¹⁸F-FDG/PET may help to identify a subgroup of patients with T1-T2 breast cancer and 1-3 positive lymph nodes who are at a high risk of recurrence after mastectomy

Purpose The purpose of this study is to assess the utility of positron emission tomography (PET) for predicting recurrence among patients with T1-T2/N1 breast cancer who were treated with mastectomy. Materials and Methods Of 712 consecutive patients with T1-T2/N1 breast cancer treated during 2003-2012, 109 had undergone preoperative ¹⁸F-fluorodeoxyglucose/PET and were included. Metabolic (maximum standardized uptake value [SUV_max]), volumetric (metabolic tumor volume [MTV]), and combined (total lesion glycolysis [TLG]) indices were measured. The resulting values were analyzed and compared with clinical outcome. Results At the median follow-up of 46.7 months, the 3-year relapse-free survival (RFS) rate was 95.2%. SUV_max (area under curve, 0.824) was more useful than MTV or TLG as a means of identifying patients at high risk for any recurrence. In multivariate analysis, SUV_max remained an independent risk factor for RFS (p=0.006). Using the method of Contal and O'Quigley, a SUV_max threshold of 5.36 showed the best predictive performance. The PET-based highrisk group (≥ 5.36 in either breast or nodes) had more T1c-T2, high-grade, hormone-receptor negative, and invasive ductal carcinoma tumors than the low-risk group (< 5.36 in both breast and nodes). The prognosis was much worse when high SUV_max (≥ 5.36) was detected in nodes (p < 0.001). In the no-radiotherapy cohort, the PET-based high-risk group had increased risk of locoregional recurrence when compared to the low-risk group (p=0.037). Conclusion High SUV_max on preoperative PET showed association with elevated risk of locoregional recurrence and any recurrence. Pre-treatment PET may improve assessments of recurrence risk and clarify indications for post-mastectomy radiotherapy in this subset of patients.