Differential 18F-FDG and 18F-FLT Uptake on Serial PET/CT Imaging Before and During Definitive Chemoradiation for Non–Small Cell Lung Cancer

Advances in the Imaging of Esophageal and Gastroesophageal Junction Malignancies

Accurate imaging is key for the diagnosis and treatment of esophageal and gastroesophageal junction cancers . Current imaging modalities, such as computed tomography (CT) and 18F-FDG (2-deoxy-2-[18F]fluoro-D-glucose) positron emission tomography (PET)/CT, have limitations in accurately staging these cancers. MRI shows promise for T staging and residual disease assessment. Novel PET tracers, like FAPI, FLT, and hypoxia markers, offer potential improvements in diagnostic accuracy. 18F-FDG PET/MRI combines metabolic and anatomic information, enhancing disease evaluation. Radiomics and artificial intelligence hold promise for early detection, treatment planning, and response assessment. Theranostic nanoparticles and personalized medicine approaches offer new avenues for cancer therapy.

Feasibility of omitting the clinical target volume under PET-CT guidance in unresectable stage III non-small-cell lung cancer: A phase II clinical trial

BACKGROUND

This clinical trial aims at investigate the feasibility of CTV-omitted, positron-emission tomography computed tomography (PET-CT) combined with intensity-modulated radiation therapy (IMRT) for unresectable stage III NSCLC.

METHODS AND MATERIALS

This was a single-center, phase II clinical trial initiated in July 2016. Patients with unresectable stage III NSCLC undergoing routine IMRT were randomly enrolled into the study group (CTV-omitted under PET-CT guidance) and the control group (CTV-delineated). Patients received platinum-based dual-drug concurrent chemoradio therapy. In the study group, the PGTV dose was 60 Gy given in 30 daily 2 Gy fractions; in the control group, the PCTV dose was 54 Gy given in 30 daily 1.8 Gy fractions, and the PGTV dose was 60 Gy given in 30 daily 2 Gy fractions. The primary endpoint was the incidence of radiation respiratory events or esophagitis with grade 3 or higher. The secondary endpoints included objective response rate (ORR), locate control rate, progression-free survival (PFS), failure pattern and overall survival (OS).

RESULTS

A total of 90 patients were enrolled between July 2016 and March 2019. The incidence of radiation respiratory events or esophagitis with grade 3 or higher was 11.1 % in the study group, significantly lower than the rate of 28.9 % in the control group (P = 0.035), basically due to the reduced irradiated volumes of the lungs and esophagus in the study group. The median PFS was 9.0 months versus 10.0 months (P = 0.597), and the median OS 31.0 months versus 26.0 months (P = 0.489) in the study group and the control group, respectively. The failure pattern was not significantly different between the two groups (P = 0.826).

CONCLUSION

Omitting the CTV under PET-CT guidance has high feasibility to reduce severe radiation associated toxicity in IMRT for unresectable stage III NSCLC, without compromising the efficacy.

An epithelial-to-mesenchymal transition induced extracellular vesicle prognostic signature in non-small cell lung cancer

Despite significant therapeutic advances, lung cancer remains the leading cause of cancer-related death worldwide¹. Non-small cell lung cancer (NSCLC) patients have a very poor overall five-year survival rate of only 10-20%. Currently, TNM staging is the gold standard for predicting overall survival and selecting optimal initial treatment options for NSCLC patients, including those with curable stages of disease. However, many patients with locoregionally-confined NSCLC relapse and die despite curative-intent interventions, indicating a need for intensified, individualised therapies. Epithelial-to-mesenchymal transition (EMT), the phenotypic depolarisation of epithelial cells to elongated, mesenchymal cells, is associated with metastatic and treatment-refractive cancer. We demonstrate here that EMT-induced protein changes in small extracellular vesicles are detectable in NSCLC patients and have prognostic significance. Overall, this work describes a novel prognostic biomarker signature that identifies potentially-curable NSCLC patients at risk of developing metastatic NSCLC, thereby enabling implementation of personalised treatment decisions.

