Total metabolic tumour volume: a new potential prognostic factor in SCLC

In patients with small cell lung cancer (SCLC), total metabolic tumour volume at baseline correlated with progression-free survival (PFS) and overall survival (OS) on first-line treatment in preliminary results from a retrospective study.

The introduction of chemoimmunotherapy as first-line therapy for extensive-stage (ES-) SCLC has only improved the survival of a limited number of patients, highlighting the importance to predict treatment susceptibility. ¹⁸FDG-PET/CT is commonly used for the staging of SCLC and derived metabolic parameters could predict patient outcomes by measuring the extension of metabolically active tumour (metabolic tumour volume [MTV]) or its metabolic heterogeneity (total lesion glycolysis [TLG]). Italian investigators evaluated whether these parameters derived from ¹⁸FDG-PET are predictive of patient outcomes. Dr Elisa Andrini (Sant'Orsola-Malpighi University Hospital, Italy) presented the results [1].

The study enrolled 76 patients with pathologically-confirmed ES-SCLC who had undergone an ¹⁸FDG-PET/CT scan within 30 days from the start of first-line treatment. Participants (n=10) with limited disease (LS-SCLC) at diagnosis were included if relapse occurred ≥90 days after the end of treatment with radical intent. Total MTV and total TLG were calculated by summing every single lesion’s MTV and TLG respectively.

At a median follow-up of 20.9 months, median PFS was 6.2 months and median OS was 11.1 months. After correcting for potential confounding factors, total MTV was independently associated with PFS (HR 1.003; P=0.034) and OS (HR 1.003; P<0.001). Receiver operating characteristic (ROC) curve analysis calculated a total MTV of 245.7 cm³ to be the best cut-off to predict survival status at 6 months (AUC 0.722; sensitivity 57.7%; specificity 83.3%). Based on this cut-off, patients with low total MTV had a longer median PFS (7.1 vs 4.7 months) and longer median OS (11.9 v 4.8 months) compared with those with high total MTV. Total MTV above the cut-off was independently associated with the risk of death (P<0.001) but not with the risk of progression. Primary tumour standardised uptake value (SUVmax) was independently associated with PFS (HR 1.04; P<0.001). In addition, hyponatremia (<135 mEq/L), hypoalbuminemia (<35 g/L), and elevated LDH levels (≥250 UI/L) were all associated with a greater number of lesions, greater total MTV, and higher total TLG.

“Our preliminary data showed that total MTV, but not total TLG, provided prognostic information in EC-SCLC patients, suggesting a potential role as a stratification factor in patient candidates for first-line treatment as well as in clinical trials,” concluded Dr Andrini.

1. Andrini E, et al. Total metabolic tumor volume: A new potential prognostic factor in SCLC. Abstract 149P. ELCC 2022 Virtual Meeting, 30 March–02 April.

 

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Posted on 25 May, 2022