MRI O-RADS: Learning about the New Risk Stratification System
2022; Radiological Society of North America; Volume: 303; Issue: 1 Linguagem: Inglês
10.1148/radiol.211307
ISSN1527-1315
Autores Tópico(s)Endometriosis Research and Treatment
ResumoHomeRadiologyVol. 303, No. 1 PreviousNext Reviews and CommentaryFree AccessEditorialMRI O-RADS: Learning about the New Risk Stratification SystemDeborah Levine Deborah Levine Author AffiliationsFrom the Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Ave, Boston, MA 02493.Address correspondence to the author (e-mail: [email protected]).Deborah Levine Published Online:Jan 18 2022https://doi.org/10.1148/radiol.211307MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In See also the article by Sadowski and Thomassin-Naggara et al in this issue.Dr Deborah Levine is professor of radiology at Harvard Medical School and interprets US at Beth Israel Deaconess Medical Center. Her research focuses on OB/GYN imaging. She wrote early works on the frequency of postmenopausal adnexal cysts and was first author for the 2010 SRU consensus conference on adnexal masses and the 2019 update on follow-up of benign simple cysts. In 2018 she was awarded the RSNA Gold Medal. Download as PowerPointOpen in Image Viewer In their review article entitled “O-RADS MRI Risk Stratification System: Guide for Assessing Adnexal Lesions from the ACR O-RADS Committee” in this issue of Radiology (1), Sadowski and Thomassin-Naggara et al provide a complete overview of the new MRI Ovarian-Adnexal Reporting and Data System (O-RADS) lexicon, from inclusion of ovary and adnexa to tissue descriptors and enhancement kinetics to risks of cancer. The American College of Radiology (ACR) O-RADS working groups were started in 2015. Because US is the primary imaging modality in the evaluation of adnexal masses and MRI is the problem-solving tool, parallel working groups (US and MRI) were formed to develop consistent terms and groupings specific to each modality.The ovary and adnexa present several challenges to standardized reporting that do not exist for other lexicons, such as the Breast Imaging Reporting and Data System (BI-RADS), the Prostate Imaging Reporting and Data System, and the Liver Imaging Reporting and Data System. The ovary in premenopausal women is constantly changing, with physiologic cysts that cycle through appearances that while “normal” may temporarily grow larger than the majority of physiologic cysts and may have thick irregular walls with enhancement that can mimic malignancy. How to categorize these minimally atypical but clearly physiologic cysts is problematic. A recent article on the Society of Radiologists in Ultrasound consensus conference on simple adnexal cyst (2) and the ACR white paper on MRI and CT of incidental adnexal cysts (3) allow for simple adnexal cysts up to 5 cm to be described in imaging reports, but include no recommendations for follow-up given their benign nature. The ACR incidental findings white paper also allows for asymptomatic premenopausal hemorrhagic cysts up to 5 cm in maximal diameter, hydrosalpinx, para-ovarian cysts, and peritoneal inclusion cysts to not require follow-up (3). These recommendations were made to decrease unnecessary imaging studies for what are known to be benign findings.Because the MRI O-RADS management recommendations have not yet been released, and because the malignant potential for each of these findings (if well characterized with MRI) is known to be negligible, it would be beneficial for the imaging community, our referring clinicians, and, particularly, our patients if the lack of need for follow-up of these asymptomatic benign lesions is clearly stated. The lexicon needs a benign findings category (either a new 1B category or perhaps a renaming of O-RADS 2 similar to BI-RADS 2 as just “benign”), where no follow-up will be the standard. For patients, simply characterizing the majority of their cysts as benign would be much more reassuring than listing them as “almost certainly benign,” when that description is used for both MRI and US O-RADS 2 with risks reported as less than 0.5% and less than 1%, respectively.Postmenopausal women also frequently have simple adnexal cysts that can change in size and appearance over time (4). Para-ovarian cysts, small hydrosalpinges, and even small benign serous cystadenomas can all be detected in postmenopausal women. The ability to include these cysts, when completely characterized with MRI as simple, in the benign appearance of the ovary is important and must be added to the MRI O-RADS summary table. Moreover, Sadowski and Thomassin-Naggara et al (1) need to be explicit in listing the size of a postmenopausal simple cyst that can be included