Early Prediction of Radiotherapeutic Efficacy in a Mouse Model of Non-Small Cell Lung Carcinoma Using 18F-FLT and 18F-FDG PET/CT

This study investigated the usefulness of [18F]-3'-deoxy-3'-fluorothymidine (18F-FLT) and [18F]-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT) imaging for predicting the therapeutic efficacy of non-small cell lung cancer (NSCLC) irradiation at an early stage after radiation treatment. Mice were xenografted with the human lung adenocarcinoma line A549 or large cell lung cancer line FT821. Tumour uptake of 18F-FLT and 18F-FDG was imaged using PET/CT before and 1 week after irradiation. In A549 tumours, 18F-FLT uptake was significantly decreased, and 18F-FDG uptake was unchanged post-irradiation compared with pre-irradiation. In FT821 tumours, uptake of both 18F-FLT and 18F-FDG uptake was substantially decreased post-irradiation compared with pre-irradiation. In both xenografts, tumour volumes in the irradiated groups were significantly decreased compared with those in the control group. 18F-FLT is expected to contribute to individual NSCLC therapy because it accurately evaluates the decrease in tumour activity that cannot be captured by 18F-FDG. 18F-FDG may be useful for evaluating surviving cells without being affected by the inflammatory reaction at an extremely early stage, approximately 1 week after irradiation. Combined use of 18F-FLT and 18F-FDG PET/CT imaging may increase the accurate prediction of radiotherapy efficacy, which may lead to improved patient outcomes and minimally invasive personalised therapy. J. Med. Invest. 70 : 361-368, August, 2023.

Positron emission tomography imaging of lung cancer: An overview of alternative positron emission tomography tracers beyond F18 fluorodeoxyglucose

Lung cancer has been the leading cause of cancer-related mortality in China in recent decades. Positron emission tomography-computer tomography (PET/CT) has been established in the diagnosis of lung cancer. ¹⁸F-FDG is the most widely used PET tracer in foci diagnosis, tumor staging, treatment planning, and prognosis assessment by monitoring abnormally exuberant glucose metabolism in tumors. However, with the increasing knowledge on tumor heterogeneity and biological characteristics in lung cancer, a variety of novel radiotracers beyond ¹⁸F-FDG for PET imaging have been developed. For example, PET tracers that target cellular proliferation, amino acid metabolism and transportation, tumor hypoxia, angiogenesis, pulmonary NETs and other targets, such as tyrosine kinases and cancer-associated fibroblasts, have been reported, evaluated in animal models or under clinical investigations in recent years and play increasing roles in lung cancer diagnosis. Thus, we perform a comprehensive literature review of the radiopharmaceuticals and recent progress in PET tracers for the study of lung cancer biological characteristics beyond glucose metabolism.

PD1 blockade alters cell-cycle distribution and affects 3'-deoxy-3'-[18F]fluorothymidine uptake in a mouse CT26 tumor model

OBJECTIVE

We previously reported that alterations of the tumor microenvironment (TME) by programmed death receptor-1 (PD1) blockade affected tumor glucose metabolism and tumor 2-deoxy-2-[¹⁸F]fluoro-D-glucose ([¹⁸F]FDG) uptake. In cancer cells, high glycolysis allows cells to sustain rapid proliferation since glycolysis is closely related to the proliferation of cancer cells. Therefore, imaging of cellular proliferation may provide more detail of TME alterations. In this study, we investigated how TME alterations by PD1 blockade affects the uptake of 3'-deoxy-3'-[¹⁸F]fluorothymidine ([¹⁸F]FLT), which is a ¹⁸F-radiolabeled thymidine derivative and is taken up by proliferating cells.

