Metabolic Tumor Volume Predicts Disease Progression and Survival in Patients with Squamous Cell Carcinoma of the Anal Canal

Abstract

PET imaging has become a useful diagnostic tool in patients with anal cancer. We evaluated the prognostic value of metabolic tumor volume (MTV) in patients with anal cancer treated with definitive chemoradiotherapy. Methods: Patients with anal cancer who underwent PET imaging for pretreatment staging or radiation therapy planning from 2003 to 2011 were included. PET parameters included MTV and maximum standardized uptake value (SUVmax). Total MTV (MTV-T) was defined as the sum of the volumes above a standardized uptake value 50% of the SUVmax within the primary tumor and involved nodes. KaplanMeier and Cox regression models were used to test for associations between metabolic or clinical endpoints and overall survival (OS), progression-free survival (PFS), and event-free survival (EFS). Results: Thirty-nine patients were included. Median follow-up for the cohort was 22 mo. Overall, 6 patients died and 9 patients had disease progression. The 2-y OS, PFS, and EFS for the entire cohort were 88%, 74%, and 69%, respectively. Higher MTV-T was associated with worse OS (P 5 0.04), PFS (P 5 0.004), and EFS (P 5 0.002) on univariate analysis. Patients with an MTV greater than 26 cm 3 had worse PFS than did those with an MTV of 26 cm 3 or less (33% vs. 82%, P 5 0.003). SUVmax was not prognostic for any outcome. Higher T classification (T3/T4 vs. T1/T2) was associated with worse PFS and EFS. When adjusting for T classification, MTV-T remained a significant predictor for PFS (P 5 0.01) and EFS (P 5 0.02). Conclusion: MTV-T yields prognostic information on PFS and EFS beyond that of established prognostic factors in patients with anal cancer.

Anal cancer FDG-PET standard uptake value: correlation with tumor characteristics, treatment response and survival

“…In this regard, other studies in lung, oesophageal, head and neck and cervical cancers showed that higher SUVmax correlates with worse local control and diseasefree survival rate [20,21,28,29]. On the other hand, the more recent study of Bazan et al, similarly to us, found no correlation between SUVmax and DFS and OS in a sample of 39 patients [25]. In clinical practice, SUVmax is considered the most reproducible parameter that can estimate metabolic activity of FDG uptake.…”

“…The present study did not show a significant direct correlation between SUVmax and DFS and OS. In this regard, other literature studies [24,25] on the use of SUVmax in anal cancer reported controversial results. Kidd et al did not find higher baseline SUVmax significantly associated with an increased risk of persistent disease.…”

“…Actually, SUVmean represents the average of the intensity of uptake within a designated region of interest and MTV reflects the volume of tumor tissue with increased metabolic activity on PET. In this regard, Bazan et al [25] analyzed SUVmax and MTV that resulted in a significant prognosticator for both DFS and OS.…”

“…As a matter of fact, data regarding the prognostic value of baseline PET SUV in anal cancer come from relatively few retrospective studies with inconsistent results [24,25].…”

“…A possible limitation is that it represents the highest voxel value within a lesion. In this direction a growing body of literature has started to analyze more in deep SUVmean and metabolic tumor volume (MTV) [25,[30][31][32]. Actually, SUVmean represents the average of the intensity of uptake within a designated region of interest and MTV reflects the volume of tumor tissue with increased metabolic activity on PET.…”