Total Lesion Glycolysis Reduction Research Articles

Predictive Value of PERCIST for Locally Advanced Non-Small Cell Lung Cancer Treated with Preoperative Induction Therapy - A Multicenter Study in Japan.

Induction therapy followed by surgery is recommended as an alternative treatment strategy for locally advanced non-small cell lung cancer (NSCLC). Patients who achieve pathologic response after induction therapy have better outcomes than non-responders; therefore, therapeutic response must be evaluated. Recently, new approaches for monitoring therapeutic responses, which are based on 18F-Fluorodeoxyglucose positron emission tomography (FDG-PET), have been developed. In this study, we evaluated the predictive value of Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST), which uses standardized uptake values corrected for lean body mass (SUL) and total lesion glycolysis (TLG). A total of 130 patients in the Setouchi Lung Cancer Group who underwent FDG-PET imaging before and after induction therapy prior to a planned surgical resection for NSCLC between 2007 and 2016 were studied retrospectively. The pathologic responses of the primary lung tumors and metastatic lymph nodes were compared with their responses based on evaluation using PERCIST. Postoperative pathologic studies revealed pathologic complete response (pCR) in 42 (32.3%) patients. PERCIST was significantly correlated with pathologic response (p < 0.001). The sensitivity, specificity, and accuracy of PERCIST for predicting pCR were 16.7% (7/42), 88.6% (78/88), and 65.4% (85/130), respectively. Patients with pCR had significantly higher reduction rates in SULpeak for both primary lung tumors and metastatic lymph nodes and TLG for primary tumors than non-responders. In a multivariate Cox regression analysis, tumor site in upper lobes, reduction rate of TLG in primary tumor, and pathologic N0 were independent predictors of favorable recurrence-free survival (RFS). Our study suggested that PERCIST, especially the rate of TLG reduction rate, are useful to predict the pathological response and prognosis after induction therapy. Although improvement is necessary, PERCIST can be a promising method of the post-induction status in lung cancer. Further research is needed to confirm our findings.

Risk stratification of oesophageal squamous cell carcinoma using change in total lesion glycolysis and number of PET-positive lymph nodes

BackgroundThe efficacy of neoadjuvant chemotherapy (NACT) correlates with patient survival in oesophageal squamous cell carcinoma (OSCC), but optimal evaluation of the treatment response based on PET-CT parameters has not been established.MethodsWe analysed 226 OSCC patients who underwent PET-CT before and after NACT followed by surgery. We assessed SUVmax, metabolic tumour volume (MTV), and total lesion glycolysis (TLG) for the primary tumour and the number of PET-positive lymph nodes before and after NACT to predict patient survival.ResultsIn a stepwise analysis, we defined 60%, 80%, and 80% as the optimal cut-off values for SUVmax, MTV, and TLG reduction, respectively, to distinguish responders and non-responders to NACT. In the ROC analysis, the TLG reduction rate was the best predictor of recurrence among PET-CT parameters. The TLG responders achieved significantly more favourable prognoses than non-responders (2-year progression-free survival [PFS] rate: 64.1% vs. 38.5%; P = 0.0001). TLG reduction rate (HR 2.58; 95% CI 1.16–5.73) and the number of PET-positive lymph nodes after NACT (HR 1.79; 95% CI 1.04–3.08) were significant independent prognostic factors.ConclusionsTLG reduction is the best predictor of prognosis. Preoperative PET-CT evaluation of both the primary tumour and lymph nodes could accurately stratify risk in OSCC patients.

Durvalumab (D) and PET-directed chemoradiation (CRT) after induction FOLFOX for esophageal adenocarcinoma: Final results.