METHODS

Mice inoculated with murine colon carcinoma CT26 cells were intraperitoneally administered an anti-PD1 antibody on Day 0, when the tumor volume exceeded 50 mm³, and Day 5. [¹⁸F]FLT-PET imaging was performed pre-treatment (Day 0) and post treatment (Day 7). Tumor infiltrating lymphocytes (TILs) were identified by flow cytometry. [¹⁸F]FLT accumulation and localization in tumor tissue was evaluated by autoradiography and immunohistochemistry. The cell-cycle distribution of tumors and CT26 cells exposed to cytokines (interleukin-2, interferon [INF]-γ, and tumor necrosis factor [TNF]-α) was analyzed by flow cytometry.

RESULTS

PD1 blockade increased CD8⁺ and CD4⁺ T cells in tumor tissue and significantly suppressed tumor proliferation; however, tumor [¹⁸F]FLT uptake remained unchanged. Autoradiography and immunohistochemistry showed that [¹⁸F]FLT was mainly taken up by cancer cells, but not TILs. Flow cytometric analysis demonstrated that the population of cells in G2/M phase increased after PD1 blockade. Moreover, INF-γ and TNF-α significantly increased cells in G2/M phase in vitro.

CONCLUSION

PD1 blockade-induced alteration of the TME increased CT26 tumor cells in the G2/M phase, which have high thymidine kinase 1 activity. Therefore, [¹⁸F]FLT is taken up by tumor cells even if tumor proliferation is suppressed. This observation may be useful for evaluating the response to immunotherapy.

New PET Tracers: Current Knowledge and Perspectives in Lung Cancer

PET/CT with the tracer 2-[¹⁸F]fluoro-2-deoxy-D-glucose ([¹⁸F]FDG) has improved diagnostic imaging in cancer and is routinely used for diagnosing, staging and treatment planning in lung cancer patients. However, pitfalls of [¹⁸F]FDG-PET/CT limit the use in specific settings. Additionally, lung cancer is still the leading cause of cancer associated death and has high risk of recurrence after curative treatment. These circumstances have led to the continuous search for more sensitive and specific PET tracers to optimize lung cancer diagnosis, staging, treatment planning and evaluation. The objective of this review is to present and discuss current knowledge and perspectives of new PET tracers for use in lung cancer. A literature search was performed on PubMed and clinicaltrials.gov, limited to the past decade, excluding case reports, preclinical studies and studies on established tracers such as [¹⁸F]FDG and DOTATE. The most relevant papers from the search were evaluated. Several tracers have been developed targeting specific tumor characteristics and hallmarks of cancer. A small number of tracers have been studied extensively and evaluated head-to-head with [¹⁸F]FDG-PET/CT, whereas others need further investigation and validation in larger clinical trials. At this moment, none of the tracers can replace [¹⁸F]FDG-PET/CT. However, they might serve as supplementary imaging methods to provide more knowledge about biological tumor characteristics and visualize intra- and inter-tumoral heterogeneity.

Multimodal Imaging-Based Potential Visualization of the Tumor Microenvironment in Bone Metastasis

Bone metastasis (BM) is the most common malignant bone tumor and a significant cause of morbidity and mortality for patients with cancer. Compared to other metastatic organs, bone has unique characteristics in terms of the tumor microenvironment (TME). Precise assessments of the TME in BM could be an important step for developing an optimized management plan for patient care. Imaging approaches for BM have several advantages, such as biopsy not being required, multiple site evaluation, and serial assessment in the same sites. Owing to the developments of new imaging tracers or imaging modalities, bone TME could be visualized using multimodal imaging techniques. In this review, we describe the BM pathophysiology, diagnostic principles of major imaging modalities, and clinically available imaging modalities to visualize the TME in BM. We also discuss how the interactions between various factors affecting the TME could be visualized using multimodal imaging techniques.

