The Predictive Value of Baseline Volumetric PET/CT Parameters on Treatment Response and Prognosis in Locally Advanced Rectal Cancer Treated with Neoadjuvant Chemoradiotherapy

Abstract

Purpose:To investigate the prognostic effects of baseline volumetric PET/CT parameters including the maximum standard uptake value(SUVmax), metabolic tumor volume(MTV), and tumor lesion glycolysis(TLG) on treatment response and prognosis in locally-advanced rectal cancer(LARC) treated with neoadjuvant chemoradiotherapy(NACRT). Methods:Between 2015 and 2018, 51 patients with LARC treated with NACRT followed by surgery were included in this retrospective study. Patients were divided into 2 groups by tumor regression grade(TRG) as follows;Group I=TRG 1(No detectable cancer cells)+TRG 2(single cells and/or small groups of cancer cells) and Group II=TRG3(residual tumor outgrown by brosis)+TRG 4(remarkable brosis outgrown by tumor cells)+TRG 5(No brosis with extensive residual cancer).Results:Of the 51 patients, 34(66.7%) were male. The median age was 55(range,37-78) years. According to TRG status, 14(27.4%) patients were in group I and 37(72.6%) patients were in group II. The area under the curve(95% CI) was 0.749(0.593-0.905) in the ROC curve plotted for MTV. The cut of value for MTV was 12, with 70% sensitivity and 65% speci city. MTV was≥12 in 32(62.8%) patients. MTV and TLG values were signi cantly different between Group I and II, whereas there was no signi cant difference between the groups in terms of SUVmax values (p=0.006, p=0.033, and p=0.673, respectively). The disease-free survival was not reached in patients with MTV<12 vs. 20 months in those with MTV≥12 (p=0.323). In multivariate analysis, MTV(OR, 95% Cl, 5.00 [1.17-21.383]) was found to be the factor that affected pathological complete response. Conclusion:In LARC treated with NACRT, MTV prior to treatment can help predict the response to treatment.

18F-FDG PET/CT parameters for prediction of response to neoadjuvant therapy and prognosis in rectal cancer

“…In another study conducted on 51 patients receiving nCRT for locally advanced disease, Sakin et al . [28] suggested that, from baseline PET CT parameters, MTV could be a predictor of DFS and reported a cutoff value of 12 cm 3 . A study by Lovinfosse et al .…”

“…In another study, SUVmax, MTV and TLG values from the baseline PET parameters of 81 patients receiving nCRT for locally advanced rectal cancer were examined with regard to their value in predicting treatment response, and from these parameters, high baseline TLG values were concluded to be associated with poor DFS outcomes [27]. In another study conducted on 51 patients receiving nCRT for locally advanced disease, Sakin et al [28] suggested that, from baseline PET CT parameters, MTV could be a predictor of DFS and reported a cutoff value of 12 cm 3 . A study by Lovinfosse et al [29] that analyzed the relationship of various clinical and PET CT parameters with survival reported TLG to be an independent predictor of DFS.…”