4029 Background: Induction FOLFOX followed by PET-directed CRT prior to surgery demonstrated positive results in the CALGB 80803 study. We investigated the safety and efficacy of adding D, an anti-PD-L1 antibody, to PET-directed CRT. Methods: Patients (pts) with locally advanced esophageal/GEJ adenocarcinoma were enrolled. Pts received 2 cycles of mFOLFOX6 prior to repeat PET/CT. PET responders (≥35% reduction in SUV (PETr)) received 5-FU/capecitabine and oxaliplatin with RT to 50.4Gy, while induction PET non-responders (PETnr) received carboplatin/paclitaxel with RT. All Pts received D 1,500 mg q4W ×2 starting 2 weeks prior to CRT. Esophagectomy was planned 6-8 weeks after CRT. Pts with R0 resections received adjuvant D 1,500mg q4W ×6. The primary endpoint was the pathologic complete response (pCR) rate. Results: 36 pts were enrolled. Clinical ≥T3 disease was seen in 32 pts (88.9%, cT4 = 3) and ≥N1 in 23 (63.9%) pts. PD-L1 CPS was ≥1 in 25 (71.4%) of 35 tested with 14 (40%) ≥5. Microsatellite instability (MSI) was identified in 3 (8.3%) pts. 25 (70%) pts were PETr. Preop treatment was well tolerated with no new safety signals. Three pts had disease progression prior to surgery. pCR was identified in 8 (22.2%) pts and 22 (64.7%) had major pathologic response (MPR; ypTanyN0 + ≥90% response). Those with MSI tumors had ≥90% treatment response (1 pCR, 1: ypT1aN0 99% response, 1: ypT2N0, 90% response). 17 (73.9%) of 23 cN+ pts had ypN0 disease. MPR was associated with PD-L1 ≥1 (p = 0.03) and with a higher tumor mutational burden (TMB; p = 0.016) on MSK-IMPACT testing. Adjuvant D was commenced in 27 pts, with a median number of 6 cycles. Early discontinuation was due to risks of visits due to COVID19 (4, 15%), progressive disease (3, 11%), late surgical complications (2, 7%) and immune toxicity (1, 4%). With a median follow-up of 30 months, OS rates were 92% [95%CI: 83%-100%] and 85 % [95%CI: 74%-98%] at 12 and 24 months post induction. 12 and 24-month PFS rates were 81% [95%CI: 69%-95%] and 71% [95%CI: 58%-88%] respectively. In the 33 operated pts, 12 and 24-month disease free survival was 82% [95%CI: 70%-96%] and 78% [95%CI: 65%-94%], respectively. In addition to SUV on PET, total lesion glycolysis (TLG) was correlated with pathologic response. In cases with borderline change in SUV, TLG could predict response to treatment. One PETnr with 30.8% reduction in SUV had 88.1% reduction in TLG and pCR. Conversely, a PETr (-36.3%) who had an increase in TLG (39.3%) had only 40% treatment response on pathology. Conclusions: The addition of D to induction FOLFOX and PET-directed CRT prior to surgery is safe and appears effective with a high rate of pathologic response, as well as encouraging survival data. PD-L1 CPS≥1 and higher TMB may be associated with MPR. TLG is a novel PET variable that should be studied prospectively. Additional correlatives and comparison to a cohort treated with standard PET-directed CRT will be presented. Clinical trial information: NCT02962063.

18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography Metabolic Parameters Before and After Neoadjuvant Chemotherapy Can Predict the Postoperative Prognosis of Locally Advanced Gastric Cancer.

