Somatostatin Receptor-targeted Theranostics in Patients with Estrogen Receptor-positive Metastatic Breast Cancer-a Prospective Exploratory Study

Overview

Journal Breast Cancer Res Treat

Specialty Oncology

Date 2025 Feb 25

PMID 40000538

Authors

Kunal Ramesh Chandekar

Swayamjeet Satapathy

Yamini Dharmashaktu

Sanjana Ballal

Piyush Ranjan

Atul Batra

Ajay Gogia

Sandeep Mathur

Chandrasekhar Bal

Affiliations

Soon will be listed here.

Abstract

Purpose: Somatostatin receptor (SSTR) expression has been reported in estrogen receptor-positive (ER +) metastatic breast cancer (mBC) by pathology and immunohistochemistry studies. We aimed to investigate whether SSTR could be a viable target for PET imaging and potential theranostics in ER + mBC.

Methods: Thirty prospectively recruited patients with ER + mBC underwent PET/CT imaging with [F]FDG and [Ga]Ga-DOTATATE (within three weeks). Detection rates (per-patient, per-region), number of lesions detected, SUVmax values, Krenning scores, SSTR-FDG visual scores, and PET-based staging with both radiotracers were compared.

Results: [F]FDG and [Ga]Ga-DOTATATE PET/CT had similar per-patient detection rates (100% vs 96.7%, P = 1.0). Per-region and per-lesion analyses revealed comparable detection of local/breast lesions, nodal, and skeletal metastases. However, [F]FDG outperformed [Ga]Ga-DOTATATE in detecting visceral/other metastases (235 vs 128 lesions, P = 0.003). [Ga]Ga-DOTATATE resulted in a lower PET-based M-stage compared to [F]FDG in 10% of patients, although T-/N-stages were concordant in all patients. HER2- patients showed a trend of higher [Ga]Ga-DOTATATE lesional SUVmax values compared to the HER2 + sub-group (median 9.0 vs 3.8, P = 0.078). 3/30 (10%) participants had a patient-level Krenning score ≥ 3 ([Ga]Ga-DOTATATE uptake higher than liver background in majority of the lesions), potentially making them suitable for SSTR-targeted radionuclide therapy.

Conclusions: SSTR-targeted theranostics may represent a novel potential alternative in a subset of patients with ER + mBC. Its generalized applicability is limited by poor sensitivity for visceral metastases and significant inter-lesion heterogeneity. Future studies must identify how tumor subtype, proliferation, and prior systemic therapies impact SSTR expression levels in these patients to ensure meaningful clinical translation.

Clinical Trial Registration: Clinical Trials Registry-India: CTRI/2023/03/051025 (prospectively registered on 23.03.2023).

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