What is the best way to contour lung tumors on PET scans? Multiobserver validation of a gradient-based method using a NSCLC digital PET phantom

Semiautomatic methods for segmentation of the proliferative tumour volume on sequential FLT PET/CT images in head and neck carcinomas and their relation to clinical outcome

PURPOSE

Radiotherapy of head and neck cancer induces changes in tumour cell proliferation during treatment, which can be depicted by the PET tracer (18)F-fluorothymidine (FLT). In this study, three advanced semiautomatic PET segmentation methods for delineation of the proliferative tumour volume (PV) before and during (chemo)radiotherapy were compared and related to clinical outcome.

METHODS

The study group comprised 46 patients with 48 squamous cell carcinomas of the head and neck, treated with accelerated (chemo)radiotherapy, who underwent FLT PET/CT prior to treatment and in the 2nd and 4th week of therapy. Primary gross tumour volumes were visually delineated on CT images (GTV CT). PVs were visually determined on all PET scans (PV VIS). The following semiautomatic segmentation methods were applied to sequential PET scans: background-subtracted relative-threshold level (PV RTL), a gradient-based method using the watershed transform algorithm and hierarchical clustering analysis (PV W&C), and a fuzzy locally adaptive Bayesian algorithm (PV FLAB).

RESULTS

Pretreatment PV VIS correlated best with PV FLAB and GTV CT. Correlations with PV RTL and PV W&C were weaker although statistically significant. During treatment, the PV VIS, PV W&C and PV FLAB significant decreased over time with the steepest decline over time for PV FLAB. Among these advanced segmentation methods, PV FLAB was the most robust in segmenting volumes in the third scan (67 % of tumours as compared to 40 % for PV W&C and 27 % for PV RTL). A decrease in PV FLAB above the median between the pretreatment scan and the scan obtained in the 4th week was associated with better disease-free survival (4 years 90 % versus 53 %).

CONCLUSION

In patients with head and neck cancer, FLAB proved to be the best performing method for segmentation of the PV on repeat FLT PET/CT scans during (chemo)radiotherapy. This may potentially facilitate radiation dose adaptation to changing PV.

A comparison of amplitude-based and phase-based positron emission tomography gating algorithms for segmentation of internal target volumes of tumors subject to respiratory motion

PURPOSE

To quantitatively compare the accuracy of tumor volume segmentation in amplitude-based and phase-based respiratory gating algorithms in respiratory-correlated positron emission tomography (PET).

METHODS AND MATERIALS

List-mode fluorodeoxyglucose-PET data was acquired for 10 patients with a total of 12 fluorodeoxyglucose-avid tumors and 9 lymph nodes. Additionally, a phantom experiment was performed in which 4 plastic butyrate spheres with inner diameters ranging from 1 to 4 cm were imaged as they underwent 1-dimensional motion based on 2 measured patient breathing trajectories. PET list-mode data were gated into 8 bins using 2 amplitude-based (equal amplitude bins [A1] and equal counts per bin [A2]) and 2 temporal phase-based gating algorithms. Gated images were segmented using a commercially available gradient-based technique and a fixed 40% threshold of maximum uptake. Internal target volumes (ITVs) were generated by taking the union of all 8 contours per gated image. Segmented phantom ITVs were compared with their respective ground-truth ITVs, defined as the volume subtended by the tumor model positions covering 99% of breathing amplitude. Superior-inferior distances between sphere centroids in the end-inhale and end-exhale phases were also calculated.

RESULTS

Tumor ITVs from amplitude-based methods were significantly larger than those from temporal-based techniques (P=.002). For lymph nodes, A2 resulted in ITVs that were significantly larger than either of the temporal-based techniques (P<.0323). A1 produced the largest and most accurate ITVs for spheres with diameters of ≥2 cm (P=.002). No significant difference was shown between algorithms in the 1-cm sphere data set. For phantom spheres, amplitude-based methods recovered an average of 9.5% more motion displacement than temporal-based methods under regular breathing conditions and an average of 45.7% more in the presence of baseline drift (P<.001).

CONCLUSIONS

Target volumes in images generated from amplitude-based gating are larger and more accurate, at levels that are potentially clinically significant, compared with those from temporal phase-based gating.

Variation in background intensity affects PET-based gross tumor volume delineation in non-small-cell lung cancer: the need for individualized information

PURPOSE

Efficient tumor volume delineation by the combined use of PET/CT scanning is necessary for the proper treatment of non-small cell lung cancer (NSCLC). To understand the effect of variation in background intensity on PET-based gross tumor volume (GTV) delineation, we determined the background standard uptake values (SUVs) in normal lung, aorta (blood pool), and liver tissues and determined GTVs using different methods.