in the O-RADS 1 category.An important aspect of the MRI O-RADS system is that the scoring of groups 3–5 is based on differential enhancement of the myometrium compared with the tumor. The enhancement kinetics of low-risk (minimal and gradual increase in signal intensity over time with no well-defined shoulder and no plateau), intermediate-risk (an initial slope less than or equal to myometrium, moderate increase in signal intensity with a plateau), and high-risk (an initial slope greater than the myometrium, marked increase in signal intensity with a plateau) time-intensity curves can be used to stratify the lesion as low, intermediate, or high risk for malignancy (1). Thus, understanding and using the lexicon will aid in standardizing how dynamic contrast-enhanced MRI of adnexal masses should be performed, how time-intensity curves are analyzed, and why this method is preferred over non–dynamic contrast-enhanced MRI for risk assessment (1).Keeping the MRI and US O-RADS in alignment, and in agreement with other organized radiology society recommendations, is also going to be important going forward (Table). This is made difficult by the differing populations seen in each group: US is used for screening, and MRI is used for problem-solving. Thus, US has broader ranges for its risk categories because some lesions will be incorrectly or inadequately characterized and diagnosed. The O-RADS tables might benefit from footnotes that describe key differences in lesion categorization and why risk ranges differ among comparable categories in the two O-RADS versions. This is made clear by the positive predictive values (PPVs) seen in score 4 of the US and MRI O-RADS. The PPV for cancer with a score of 4, intermediate risk, is 10%–50% with the US O-RADS system and 50% with the MRI system. Other key differences are in scores of certain specific lesions. For example, hemorrhagic cysts in premenopausal women are scored 2 (almost certainly benign, <1% risk of cancer) in the US O-RADS and are scored as 3 (low risk, <5% risk of cancer) in the MRI O-RADS. Both of these risks vastly differ from classic hemorrhagic cysts described by the ACR incidental findings committee; these cysts can be described in the report and then not followed up if they are smaller than 5 cm (3). Future iterations of the O-RADS will need to address these issues.O-RADS US and MRI Risk-Stratification ComparisonsIn MRI O-RADS, Sadowski and Thomassin-Naggara et al relied on previous research for the data on which they based their categorization (5). In addition, they relied on a larger, more recent single study to create the PPVs given in their summary chart (6). This background is important: The PPVs used in the MRI O-RADS are based on a single study of MRI performed after indeterminate US findings in 1194 women from 15 referral centers. From that study, the area under the receiver operating characteristic curve was 0.96 among experienced readers, with a sensitivity of 93% (189 of 203 patients) and a specificity of 91% (848 of 927 patients) for the detection of cancer. If O-RADS is used correctly, most patients with adnexal cysts will either not undergo follow-up or will show resolution of the cyst at US. Lesions with classic US appearances will not need to undergo MRI, only those in which problem-solving is needed. But, as the system moves out of the research arena and into general practice, the PPV risk categories with MRI will likely need to be broadened, dependent on the quality of US performed around the world, the expertise of the sonologists interpreting the studies, the threshold for when radiologists recommend and clinicians actually order MRI examinations, and the expertise of the radiologists interpreting the MRI examinations. In the article by Thomassin-Naggara et al (6), the reproducibility between experienced and junior readers (κ value, 0.78) was similar to that between experienced readers (κ value, 0.8). While these κ values showed substantial agreement, they clearly are not perfect. This may mean that additional teaching, more refinement of the categories, or more experience with the system is needed for improved reproducibility.In O-RADS categorization, reported cancer risks can vary widely by modality (Table). This is different from BI-RADS, where the category descriptor and associated risk are independent of the modality (the BI-RADS score and the risk of cancer is the same for categories 1–5 whether imaged with mammography, US, or MRI). For adnexal lesions, US is used to screen patients and MRI is used to problem solve; thus, the patient populations are quite different. Another reason for the difference is because image contrast mechanisms are different for US and MRI and because