Combined PET/CT-perfusion in patients with head and neck cancers might predict failure after radio-chemotherapy: a proof of concept study

Total Body PET/CT: Future Aspects

Total-body (TB) positron emission tomography (PET) scanners are classified by their axial field of view (FOV). Long axial field of view (LAFOV) PET scanners can capture images from eyes to thighs in a one-bed position, covering all major organs with an axial FOV of about 100 cm. However, they often miss essential areas like distal lower extremities, limiting their use beyond oncology.TB-PET is reserved for scanners with a FOV of 180 cm or longer, allowing coverage of most of the body. LAFOV PET technology emerged about 40 years ago but gained traction recently due to advancements in data acquisition and cost. Early research highlighted its benefits, leading to the first FDA-cleared TB-PET/CT device in 2019 at UC Davis. Since then, various LAFOV scanners with enhanced capabilities have been developed, improving image quality, reducing acquisition times, and allowing for dynamic imaging. The uEXPLORER, the first LAFOV scanner, has a 194 cm active PET AFOV, far exceeding traditional scanners. The Panorama GS and others have followed suit in optimizing FOVs. Despite slow adoption due to the COVID pandemic and costs, over 50 LAFOV scanners are now in use globally. This review explores the future of LAFOV technology based on recent literature and experiences, covering its clinical applications, implications for radiation oncology, challenges in managing PET data, and expectations for technological advancements.

PET Imaging of Tumor Perfusion: A Potential Cancer Biomarker?

Perfusion, as measured by imaging, is considered a standard of care biomarker for the evaluation of many tumors. Measurements of tumor perfusion may be used in a number of ways, including improving the visual detection of lesions, differentiating malignant from benign findings, assessing aggressiveness of tumors, identifying ischemia and by extension hypoxia within tumors, and assessing treatment response. While most clinical perfusion imaging is currently performed with CT or MR, a number of methods for PET imaging of tumor perfusion have been described. The inert PET radiotracer 15O-water PET represents the recognized gold standard for absolute quantification of tissue perfusion in both normal tissue and a variety of pathological conditions including cancer. Other cancer PET perfusion imaging strategies include the use of radiotracers with high first-pass uptake, analogous to those used in cardiac perfusion PET. This strategy produces more visually pleasing high-contrast images that provide relative rather than absolute perfusion quantification. Lastly, multiple timepoint imaging of PET tracers such as 18F-FDG, are not specifically optimized for perfusion, but have advantages related to availability, convenience, and reimbursement. Multiple obstacles have thus far blocked the routine use of PET imaging for tumor perfusion, including tracer production and distribution, image processing, patient body coverage, clinical validation, regulatory approval and reimbursement, and finally feasible clinical workflows. Fortunately, these obstacles are being overcome, especially within larger imaging centers, opening the door for PET imaging of tumor perfusion to become standard clinical practice. In the foreseeable future, it is possible that whole-body PET perfusion imaging with 15O-water will be able to be performed in a single imaging session concurrent with standard PET imaging techniques such as 18F-FDG-PET. This approach could establish an efficient clinical workflow. The resultant ability to measure absolute tumor blood flow in combination with glycolysis will provide important complementary information to inform prognosis and clinical decisions.

The diagnostic performance of perfusion CT in the detection of local tumor recurrence in head and neck cancer

BACKGROUND

Detecting local tumor recurrence from post-treatment changes in head and neck cancer (HNC) remains a challenge. Based on the hypothesis that post-therapeutically altered tissue is bradytroph, lower perfusion values are expected in perfusion CT (PCT) while higher perfusion values are expected in recurrent malignant tissue.

OBJECTIVES

This prospective study investigates PCT for post-treatment recurrent HNC detection with a maximum slope algorithm.

METHODS

A total of 80 patients who received PCT of the head and neck for post-therapy follow-up, of which 63 had no tumor recurrence and 17 presented a histopathologically confirmed recurrence were examined. Regions of interest were placed in the location of the initial tumor, in reference ipsilateral nuchal muscle tissue and the corresponding internal carotid artery. Perfusion was calculated using a single-input maximum slope algorithm.

RESULTS

With PCT, recurrent HNC can be differentiated from post-treatment tissue (p < 0.05). It further allows delineating recurrent tumor tissue from benign nuchal tissue of reference (p < 0.05). PCT data of patients with and without recurrent HNC are comparable as perfusion values of reference tissues in patients with and without HNC do not differ (p > 0.05).

CONCLUSIONS

PCT in combination with a commercially available maximum slope algorithm offers radiologists a reliable imaging tool to detect recurrent head and neck cancer within post-therapeutically altered tissue.