METHODS

Thirty-seven previously untreated patients with pathologically confirmed NSCLC underwent PET/CT scanning with (18)F-fluorodeoxyglucose ((18)F-FDG). To obtain (18)F-FDG uptake values in normal tissues, regions of interest in the lung lobes (left upper, left lower, right upper, right middle, and right lower), aorta, and liver zones (left, intermediate, and right) were measured. The coefficient of variation (CV) of the SUV was measured for each normal structure. The CT-based GTV (GTV(CT)) was considered as the standard to which all PET-based GTVs were compared, and the correlation coefficient was analyzed to compare GTV obtained by the various delineation methods. Linear and logarithmic regression analyses were used to determine the relationship between GTV(CT) and GTV(PET).

RESULTS

Normal lung tissue showed a significantly lower SUV and less stability than tissue of the aorta or liver. For the lung, aorta, and liver, the maximum SUV (SUV(max)) was 0.82 ± 0.32, 2.35 ± 0.37, and 3.24 ± 0.50 (CV: 38.79%, 15.82%, and 15.30%) and average SUV (SUV(ave)) was 0.49 ± 0.18, 1.68 ± 0.32, and 2.34 ± 0.36 (CV: 36.38%, 18.92%, and 15.44%), respectively. The SUVs of the lung varied from lobe to lobe. The GTV delineation method using the SUV(ave) of the lung lobe in which the tumor was found as background in the source-to-background ratio (SBR) method showed the best correlation with the volume of CT-based GTV (r=0.81).

CONCLUSIONS

Our results show vast variation in the SUV among normal tissues, as well as in the different lung lobes. The tumor volume delineated using the SBR method correlated well with the CT-based tumor volume. We conclude that it is reasonable and precise to contour GTV in patients with NSCLC after taking into account the background intensity of the lung lobe in which the tumor is found.

Interim 18F-FDG PET in Hodgkin lymphoma: would PET-adapted clinical trials lead to a paradigm shift?

Hodgkin lymphoma (HL) is a curable disease with currently available chemotherapy regimens. Major late morbidities can potentially be avoided in most limited-stage HL patients if the treatment can be adapted to the patient's early response profile. The therapy efficacy can also be increased early during therapy in nonresponding HL patients with the addition of involved-field radiation therapy or a switch to an escalated therapy protocol, particularly in advanced-stage or unfavorable-risk patients. (18)F-FDG PET is a well-established surrogate for tumor chemosensitivity early during therapy. The ongoing PET-adaptive clinical trials are testing the hypothesis that a decision can reliably be made on escalating or deescalating therapy based on interim PET results. Discussed in this review is the integral role of interim (18)F-FDG PET in HL, challenges, critical issues to improve its accuracy, and the observations from completed interim PET studies and ongoing PET-adaptive clinical trials.

State-of-the-Art Research on "Lymphomas: Role of Molecular Imaging for Staging, Prognostic Evaluation, and Treatment Response"

Lymphomas are heterogeneous but potentially curable group of neoplasms. Treatment of lymphomas has rapidly evolved overtime with significant improvement in the cure rate and reductions in treatment-related toxicities. Despite excellent results, treatment programs are continued to be developed to achieve better curative and safety profiles. In these patients individualized therapy schemes can be devised based on a well-defined risk categorization. The therapy efficacy can be increased early during therapy in non-responding patients with escalated therapy protocols or with the addition of radiation therapy, particularly, in advanced-stage or unfavorable risk patients. The increasing availability of positron emission tomography using 18F-fluorodeoxyglucose, particularly fused with computed tomography (FDG-PET/CT) has lead to the integration of this modality into the routine staging and restaging for lymphoma with convincing evidence that it is a more accurate imaging modality compared with conventional imaging techniques. FDG-PET/CT is also is a promising surrogate for tumor chemosensitivity early during therapy. This review will summarize published data on the utility of FDG-PET/CT imaging in the staging, restaging, and predicting therapy response in patients with lymphoma.

Head and neck squamous cell cancer (stages III and IV) induction chemotherapy assessment: value of FDG volumetric imaging parameters

INTRODUCTION

To evaluate whether the change in the metabolic tumour volume (MTV) or total lesion glycolysis (TLG) of the primary tumour, before and after induction chemotherapy, predicts outcome for patients with advanced head and neck squamous cell cancer (SCC).

