This phase IIb pilot study will enrol 20 patients (women) presenting with metastatic breast cancer (ER/PR + HER2- on histology) who require imaging for staging or re-staging of their disease.

There is little published literature evaluating the usefulness of Ga Bombesin-PET imaging in comparison to currently accepted imaging modalities for detecting progressive metastatic breast cancer. This study aims to produce preliminary research to evaluate its clinical value in breast cancer, given the promising previously published cell line and mouse work in ER/PR+ HER2- tumours. It further aims to ascertain the theranostic potential of the NeoB peptide in the ER/PR + Her 2- population, particularly assessing the level of heterogeneity at sites of active malignancy compared to FDG PET.

This study will add PET CT imaging using a tracer agent (NeoB) that directly targets the breast cancer cell. The ability of this new PET CT scan to detect sites of metastatic disease will be compared to standard procedures which include Diagnostic CT, bone scan and 18F-FDG PET.

All patients will undergo a single time point imaging at Day 0 with PET CT to be conducted 120 (+/- 30) minutes after intravenous administration with 68Ga NeoB (3.0MBq/kg).

Inclusion Criteria:

• Female patients aged 18 or above
• Ability to provide informed consent documentation indicating that they understand the purpose of and procedures required for the study, and are willing to participate in the study
• Estrogen/Progesterone receptor +ve HER2 negative disease confirmed on prior biopsy (primary or metastatic site).
• Metastatic breast cancer being staged or re-staged prior to treatment of metastatic disease (including those presenting with up-front metastatic disease with primary breast cancer in-situ and those who have progressed on a line of treatment for metastatic breast cancer that are suitable for another line of treatment)
• Metastatic breast cancer being staged or restaged prior to change in treatment with standard imaging within 3 weeks of enrolment (CT CAP, bone scan, FDG PET CT)

Exclusion Criteria:

• Pregnancy or lactation (patients should use highly effective methods of contraception during and for 12h after administration)
• Significant inter-current acute illness as per investigator discretion that prevent undertaking study procedures
• History of current active malignancy as per investigator discretion other than breast cancer.
• Known or expected hypersensitivity to 68Ga NeoB

women with ER/PR+ HER2 - metastatic breast cancer

Results from both the 68NeoB PET CT and conventional imaging will be provided to the referring physician. It will be made clear to the physician that the 68NeoB PET results are experimental prior to participant enrolment. While the findings of the experimental agent are conveyed to the treating clinician, it is made clear that the results are experimental and should not be used for clinical purposes.