Objective: To explore the value of 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) metabolic parameters before and after neoadjuvant chemotherapy in predicting histopathological response and prognosis of locally advanced gastric cancer. Materials and Methods: A total of 56 patients with locally advanced gastric cancer underwent 18F-FDG PET/CT before and after neoadjuvant chemotherapy. The maximum standardized uptake value (SUVmax), mean standardized uptake value (SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the lesions were measured before and after neoadjuvant chemotherapy. The percentage changes in the maximum standardized uptake value (ΔSUVmax%), mean standardized uptake value (ΔSUVmean%), metabolic tumor volume (ΔMTV%), and total lesion glycolysis (ΔTLG%), which were derived from 18F-FDG PET/CT, were calculated, and the cutoff values were determined by receiver operating characteristic curve analysis. Differences in progression-free survival (PFS) and overall survival (OS) between groups dichotomized by these cutoffs were analyzed using the Kaplan-Meier method and Cox proportional hazards regression model. Results: The patients were divided into histopathological responders and nonresponders according to the following cutoff values: 58.8% SUVmax reduction, 45.8% SUVmean reduction, 36.9% MTV reduction, and 57.8% TLG reduction. The differences in PFS and OS between groups dichotomized by these cutoffs were significant (all p < 0.01). Multivariate analysis suggested that a ΔTLG% > 57.8% was an independent postoperative risk factor for PFS (hazard ratio [HR] 0.348, 95% confidence interval [CI] 0.131-0.926, p = 0.035) and OS (HR 0.107, 95% CI 0.023-0.498, p = 0.004). Conclusions: The metabolic parameters before and after neoadjuvant chemotherapy of 18F-FDG PET/CT accurately reflected the chemotherapy effect, and ΔTLG% was the only independent postoperative predictive factor of PFS and OS for locally advanced gastric cancer.

Assessment of tumor response to definitive chemoradiotherapy and prognosis prediction in patients with esophageal cancer judged by PET response criteria in solid tumors: multicenter study in Japan.

The aim of the study was to evaluate PET response criteria in solid tumors (PERCIST) to indicate therapeutic response to definitive chemoradiotherapy, as well as prediction of recurrence and death in patients with esophageal cancer. Before and after recieving definitive chemoradiotherapy, 181 patients with esophageal cancer underwent fluorodeoxyglucose-PET/computed tomography (FDG-PET/CT). PERCIST, reduction rates of tumor uptake and volume of whole lesions, tumor node metastasis (TNM) staging regarding progression-free survival (PFS), and overall survival (OS) were analyzed using log-rank and Cox methods. Complete metabolic response (CMR), partial metabolic response (PMR), stable metabolic disease (SMD), and progressive metabolic disease (PMD) shown by PERCIST were seen in 42 (23.2%), 113 (62.4%), 14 (7.7%), and 12 (6.6%) patients, respectively. Progression developed in 137 (75.7%) patients and 101 (56.1%) patients died (median follow-up 16.9, range 3.2-124.9 months). Those who achieved CMR showed significantly longer PFS and OS as compared with patients who did not (PMR, SMD, and PMD) (both P < 0.0001). In univariate analysis, initial clinical T status (P = 0.0048), N status (P = 0.011), and TNM stage (P = 0.0006), PERCIST (P < 0.0001), and reduction rate of peak lean body mass standardized uptake value (P < 0.0001), of metabolic tumor volume (P < 0.0001), and of total lesion glycolysis (TLG) (P < 0.0001) were associated with significantly increased OS. Multivariate analysis confirmed PERCIST [hazard ratio (HR): 13.15, 95% confidence interval (CI), 4.54-55.8; P < 0.0001], and TLG reduction rate (HR: 2.21, 95% CI, 1.04-4.68; P = 0.040) as independent OS predictors. PERCIST is useful for evaluating therapeutic response to definitive chemoradiotherapy, and predicting progression and death in patients with esophageal cancer.

Prognostic role of ΔMTV and ΔTLG in Burkitt lymphoma.