METHODS

Twenty-eight patients with advanced (American Joint Committee on Cancer stage III and IV) head and neck SCC who underwent positron emission tomography (PET)/CT were included in this retrospective study. Primary tumour MTV and TLG were measured using gradient and fixed percentage threshold segmentations. Outcome endpoint was disease progression or mortality. Pearson correlation, Bland-Altman and receiver operator characteristic analysis were performed.

RESULTS

The Pearson's correlation coefficients between percentage changes (pre- and post-induction chemotherapy) from gradient MTV (MTVG) and the 38% SUVmax threshold MTV (MTV38) was 0.96 and between MTVG and the 50% threshold MTV (MTV50) was 0.95 (P < 0.0001). The corresponding Pearson r between TLGG and TLG38 was 0.94 and between TLGG and TLG50 was 0.96 (P < 0.0001). The least bias was 1.89% (standard deviation = 25.30%) between the percentage changes of MTVG and MTV50. The areas under the curve for predicting progression or mortality were 0.76 (P = 0.03) for MTVG and 0.82 for TLGG (P = 0.009). Optimum cut points of a 42% reduction in MTVG and a 55% reduction in the TLGG predict event-free survival with a sensitivity of 62.5% and a specificity of 90% and a hazards ratio of 6.25.

CONCLUSION

A reduction in primary tumour MTV of at least 42% or in TLG of at least 55% after induction chemotherapy may predict event-free survival in patients with advanced head and neck SCC.

PET-based primary tumor volumetric parameters and survival of patients with non-small cell lung carcinoma

OBJECTIVE

The purpose of the study was to assess metabolic tumor volume and total glycolytic activity of the primary tumor as prognostic parameters for outcome in patients with non-small cell lung carcinoma (NSCLC).

MATERIALS AND METHODS

Thirty-nine patients who had undergone a baseline staging PET/CT examination at our institution for the diagnosis of NSCLC were retrospectively identified. The maximum standardized uptake value (SUV(max)), metabolic tumor volume, and total glycolytic activity were segmented from PET using the gradient method; 12-month survival and overall survival at the end of follow-up were used as outcome measures. Multivariate logistic regression, receiver operating characteristic curve analysis, and Kaplan-Meier curves for survival analysis were generated and compared using the Mantel-Cox log-rank test.

RESULTS

The mean gradient-based metabolic tumor volume and gradient-based total glycolytic activity were significantly greater in the patients who died (93.3 mL and 597.5 g) than in those who survived (19.3 mL and 193.9 g, respectively) (p < 0.003 and p < 0.031). There was no statistically significant difference in the mean SUV(max) between the patients who survived (12.7) at 12 months and those who had died (13.1) (p = 0.85). On multivariate analysis, gradient-based metabolic tumor volume was the only variable associated with 12-month mortality when adjusted for all other factors.(.) The area under the curve (AUC) for gradient-based metabolic tumor volume was 0.77 (p < 0.006). A significant difference in the time to survival was observed between high and low gradient-based metabolic tumor volume (log-rank p < 0.05) cohorts using the median gradient-based metabolic tumor volume (9.7 mL) as the cut point.

CONCLUSION

PET-based volumetric imaging parameters are potential prognostic markers of outcome in patients with NSCLC.

Prognostic value of metabolic tumor burden from (18)F-FDG PET in surgical patients with non-small-cell lung cancer

OBJECTIVE

To assess the prognostic value of metabolic tumor burden as measured with metabolic tumor volume (MTV) and total lesion glycolysis (TLG) on 2-deoxy-2-((18)F)fluoro-D-glucose ((18)F-FDG) positron emission tomography (PET)/computed tomography (CT), independent of current Union Internacional Contra la Cancrum/American Joint Committee on Cancer tumor, node, and metastasis (TNM) stage; in comparison with that of standardized uptake value (SUV) in surgical patients with non-small-cell lung cancer (NSCLC).

MATERIAL AND METHODS

This study retrospectively reviewed 104 consecutive surgical patients (47 males, 57 females, median age at PET/CT scan of 67.92 years) with diagnosed stage I to IV NSCLC who had baseline (18)F-FDG PET/CT scans. The (18)F-FDG PET/CT scans were performed in accordance with National Cancer Institute guidelines. The MTV of tumors in the whole body (MTV(WB)), TLG of tumors in the whole body (TLG(WB)), the maximum standardized uptake value of tumors in the whole body (SUV(maxWB)) as well as the mean standardized uptake value of tumor in the whole body (SUV(meanWB)) were measured. The median follow-up among 67 survivors was 42.07 months from the PET/CT (range 2.82-80.95 months). Statistical methods included Kaplan-Meier curves, Cox regression, and C-statistics. The interobserver variability of SUV(maxWB), SUV(meanWB), MTV(WB), and TLG(WB) between two observers was analyzed using concordance correlation coefficients (CCCs).

