Exploration of tumor size measurement methods in preoperative breast cancer assessment using whole-body silicon photomultiplier PET: feasibility and first results.

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. MATERIALS AND METHODS: We retrospectively reviewed 35 breast cancer lesions in 32 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 tumor sizes, including the extensive intraductal component (EIC). RESULTS: The lesion detection sensitivity was 97% for WB SiPM PET. PET detected 34 lesions, excluding 4-mm ductal carcinomas in situ (DCIS). PET measurements at the '1.5 SUVmean + 2 SD' threshold demonstrated values closest to the pathological tumor sizes, including EIC. Moreover, '1.5 SUVmean + 2 SD' had the highest concordance (63%). CONCLUSIONS: The study demonstrated that among various PET thresholds, the '1.5 SUVmean + 2 SD' threshold exhibited the best performance. However, even with this threshold, the concordance rate was limited to only 63%.

Assessment of tumor response to chemoradiotherapy and predicting prognosis in patients with head and neck squamous cell carcinoma by PERCIST.

PURPOSE: To evaluate therapeutic response to chemoradiotherapy and prediction of recurrence and death in patients with head and neck squamous cell carcinoma (HNSCC) using Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST). MATERIALS AND METHODS: Forty-two patients (mean 63.4, range 20-79 years) with nasopharyngeal (n = 10), oropharyngeal (n = 13), hypopharyngeal (n = 11), or laryngeal (n = 8) cancer underwent fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) before and approximately 3 months (mean 95.0, range 70-119 days) after undergoing concurrent chemoradiotherapy. The effect of PERCIST regarding progression-free survival (PFS) and overall survival (OS) was examined using log-rank and Cox methods. RESULTS: Complete metabolic response (CMR), partial metabolic response (PMR), stable metabolic disease (SMD), and progressive metabolic disease shown by PERCIST were seen in 30 (71.4%), 9 (21.4%), 3 (7.1%), and 0 patients, respectively. Fourteen (33.3%) developed recurrent disease (median follow-up 27.2, range 8.7-123.1 months) and 9 (21.4%) died (median follow-up 43.6, range 9.6-132.6 months). Furthermore, 4 (13.3%) of 30 patients with CMR developed recurrence, while 7 (77.8%) of 9 with PMR and all 3 (100%) with SMD developed recurrence. Two (6.7%) of 30 patients with CMR, 4 (44.4%) of 9 with PMR, and all 3 (100%) with SMD died. Patients who achieved CMR showed significantly longer PFS and OS as compared to those who did not (PMR and SMD) (both, p < 0.0001). CONCLUSION: PERCIST is useful for evaluating therapeutic response to chemoradiotherapy and predicting recurrence and death in HNSCC patients.