PET-SUV Max and Upstaging of Lung Cancer

Lung cancers managed surgically with curative intent are sometimes upstaged postoperatively. The potential contributions from surgical waiting time and primary tumour ¹⁸F-FDG avidity on positron emission tomography (PET)/computed tomography (CT) are unknown.

We reviewed the records of 153 Royal Adelaide Hospital surgical patients with primary lung cancers from 2013 to 2016 who had preoperative staging combining CT, ¹⁸F-FDG PET/CT and biopsy. Subjects were divided into two cohorts: postoperative Tumour, Node, Metastases (TNM) upstaged (US) and not upstaged (UN). The parameters of standardised uptake value (SUV max), pre-scan blood glucose level (BGL), the time interval between staging and surgery were analysed using a two-tailed Mann-Whitney U test.

Subjects were aged 31 to 85 years; 75 were male. Ninety-three had adenocarcinoma (AC), 42 had squamous cell carcinoma (SCC). Sixty-four were upstaged after surgery, 40 AC and 18 SCC. For AC, US SUV max was significantly higher (mean US 6.4 (SD 4.6) vs. UN 4.6 (SD 3.4), p=0.03) but not time to surgery (mean US 55 (SEM 7.1) vs. UN 71 (SEM 14.8) days p=0.74). Upstaged were mainly T (imaging and histopathology discordance) and N (unexpected mediastinal or hilar nodal metastases). For SCC, US vs. UN SUV max (mean US 12.0 (SD 5.6) vs. UN 9.4 (SD 5.6), p=0.08) and time to surgery (mean US 48 (SEM 5.3) vs. UN 47 (SEM 5.0) days p=0.66) were not significantly different. Standardised uptake value max and surgical waiting time were not analysed for other tumour types due to small numbers. Pre-PET BGL US vs. UN was not significantly different for all (p=0.52), AC (p=0.32) and SCC (p=0.37) subjects, thus not a confounding factor.

For lung cancers assigned to curative surgery, high primary tumour SUV max of AC but not SCC may predict surgical upstaging with implications for ¹⁸F-FDG PET/CT nodal assessments. Surgical waiting time appears not to be a predictor for both tumour types.