A prognostic volumetric threshold of gross tumor volume in head and neck cancer patients treated with radiotherapy

The influence of tumor volume on the risk of distant metastases in head and neck squamous cell carcinomas

BACKGROUND AND PURPOSE

Distant metastases (DM) in head and neck squamous cell carcinomas (HNSCC) are in most circumstances non-curable. The TNM staging system is insufficient to predict the risk of DM. This study investigates if the DM risk can be predicted using a multivariate model including pre-treatment total tumor volume for both p16-positive oropharyngeal squamous cell carcinoma (OPSCC) and all other sites (other HNSCC).

MATERIALS AND METHODS

The study includes patients with localized pharyngeal and laryngeal squamous cell carcinomas treated with primary radiotherapy from 2008-2017 from three head and neck cancer centers. Patients were identified in the Danish Head and Neck Cancer (DAHANCA) database. Total (nodal and primary) tumor volume (Gross Tumor Volume, GTV) was extracted from local treatment planning systems. The GTV was grouped by volume (cm3) in four intervals and included in a multivariate Cox proportional hazard regression controlled for pre-selected clinical values incl. stage.

RESULTS

The study includes 2,865 patients, of which 321 (11 %) had DM post-treatment. The risk of DM was assessed in a multivariate model based on 2,751 patients (p16-positive OPSCC: 1,032; and other HNSCC: 1,719). There was a significant association between GTV and the risk of DM, and in tumor volumes ≥ 50 cm3 hazard ratios of 7.6 (2.5-23.4) for p16-positive OPSCC and 4.1 (2.3-7.2) in other HNSCC were observed.

CONCLUSION

Tumor volume is an independent risk factor for DM. The addition of total tumor volume to a predictive model is important to identify subgroups of HNSCC patients at high risk of DM.

The Utility of Interim Positron Emission Tomography Imaging to Inform Adaptive Radiotherapy for Head and Neck Squamous Cell Carcinoma

ABSTRACT

In this article, as part of this special issue on biomarkers of early response, we review the current evidence to support the use of positron emission tomography (PET) imaging during chemoradiation therapy to inform biologically adaptive radiotherapy for head and neck squamous cell carcinoma. We review literature covering this topic spanning nearly 3 decades, including the use of various radiotracers and discoveries of novel predictive PET biomarkers. Through understanding how observational trials have informed current interventional clinical trials, we hope that this review will encourage researchers and clinicians to incorporate PET response criteria in new trial designs to advance biologically optimized radiotherapy.

Prognosticating Gross Tumor Volume in Head-and-Neck Cancer - Redefining Gross Tumor Volume Beyond Contouring

Purpose

Precision radiotherapy (RT) requires accurate delineation of gross tumor volumes (GTVs) for targeted dose delivery. Volumetric measurement of this GTV can predict the treatment outcomes. This volume has been limited for mere contouring and its potential as the prognostic factor is less explored.

Materials and Methods

The data of 150 patients with oropharynx, hypopharynx, and larynx cancer undergoing curative intensity-modulated RT and weekly cisplatin between April 2015 and December 2019 were retrospectively evaluated. GTV-P (primary), GTV-N (nodal), and GTV-P+N were defined, and volumetric parameters were generated. Volume thresholds were defined as per the receiver operating characteristics, and the prognostic value of these tumor volumes (TVs) with respect to treatment outcomes was analyzed.

Results

All patients completed 70 Gy, median chemotherapy cycles were six. Mean GTV-P, GTV-N, and GTV-P+N were 44.5 cc, 13.4 cc, and 57.9 cc, respectively. Oropharynx constituted 45% of cases. Forty-nine percent had Stage III disease. Sixty-six percent had complete response (CR). As per the defined cutoff values, GTV-P <30cc, GTV-N <4 cc, and GTV-P+N <50 cc had better CR rates with P < 0.05 (82.6% vs. 51.9%; 74% vs. 58.4% and 81.5% vs. 47.8%, respectively). At median follow-up of 21.4 months, overall survival (OS) was 60% and median OS was 32.3 months. The median OS in patients with GTV-P <30 cc, GTV-N <4 cc, and GTV-P+N <50 cc was better with P < 0.05 (59.2 vs. 21.4; 59.2 vs. 22.2, and 59.2 vs. 19.8 months, respectively).