Predictive value of 3'-deoxy-3'-18F-fluorothymidine PET in the early response to anti-programmed death-1 therapy in patients with advanced non-small cell lung cancer

Background

Anti-programmed death-1 (anti-PD-1) therapy has shown clinical success in patients with advanced non-small cell lung cancer (NSCLC). However, it is difficult to evaluate the early response to anti-PD-1 therapy. We determined whether changes in 3′-deoxy-3′-[¹⁸F]-fluorothymidine (¹⁸F-FLT) PET parameters before and soon after treatment initiation predicted the therapeutic effect of anti-PD-1 antibody.

Methods

Twenty-six patients with advanced NSCLC treated with anti-PD-1 antibody were enrolled prospectively and underwent ¹⁸F-FLT PET before and at 2 and 6 weeks after treatment initiation. Changes in maximal standardized uptake value (ΔSUV_max), proliferative tumor volume (ΔPTV) and total lesion proliferation (ΔTLP) of the lesions were calculated and evaluated for their associations with the clinical response to therapy.

Results

The disease control rate was 64%. Patients with non-progressive disease (non-PD) had significantly decreased TLP at 2 weeks, and decreased SUV_max, PTV, and TLP at 6 weeks, compared with those with PD, while three of eight (37.5%) patients who responded had increased TLP from baseline at 2 weeks (ie, pseudoprogression). Among the parameters that changed between baseline and 2 weeks, ΔPTV0-2 and ΔTLP0-2 had the highest accuracy (76.0%) to predict PD. Among the parameters that changed between baseline and 6 weeks, ΔSUV_max0-6, ΔPTV0-6 and ΔTLP0-6 had the highest accuracy (90.9%) to predict PD. ΔTLP0-2 (≥60%, HR 3.41, 95% CI 1.34–8.65, p=0.010) and ΔTLP0-6 (≥50%, HR 31.4, 95% CI 3.55 to 276.7, p=0.0019) were indicators of shorter progression-free survival.

Conclusions

Changes in ¹⁸F-FLT PET parameters may have value as an early predictive biomarker for the response to anti-PD-1 therapy in patients with NSCLC. However, it should be noted that pseudoprogression was observed in ¹⁸F-FLT PET imaging at 2 weeks after treatment initiation.

Trial registration number

jRCTs051180147.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Value of PET imaging for radiation therapy

This comprehensive review written by experts in their field gives an overview on the current status of incorporating positron emission tomography (PET) into radiation treatment planning. Moreover, it highlights ongoing studies for treatment individualisation and per-treatment tumour response monitoring for various primary tumours. Novel tracers and image analysis methods are discussed. The authors believe this contribution to be of crucial value for experts in the field as well as for policy makers deciding on the reimbursement of this powerful imaging modality.

Clinical value of 3'-deoxy-3'-[18F]fluorothymidine-positron emission tomography for diagnosis, staging and assessing therapy response in lung cancer

Lung cancer has the highest mortality rate of any tumour type. The main driver of lung tumour growth and development is uncontrolled cellular proliferation. Poor patient outcomes are partly the result of the limited range of effective anti-cancer therapies available and partly due to the limited accuracy of biomarkers to report on cell proliferation rates in patients. Accordingly, accurate methods of diagnosing, staging and assessing response to therapy are crucial to improve patient outcomes. One effective way of assessing cell proliferation is to employ non-invasive evaluation using 3'-deoxy-3'-[¹⁸F]fluorothymidine ([¹⁸F]FLT) positron emission tomography [¹⁸F]FLT-PET. [¹⁸F]FLT, unlike the most commonly used PET tracer [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG), can specifically report on cell proliferation and does not accumulate in inflammatory cells. Therefore, this radiotracer could exhibit higher specificity in diagnosis and staging, along with more accurate monitoring of therapy response at early stages in the treatment cycle. This review summarises and evaluates published studies on the clinical use of [¹⁸F]FLT to diagnose, stage and assess response to therapy in lung cancer.

