{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T04:52:04Z","timestamp":1791348724538,"version":"4.3.1"},"reference-count":27,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T00:00:00Z","timestamp":1791331200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Oncol."],"abstract":"<jats:p>Hormone receptor-positive, human epidermal growth factor receptor 2-low (HER2-low) metastatic breast cancer (MBC) constitutes the predominant subtype of advanced breast cancer, with most patients eventually developing resistance to endocrine therapy (ET) and cyclin-dependent kinase 4\/6 inhibitors (CDK4\/6i). This case report describes a 64-year-old woman with hormone receptor (HR)-positive, HER2-low MBC involving lung, pleural, and lymph node metastases who achieved a remarkable and sustained radiographic complete response (rCR) to palbociclib plus fulvestrant, followed by letrozole after fulvestrant injection intolerance. The patient exhibited near-complete regression of metastatic lesions within 18 months and maintained remission for over 6 years, far exceeding the typical median progression-free survival observed in clinical trials. The prolonged remission observed underscores the existence of biologically distinct tumor subsets with exceptional sensitivity to CDK4\/6 inhibition, warranting investigation into underlying molecular mechanisms.<\/jats:p>","DOI":"10.3389\/fonc.2026.1856673","type":"journal-article","created":{"date-parts":[[2026,10,7]],"date-time":"2026-10-07T04:48:49Z","timestamp":1791348529000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["A surprising complete radiographic response to palbociclib plus endocrine therapy in an HR-positive, HER2-low lung, pleural, and lymph node metastatic breast cancer patient: a case report"],"prefix":"10.3389","volume":"16","author":[{"given":"Mingzhi","family":"Cha","sequence":"first","affiliation":[{"name":"Department of Breast Surgery, Pingxiang People\u2019s Hospital","place":["Pingxiang, Jiangxi, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hao","family":"Yi","sequence":"additional","affiliation":[{"name":"Department of Breast Surgery, Pingxiang People\u2019s Hospital","place":["Pingxiang, Jiangxi, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"HuiMing","family":"Li","sequence":"additional","affiliation":[{"name":"Department of Pathology, Pingxiang People\u2019s Hospital","place":["Pingxiang, Jiangxi, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Rongrong","family":"Peng","sequence":"additional","affiliation":[{"name":"Department of Breast Surgery, Pingxiang People\u2019s Hospital","place":["Pingxiang, Jiangxi, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,10,7]]},"reference":[{"key":"B1","doi-asserted-by":"publisher","first-page":"19669","DOI":"10.1038\/s41598-023-47033-8","article-title":"Prognostic impact of HER2-low 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