Conclusion

GTV should not just be limited for contouring but its role as an important prognostic factor has to be recognized.

Tumour volume and radiotherapy prolongation in locally advanced head and neck cancer patients treated with radical IMRT

AIMS

The relationship of tumour volume, radiotherapy treatment time and other prognostic factors affecting prognosis was evaluated.

METHODS

184 patients with locally advanced head and neck cancer were treated with radical intensity modulated radiotherapy (IMRT) and compared retrospectively.

RESULTS

In the multivariate analysis the overall survival was dependent on gross tumour volume (GTV), clinical stage (CS), radiotherapy treatment time (RTT) and p16 status. Local control was influenced by GTV, overall RTT and age. DFS was significantly affected by GTV, CS, RTT, p16 status and concomitant chemotherapy (CHT).

CONCLUSIONS

The tumour volume and the radiotherapy treatment time were the most significant prognostic factors with the best outcomes in patients with GTV ≤ 55 cc and RTT ≤ 48 days (mean LC 8.1, DFS 7.1 and OS 6.4 years) and worst outcomes with GTV > 55 cc and RTT >48 days (mean LC 4.4, mean DFS 3.2 and mean OS 2.6 years).

Primary tumor volume and prognosis for patients with p16-positive and p16-negative oropharyngeal squamous cell carcinoma treated with radiation therapy

BACKGROUND

The prescribed radiation dose to patients with oropharyngeal squamous cell carcinoma (OPSCC) is standardized, even if the prognosis for individual patients may differ. Easy-at-hand pre-treatment risk stratification methods are valuable to individualize therapy. In the current study we assessed the prognostic impact of primary tumor volume for p16-positive and p16-negative tumors and in relationship to other prognostic factors for outcome in patients with OPSCC treated with primary radiation therapy (RT).

METHODS

Five hundred twenty-three OPSCC patients with p16-status treated with primary RT (68.0 Gy to 73.1 Gy in 7 weeks, or 68.0 Gy in 4.5 weeks), with or without concurrent chemotherapy, within three prospective trials were included in the study. Local failure (LF), progression free survival (PFS) and overall survival (OS) in relationship to the size of the primary gross tumor volume (GTV-T) and other prognostic factors were investigated. Efficiency of intensified RT (RT with total dose 73.1 Gy or given within 4.5 weeks) was analyzed in relationship to tumor volume.

RESULTS

The volume of GTV-T and p16-status were found to be the strongest prognostic markers for LF, PFS and OS. For p16-positive tumors, an increase in tumor volume had a significantly higher negative prognostic impact compared with p16-negative tumors. Within a T-classification, patients with a smaller tumor, compared with a larger tumor, had a better prognosis. The importance of tumor volume remained after adjusting for nodal status, age, performance status, smoking status, sex, and hemoglobin-level. The adjusted hazard ratio for OS per cm3 increase in tumor volume was 2.3% (95% CI 0-4.9) for p16-positive and 1.3% (95% 0.3-2.2) for p16-negative. Exploratory analyses suggested that intensified RT could mitigate the negative impact of a large tumor volume.

CONCLUSIONS

Outcome for patients with OPSCC treated with RT is largely determined by tumor volume, even when adjusting for other established prognostic factors. Tumor volume is significantly more influential for patients with p16-positive tumors. Patients with large tumor volumes might benefit by intensified RT to improve survival.

Chorioallantoic membrane tumor models highlight the effects of cisplatin compounds in oral carcinoma treatment

The European Society for Medical Oncology (ESMO) suggests the use of chemotherapy as neoadjuvant, adjuvant, and concomitant to surgery and radiotherapy for the treatment of oral carcinoma by depending on the cancer stage. The usual drug of choice belongs to the platinum compounds. In this context, the evaluation of the cancer behavior associated with the administration of standard or emerging cisplatin compounds supports the establishment of optimal cancer management. Here, we have assessed and compared the performance of cisplatin alone and contained in biodegradable nanocapsules on standardized chorioallantoic membrane (CAM) tumor models. The vascularized environment and optimized grafting procedure allowed the establishment of solid tumors. The treatments showed antitumor and anti-angiogenic activities together with deregulation of pivotal genes responsible of treatment resistance and tumor aggressiveness. This study further supports the significance of CAM tumor models in oncological research for the comprehension of the molecular mechanisms involved in tumor treatment response.