RESULTS

The interobserver variability of SUV(maxWB), SUV(meanWB), MTV(WB) and TLG(WB) was very low with CCCs greater than 0.882. There was a statistically significant association of stage with overall survival (OS). The hazard ratio (HR) of stage III and stage IV as compared with stage I was 3.60 (P = .001) and 4.00 (P = .013), respectively. The MTV(WB) was significantly associated with OS with a HR for 1-unit increase of ln(MTV(WB)) of 1.40/1.32 (P = .004/.039), before/after adjusting for stage and other prognostic factors including chemoradiation therapy, and surgical procedure, respectively. TLG(WB) had a statistically significant association with OS before and after adjusting for stage and the other prognostic factors. The HR for 1-unit increase in ln(TLG(WB)) was 1.26 (P = .011) and 1.25 (P = .031), before and after the adjustment, respectively. Subjects with conditions that led to pneumonectomy (HR = 2.82, P = .035) or segmental resection (HR = 3.44, P = .044) had significantly worse survival than those needing lobectomy. There was no statistically significant association between OS and age, gender, tumor histology, ln(SUV(maxWB)), and ln(SUV(meanWB)) (all P > .05). There were 37 deaths during follow-up.

CONCLUSION

Baseline whole-body metabolic tumor burden as measured with MTV(WB) and TLG(WB) on FDG PET is a prognostic measure independent of clinical stage and other prognostic factors including chemoradiation therapy and surgical procedure with low interobserver variability and may be used to further risk stratify surgical patients with NSCLC. This study also suggests that MTV and TLG are better prognostic measures than SUV(max) and SUV(mean). These results will need to be validated in larger cohorts in a prospective study.

Intra-reader reliability of FDG PET volumetric tumor parameters: effects of primary tumor size and segmentation methods

OBJECTIVE

To establish the effects of size and segmentation methods on intra-reader reliability of primary tumor metabolic tumor volume (MTV) and total glycolytic activity (TGA) in human solid tumors.

METHODS

This is a retrospective study of 121 patients who had a baseline FDG PET/CT scan for oncologic staging. Volumetric parameter readings were performed in random order on two separate occasions, 12 weeks apart, by the same reader. The MTV and TGA were segmented using gradient and fixed maximum standardized uptake value (SUVmax) threshold methods. Intra-reader reliability was established by the intraclass correlation coefficient (ICC) and Bland-Altman analysis.

RESULTS

The biases for MTV were 2.95, 14.76 and 11.13% for gradient segmentation, 38 and 50% SUVmax fixed threshold segmentations, respectively (p < 0.0001). For TGA, the corresponding biases were 0.76, 10.36 and 7.46% (p < 0.0001). There were no statistically significant differences in the biases between the first and second reads for MTV segmented for small and large volume tumors by the gradient method (p < 0.34) or 50% SUVmax threshold segmentation (p < 0.08). However, there were statistically significant differences in the corresponding biases for the 38% SUVmax threshold segmentation (p < 0.04). There were no statistically significant differences in the biases between the first and second reads for TGA segmented for small and large volume tumors (p < 0.98).

CONCLUSION

Intra-reader reliability for primary tumor FDG MTV and TGA is affected by the tumor size and segmentation methods. The segmentation bias was smaller for gradient method than percentage fixed threshold method for MTV. The segmentation biases were smaller for TGA than MTV.

Independent prognostic value of whole-body metabolic tumor burden from FDG-PET in non-small cell lung cancer

PURPOSE

To determine whether whole-body metabolic tumor burden, measured as either metabolic tumor volume (MTVWB) or total lesion glycolysis (TLGWB), using FDG-PET/CT is an independent prognostic marker in non-small cell lung cancer (NSCLC).

METHODS

328 patients with histologically proven NSCLC were identified for this retrospective analysis. This study was approved by our Institutional Review Board. All patients underwent baseline (18)F-FDG-PET/CT scan imaging before therapy. The MTVWB, TLGWB, maximum standardized uptake value (SUVmaxWB) and mean standardized uptake value (SUVmeanWB) of tumors throughout the whole body were measured from FDG-PET images with semi-automated 3D contouring software.

