{
  "abstract": "Background/Objectives: Despite the established benefits of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors, survival outcomes remain heterogeneous among patients with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2−) metastatic breast cancer. We developed the Metabolic–Muscle Reserve Index (MMRI), integrating tumor metabolic activity, biochemical status, and skeletal muscle quantity, and investigated its relationship with progression-free survival (PFS) and overall survival (OS). Methods: We conducted a retrospective study involving 168 patients with HR+/HER2− metastatic breast cancer who were treated with CDK4/6 inhibitors. MMRI incorporated baseline PET/CT-derived maximum standardized uptake value (SUVmax), serum lactate dehydrogenase (LDH), albumin, and CT-derived psoas volume index (PVI). Receiver operating characteristic (ROC) analysis identified an exploratory MMRI cut-off. We examined survival using Kaplan–Meier analysis and Cox regression. Results: ROC analysis identified an MMRI cut-off of 10.68 for mortality discrimination, with an AUC of 0.642 (95% CI: 0.563–0.716). Patients with MMRI > 10.68 had shorter median PFS (14.1 vs. 28.1 months; p < 0.001) and OS (29.7 months vs. not reached; p < 0.001) than those with MMRI ≤ 10.68. In multivariable Cox analysis, higher MMRI was associated with shorter PFS (HR: 1.857, 95% CI: 1.329–2.596; p = 0.0003) and OS (HR: 1.974, 95% CI: 1.368–2.846; p = 0.0003). Conclusions: Patients with higher MMRI values experienced shorter PFS and OS during CDK4/6 inhibitor treatment for HR+/HER2− metastatic breast cancer. Given its modest discriminative performance, these findings remain exploratory and require prospective external validation before clinical application.",
  "abstract_shown": true,
  "affiliations": [
    "Department of Medical Oncology, Manisa Celal Bayar University Faculty of Medicine, Manisa 45030, Turkey",
    "Department of Nuclear Medicine, Manisa Celal Bayar University Faculty of Medicine, Manisa 45030, Turkey"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Nagihan Kolkıran",
      "orcid": "0000-0001-9344-7212"
    },
    {
      "affs": [
        0
      ],
      "name": "Atike Pınar Erdoğan"
    },
    {
      "affs": [
        0
      ],
      "name": "Mustafa Şahbazlar"
    },
    {
      "affs": [
        1
      ],
      "name": "Gözde Mütevelizade",
      "orcid": "0000-0001-5986-8777"
    },
    {
      "affs": [
        0
      ],
      "name": "Ferhat Ekinci",
      "orcid": "0000-0002-9317-942X"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7mj1c016fhbqn.bib",
  "cited_by": 0,
  "doi": "10.3390/jcm15218641",
  "fulltext_url": null,
  "id": "7mj1c016fhbqn",
  "issns": [
    "2077-0383"
  ],
  "landing_url": "https://www.mdpi.com/2077-0383/15/21/8641",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [],
  "openalex": null,
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-06",
  "publisher": "MDPI AG",
  "ris": "https://research.draconitic.com/paper/7mj1c016fhbqn.ris",
  "sources": [
    {
      "first_seen": "2026-11-07T00:21:23Z",
      "native_id": "10.3390/jcm15218641",
      "source": "crossref",
      "url": "https://www.mdpi.com/2077-0383/15/21/8641"
    }
  ],
  "subjects": [
    {
      "field": "medicine",
      "origin": "journal-openalex:F27",
      "subfield": "general"
    }
  ],
  "title": "Prognostic Value of Metabolic–Muscle Reserve Index in HR+/HER2− Metastatic Breast Cancer Treated with CDK4/6 Inhibitors",
  "title_text": "Prognostic Value of Metabolic–Muscle Reserve Index in HR+/HER2− Metastatic Breast Cancer Treated with CDK4/6 Inhibitors",
  "type": "peer-reviewed",
  "updated_at": "2026-11-08T00:23:02Z",
  "url": "https://research.draconitic.com/paper/7mj1c016fhbqn",
  "venue": "Journal of Clinical Medicine",
  "versions": []
}