Stereotactic body ablative radiotherapy for reirradiation of small volume head and neck cancers is associated with prolonged survival: Large, single-institution, modern cohort study

BACKGROUND

Recurrent head and neck cancer has poor prognosis. Stereotactic body radiotherapy (SBRT) may improve outcomes by delivering ablative radiation doses.

METHODS

We reviewed patients who received definitive-intent SBRT reirradiation at our institution from 2013 to 2020. Patterns of failure, overall survival (OS), and toxicities were analyzed.

RESULTS

One hundred and thirty-seven patients were evaluated. The median OS was 44.3 months. The median SBRT dose was 45 Gy and median target volume 16.9 cc. The 1-year local, regional, and distant control was 78%, 66%, and 83%, respectively. Systemic therapy improved regional (p = 0.004) and distant control (p = 0.04) in nonmetastatic patients. Grade 3+ toxicities were more common at mucosal sites (p = 0.001) and with concurrent systemic therapy (p = 0.02).

CONCLUSIONS

In a large cohort of SBRT reirradiation for recurrent, small volume head and neck cancers, a median OS of 44.3 months was observed. Systemic therapy improved regional and distant control. Toxicities were modulated by anatomic site and systemic therapy.

Functional Larynx Preservation in Patients With Locally Advanced Squamous Cell Carcinoma of the Larynx and Hypopharynx Treated With Induction Chemotherapy vs. Concurrent Chemoradiation Alone

Objectives

Chemoradiation therapy (CRT) has been established as a standard treatment for locally advanced hypopharynx/larynx squamous cell carcinoma (SCC) but the role of induction chemotherapy (IC) remains unclear. The primary outcome of this study is to determine whether functional larynx-preservation survival (FLPS) is improved with the addition of IC in these patients. Secondary outcomes were overall survival (OS), progression-free survival (PFS), distant metastasis-free survival (DMFS), and laryngectomy rates.

Methods

Records for patients with AJCC 8th edition clinical stage III-IVB laryngeal and hypopharyngeal SCC treated with CRT +/- IC from 2005-2019 were reviewed. FLPS was defined as time until death, progression, laryngectomy, or non-functional larynx. Kaplan-Meier curves were generated for FLPS, OS, PFS, and DMFS. Outcomes were compared using the stratified log-rank test. Laryngectomy rates were compared using Fisher’s exact test.

Results

We included 52 patients with laryngeal and 38 with hypopharyngeal SCC (n=90); 19 patients with laryngeal SCC and 19 with hypopharyngeal SCC received IC (median three cycles). There were no differences in the three-year FLPS (61% vs 67.8%; p=0.88), OS (73.9% vs 86.2%; p=0.42), PFS (53.6% vs 62.6%; p=0.44), or DMFS (65.2% vs 71.5%, p= 0.85) between patients who did and did not receive IC all patients. Laryngectomy rates did not differ with and without IC (18.4 % vs 7.7%; p=0.19).

Conclusion

In this study of advanced laryngeal and hypopharyngeal SCC, IC did not improve three-year FLPS, OS, PFS, or laryngectomy rates compared to CRT alone. A large prospective series would provide a more robust understanding of the role of IC in this group of patients. 

Value of Nomogram Incorporated Preoperative Tumor Volume and the Number of Postoperative Pathologically Lymph Node Metastasis Regions on Predicting the Prognosis of Thoracic Esophageal Squamous Cell Carcinoma

Background

The aim of this study was to explore the influence of preoperative tumor volume, length, maximum diameter and the number of postoperative pathologically lymph node metastasis (LNM) regions on survival prognosis of esophageal squamous cell carcinoma (ESCC) patients.

Methods

A total of 296 patients with ESCC treated by standard curative esophagectomy were retrospectively analyzed. These patients were grouped for further analysis according to the optimal threshold of preoperative tumor volume, length, maximum diameter and the number of postoperative pathologically LNM regions. Kaplan–Meier method was used to calculate survival rate and survival comparison was performed by Log rank test. The Cox proportional hazards model was used to carry out univariate and multivariate analyses. Nomogram model was established by integrating statistically significant clinicopathological parameters, and the predictive value was further verified by calibration curve, concordance index (C-index) and decision curve.

