Assessment of Hormone Receptor Profile in Breast Cancer Using 18F‐Fluro‐Estradiol PET CT: A Pilot Study

Hormone Receptor (HR) status has vital implications in prognosis and therapy of breast cancer. Currently, HR status is assessed by immunohistochemistry (IHC) of core needle biopsy or surgical specimen. In this technique tumor is not studied in entiretyThis technique & has 3–5% false negative rate.AimEvaluate use of 18F‐FES PET‐CT in determining receptor status of breast cancer.MethodsER expression on IHC: Core needle biopsy/excision specimens were fixed in formalin and paraffin embedded sections made & subjected to IHC. Proportion of positive cells was given score of 0 to 5 & intensity of uptake was given a score of 0 to 3. Total score was then calculated by summing up the total. Imaging with FES PET CT performed using standard protocol and images acquired. SUV of lesion, SUV ratio between lesion and background activity & visual interpretation grading were correlated to ER expression on IHC. For SUV ratio, SUV of the breast lesion was compared to the SUV of the mediastinal blood pool in the thoracic aorta. Visual grading of the breast lesion on 18F‐FES PET‐CT CT was done as follows:Grade 1‐ no uptake on 18F‐FES PET‐CT;Grade 2‐uptake of lesion less than mediastinal blood pool; Grade 3‐uptake of lesion similar to mediastinal blood pool.; Grade 4‐Lesion well defined, uptake more than mediastinal blood pool/similar to liver. Correlation between lesion SUV, SUV ratio of lesion and mediastinal blood pool & visual grading score with ER score as on IHC was calculated using the Spearman's correlation coefficient. The value of SUV ratio above which the lesion was considered ER positive was calculated using the receiver operating characteristic curve (ROC curve). P value of < 0.05 was considered significant. Data analysis was done using Stata 11.2.ResultsTwenty four patients were enrolled for the study. Most of the patients were females (F:M= 22:2). All patients had invasive ductal carcinoma (NST) except for a 55 yr old lady who had high grade DCIS and no invasive component was found. IHC done on core needle biopsy specimens was used to determine the receptor status of the breast lumps. 16 patients were HR +ve ( 12 strongly +ve and 4 moderately +ve) and 8 were HR −ve. ROC curve (Fig 1) was plotted for SUV and tumours with SUV of >/= 1.8 on 18F‐FES PET‐CT were categorized as ER+ (AUC=0.8190, sensitivity =73.33% & specificity=71.43%). Comparison of HR status as assessed by FES PETCT and IHC is given in Table I. The sensitivity, specificity, false negative rates of of FES PETCT in evaluating HR status were 87.5%, 100% and 12,5% respectively. Out of the two false negative patients, one patient was on tablet anastrazole (anti estrgoen medication). Correlation between HR status of tumor as assessed by IHC & SUV of tumour, tumour to background ratio and visual grading (Table II) was assessed and it was found that correlation was strongest for visual grading (0.7737) followed by tumour to background ratio (0.6640) & SUV of lesion(0.5305).Conclusions18FES PETCT shows promise in evaluating HR status of breast cancer as it is high sensitive and specific. It scores over the currently used technique of IHC as it assesses the tumor in its entirety. Among the various parameters of assessment of HR expression on FES PETCT, we recommend visual grading as it correlates the best with HR expression on IHC. Limitations of the Study: Small sample size. Larger studies are needed before FES PET CT is recommended to be included in the routine clinical armamentarium for management of breast cancer.Support or Funding InformationnoneThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.