Role of intravoxel incoherent motion parameters in gastroesophageal cancer: relationship with 18F-FDG-positron emission tomography, computed tomography perfusion and magnetic resonance perfusion imaging parameters

BACKGROUND

Identification of pretherapeutic predictive markers in gastro-esophageal cancer is essential for individual-oriented treatment. This study evaluated the relationship of multimodality parameters derived from intravoxel incoherent motion method (IVIM), 18F-FDG-positron emission tomography (PET), computed tomography (CT) perfusion and dynamic contrast enhanced magnetic resonance imaging (MRI) in patients with gastro-esophageal cancer and investigated their histopathological correlation.

METHODS

Thirty-one consecutive patients (28 males; median age 63.9 years; range 37-84 years) with gastro-esophageal adenocarcinoma (N.=22) and esophageal squamous cell carcinoma (N.=9) were analyzed. IVIM parameters: pseudodiffusion (D*), perfusion fraction (fp), true diffusion (D) and the threshold b-value (bval); PET-parameters: SUV<inf>max</inf>, metabolic tumor volume (MTV) and total lesion glycolysis (TLG); CT perfusion parameters: blood flow (BF), blood volume (BV) and mean transit time (MTT); and MR perfusion parameters: time to enhance, positive enhancement integral, time-to-peak (TTP), maximum-slope-of-increase, and maximum-slope-of-decrease were determined, and correlated to each other and to histopathology.

RESULTS

IVIM and PET parameters showed significant negative correlations: MTV and bval (r<inf>s</inf> =-0.643, P=0.002), TLG and bval (r<inf>s</inf>=-0.699, P<0.01) and TLG and fp (r<inf>s</inf>=-0.577, P=0.006). Positive correlation was found for TLG and D (r<inf>s</inf>=0.705, P=0.000). Negative correlation was found for bval and staging (r<inf>s</inf>=0.590, P=0.005). Positive correlation was found for positive enhancement interval and BV (r<inf>s</inf>=0.547, P=0.007), BF and regression index (r<inf>s</inf>=0.753, P=0.005) and for time-to-peak and staging (r<inf>s</inf>=0.557, P=0.005).

CONCLUSIONS

IVIM parameters (bval, fp, D) provide quantitative information and correlate with PET parameters (MTV, TLG) and staging. IVIM might be a useful tool for additional characterization of gastro-esophageal cancer.

Prognostic role of diffusion weighted and dynamic contrast-enhanced MRI in loco-regionally advanced head and neck cancer treated with concomitant chemoradiotherapy

Background In the study, the value of pre-treatment dynamic contrast-enhanced (DCE) and diffusion weighted (DW) MRI-derived parameters as well as their changes early during treatment was evaluated for predicting disease-free survival (DFS) and overall survival (OS) in patients with locoregionally advanced head and neck squamous carcinoma (HNSCC) treated with concomitant chemoradiotherapy (cCRT) with cisplatin. Patients and methods MRI scans were performed in 20 patients with locoregionally advanced HNSCC at baseline and after 10 Grays (Gy) of cCRT. Tumour apparent diffusion coefficient (ADC) and DCE parameters (volume transfer constant [Ktrans], extracellular extravascular volume fraction [ve], and plasma volume fraction [Vp]) were measured. Relative changes in parameters from baseline to 10 Gy were calculated. Univariate and multivariate Cox regression analysis were conducted. Receiver operating characteristic (ROC) curve analysis was employed to identify parameters with the best diagnostic performance. Results None of the parameters was identified to predict for DFS. On univariate analysis of OS, lower pre-treatment ADC (p = 0.012), higher pre-treatment Ktrans (p = 0.026), and higher reduction in Ktrans (p = 0.014) from baseline to 10 Gy were identified as significant predictors. Multivariate analysis identified only higher pre-treatment Ktrans (p = 0.026; 95% CI: 0.000-0.132) as an independent predictor of OS. At ROC curve analysis, pre-treatment Ktrans yielded an excellent diagnostic accuracy (area under curve [AUC] = 0.95, sensitivity 93.3%; specificity 80 %). Conclusions In our group of HNSCC patients treated with cisplatin-based cCRT, pre-treatment Ktrans was found to be a good predictor of OS.

Dual-energy computed tomography for prediction of loco-regional recurrence after radiotherapy in larynx and hypopharynx squamous cell carcinoma

PURPOSE

To investigate the role of quantitative pre-treatment dual-energy computed tomography (DECT) for prediction of loco-regional recurrence (LRR) in patients with larynx/hypopharynx squamous cell cancer (L/H SCC).