Results

The univariate and multivariate Cox regression analysis all showed that differentiation grade, TNM stage, adjuvant therapy, preoperative tumor volume and the number of post operative pathologically LNM regions were independent prognostic factors for PFS and OS (all P<0.05). The C-indexes of PFS and OS by nomograms were predicted to be 0.747 (95% CI: 0.717–0.777) and 0.732 (95% CI: 0.697–0.767), respectively, which were significantly higher than the 7th AJCC TNM stage, the C-indexes 0.612 (95% CI: 0.574–0.650) and 0.633 (95% CI: 0.595–0.671), separately. In addition, the calibration curves of nomogram models were highly consistent with actual observation for the five-year PFS and OS rate, and the decision curve analysis also showed that nomogram models had higher clinical application potentials than TNM staging model in predicting survival prognosis of thoracic ESCC after surgery.

Conclusion

The nomograms incorporated preoperative tumor volume and the number of postoperative pathologically LNM areas are of great value in predicting survival prognosis of patients with thoracic ESCC.

Correlation between initial tumour volume and treatment duration on Dabrafenib: observation study of subjects with BRAF mutant melanoma on the BRF112680 trial

BACKGROUND

Planar-based measurements of lesions in metastatic melanoma have limitations in estimating tumor burden of a patient and in predicting response to treatment. Volumetric imaging might add predictive value to Response criteria in Solid Tumor (RECIST)-measurement. Based on clinical observations, we explored the association between baseline tumor volume (TV) and duration of treatment with dabrafenib in patients with metastatic melanoma. We have also explored the prognostic value of TV for overall survival (OS) and progression free survival (PFS).

METHODS

This is a retrospective, chart-review of primary source documents and medical imaging of a cohort of patients participating in the BRF112680 phase 1 clinical trial at the Prince of Wales Hospital. TV was quantified by contouring all the measurable baseline target lesions in the standard manner for radiation planning using Voxxar™ software. We used Cox regression models to analyse associations between TV and duration of treatment with dabrafenib and between TV, PFS and OS.

RESULTS

Among 13 patients of BRAF 112680 trial, 10 were included in the retrospective analysis. Target lesion sum volume ranged from 0.3 to 1065.5 cm³ (cc), with a median of 27.5 cc. The median PFS and OS were 420 days (range 109-1765) and 1680 days (range 390-2940), respectively. The initial TV was inversely correlated with duration of treatment with dabrafenib (rho - 0.6; P 0.03). In multivariate analysis, TV was a predictor for OS (HR 2.81 CI 1.06-6.19) and PFS (8.76 (CI 1.05-43.58). Patients with tumour volume above the median had significantly lower OS of 6-months compared to 56-months survival for patients with smaller volumes; P = 0.019.

CONCLUSIONS

TV is a predictor for treatment duration and is prognostic of OS and PFS in patients with metastatic melanoma. These findings need to be validated prospectively in clinical trials.

Intratreatment Tumor Volume Change During Definitive Chemoradiotherapy is Predictive for Treatment Outcome of Patients with Esophageal Carcinoma

BACKGROUND

This study aimed to assess the predictive value of tumor volume changes of esophagus evaluated by serial computed tomography (CT) scans before, during, and after radical chemoradiotherapy (CRT) for treatment outcomes in patients with esophageal cancer (EC).

METHODS

Fifty-three patients with histologically confirmed EC were included for analysis. Gross tumor volume of esophagus (GTVe) was manually contoured on the CT images before treatment, at a twentieth fraction of radiotherapy, at completion of CRT and three months after treatment. GTVe reduction ratio (RR) was calculated to reveal changes of tumor volume by time. The Kaplan-Meier method was used to estimate survival and for univariate analysis. The Cox regression model was performed for multivariate analysis.

RESULTS

Predominant reduction of GTVe was observed during the first 20 fractions of radiotherapy. Age, pretreatment GTVe, GTVe three months after treatment and GTVe RR at twentieth fraction of radiotherapy were all significantly associated with overall survival (OS) in a univariate analysis. Gender was correlated with locoregional recurrence-free survival (LRRFS) in univariate analysis. Multivariate analysis showed that GTVe ≤20 cc, GTVe RR at twentieth fraction of radiotherapy ≥35% were positive predictive factors of OS and pretreatment GTVe ≤20 cc was prognostic for a favorable LRRFS.

