PET-SUV Max and Upstaging of Lung Cancer.

BACKGROUND

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

METHODS

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, F-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.

RESULTS

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.

CONCLUSIONS

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