Burkitt's lymphoma (BL) is an aggressive lymphoma sub-type with high 18F-FDG avidity, but no well established evidence of PET/CT's role in treatment evaluation or prognosis is currently available. The prognostic role of visual analysis and Deauville criteria for BL have already been demonstrated, while the potential usefulness of semi-quantitative PET/CT features remains unclear, especially the value of the rate of reduction in metabolic tumor volume (MTV) and total lesion glycolysis (TLG). The aim of this retrospective study was to investigate whether ΔMTV and ΔTLG can predict treatment response at the end of therapy and prognosis in BL. We retrospectively included 61 patients (mean age 61; 40 male, 21 female) who underwent baseline, interim and end-of-treatment 18F-FDG PET/CT. The PET/CT images were analyzed visually and semi-quantitatively by measuring total metabolic tumor volume (MTV) and total lesion glycolysis (TLG) for every scan. Then we calculated volume changes based on the percentage of MTV and TLG reduction between the baseline and interim PET (ΔMTVi and ΔTLGi) and between baseline and end-of-treatment PET/CT (ΔMTVeot and ΔTLGeot) and correlated them with clinical response and progression-free survival (PFS) and overall survival (OS). Survival curves were plotted according to the Kaplan-Meier method. Forty patients had a complete response and 21 patients a partial response on interim 18F-FDG PET/CT. At end of treatment, 45 had a complete response, 11 partial response and 5 disease progression. At a median follow-up of 43 months, relapse/progression occurred in 18 patients and death in 11. ΔMTV and ΔTLG values were significantly higher in patients with complete response compared to no complete response. ΔMTVeot and ΔTLGeot were demonstrated to be independent prognostic factors for both PFS and OS, while ΔMTVi and ΔTLGi were not related to survival. Metabolic tumor features (ΔMTV and ΔTLG) were significantly correlated with response to treatment and long-term outcome in BL.

Value of early evaluation of treatment response using 18F-FDG PET/CT parameters and the Epstein-Barr virus DNA load for prediction of outcome in patients with primary nasopharyngeal carcinoma.

To determine the value of early evaluation of response to concurrent chemoradiotherapy (CCRT) using 18F-FDG PET-derived parameters and the Epstein-Barr virus (EBV) DNA titre in outcome prediction in patients with primary nasopharyngeal carcinoma (NPC). Sixty patients with primary NPC were prospectively enrolled. All patients underwent 18F-FDG PET/CT before and during CCRT. The plasma EBV DNA titre was measured along with the PET/CT-derived parameters. Changes in EBV DNA titre and PET/CT-derived parameters during CCRT were analysed in relation to response to treatment, recurrence-free survival (RFS) and overall survival (OS). A total lesion glycolysis (TLG) reduction ratio of ≤0.6 and a detectable EBV DNA titre during CCRT were predictors of an unfavourable response to treatment, RFS and OS. In multivariate analysis, a TLG reduction ratio of ≤0.6 predicted incomplete remission (p = 0.002) and decreased RFS (p = 0.003). The proportion of patients with a TLG reduction ratio of >0.6 who achieved a complete response was more than twice that of patients with a TLG reduction ratio of ≤0.6. A detectable EBV DNA titre, a TLG reduction ratio of ≤0.6 and older age were independently associated with a poorer OS (p = 0.037, 0.009 and 0.016, respectively). A scoring system was developed based on these independent predictors of OS. Patients with a score of 1 and 2/3 had poorer survival outcomes than those with a score of 0 (hazard ratio 4.756, p = 0.074, and hazard ratio 18.973, p = 0.001, respectively). This scoring system appeared to be superior to the traditional TNM staging system (p < 0.001 versus p = 0.175). Early evaluation of response to CCRT using 18F-FDG PET-derived parameters and the EBV DNA titre can predict outcome in patients with primary NPC. A combination of interim PET parameters and the EBV DNA titre enables better stratification of patients into subgroups with different survival rates.

Early Response Assessment in Pancreatic Ductal Adenocarcinoma Through Integrated PET/MRI.