18F-FLT PET/CT Adds Value to 18F-FDG PET/CT for Diagnosing Relapse After Definitive Radiotherapy in Patients with Lung Cancer: Results of a Prospective Clinical Trial

Diagnosing relapse after radiotherapy for lung cancer is challenging. The specificity of both CT and ¹⁸F-FDG PET/CT is low because of radiation-induced changes. 3'-deoxy-3'-¹⁸F-fluorothymidine (¹⁸F-FLT) PET has previously demonstrated higher specificity for malignancy than ¹⁸F-FDG PET. We investigated the value of ¹⁸F-FLT PET/CT for diagnosing relapse in irradiated lung cancer. Methods: Patients suspected of relapse of lung cancer after definitive radiotherapy (conventional fractionated radiotherapy [cRT] or stereotactic body radiotherapy [SBRT]) were included. Sensitivity and specificity were analyzed both within the irradiated high-dose volume (HDV) and on a patient basis. Marginal differences and interobserver agreement were assessed. Results: Sixty-three patients who had received radiotherapy in 70 HDVs (34 cRT; 36 SBRT) were included. The specificity of ¹⁸F-FLT PET/CT was higher than that of ¹⁸F-FDG PET/CT (HDV, 96% [95% CI, 87-100] vs. 71% [95% CI, 57-83] [P = 0.0039]; patient-based, 90% [95% CI, 73-98] vs. 55% [95% CI, 36-74] [P = 0.0020]). The difference in specificity between ¹⁸F-FLT PET/CT and ¹⁸F-FDG PET/CT was higher after cRT than after SBRT. The sensitivity of ¹⁸F-FLT PET/CT was lower than that of ¹⁸F-FDG PET/CT (HDV, 69% [95% CI, 41-89] vs. 94% [95% CI, 70-100] [P = 0.1250]; patient-based, 70% [95% CI, 51-84] vs. 94% [95% CI, 80-99] [P = 0.0078]). Adding ¹⁸F-FLT PET/CT when ¹⁸F-FDG PET/CT was positive or inconclusive improved the diagnostic value compared with ¹⁸F-FDG PET/CT alone. In cRT HDVs, the probability of malignancy increased from 67% for ¹⁸F-FDG PET/CT alone to 100% when both tracers were positive. Conclusion: ¹⁸F-FLT PET/CT adds diagnostic value to ¹⁸F-FDG PET/CT in patients with suspected relapse. The diagnostic impact of ¹⁸F-FLT PET/CT was highest after cRT. We suggest adding ¹⁸F-FLT PET/CT when ¹⁸F-FDG PET/CT is inconclusive or positive within the previously irradiated volume to improve diagnostic value in patients for whom histologic confirmation is not easily obtained.

Evolving target volume concepts in locally advanced non-small cell lung cancer

Radiotherapy (RT) target volume concepts for locally advanced lung cancer have been under discussion for years. Although they may be as important as treatment doses, many aspects of them are still based on conventions, which, due to the paucity of prospective data, rely on long-term practice or on clinical knowledge and experience (e.g., on patterns of spread or recurrence). However, in recent years, large improvements have been made in medical imaging and molecular imaging methods have been implemented, which are of great interest in RT. For lung cancer, in recent years, 18F-fluoro-desoxy-glucose (FDG)-positron-emission tomography (PET)/computed tomography (CT) has shown a superior diagnostic accuracy as compare to conventional imaging and has become an indispensable standard tool for diagnostic workup, staging and response assessment. This offers the chance to optimize target volume concepts in relation to modern imaging. While actual recommendations as the EORTC or ESTRO-ACROP guidelines already include imaging standards, the recently published PET-Plan trial prospectively investigated conventional versus imaging guided target volumes in relation to patient outcome. The results of this trial may help to further refine standards. The current review gives a practical overview on procedures for pre-treatment imaging and target volume delineation in locally advanced non-small cell lung cancer (NSCLC) in synopsis of the procedures established by the PET-Plan trial with the actual EORTC and ACROP guidelines.

