total FSFI scores at Phase 3 compared to those with PS 1 (p<0.05). Even though depression was not related to SF, 53% of all patients reported some kind of depressive symptoms at baseline (Phase 1). Conclusions: Overall, the current study showed that the majority of patients with cancer treated with RT experienced intense sexual dysfunction. Pelvic RT affected SF to a higher degree than breast RT. We conclude that cancer patients undergoing RT, mainly in the pelvic region, experience an important degree of sexual dysfunction and depression, which the radiation oncologist should not ignore.

Treatment interruption among head and neck cancer patients undergoing radical radiotherapy

Objective: To determine the incidence of treatment interruption among head and neck cancer patients undergoing radical radiotherapy.Design: Prospective studySetting: Kenyatta National Hospital (KNH), Nairobi.Subjects: Twenty six (M=16, F=10) patients undergoing radiotherapy for head and neck cancer between March and June 2006.Main outcome measures: Frequency of radiation morbidities and treatment interuptions.Results: There were 26 patients consisting of 16 males and 10 females aged between 21 and 70 years (mean = 49.6 years). Among these patients 12 (46.2%) had tumours in the oral cavity, six (23.1%) had nasopharyngeal tumours, two (7.7%) had pharyngeal tumours, and six (23.1%) had laryngeal tumours. All tumours were primary carcinomas except two pharyngeal tumours which were metastatic. Among the 26 patients, 13(50%) completed the course of radiotherapy within the prescribed duration while another 13(50%) had treatment interruption. Of the 13 patients who had treatment interruption, one patient had a treatment gap of four days, seven patients had treatment gaps ranging between six and ten days, and five patients had treatment gaps of over ten days. The duration of treatment gaps ranged between four and 30 days. At the time of treatment interruption the cumulative radiation dose ranged from 22 to 58 Grey with a mean of 38 Grey (Mode = 44 Grey). The most common side effect was xerostomia (92%). This was closely followed by mucositis (88.5%), skin reactions (88.5%) dysphagia (84.5%) pain and suffering (76.9%). Loss of taste (61.5%), trismus (34.6%) and voice change (30.89%) were relatively less common.Conclusion: Our findings show that the probability of cancer control and cure among head and neck cancer patients treated at KNH could be severely eroded by treatment interruptions as a result of severe radiation morbidity.

Dose-volume histogram analysis as predictor of radiation pneumonitis in primary lung cancer patients treated with radiotherapy

To determine the relationship between various parameters derived from lung dose-volume histogram analysis and the risk of symptomatic radiation pneumonitis (RP) in patients undergoing radical radiotherapy for primary lung cancer. The records of 156 patients with lung cancer who had been treated with radical radiotherapy (>/=45 Gy) and for whom dose-volume histogram data were available were reviewed. The incidence of symptomatic RP was correlated with a variety of parameters derived from the dose-volume histogram data, including the volume of lung receiving 10 Gy (V(10)) through 50 Gy (V(50)) and the mean lung dose (MLD). The rate of RP at 6 months was 15% (95% confidence interval 9-22%). On univariate analysis, only V(30) (p = 0.036) and MLD (p = 0.043) were statistically significantly related to RP. V(30) correlated highly positively with MLD (r = 0.96, p < 0.001). V(30) and MLD can be used to predict the risk of RP in lung cancer patients undergoing radical radiotherapy.

Preliminary Reliability and Validity Testing of a New Skin Toxicity Assessment Tool (STAT) in Breast Cancer Patients Undergoing Radiotherapy

Clear consensus on the clinical evaluation of acute skin toxicity among cancer patients undergoing radical radiotherapy (RT) is currently lacking. This study investigates the reliability and validity of a new Skin Toxicity Assessment Tool (STAT) to evaluate the objective and subjective manifestations of RT-induced acute skin effects. The STAT was designed by a multidisciplinary team involved in the management of radiation skin reactions. The tool has 3 components: patient and treatment parameters, observer scoring, and patient-reported symptoms, and was piloted in a cohort of 27 breast cancer patients by pairs of independent blinded observers. Each patient was assessed weekly during RT and 2 weeks after therapy completion. Validity and reliability testing of the STAT was performed. Information on the tool's ease of use was obtained by recording the time necessary to complete the assessment at each visit and by a survey among the tool's users. All subjects developed some degree of skin reaction during breast RT. The level of agreement between observers in eliciting subjective complaints ranged from 72% to 92% (95% CI = 63-96%; kappa = 0.33-0.68). The interobserver agreement in scoring skin reactions ranged from 65.0 to 97.5% (kappa = 0.46-0.81). Objective and subjective toxicity scores were significantly correlated (P < 0.05). The STAT was easy to use and required on average a few minutes to complete at each visit. The STAT is an easy-to-use, standardized instrument to evaluate acute skin reaction and may be applied to clinical care and research in patients undergoing radiotherapy.