--- title: "Scientific evidence: FGFR1, PRRT/SSTR and BC-NED · Miriam González" canonical_url: "https://helpmiriam.com/en/science/evidence" last_updated: "2026-06-10T22:50:16.810Z" meta: description: "Peer-reviewed literature and clinical trials backing each hypothesis in the case: FGFR1 amplification, PRRT/SSTR radioligands, neuroendocrine differentiation (BC-NED) and N-of-1 precision oncology." "og:description": "Peer-reviewed literature and clinical trials backing each hypothesis in the case: FGFR1 amplification, PRRT/SSTR radioligands, neuroendocrine differentiation (BC-NED) and N-of-1 precision oncology." "og:title": "Scientific evidence: FGFR1, PRRT/SSTR and BC-NED · Miriam González" --- [Back to science](https://helpmiriam.com/en/science) Scientific evidence # Key scientific evidence Every hypothesis in this case is grounded in peer-reviewed literature and clinical trials. Here is the evidence behind the therapeutic axes, grouped by theme. ## Neuroendocrine Transformation and RB1 Loss NE transformation Most critical finding: 3 RB1 variants (p.V622Yfs*33, p.R661W, p.F226*) in Guardant360 ctDNA, April 2026 - Park et al., 2018 — Science (DOI: 10.1126/science.aat5749) ### **RB1 + TP53 loss: reprogramming toward a neuroendocrine phenotype** Foundational experimental study showing that combined RB1 and TP53 loss reprograms hormone-dependent epithelial tissues toward an aggressive neuroendocrine phenotype. It is the direct biological basis of neuroendocrine transformation risk in this case, where 3 distinct RB1 mutations were detected in Guardant360 liquid biopsy (April 2026). [View reference Park et al., 2018 — Science (DOI: 10.1126/science.aat5749) (new tab)](https://doi.org/10.1126/science.aat5749) - Aggarwal et al., 2018 — Journal of Clinical Oncology (DOI: 10.1200/JCO.2017.77.6880) ### **Neuroendocrine transformation under hormonal pressure: 17% of hormone-dependent tumors** Prospective multi-institutional study documenting that 17% of patients with hormone-dependent tumors under targeted therapy develop transition to small-cell neuroendocrine phenotype through RB1 loss. This molecular paradigm is transferable to HR+ breast cancer under prolonged endocrine pressure, as in this case after 25 months of endocrine therapy + CDK4/6i. [View reference Aggarwal et al., 2018 — Journal of Clinical Oncology (DOI: 10.1200/JCO.2017.77.6880) (new tab)](https://doi.org/10.1200/JCO.2017.77.6880) - Cancer Discovery, 2025 — Integrative review (DOI: 10.1158/2159-8290.CD-24-0837) ### **Neuroendocrine transformation as an acquired resistance mechanism** Integrative review confirming combined RB1 + TP53 loss as the molecular hallmark of neuroendocrine transformation in hormone-dependent epithelial tumors (prostate, breast, lung). It synthesizes recent evidence and reinforces the biological rationale for exploring the neuroendocrine axis when RB1 alterations emerge under prolonged hormonal therapy. [View reference Cancer Discovery, 2025 — Integrative review (DOI: 10.1158/2159-8290.CD-24-0837) (new tab)](https://doi.org/10.1158/2159-8290.CD-24-0837) ## Biology of Breast Carcinoma with Neuroendocrine Differentiation BC-NED biology Subtype characterization, BC-NED with 80% Cg/Syn - Marchiò et al., 2017 — Journal of Pathology (DOI: 10.1002/path.4837) ### **Genomic landscape of breast carcinoma with neuroendocrine differentiation** Genomic characterization of breast carcinomas with extensive neuroendocrine differentiation (>50% Cg/Syn) identifying a molecular landscape distinct from classic NST, enriched for CCND1, FGFR1, and PI3K pathway alterations. The described profile matches this case (CCND1 ×20, FGFR1 ×13, amplified 11q13 cluster). [View reference Marchiò et al., 2017 — Journal of Pathology (DOI: 10.1002/path.4837) (new tab)](https://doi.org/10.1002/path.4837) - Pareja et al., 2022 — Journal of Clinical Pathology (DOI: 10.1136/jclinpath-2020-207002) ### **Breast neuroendocrine tumors: WHO 5th edition classification and comparative