Imaging Beyond Seeing: Early Prognosis of Cancer Treatment

Assessing cancer response to therapeutic interventions has been realized as an important course to early predict curative efficacy and treatment outcomes due to tumor heterogeneity. Compared to the traditional invasive tissue biopsy method, molecular imaging techniques have fundamentally revolutionized the ability to evaluate cancer response in a spatiotemporal manner. The past few years has witnessed a paradigm shift on the efforts from manufacturing functional molecular imaging probes for seeing a tumor to a vantage stage of interpreting the tumor response during different treatments. This review is to stand by the current development of advanced imaging technologies aiming to predict the treatment response in cancer therapy. Special interest is placed on the systems that are able to provide rapid and noninvasive assessment of pharmacokinetic drug fates (e.g., drug distribution, release, and activation) and tumor microenvironment heterogeneity (e.g., tumor cells, macrophages, dendritic cells (DCs), T cells, and inflammatory cells). The current status, practical significance, and future challenges of the emerging artificial intelligence (AI) technology and machine learning in the applications of medical imaging fields is overviewed. Ultimately, the authors hope that this review is timely to spur research interest in molecular imaging and precision medicine.

Impact of [18F]FDG-PET and [18F]FLT-PET-Parameters in Patients with Suspected Relapse of Irradiated Lung Cancer

Radiation-induced changes may cause a non-malignant high 2-deoxy-2-[¹⁸F]fluoro-d-glucose (FDG)-uptake. The 3′-deoxy-3′-[¹⁸F]fluorothymidine (FLT)-PET/CT performs better in the differential diagnosis of inflammatory changes and lung lesions with a higher specificity than FDG-PET/CT. We investigated the association between post-radiotherapy FDG-PET-parameters, FLT-PET-parameters, and outcome. Sixty-one patients suspected for having a relapse after definitive radiotherapy for lung cancer were included. All the patients had FDG-PET/CT and FLT-PET/CT. FDG-PET- and FLT-PET-parameters were collected from within the irradiated high-dose volume (HDV) and from recurrent pulmonary lesions. For associations between PET-parameters and relapse status, respectively, the overall survival was analyzed. Thirty patients had a relapse, of these, 16 patients had a relapse within the HDV. FDG-SUV_max and FLT-SUV_max were higher in relapsed HDVs compared with non-relapsed HDVs (median FDG-SUV_max: 12.8 vs. 4.2; p < 0.001; median FLT-SUV_max 3.9 vs. 2.2; p < 0.001). A relapse within HDV had higher FDG-SUV_peak (median FDG-SUV_peak: 7.1 vs. 3.5; p = 0.014) and was larger (median metabolic tumor volume (MTV_50%): 2.5 vs. 0.7; 0.014) than the relapsed lesions outside of HDV. The proliferative tumor volume (PTV_50%) was prognostic for the overall survival (hazard ratio: 1.07 pr cm³ [1.01–1.13]; p = 0.014) in the univariate analysis, but not in the multivariate analysis. FDG-SUV_max and FLT-SUV_max may be helpful tools for differentiating the relapse from radiation-induced changes, however, they should not be used definitively for relapse detection.

Precision radiotherapy for non-small cell lung cancer

Precision medicine is becoming the standard of care in anti-cancer treatment. The personalized precision management of cancer patients highly relies on the improvement of new technology in next generation sequencing and high-throughput big data processing for biological and radiographic information.

Systemic precision cancer therapy has been developed for years. However, the role of precision medicine in radiotherapy has not yet been fully implemented. Emerging evidence has shown that precision radiotherapy for cancer patients is possible with recent advances in new radiotherapy technologies, panomics, radiomics and dosiomics.

This review focused on the role of precision radiotherapy in non-small cell lung cancer and demonstrated the current landscape.

18F-fluorothymidine (FLT)-PET and diffusion-weighted MRI for early response evaluation in patients with small cell lung cancer: a pilot study

Background

Small cell lung cancer (SCLC) is an aggressive cancer often presenting in an advanced stage and prognosis is poor. Early response evaluation may have impact on the treatment strategy.

