Purpose We aimed to explore whether complete eradication of tumor burden with stereotactic body radiotherapy (SBRT) would affect the outcomes of oligometastatic renal cell carcinoma (RCC). Materials and methods Patients diagnosed with extracranial oligometastatic RCC (no more than five metastases) between 2007 and 2019 were reviewed. Those without nephrectomy were excluded. SBRT to all, some and no lesions were defined as complete, incomplete, and no SBRT. Progression-free survival (PFS) and cancer-specific survival (CSS) were analyzed using Kaplan–Meier method, Cox regression model and the Fine and Gray method. Result A total of 101 patients were included, 51.5% of whom had < 3 metastases. Forty (39.6%) patients received complete SBRT, and 61 (60.4%) received no or incomplete SBRT. The 1-year LC rate was 97.3%. The complete SBRT group had significantly longer PFS (26.0 vs 18.8 months; p = 0.043) and CSS (not reached vs. 55.3 months; p = 0.012) compared with the no or incomplete SBRT group. In multivariate analysis, ECOG 0–1 (HR 0.389, 95% CI 0.167–0.906, p = 0.029) and complete SBRT were prognostic factors for CSS (HR 0.307, 95% CI 0.108–0.876, p = 0.027). Complete SBRT was associated with improved CSS in the subgroups of patients with age < 55 years, ECOG 0–1, clear-cell histology, IMDC intermediate/poor risk, metachronous metastasis, and < 3 lesions. Conclusion Complete eradication of tumor burden with SBRT was associated with better survival in patients with oligometastatic RCC. The recommendation of SBRT to all lesions should be individualized.

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Objectives Assessment of viable tumor residue after definitive radiotherapy is essential in patients with nasopharyngeal carcinoma (NPC). This study aimed to investigate the use of Hopkins criteria on positron emission tomography/computed tomography (PET/CT) for posttreatment response evaluation and whether plasma Epstein‐Barr virus (EBV) DNA could bring additional value. Materials and methods NPC patients who underwent FDG‐PET/CT scan within 26 weeks after definitive radiotherapy were retrospectively reviewed. Residual disease was evaluated by Hopkins 5‐point score. Accuracy of Hopkins criteria before and after incorporating EBV DNA was calculated. Prognostic value for locoregional failure‐free survival (LRFFS) and disease‐free survival (DFS) was analyzed. Results One hundred and sixteen patients were evaluated. Median follow‐up time was 28.3 months (range 3.3‐92.0 months). Residual disease was found in 19 (16.4%) patients. Overall, Hopkins criteria had high specificity (86.6%; 95% CI, 78.2%‐92.7%) and negative prognostic value (NPV) (94.4%; 95% CI, 88.7%‐97.3%), while sensitivity and positive prognostic value (PPV) was 73.7% (95% CI, 48.8%‐90.9%), 51.9% (95% CI, 37.8%‐65.6%), respectively. Posttreatment plasma EBV DNA was not predictive of residual tumor (P = .272). PPV and accuracy were 50.0% (95% CI, 32.1%‐67.9%) and 83.0% (95% CI, 73.8%‐90.0%) after incorporating detectable EBV DNA into the scoring system. Positive PET/CT results were significantly correlated with inferior 3‐year LRFFS (95.7% vs 79.5%, P = .043) and 3‐year DFS (84.6% vs 54.4%, P = .028). Conclusions The Hopkins criteria demonstrated high NPV and specificity in posttreatment assessment, with the potential to be a reliable prognostic indicator for locoregional failure. Combining EBV DNA with PET/CT did not improve diagnostic accuracies. PET/CT should not be performed less than 12 weeks after treatment.