CONCLUSION

Pretreatment tumor volume and intratreatment volume reduction ratio are reliable prognostic factors for esophageal cancer treated with definitive CRT.

Evaluation of quantitative imaging parameters in head and neck squamous cell carcinoma

BACKGROUND

Functional imaging such as 18F-fluoro-deoxy-glucose positron emission tomography/computed tomography (FDG-PET/CT), 18F-fluoro-misonidazole (F-MISO)-PET/CT, and diffusion-weighted magnetic resonance imaging (DW-MRI) can assess complex biological phenomena in tumors reflecting underlying disease biology. The aim of this prospective observational study was to correlate quantitative imaging parameters derived from pre-treatment biological imaging such as FDG-PET/CT, F-MISO-PET/CT, and DW-MRI with each other andì with clinical outcomes in patients with head and neck squamous cell carcinoma (HNSCC) treated with definitive radio(chemo)therapy.

METHODS

Twenty patients with pharyngo-laryngeal cancers underwent pre-treatment biological imaging. Gross tumor volume (GTV) was delineated on axial planning CT (GTVCT). Quantitative FDG-PET/CT parameters included maximum, mean, minimum standardized uptake values (SUVmax-FDG, SUVmean-FDG, SUVmin-FDG); metabolic tumor volume (MTV); and total lesion glycolysis (TLG). F-MISO-PET/CT parameters included hypoxic tumor volume (HTV); maximum, mean, minimum SUV; and fractional hypoxic volume (FHV). Mean apparent diffusion coefficient (ADCmean) was derived from DW-MRI.

RESULTS

There was moderately strong positive correlation (r=0.616, p=0.005) between GTVCT and MTV. HTV derived from F-MISO-PET/CT at 3-hours (HTV3hrs-F-MISO) showed strong positive correlation with GTVCT (r=0.753, p<0.0001) and MTV (r=0.796, p<0.0001) respectively. ADCmean showed strong positive correlations with SUVmean-5hrs-F-MISO (r=0.713, p=0.021) and SUVmin-5hrs-FMISO (r=0.731, p=0.016) respectively. A moderate negative correlation (r=-0.500, p=0.049) was observed between ADCmean and MTV. At a median follow up of 44 months, the 5-year Kaplan-Meier estimates of loco-regional control, disease-free survival, and overall survival were 53%, 43%, and 40% respectively. Larger volume of primary tumor (GTVCT>22cc and MTV>7.9cc) and increasing hypoxia (HTV3hr-F-MSO>4.9cc) were associated with worse outcomes.

CONCLUSIONS

Functional imaging represents an attractive and non-invasive modality to assess complex biological phenomena in solid tumors. Larger tumor volume and increasing hypoxia emerged as putative prognostic imaging biomarkers in HNSCC.

Prognostic Value of FDG PET/CT-Derived Parameters in Pancreatic Adenocarcinoma at Initial PET/CT Staging

OBJECTIVE

The purpose of this study is to evaluate the performance of PET-derived parameters as prognostic markers for overall survival (OS) and progression-free survival (PFS) outcome in patients with pancreatic adenocarcinoma.

MATERIALS AND METHODS

We conducted a retrospective study of 106 patients (62 men and 44 women) with histologically proven pancreatic adenocarcinoma who underwent initial staging FDG PET/CT before treatment. Peak standardized uptake value (SUV), maximum SUV (SUVmax), metabolic tumor volume, and tumor glycolytic activity of the primary pancreatic tumor were measured. Two segmentation methods were performed to obtain the metabolic tumor volume and tumor glycolytic activity for all tumors: a gradient-based segmentation model (metabolic tumor volume and tumor glycolytic activity by gradient edge detection) and a fixed-threshold model with a threshold of 50% of the lesion's SUVmax and peak SUV. Univariate and multivariate Cox regression models were developed including clinical and imaging parameters for OS and PFS.

RESULTS

Multivariate Cox regression analysis showed a statistically significant association between PFS and age, SUVmax, peak SUV, and tumor glycolytic activity by gradient edge detection. There was a statistically significant difference in PFS for patients with values above and below the median cutoff points for SUVmax (hazard ratio [HR], 1.12; p < 0.01), peak SUV (HR, 1.25; p < 0.02), and tumor glycolytic activity measured by gradient edge detection (HR, 1.00; p < 0.02) of the primary tumor. However, multivariate Cox regression analysis showed a statistically significant association only between tumor glycolytic activity by gradient edge detection and OS (p = 0.04), and there was a statistically significant difference in OS between patients with values above and below the median cutoff point for the tumor glycolytic activity by gradient edge detection of the primary tumor (HR, 1.42; p = 0.05).

