ABSTRACT
Purpose/Objective(s): The delivery of safe and effective radiation therapy relies on accurate target delineation, particularly in the era of highly conformal treatment techniques. Contouring resources can improve accuracy but are fragmented and underused. We report the 5-year development and usage outcomes of a free, online, easily accessible web-based interactive contouring atlas. Materials/Methods: eContour (https://econtour.org) was developed using modern web technologies, including HTML5, Python, and an interpreted computer programming language, to interactively display images and contours from real patient cases. The viewer has standard tools for image manipulation, contour display, image overlays, and radiation dose distribution. Information from evidence-based guidelines and clinical pearls are summarized and presented next to each case. Mixpanel software was used to collect web usage statistics, including user demographics, geography, and case views. Results: In the first 5 years of operation (February 1, 2016 to February 1, 2021), a total of 22,889 users registered on eContour. Users represented a total of 146 countries, with the largest cohort from the United States (7,096, 31%). Other countries with > 700 registered users included Spain, India, Brazil, China, and Russia. The majority of registered users (58%) reported their profession as physicians, including 10,869 practicing radiation oncologists (47%) and 2,583 resident physicians (11%). There are 3,107 users who identified as physicians and were geographically within the US. The remaining users identified as radiation therapists (10%), dosimetrists (10%), medical physicists (8.7%), and medical students (6.6%). As of February 2021, a total of 65 cases have been developed covering 9 disease sites. The most commonly viewed disease site was head and neck (23% of all case views), followed by gynecological, gastrointestinal, and breast cancer. The most commonly viewed cases include pre-operative rectal cancer, head and neck organs-at-risk, and intact prostate cancer. Over 5 years, usage of eContour has increased both in terms of total users and case views. Total users have grown > 600% since 2017;3,613 (2017), to 12,248 (2019), to 22,889 cumulative total users (2021). In the fourth quarter of 2020, eContour averaged 1,018 case views per weekday. Since the onset of the COVID pandemic, usage of eContour has accelerated. Annual case views increased 56% year-over-year from 2019 to 2020 (147,846 to 230,304 views) as compared to essentially stable from 2018 to 2019 (144,769 to 147,846). Conclusion: With approximately 5,000 radiation oncologists in the US, we estimate 60% of US radiation oncologists are registered users. Growth in users and web site traffic over the first 5 years of eContour show its strong potential to increase the use of evidence-based contouring information at the point of care.