intravenous contrast material use is routine in pelvic MRI examinations, such that the risks of cancer after the MRI can be more well defined.The MRI group is waiting for two upcoming studies on the impact of their categorization scheme before they create the management part of their lexicon. Thus, the full O-RADS schema has not yet been completely developed. Given the thoughtful approach used by the MRI O-RADS group for issues of tissue definitions, categorization, and risk of cancer, the radiology community can look forward to new updates for the lexicon in the future.Disclosures of Conflicts of Interest: D.L. Royalties from Elsevier and UpToDate; payment for expert testimony; board member, Massachusetts Board of Registration in Medicine; consultant to the Editor, Radiology.AcknowledgmentI thank Herbert Y. Kressel, MD, for his editorial comments on this targeted editorial.References1. Sadowski EA, Thomassin-Naggara I, Rockall A, et al. O-RADS MRI Risk Stratification System: Guide for Assessing Adnexal Lesions from the ACRO-RADS Committee. Radiology 2022;303(1):35–47. Link, Google Scholar2. Levine D, Patel MD, Suh-Burgmann EJ, et al. Simple Adnexal Cysts: SRU Consensus Conference Update on Follow-up and Reporting. Radiology 2019;293(2):359–371. Link, Google Scholar3. Patel MD, Ascher SM, Horrow MM, et al. Management of Incidental Adnexal Findings on CT and MRI: A White Paper of the ACR Incidental Findings Committee. J Am Coll Radiol 2020;17(2):248–254. Crossref, Medline, Google Scholar4. Levine D, Gosink BB, Wolf SI, Feldesman MR, Pretorius DH. Simple adnexal cysts: the natural history in postmenopausal women. Radiology 1992;184(3):653–659. Link, Google Scholar5. Thomassin-Naggara I, Aubert E, Rockall A, et al. Adnexal masses: development and preliminary validation of an MR imaging scoring system. Radiology 2013;267(2):432–443. Link, Google Scholar6. Thomassin-Naggara I, Poncelet E, Jalaguier-Coudray A, et al. Ovarian-Adnexal Reporting Data System Magnetic Resonance Imaging (O-RADS MRI) Score for Risk Stratification of Sonographically Indeterminate Adnexal Masses. JAMA Netw Open 2020;3(1):e1919896. Crossref, Medline, Google Scholar7. O-RADS Ultrasound Risk Stratification and Management System. https://www.acr.org/-/media/ACR/Files/RADS/O-RADS/O-RADS_US-Risk-Stratification-Table.pdf. Accessed December 21, 2021. Google Scholar8. O-RADS MRI Risk Score Governing Concepts. www.acr.org/-/media/ACR/Files/RADS/O-RADS/O-RADS-MR-Risk-Stratification-System-Table-September-2020.pdf. Accessed December 21, 2021. Google ScholarArticle HistoryReceived: May 22 2021Revision requested: June 3 2021Revision received: June 4 2021Accepted: June 4 2021Published online: Jan 18 2022Published in print: Apr 2022 FiguresReferencesRelatedDetailsCited ByOvarian-Adnexal Reporting and Data System for Magnetic Resonance Imaging (O-RADS MRI): Genesis and Future DirectionsStephanieNougaret, YuliaLakhman, SuzanBahadir, ElizabethSadowski, IsabelleThomassin-Naggara, CarolineReinhold2023 | Canadian Association of Radiologists Journal, Vol. 74, No. 2O-RADS: a evolução do sistema de classificação de lesões ovarianasJorgeElias Jr., Luis Ronan Marquez Ferreira deSouza2022 | Radiologia Brasileira, Vol. 55, No. 4O-RADS: the evolution of the ovarian lesion classification systemJorgeElias Jr., Luis Ronan Marquez Ferreira deSouza2022 | Radiologia Brasileira, Vol. 55, No. 4Diffusion-Weighted MRI in the Genitourinary SystemThomasDe Perrot, ChristineSadjo Zoua, Carl G.Glessgen, DiomidisBotsikas, LenaBerchtold, RaresSalomir, SophieDe Seigneux, Harriet C.Thoeny, Jean-PaulVallée2022 | Journal of Clinical Medicine, Vol. 11, No. 7Accompanying This ArticleO-RADS MRI Risk Stratification System: Guide for Assessing Adnexal Lesions from the ACR O-RADS CommitteeJan 18 2022RadiologyRecommended Articles O-RADS MRI Risk Stratification System: Guide for Assessing Adnexal Lesions from the ACR O-RADS CommitteeRadiology2022Volume: 303Issue: 1pp. 35-47Invited Commentary: Categorizing Adnexal Masses at US, CT, and MRI—the Radiologist's Not-Impossible MissionRadioGraphics2022Volume: 42Issue: 2pp. E77-E79O-RADS US Risk Stratification and Management System: A Consensus Guideline from the ACR Ovarian-Adnexal Reporting and Data System CommitteeRadiology2019Volume: 294Issue: 1pp. 168-185Benign-appearing Incidental Adnexal Cysts at US, CT, and MRI: Putting the ACR, O-RADS, and SRU Guidelines All TogetherRadioGraphics2022Volume: 42Issue: 2pp. 609-624Simple Adnexal Cysts: SRU Consensus Conference Update on Follow-up and ReportingRadiology2019Volume: 293Issue: 2pp. 359-371See More RSNA Education Exhibits O-RADS: Case Based LearningDigital Posters2021Reporting O-RADS MRI: How We Do It. 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