{"entity":{"id":"comet-dcis","kind":"trial","name":"COMET (Comparison of Operative versus Monitoring and Endocrine Therapy)","aka":["COMET","AFT-25"],"tldr":"COMET asked whether women with low-risk DCIS could safely be watched rather than operated on; after two years the rate of invasive cancer in the monitored group was no worse than with surgery, so careful monitoring is now a reasonable choice for some women.","summary":"Most ductal carcinoma in situ is treated with surgery and often radiotherapy although only a fraction would ever become invasive. COMET, run by the Alliance Foundation Trials group, was a pragmatic randomised non-inferiority trial of 995 women aged 40 or over with low-risk (grade 1 or 2, hormone receptor-positive, HER2-negative) DCIS, comparing active monitoring with mammography every six months, with endocrine therapy offered, against standard surgery with or without radiotherapy. The primary endpoint was the rate of ipsilateral invasive cancer at two years.\n\nAt two years the invasive cancer rate in the monitoring arm was not inferior to that in the surgery arm, and quality of life was similar. The follow-up is short and many monitored women's cancers were found at planned surgery, so longer results and the parallel LORD and LORIS trials are awaited, but COMET is the first randomised evidence that active monitoring of low-risk DCIS is safe in the short term.","status":"positive","asOf":"2026-09-17","links":[{"label":"ClinicalTrials.gov NCT02926911","url":"https://clinicaltrials.gov/study/NCT02926911"}],"tags":["subtype-trials"],"related":[],"cancers":["ductal-carcinoma-in-situ","breast-cancer"],"sections":[],"technologies":["endocrine-therapy"],"targets":[],"drugs":["tamoxifen","letrozole"],"companies":["alliance-oncology"],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":["shelley-hwang"],"bottlenecks":[],"keyPapers":["paper-comet-dcis-jama-2025"],"journals":[],"dependsOn":[],"notes":[],"nct":"NCT02926911","phase":"3","setting":"Low-risk, hormone receptor-positive, HER2-negative ductal carcinoma in situ in women aged 40 or over: active monitoring with optional endocrine therapy against guideline-concordant care (surgery with or without radiotherapy)","sponsor":"Alliance Foundation Trials","result":"At two years the rate of ipsilateral invasive cancer with active monitoring was non-inferior to guideline-concordant surgery.","started":"2017-02-22","startedType":"actual","yearReported":2024,"enrolled":997,"enrolledBasis":"registry","outcomes":[{"endpoint":"Ipsilateral invasive cancer at 2 years (non-inferiority)","primary":true,"unit":"%","arms":[{"name":"Active monitoring","n":484,"value":4.2,"note":"Difference -1.7 percentage points (upper 95% CI limit 0.95); non-inferiority bound 5 points; median follow-up 36.9 months"},{"name":"Guideline-concordant care (surgery with or without radiotherapy)","n":473,"value":5.9}],"source":"https://doi.org/10.1001/jama.2024.26698"}]},"route":"/trials/comet-dcis/","neighbours":{"cancer":[{"id":"breast-cancer","kind":"cancer","name":"Breast cancer (all types)","route":"/cancers/breast-cancer/"},{"id":"ductal-carcinoma-in-situ","kind":"cancer","name":"Ductal carcinoma in situ (DCIS)","route":"/cancers/ductal-carcinoma-in-situ/"}],"technology":[{"id":"endocrine-therapy","kind":"technology","name":"Endocrine therapy (SERMs, AIs, SERDs)","route":"/technologies/endocrine-therapy/"}],"drug":[{"id":"letrozole","kind":"drug","name":"Letrozole (and other aromatase inhibitors)","route":"/drugs/letrozole/"},{"id":"tamoxifen","kind":"drug","name":"Tamoxifen","route":"/drugs/tamoxifen/"}],"company":[{"id":"alliance-oncology","kind":"company","name":"Alliance for Clinical Trials in Oncology","route":"/companies/alliance-oncology/"}],"person":[{"id":"shelley-hwang","kind":"person","name":"E. Shelley Hwang","route":"/people/shelley-hwang/"}],"paper":[{"id":"paper-comet-dcis-jama-2025","kind":"paper","name":"Active Monitoring With or Without Endocrine Therapy for Low-Risk Ductal Carcinoma In Situ: The COMET Randomized Clinical Trial","route":"/key-papers/paper-comet-dcis-jama-2025/"}]}}