The purpose of this study is to investigate early changes in 18F-FDG PET/MRI metrics after treatment in patients with advanced pancreatic ductal adenocarcinoma (PDAC) and to correlate those changes with eventual tumor response at standard-of-care CT. Thirteen patients with advanced PDAC underwent integrated FDG PET/MRI before and 4 weeks after treatment initiation. Patients were classified as responders or nonresponders according to Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 at subsequent CT performed 8-12 weeks after treatment initiation. Changes in the primary tumor's maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) determined at PET and apparent diffusion coefficient (ADC) determined at DWI at 4 weeks were compared between responders and nonresponders. Seven patients had a partial response according to RECIST, and six did not. Responders displayed significantly greater decreases in MTV (p = 0.003) and TLG (p = 0.006) in the primary pancreatic tumor at 4 weeks. Responders also displayed a greater increase in the mean (p = 0.004) and minimum (p = 0.024) ADC of the primary tumors. Tumor size change at 4 weeks was not significantly different between responders and nonresponders (p = 0.11). PET responders enjoyed longer progression-free survival (PFS) (p = 0.0004) and overall survival (OS) (p = 0.013) than did nonresponders, using either a 60% reduction in MTV or 65% reduction in TLG as a threshold. MRI responders had significantly longer PFS (p = 0.0002) and OS (p = 0.027) than did nonresponders, using a 20% increase in either mean or minimum ADC as a threshold. Integrated PET/MRI can provide early response assessment in patients with advanced PDAC, thus potentially allowing early treatment adaptation in nonresponders.

Anatomic versus Metabolic Tumor Response Assessment after Radioembolization Treatment

PurposeTo assess applicability of metabolic tumor response assessment on 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) after radioembolization (RE) in patients with colorectal liver metastases (CRLM) by comparison with one-dimensional size-based response assessment on MR imaging. Materials and MethodsThis prospective cohort study comprised 38 patients with CRLM undergoing RE. MR imaging and 18F-FDG PET/CT imaging were performed at baseline, 1 month (n = 38), and 3 months (n = 21). Longest tumor diameter (LTD) reduction on MR imaging at these time points was compared with reduction in total lesion glycolysis (TLG) on 18F-FDG PET/CT. Hepatic response was compared between RECIST and total liver TLG and correlated with overall survival (OS). ResultsTLG and LTD were positively correlated in 106 analyzed metastases (38 patients) at 1 month and 58 metastases (22 patients) at 3 months. Agreement was poor, with LTD underestimating TLG response. A significant association with prolonged OS was found in total liver TLG at 1 month (HR 0.64, P < .01) and 3 months (HR 0.43, P < .01). For LTD, a significant association with OS was found at 3 months (HR 0.10, P < .01). Important differences in liver response classification were found, with total liver TLG identifying more patients and situations where there appeared to be treatment benefit compared with RECIST. ConclusionsTLG response assessment on 18F-FDG PET/CT appears to be more sensitive and accurate, especially at early follow-up, than size-based response assessment on MR imaging in patients with CRLM treated by RE. Semiautomated liver response assessment with total liver TLG is objective, reproducible, rapid, and prognostic.

Prognostic and predictive role of [18 F]fluorodeoxyglucose positron emission tomography (FDG-PET) in patients with unresectable malignant pleural mesothelioma (MPM) treated with up-front pemetrexed-based chemotherapy.

The aim of this study was to evaluate the role of metabolic parameters analyzed at baseline and at interim FDG‐PET in predicting disease outcome in unresectable MPM patients receiving pemetrexed‐based chemotherapy. A consecutive series of MPM patients treated between February 2004 and July 2013 with first‐line pemetrexed‐based chemotherapy, and evaluated by FDG‐PET and CT scan at baseline and after two cycles of chemotherapy, was reviewed. Best CT scan response was assessed according to modified RECIST criteria. Progression‐free survival (PFS) and overall survival (OS) were correlated with FDG‐PET parameters, such as maximum standardized uptake value (SUVmax), total lesion glycolysis (TLG), and percentage changes in SUVmax (∆SUV) and TLG (∆TLG). Overall, 142 patients were enrolled; 77 (54%) received talc pleurodesis before chemotherapy. Baseline SUVmax and TLG showed a statistically significant correlation with PFS and OS (P < 0.05) in both group of patients (treated and untreated with pleurodesis). In 65 patients not receiving pleurodesis, SUVmax reduction ≥25% (∆SUV ≥ 25%) and TLG reduction ≥30% (∆TLG ≥ 30%) were significantly associated with longer PFS (P < 0.05). Patients showing both ∆SUV ≥ 25% and ∆TLG ≥ 30% responses had a significant reduction in the risk of disease progression (HR:0.31, P < 0.001) and death (HR:0.52, P = 0.044). Neither ∆SUV nor ∆TLG showed similar association with survival outcomes in patients treated with pleurodesis. Our study confirmed the prognostic role of baseline FDG‐PET in a large series of MPM patients treated with first‐line pemetrexed‐based chemotherapy. Moreover, use of ∆SUV ≥ 25% and ∆TLG ≥ 30% as cut‐off values to define early metabolic response supported the role of FDG‐PET in predicting disease outcome and treatment response in patients not receiving pleurodesis.