Aim

We evaluated ¹⁸F-fluorothymidine-(FLT)-PET/diffusion-weighted-(DW)-MRI early after treatment start to describe biological changes during therapy, the potential of early response evaluation, and the added value of FLT-PET/DW-MRI.

Methods

Patients with SCLC referred for standard chemotherapy were eligible. FLT-PET/DW-MRI of the chest and brain was acquired within 14 days after treatment start. FLT-PET/DW-MRI was compared with pretreatment FDG-PET/CT. Standardized uptake value (SUV), apparent diffusion coefficient (ADC), and functional tumor volumes were measured. FDG-SUV_peak, FLT-SUV_peak, and ADC_median; spatial distribution of aggressive areas; and voxel-by-voxel analyses were evaluated to compare the biological information derived from the three functional imaging modalities. FDG-SUV_peak, FLT-SUV_peak, and ADC_median were also analyzed for ability to predict final treatment response.

Results

Twelve patients with SCLC completed FLT-PET/MRI 1–9 days after treatment start. In nine patients, pretreatment FDG-PET/CT was available for comparison. A total of 16 T-sites and 12 N-sites were identified. No brain metastases were detected. FDG-SUV_peak was 2.0–22.7 in T-sites and 5.5–17.3 in N-sites. FLT-SUV_peak was 0.6–11.5 in T-sites and 1.2–2.4 in N-sites. ADC_median was 0.76–1.74 × 10^− 3 mm²/s in T-sites and 0.88–2.09 × 10⁻³ mm²/s in N-sites. FLT-SUV_peak correlated with FDG-SUV_peak, and voxel-by-voxel correlation was positive, though the hottest regions were dissimilarly distributed in FLT-PET compared to FDG-PET. FLT-SUV_peak was not correlated with ADC_median, and voxel-by-voxel analyses and spatial distribution of aggressive areas varied with no systematic relation. LT-SUV_peak was significantly lower in responding lesions than non-responding lesions (mean FLT-SUV_peak in T-sites: 1.5 vs. 5.7; p = 0.007, mean FLT-SUV_peak in N-sites: 1.6 vs. 2.2; p = 0.013).

Conclusions

FLT-PET and DW-MRI performed early after treatment start may add biological information in patients with SCLC. Proliferation early after treatment start measured by FLT-PET is a promising predictor for final treatment response that warrants further investigation.

Trial registration

Clinicaltrials.gov, NCT02995902. Registered 11 December 2014 - Retrospectively registered.

Early Response Assessment to Targeted Therapy Using 3'-deoxy-3'[(18)F]-Fluorothymidine (18F-FLT) PET/CT in Lung Cancer

Although 2-deoxy-2-[18F]-fluoro-D-glucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) is a sensitive nuclear medicine modality, specificity for characterizing lung cancer is limited. Tumor proliferation and early response to molecularly targeted therapy could be visualized using 3′-deoxy-3′[(18)F]-fluorothymidine (¹⁸F-FLT) PET/CT. The superiority of ¹⁸F-FLT PET/CT over ¹⁸F-FDG PET/CT in early therapeutic monitoring has been well described in patients after chemotherapy, radiotherapy, and/or chemo/radiotherapy. In thispilot study, we explorethe use of ¹⁸F-FLT PET/CT as an early response evaluation modality in patients with lung cancerand provide specific case studies of patients with small cell lung cancer and non-small cell lung cancer who received novel targeted therapies. Early response for c-MET inhibitor was observed in four weeks and for MDM2 inhibitor in nine days.

Alternative and New Radiopharmaceutical Agents for Lung Cancer

BACKGROUND

FDG PET/CT imaging has an established role in lung cancer (LC) management. Whilst it is a sensitive technique, FDG PET/CT has a limited specificity in the differentiation between LC and benign conditions and is not capable of defining LC heterogeneity since FDG uptake varies between histotypes.

