Quantitative Assessment of Treatment Response in Metastatic Breast Cancer Patients by SPECT-CT Bone Imaging—Getting Closer to PET-CT

SIMPLE SUMMARY: The aim of our study is to demonstrate the added value of the quantitative interpretation of SPECT-CT images compared to qualitative assessment regarding changes in radiotracer uptake between the baseline and follow-up scans in breast cancer patients treated for metastatic bone disease. By implementing this method of imaging interpretation, a more standardized and robust approach of patient follow-up evaluation can be obtained, which is particularly important for research purposes. ABSTRACT: Background: Cancer represents the major cause of death mainly through its ability to spread to other organs, highlighting the importance of metastatic disease diagnosis and accurate follow up for treatment management purposes. Although until recently the main method for imaging interpretation was represented by qualitative methods, quantitative analysis of SPECT-CT data represents a viable, objective option. Methods: Seventy-five breast cancer patients presenting metastatic bone disease underwent at least two Bone SPECT-CT studies using [(99m)Tc]-HDP between November 2019 to October 2022. Results: Our findings show a good positive relationship between the qualitative methods of imaging interpretation and quantitative analysis, with a correlation coefficient of 0.608 between qualitative whole body scintigraphy and quantitative SPECT-CT, and a correlation coefficient of 0.711 between the qualitative and quantitative interpretation of SPECT-CT data; nevertheless, there is a need for accurate, objective and reproducible methods for imaging interpretation, especially for research purposes. Conclusions: Quantitative evaluation of the SPECT-CT data has the potential to be the first choice of imaging interpretation for patient follow up and treatment response evaluation, especially for research purposes, because of its objectivity and expression of uptake changes in absolute units.