Clinical and imaging-based prognostic factors in radioembolisation of liver metastases from colorectal cancer: a retrospective exploratory analysis

BackgroundThe aim of this study was to investigate the relationship between absorbed dose and response of colorectal cancer liver metastases treated with [90Y]-resin microspheres and to explore possible clinical and imaging derived prognostic factors.MethodsFDG PET/CT was used to measure response of individual lesions to a measured absorbed dose, derived from post-treatment 90Y PET imaging. Predicted dose was also derived from planning [99mTc]-MAA SPECT data. Peak standardised uptake value and total lesion glycolysis (TLG) were explored as response measures, and compared to dose metrics including average dose (Davg), biologically effective dose, minimum dose to 70% of lesion volume and volume receiving at least 50 Gy. Prognostic factors examined included baseline TLG, RAS mutation status, FDG heterogeneity and dose heterogeneity. In an exploratory analysis, response and clinico-pathological variables were evaluated and compared to overall survival.ResultsSixty-three lesions were analysed from 22 patients. Poor agreement was seen between predicted and measured dose values. TLG was a superior measure of response, and all dose metrics were significant prognostic factors, with a Davg of ~50 Gy derived as the critical threshold for a significant response (>50% reduction in TLG). No significant correlation was found between baseline TLG or RAS mutation status and response. Measured dose heterogeneity was a significant prognostic factor and when combined with Davg had a positive predictive value for response >80%. In the exploratory analysis for prognostic factors of survival, low hepatic tumour burden and mean reduction in TLG >65% were independently associated with improved overall survival.ConclusionsLesions receiving an average dose greater than 50 Gy are likely to have a significant response. For lesions receiving less than 50 Gy, dose heterogeneity is a significant prognostic factor. Lesions receiving an average dose less than 20 Gy are unlikely to respond. A reduction in TLG may be associated with improved overall survival.

The value of 18F-FDG PET before and after induction chemotherapy for the early prediction of a poor pathologic response to subsequent preoperative chemoradiotherapy in oesophageal adenocarcinoma

PurposeThe purpose of our study was to determine the value of 18F-FDG PET before and after induction chemotherapy in patients with oesophageal adenocarcinoma for the early prediction of a poor pathologic response to subsequent preoperative chemoradiotherapy (CRT).MethodsIn 70 consecutive patients receiving a three-step treatment strategy of induction chemotherapy and preoperative chemoradiotherapy for oesophageal adenocarcinoma, 18F-FDG PET scans were performed before and after induction chemotherapy (before preoperative CRT). SUVmax, SUVmean, metabolic tumour volume (MTV), and total lesion glycolysis (TLG) were determined at these two time points. The predictive potential of (the change in) these parameters for a poor pathologic response, progression-free survival (PFS) and overall survival (OS) was assessed.ResultsA poor pathologic response after induction chemotherapy and preoperative CRT was found in 27 patients (39 %). Patients with a poor pathologic response experienced less of a reduction in TLG after induction chemotherapy (p < 0.01). The change in TLG was predictive for a poor pathologic response at a threshold of −26 % (sensitivity 67 %, specificity 84 %, accuracy 77 %, PPV 72 %, NPV 80 %), yielding an area-under-the-curve of 0.74 in ROC analysis. Also, patients with a decrease in TLG lower than 26 % had a significantly worse PFS (p = 0.02), but not OS (p = 0.18).Conclusions18F-FDG PET appears useful to predict a poor pathologic response as well as PFS early after induction chemotherapy in patients with oesophageal adenocarcinoma undergoing a three-step treatment strategy. As such, the early 18F-FDG PET response after induction chemotherapy could aid in individualizing treatment by modification or withdrawal of subsequent preoperative CRT in poor responders.