CONCLUSION

Age, SUVmax, peak SUV, and total lesion glycolysis (i.e., tumor glycolytic activity) of the primary tumor are associated with PFS, and tumor glycolytic activity is associated with OS in patients with pancreatic adenocarcinoma.

The relative prognostic utility of standardized uptake value, gross tumor volume, and metabolic tumor volume in oropharyngeal cancer patients treated with platinum based concurrent chemoradiation with a pre-treatment [(18)F] fluorodeoxyglucose positron emission tomography scan

OBJECTIVES

This study compared the relative prognostic utility of the Gross Tumor Volume (GTV), maximum Standardized Uptake Value (SUVmax), and Metabolic Tumor Volume (MTV) in a uniform cohort of oropharyngeal squamous cell carcinoma (OPSCC) patients treated with platinum-based concurrent chemoradiation therapy (CCRT).

METHODS AND MATERIALS

One-hundred OPSCC with a pretreatment [(18)F] fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) were treated with CCRT. Kaplan-Meier curves and Cox proportional hazard models were generated.

RESULTS

When dichotomized by the median, a smaller MTV correlated with improved 5year locoregional control (LRC) (98.0% versus 87.0%, p=0.049), freedom from distant metastasis (FDM) (91.7% versus 65.0%, p=0.005), progression-free survival (PFS) (80.3% versus 56.7%, p=0.015), and overall survival (OS) (84.1% versus 57.8%, p=0.008), whereas a smaller GTV correlated with improved PFS (80.3% versus 57.4%, p=0.040) and OS (82.1% versus 60.1%, p=0.025). SUVmax failed to correlate with any outcome. On multivariate analysis, when adjusted for GTV, T-stage, and N-stage a smaller MTV remained independently correlated with improved FDM, PFS, and OS. GTV failed to reach significance in the multivariate model.

CONCLUSIONS

A smaller MTV correlates with improved LRC, FDM, PFS, and OS in OPSCC patients undergoing platinum-based CCRT.

Predictive value of pre-therapy (18)F-FDG PET/CT for the outcome of (18)F-FDG PET-guided radiotherapy in patients with head and neck cancer

PURPOSE

The aim of this study was to evaluate the predictive role of pre-therapy fluorodeoxyglucose (FDG) uptake parameters of primary tumour in head and neck cancer (HNC) patients undergoing intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB) on FDG-positive volume-positron emission tomography (PET) gross tumour volume (PET-GTV).

METHODS

This retrospective study included 19 patients (15 men and 4 women, mean age 59.2 years, range 23-81 years) diagnosed with HNC between 2005 and 2011. Of 19 patients, 15 (79 %) had stage III-IV. All patients underwent FDG PET/CT before treatment. Metabolic indexes of primary tumour, including metabolic tumour volume (MTV), maximum and mean standardized uptake value (SUVmax, SUVmean) and total lesion glycolysis (TLG) were considered. Partial volume effect correction (PVC) was performed for SUVmean and TLG estimation. Correlations between PET/CT parameters and 2-year disease-free survival (DFS), local recurrence-free survival (LRFS) and distant metastasis-free survival (DMFS) were assessed. Median patient follow-up was 19.2 months (range 4-24 months).

RESULTS

MTV, TLG and PVC-TLG predicting patients' outcome with respect to all the considered local and distant disease control endpoints (LRFS, DMFS and DFS) were 32.4 cc, 469.8 g and 547.3 g, respectively. SUVmean and PVC-SUVmean cut-off values predictive of LRFS and DFS were 10.8 and 13.3, respectively. PVC was able to compensate errors up to 25 % in the primary HNC tumour uptake. Moreover, PVC enhanced the statistical significance of the results.

CONCLUSION

FDG PET/CT uptake parameters are predictors of patients' outcome and can potentially identify patients with higher risk of treatment failure that could benefit from more aggressive approaches. Application of PVC is recommended for accurate measurement of PET parameters.