biology** Application of WHO 5th edition (2019) diagnostic criteria to breast neuroendocrine tumors, with genomic comparison against gastroenteropancreatic NETs and mucinous breast carcinomas. It documents that some tumors acquire late neuroendocrine differentiation under therapeutic pressure, relevant to this clinical trajectory. [View reference Pareja et al., 2022 — Journal of Clinical Pathology (DOI: 10.1136/jclinpath-2020-207002) (new tab)](https://doi.org/10.1136/jclinpath-2020-207002) ## SSTR2 Pathway and Radioligand Therapy (PRRT) SSTR2 · PRRT The 68Ga-DOTATOC PET (26 May 2026) confirmed SSTR2 overexpression in the bone metastases → opens the PRRT route (177Lu-DOTATATE); SSTR2 IHC on tissue pending the rebiopsy - Terlević et al., 2019 — Annals of Diagnostic Pathology (DOI: 10.1016/j.anndiagpath.2018.11.002) ### **SSTR2 expression in neuroendocrine breast carcinoma: 71% positive (≈36% moderate-strong)** Immunohistochemical study: 71% of neuroendocrine breast carcinomas express SSTR2A (any intensity); ~36% with moderate-strong intensity, the range most relevant for PRRT with 177Lu-DOTATATE. Supports functional 68Ga-DOTATOC PET imaging and requesting SSTR2 IHC at the rebiopsy. [View reference Terlević et al., 2019 — Annals of Diagnostic Pathology (DOI: 10.1016/j.anndiagpath.2018.11.002) (new tab)](https://doi.org/10.1016/j.anndiagpath.2018.11.002) - Sharma et al., 2021 — European Journal of Nuclear Medicine and Molecular Imaging (DOI: 10.1007/s00259-020-05054-9) ### **177Lu-DOTATATE in metastatic neuroendocrine breast cancer: clinical evidence** Clinical series of metastatic neuroendocrine breast cancer patients treated with PRRT (177Lu-DOTATATE), showing response rates and progression-free survival comparable to gastroenteropancreatic NETs. Provides the strongest available clinical evidence that PRRT can work in this breast tumor subtype. [View reference Sharma et al., 2021 — European Journal of Nuclear Medicine and Molecular Imaging (DOI: 10.1007/s00259-020-05054-9) (new tab)](https://doi.org/10.1007/s00259-020-05054-9) ## FGFR1/CCND1 Axis and CDK4/6i Resistance FGFR1 / CCND1 Molecular mechanism behind the observed clinical resistance in the first two lines - Formisano et al., 2019 — Nature Communications (DOI: 10.1038/s41467-019-09068-2) ### **FGFR1 as a resistance driver to endocrine therapy and CDK4/6i in HR+/HER2- breast cancer** Molecular study showing that FGFR1 amplification functionally activates PI3K/AKT/mTOR signaling even without PIK3CA mutation and represents a known acquired resistance mechanism to endocrine therapy and CDK4/6 inhibitors in HR+/HER2- breast cancer. It explains the clinical resistance observed in the first two treatment lines. [View reference Formisano et al., 2019 — Nature Communications (DOI: 10.1038/s41467-019-09068-2) (new tab)](https://doi.org/10.1038/s41467-019-09068-2) ## International Consensus Guidelines Guidelines Formal support for the clinical requests presented to the treating team - NCCN Guidelines — Neuroendocrine and Adrenal Tumors, Version 1.2025 ### **International algorithm for neuroendocrine tumors of breast origin** NCCN 2025 guidelines include a therapeutic algorithm for neuroendocrine tumors of breast origin with SSTR2 expression, where PRRT (177Lu-DOTATATE) is listed as an option after failure of standard hormonal therapy. Spanish SEOM guidelines do not yet include this algorithm for neuroendocrine breast disease, explaining the discrepancy between national and international recommendations. - ENETS Consensus Guidelines, 2023 — European Neuroendocrine Tumor Society ### **European recommendation: evaluate SSTR2 in advanced neuroendocrine breast carcinomas** ENETS 2023 consensus recommends assessing SSTR2 expression and considering functional DOTATATE imaging in advanced neuroendocrine carcinomas to stratify eligibility for somatostatin receptor-targeted therapies, including PRRT when appropriate. [ Back to science](https://helpmiriam.com/en/science)