Tumor size of preoperative breast cancer assessment by whole-body silicon photomultiplier PET: feasibility and first results

Abstract

Abstract Purpose: Whole-body silicon photomultiplier positron emission tomography (WB SiPM PET) could be used to diagnose breast cancer spread before lumpectomy. We aimed to investigate the method of measuring the tumor size by WB SiPM PET as a basis for diagnosing breast cancer spread in the breast. Methods: We retrospectively reviewed 24 breast cancer lesions in 21 patients who underwent WB SiPM PET/CT in the prone position as preoperative breast cancer examinations from September 2020 to March 2022. In all cases, a 20-mm spherical VOI was placed in the normal mammary gland to measure the mean standardised uptake value (SUVmean) and the standard deviation (SD) of 18F-fluorodeoxyglucose (FDG) uptake. We prepared four types of candidates (SUVmean + 2 SD, SUVmean + 3 SD, 1.5 SUVmean + 2 SD, 1.5 SUVmean + 3 SD) for thresholds for delineating tumor contours on PET images. On the semiautomatic viewer soft, the maximum tumor sizes were measured at each of the four thresholds and compared with the pathological sizes, including EIC. Results: The lesion detection sensitivity was 96% for WB SiPM PET. PET detected 23 lesions, excluding 4-mm ductal carcinomas in situ (DCIS). PET measurements at the threshold ‘1.5 SUVmean + 2 SD’ demonstrated the highest correlation coefficient (rs) with the pathologic sizes, including EIC (rs = 0.722). Moreover, ‘1.5 SUVmean + 2 SD’ had the highest concordance (62.5%). Conclusions: By using ‘1.5 SUVmean + 2 SD’ of the normal mammary gland as a patient-specific threshold, we were able to evaluate the tumor size, including EIC.