Correlation study on 18F-FDG PET/CT metabolic characteristics of primary lesion with clinical stage in lung cancer.

Background: ¹⁸F-FDG PET/CT metabolic characteristics provide the crucial biologic and molecular information for tumors. To explore the relationships between ¹⁸F-FDG PET/CT derived parameters such as maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), total lesion glycolysis (TLG) of primary tumor and clinical stage in different histopathologic subtypes of lung cancer.

Methods: A total of 97 newly diagnosed lung cancer patients (69 males, 28 females; average age 65.1 years) with pathologically proven were retrospectively analyzed, who had undergone ¹⁸F-FDG PET/CT scan before treatment from September 2016 to November 2017. SUVmax, MTV and TLG of primary tumor were measured. Clinical stage was mainly determined by ¹⁸F-FDG PET/CT, in conjunction with conventional imaging and endoscopic biopsy. Mann-Whitney U test, χ² test, Spearman correlation test and ROC curve analysis were used for statistical analysis.

Results: There were 53 adenocarcinomas (AC), 28 squamous carcinomas (SCC), 13 small cell carcinomas (SCLC), one adenosquamous carcinoma, one mucoepidermoid carcinoma, and one sarcomatoid carcinoma in 97 patients. Both AC and SCLC revealed more cases in stage IV than in stage I-III (P<0.01). There was no significant difference in four stages of SCC (P>0.05). Metabolic parameters of SCC were higher than AC including SUVmax, MTV and TLG (P<0.01). SCLC showed a higher value than AC in TLG (P<0.05). No significant differences were found between AC and SCLC in SUVmax and MTV, also between SCC and SCLC in SUVmax, MTV and TLG (P>0.05). MTV and TLG except SUVmax were positively correlated with stage in AC (P≤0.001). Only MTV showed a positive correlation with stage in SCC (P<0.05). Whereas there were no definitive relationships between metabolic parameters and stage in SCLC (P>0.05). AC with a higher MTV (MTV≥5.965 cm³) indicated a significantly higher rate of distant metastasis than those with a lower MTV (77.5% (31/40) vs. 30.8% (4/13), χ²=9.553, P<0.01), as well as AC with a higher TLG (TLG≥46.922) than those with a lower TLG (88.5% (23/26) vs. 44.4% (12/27), χ²=11.422, P<0.01).

Conclusions: Histopathologic subtypes have a significant influence on the relationships between MTV/TLG not SUVmax of primary foci and stage in lung cancer. Primary MTV/TLG is related to clinical stage closely in AC, and a higher MTV/TLG results in a higher risk of distant metastasis.