Omission of staging PET/CT linked to reduced survival in stage III non-small cell lung cancer: insights from the LUCAS project real-world data.

Background: Stage III non-small cell lung cancer (NSCLC) is a highly heterogeneous stage due to its subgroups (IIIA-IIIC) comprising both resectable and unresectable tumors. Accurate determination of the extent of the disease is essential for excluding stage IV and choosing the optimal treatment regimen. Whole body positron emission tomography and computed tomography scan (PET/CT) is recommended as an initial staging imaging in locally advanced NSCLC. Despite international guidelines for NSCLC diagnosis and treatment, they are not always adhered to due to various reasons. Even in such a groundbreaking study, the phase 3 trial PACIFIC investigating the efficacy of durvalumab as consolidation therapy in patients with stage III NSCLC PET/CT was not mandatory. With the premise that whole body PET/CT of the trunk is essential for diagnosing stage III NSCLC, we performed a retrospective study evaluating the relationship of the use of PET/CT versus conventional staging with CT of the chest and abdomen, in terms of survival. Methods: This retrospective study of stage III NSCLC patients used the Czech lung cancer registry LUCAS, which was established in June 2018. As of the data export (up to February 9, 2022), a total of 703 patients were eligible for the analysis. Overall survival (OS) was compared using Kaplan-Meier analysis and a Cox regression model. Continuous variables were tested using the Mann-Whitney test, and categorical variables using the Pearson's Chi-square or Fisher's exact test. Results: A total of 703 patients were included in the cohort with an average age of 69 years. PET/CT was performed on 354 patients, and conventional staging using chest and abdominal CT on 349 patients. The median OS among patients with PET/CT was 20.9 months [95% confidence interval (CI): 18.1-23.7], and it was statistically significantly higher (P<0.001) than among patients without PET/CT, where the median OS was 9.0 months (95% CI: 7.3-10.6). The observed effect of PET/CT was also statistically significant when comparing individual stages (IIIA, IIIB, IIIC). The multivariate Cox model confirmed the use of PET/CT as an independent prognostic factor. The most common reason for omission of PET/CT was the local or time unavailability of the examination. Conclusions: Omission of PET/CT can mean a significant decrement in survival for the patients in stage III NSCLC, likely due to poor staging and suboptimal treatment. Routine use of PET/CT is strictly recommended for the optimal management of stage III NSCLC patients even outside the high-income countries.