Usefulness of Combined Metabolic-Volumetric Indices of (18)F-FDG PET/CT for the Early Prediction of Neoadjuvant Chemotherapy Outcomes in Breast Cancer.

The purpose of this study was to investigate the usefulness of metabolic-volumetric indices of (18)F- fluorodeoxy-D-glucose ((18)F-FDG) positron emission tomography/computed tomography (PET/CT) for the evaluation of neoadjuvant chemotherapy outcomes in breast cancer. Twenty-four patients with locally advanced breast cancer were enrolled in the study. They underwent baseline (18)F-FDG PET/CT scan and received four or sixcycles of neoadjuvant chemotherapy, interim (18)F-FDG PET/CT was done after second cycle of chemotherapy. Maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) of the primary lesions were calculated. Reduction rates of these parameters were obtained between baseline and interim (18)F-FDG PET/CT. Chemotherapy outcomes were assessed using tumor size reduction rate and histological grading system (Miller and Payne system). Reduction rates of SUVmax, MTV, and TLG correlated with chemotherapy outcomes. MTV and TLG reduction rates showed significant correlation with tumor size reduction rate (R = 0.68, P = 0.0004; R = 0.62, P = 0.002, respectively). However, SUVmax reduction rate showed no significant correlation. MTV and TLG reduction rates were significantly higher in responders than nonresponders, as determined by Miller and Payne system (P < 0.0007, P < 0.002). However, SUVmax reduction rate showed no significant difference. On ROC analysis, the area under the MTV and TLG curves was 0.886, and that of SUVmax was 0.743. Sensitivity, specificity, positive predictive value, and negative predictive value to predict histopathologic response were the same for MTV and TLG, and the values were 100%, 85.7%, 83.3%, and 100%, respectively (at the reduction rate of 93.2% for MTV, and 95.8% for TLG). Changes of metabolic-volumetric indices successfully reflected the neoadjuvant chemotherapy outcomes. MTV and TLG could be robust indices in discriminating pathologic responder as SUVmax, after neoadjuvant chemotherapy.

Early prediction of pathological response in locally advanced rectal cancer based on sequential 18F-FDG PET

Background. The objectives of this study were to investigate the predictive value of sequential 18F-FDG PET scans for pathological tumor response grade (TRG) after preoperative chemoradiotherapy (PCRT) in locally advanced rectal cancer (LARC) and the impact of partial volume effects correction (PVC). Methods. Twenty-eight LARC patients were included. Responders and non-responders status were determined in histopathology. PET indices [SUV max and mean, volume and total lesion glycolysis (TLG)] at baseline and their evolution after one and two weeks of PCRT were extracted by delineation of the PET images, with or without PVC. Their predictive value was investigated using Mann-Whitney-U tests and ROC analysis. Results. Within baseline parameters, only SUVmean was correlated with response. No evolution after one week was predictive of the response, whereas after two weeks all the parameters except volume were, the best prediction being obtained with TLG (AUC 0.79, sensitivity 63%, specificity 92%). PVC had no significant impact on these results. Conclusion. Several PET indices at baseline and their evolution after two weeks of PCRT are good predictors of response in LARC, with or without PVC, whereas results after one week are suboptimal. Best predictor was TLG reduction after two weeks, although baseline SUVmean had smaller but similar predictive power.