METHODS

Patients with L/H SCC treated with curative intent loco-regional radiotherapy and that underwent treatment planning with contrast-enhanced DECT of the neck were included. Primary and nodal gross tumor volumes (GTVp and GTVn) were contoured and transferred into a Matlab® workspace. Using a two-material decomposition, GTV iodine concentration (IC) maps were obtained. Quantitative histogram statistics (maximum, mean, standard deviation, kurtosis and skewness) were retrieved from the IC maps. Cox regression analysis was conducted to determine potential predictive factors of LRR.

RESULTS

Twenty-five patients, including 20 supraglottic and 5 pyriform sinus tumors were analysed. Stage I, II, III, IVa and IVb constituted 4% (1 patient), 24%, 36%, 28% and 8% of patients, respectively; 44% had concurrent chemo-radiotherapy and 28% had neodjuvant chemotherapy. Median follow-up was 21 months. Locoregional control at 1 and 2 years were 75% and 69%, respectively. For the entire cohort, GTVn volume (HR 1.177 [1.001-1.392], p = 0.05), voxel-based maximum IC of GTVp (HR 1.099 [95% CI: 1.001-1.209], p = 0.05) and IC standard deviation of GTVn (HR 9.300 [95% CI: 1.113-77.725] p = 0.04) were predictive of LRR. On subgroup analysis of patients treated with upfront radiotherapy +/- chemotherapy, both voxel-based maximum IC of GTVp (HR 1.127 [95% CI: 1.010-1.258], p = 0.05) and IC kurtosis of GTVp (HR 1.088 [95% CI: 1.014-1.166], p = 0.02) were predictive of LRR.

CONCLUSION

This exploratory study suggests that pre-radiotherapy DECT-derived IC quantitative analysis of tumoral volume may help predict LRR in L/H SCC.

Biologically adapted radiation therapy

The aim of biologically adapted radiotherapy (RT) is to shape or paint the prescribed radiation dose according to biological properties of the tumor in order to increase local control rates in the future. Human tumors are known to present with an extremely heterogeneous tissue architecture leading to highly variable local cell densities and chaotic vascular structures leading to tumor hypoxia and regions of increased radiation resistance. The goal of biologically adapted RT or dose painting is to individually adapt the radiation dose to biological features of the tumor as non-invasively assessed with functional imaging in order to overcome increased radiation resistance. This article discusses the whole development chain of biologically adapted RT from radio-biologically relevant processes, functional imaging techniques to visualize tumor biology non-invasively and radiation prescription functions to the implementation of biologically adapted RT in clinical practice.

Role of perfusion CT in the evaluation of functional primary tumour response after radiochemotherapy in head and neck cancer: preliminary findings

OBJECTIVE

To report the initial results of a prospective study aimed at evaluating the CT perfusion parameter changes (∆PCTp) of the primary tumour after radiochemotherapy (RCT) in head and neck cancer (HNC) and to correlate with positron emission tomography (PET)/CT response.

METHODS

Eligibility criteria included HNC (Stage III-IV) candidates for RCT. Patients underwent perfusion CT (PCT) at baseline and at 3 weeks and 3 months after treatment. Blood volume, blood flow, mean transit time (MTT) and permeability surface (PS) product were computed. Moreover, PET/CT was performed at baseline and 3 months after treatment. The ∆PCTp were evaluated between baseline and 3-week/3-month evaluations, whereas PET/CT response was based on the maximum standardized uptake value changes according to the European Organization for Research and Treatment of Cancer criteria.

RESULTS

Between July 2012 and July 2015, 25 patients were enrolled. A significant reduction of all CT tumour perfusion parameters (PCTp) was observed from the baseline to after RCT (p < 0.001). Specifically, a significant reduction was shown at 3 weeks for all PCTp except MTT (from 6.18 to 5.14 s; p = 0.722). Differently, a significant reduction of all PCTp (p < 0.001) including MTT (from 6.18 to 2.24 s; p = 0.001) was shown at 3 months. Moreover, the reduction of PS resulted in a significant prediction of PET/CT response at 3 months (p = 0.037) with the trend also at 3 weeks (p = 0.099) at the multivariate analysis.

CONCLUSION

Our preliminary findings seem to show that almost all PCTp are significantly reduced after RCT, whereas PS seems to come out as the strongest factor in predicting the PET/CT response.

ADVANCES IN KNOWLEDGE

This article provides information on the potential useful role of PCT in evaluating tumour response after both early and late RCT.