RESULTS

In univariate analysis, there was a statistically significant association of overall survival (OS) with the MTVWB (hazard ratio (HR) = 1.62, p < 0.001), TLGWB (HR = 1.47, p < 0.001). The patients with a MTVWB ≤ median of 65.7 ml and TLGWB ≤ median of 205.11 SUVmean * ml had a median OS of 41.1 and 35.4 months compared with 9.5 and 9.7 months for those with a MTVWB > 65.7 ml and TLGWB > 205.11 SUVmean * ml, respectively. From a series of multivariate Cox regression models, the MTVWB and TLGWB were significantly better than SUVmaxWB and SUVmeanWB at prognostication and significantly associated with patients' OS with HRs of 1.50 (p < 0.001) and 1.42 (p < 0.001), respectively, after adjustment for patient's age, gender and treatment intent as well as the tumor SUVmaxWB, histology and stage.

CONCLUSIONS

MTVWB and TLGWB as metabolic tumor burden measurements in (18)F-FDG-PET/CT are independent prognostic markers and are significantly better than SUVmaxWB and SUVmeanWB at prognostication.

Superior prognostic utility of gross and metabolic tumor volume compared to standardized uptake value using PET/CT in head and neck squamous cell carcinoma patients treated with intensity-modulated radiotherapy

OBJECTIVE

To compare the prognostic utility of the 2-[(18)F] fluoro-2-deoxy-D: -glucose (FDG) maximum standardized uptake value (SUV(max)), primary gross tumor volume (GTV), and FDG metabolic tumor volume (MTV) for disease control and survival in patients with head and neck squamous cell carcinoma (HNSCC) undergoing intensity-modulated radiotherapy (IMRT).

METHODS

Between 2007 and 2011, 41 HNSCC patients who underwent a staging positron emission tomography with computed tomography and definitive IMRT were identified. Local (LC), nodal (NC), distant (DC), and overall (OC) control, overall survival (OS), and disease-free survival (DFS) were assessed using the Kaplan-Meier product-limit method.

RESULTS

With a median follow-up of 24.2 months (range 2.7-56.3 months) local, nodal, and distant recurrences were recorded in 10, 5, and 7 patients, respectively. The median SUV(max), GTV, and MTV were 15.8, 22.2 cc, and 7.2 cc, respectively. SUV(max) did not correlate with LC (p = 0.229) and OS (p = 0.661) when analyzed by median threshold. Patients with smaller GTVs (<22.2 cc) demonstrated improved 2-year actuarial LC rates of 100 versus 56.4 % (p = 0.001) and OS rates of 94.4 versus 65.9 % (p = 0.045). Similarly, a smaller MTV (<7.2 cc) correlated with improved 2-year actuarial LC rates of 100 versus 54.2 % (p < 0.001) and OS rates of 94.7 versus 64.2 % (p = 0.04). Smaller GTV and MTV correlated with improved NC, DC, OC, and DFS, as well.

CONCLUSION

GTV and MTV demonstrate superior prognostic utility as compared to SUV(max), with larger tumor volumes correlating with inferior local control and overall survival in HNSCC patients treated with definitive IMRT.

Use of FDG-PET in Radiation Treatment Planning for Thoracic Cancers

Radiotherapy plays an important role in the treatment for thoracic cancers. Accurate diagnosis is essential to correctly perform curative radiotherapy. Tumor delineation is also important to prevent geographic misses in radiotherapy planning. Currently, planning is based on computed tomography (CT) imaging when radiation oncologists manually contour the tumor, and this practice often induces interobserver variability. F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) has been reported to enable accurate staging and detect tumor extension in several thoracic cancers, such as lung cancer and esophageal cancer. FDG-PET imaging has many potential advantages in radiotherapy planning for these cancers, because it can add biological information to conventional anatomical images and decrease the inter-observer variability. FDG-PET improves radiotherapy volume and enables dose escalation without causing severe side effects, especially in lung cancer patients. The main advantage of FDG-PET for esophageal cancer patients is the detection of unrecognized lymph node or distal metastases. However, automatic delineation by FDG-PET is still controversial in these tumors, despite the initial expectations. We will review the role of FDG-PET in radiotherapy for thoracic cancers, including lung cancer and esophageal cancer.

18F-FDG metabolic tumor volume and total glycolytic activity of oral cavity and oropharyngeal squamous cell cancer: adding value to clinical staging

(18)F-FDG metabolic tumor volume (MTV) and total glycolytic activity (TGA) have been proposed as potential prognostic imaging markers for patient outcome in human solid tumors. The purpose of this study was to establish whether MTV and TGA add prognostic information to clinical staging in patients with oral and oropharyngeal squamous cell carcinomas (SCCs).

METHODS

The Institutional Review Board approved this Health Insurance Portability and Accountability Act-compliant single-institution retrospective study. Forty-five patients with histologically proven oral or oropharyngeal SCC underwent PET/CT for initial cancer staging and were included in the study. MTV was measured using a gradient-based method (PET Edge) and fixed-threshold methods at 38%, 50%, and 60% of maximum standardized uptake value (SUV). The TGA is defined as MTV × mean SUV. Bland-Altman analysis was used to establish the reliability of the methods of segmentation. Outcome endpoints were overall survival (OS) and progression-free survival. Cox proportional hazards univariate and multivariate regression analyses were performed.

RESULTS

In Cox regression models, MTV and TGA were the only factors significantly associated with survival outcome after adjusting for all other covariates including American Joint Committee on Cancer (AJCC) stage, with hazards ratio of 1.06 (95% confidence interval, 1.01-1.10; P = 0.006) and 1.00 (95% confidence interval, 1.00-1.01; P = 0.02). The model fit was significantly better when MTV was added to AJCC stage in model I (χ(2) value change, 1.16-6.71; P = 0.01) and when TGA was added to AJCC stage in model II (χ(2) value change, 1.16-4.37; P = 0.04). The median cutoff point of 7.7 mL for primary tumor MTV was predictive of time to OS (log rank P = 0.04). The median cutoff point of 55 g for PET Edge primary tumor TGA was predictive of time to OS (log rank P = 0.08), though the result was not statistically significant.

CONCLUSION

Gradient-based segmentations of primary tumor MTV and TGA are potential (18)F-FDG markers for time to survival in patients with oral and oropharyngeal SCC and may provide prognostic information in addition to AJCC stage. These exploratory imaging markers need validation in larger cohort studies.

Prognostic value of the quantitative metabolic volumetric measurement on 18F-FDG PET/CT in Stage IV nonsurgical small-cell lung cancer

RATIONALE AND OBJECTIVES

Stage IV non-small-cell lung cancer (NSCLC) consists of a heterogeneous group of patients with different prognoses. We assessed the prognostic value of baseline whole body tumor burden as measured by metabolic tumor volume (MTV), total lesion glycolysis (TLG), and standardized uptake values (SUV(max) and SUV(mean)) of all tumors in nonsurgical patients with Stage IV NSCLC.

MATERIALS AND METHODS

Ninety-two consecutive patients with newly diagnosed Stage IV NSCLC who had a pretreatment F-18 fludeoxyglucose positron emission tomography/computed tomography scan were retrospectively reviewed. The MTV, TLG, SUV(mean), and SUV(max) of whole-body (WB) tumors were measured with the MIMvista workstation with manual adjustment.

RESULTS

There was a statistically significant association between overall survival (OS) and ln(MTV)/ln(TLG) at the level of WB tumor burden (MTV(WB)) and of primary tumor (MTV(T)). The hazard ratio (HR) for a 1-unit increase of ln(MTV(WB)) and ln(MTV(T)) before and after adjusting for age and gender was 1.48/1.48 (both P < .001) and 1.25/1.25 (P = .006, .007), respectively. The HR for a 1-unit increase of ln(TLG(WB)) and ln(TLG(T)) before and after adjusting for age and gender was 1.37/1.37 (both P = .001) and 1.19/1.19 (P = .001, .017), respectively. There was no statistically significant association between OS and ln(SUV(max)) and ln(SUV(mean)) at WB tumor burden, primary tumor, nodal metastasis, or distant metastasis (P > .05). There was low interobserver variability between two radiologists with concordance correlation coefficients of 0.90 for ln(MTV(WB)) and greater than 0.90 for SUV(maxWB), SUV(meanWB), and ln(TLG(WB)).

CONCLUSION

Baseline WB metabolic tumor burden, as measured with MTV and TLG, is a prognostic measurement in patients within Stage IV NSCLC with low interobserver variability. This study also suggests pretreatment MTV and TLG measurements may be used to further stratify patients with Stage IV NSCLC and are better prognostic measures than SUV(max) and SUV(mean) measurements.