OBJECTIVE

To get an overview of new radiopharmaceuticals for the study of cancer biology features beyond glucose metabolism in LC.

METHODS

A comprehensive literature review of PubMed/Medline was performed using a combination of the following keywords: "positron emission tomography", "lung neoplasms", "non-FDG", "radiopharmaceuticals", "tracers".

RESULTS

Evidences suggest that proliferation markers, such as 18F-Fluorothymidine and 11CMethionine, improve LC staging and are useful in evaluating treatment response and progression free survival. 68Ga-DOTA-peptides are already routinely used in pulmonary neuroendocrine neoplasms (NENs) management and should be firstly performed in suspected NENs. 18F-Fluoromisonidazole and other radiopharmaceuticals show a promising impact on staging, prognosis assessment and therapy response in LC patients, by visualizing hypoxia and perfusion. Radiolabeled RGD-peptides, targeting angiogenesis, may have a role in LC staging, treatment outcome and therapy. PET radiopharmaceuticals tracing a specific oncogene/signal pathway, such as EGFR or ALK, are gaining interest especially for therapeutic implications. Other PET tracers, like 68Ga-PSMA-peptides or radiolabeled FAPIs, need more development in LC, though, they are promising for therapy purposes.

CONCLUSION

To date, the employment of most of the described tracers is limited to the experimental field, however, research development may offer innovative opportunities to improve LC staging, characterization, stratification and response assessment in an era of increased personalized therapy.

Measurement Variability in Treatment Response Determination for Non-Small Cell Lung Cancer: Improvements Using Radiomics

Multimodality imaging measurements of treatment response are critical for clinical practice, oncology trials, and the evaluation of new treatment modalities. The current standard for determining treatment response in non-small cell lung cancer (NSCLC) is based on tumor size using the RECIST criteria. Molecular targeted agents and immunotherapies often cause morphological change without reduction of tumor size. Therefore, it is difficult to evaluate therapeutic response by conventional methods. Radiomics is the study of cancer imaging features that are extracted using machine learning and other semantic features. This method can provide comprehensive information on tumor phenotypes and can be used to assess therapeutic response in this new age of immunotherapy. Delta radiomics, which evaluates the longitudinal changes in radiomics features, shows potential in gauging treatment response in NSCLC. It is well known that quantitative measurement methods may be subject to substantial variability due to differences in technical factors and require standardization. In this review, we describe measurement variability in the evaluation of NSCLC and the emerging role of radiomics.

PET/CT in radiation oncology

The progressive integration of positron emission tomography/computed tomography (PET/CT) imaging in radiation therapy has its rationale in the biological intertumoral and intratumoral heterogeneity of malignant lesions that require the individual adjustment of radiation dose to obtain an effective local tumor control in cancer patients. PET/CT provides information on the biological features of tumor lesions such as metabolism, hypoxia, and proliferation that can identify radioresistant regions and be exploited to optimize treatment plans. Here, we provide an overview of the basic principles of PET-based target volume selection and definition using ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) and then we focus on the emerging strategies of dose painting and adaptive radiotherapy using different tracers. Previous studies provided consistent evidence that integration of ¹⁸F-FDG PET/CT in radiotherapy planning improves delineation of target volumes and reduces the uncertainties and variabilities of anatomical delineation of tumor sites. PET-based dose painting and adaptive radiotherapy are feasible strategies although their clinical implementation is highly demanding and requires strong technical, computational, and logistic efforts. Further prospective clinical trials evaluating local tumor control, survival, and toxicity of these emerging strategies will promote the full integration of PET/CT in radiation oncology.

Molecular imaging of bone metastases using tumor-targeted tracers

Bone metastasis is a disastrous manifestation of most malignancies, especially in breast, prostate and lung cancers. Since asymptomatic bone metastases are not uncommon, early detection, precise assessment, and localization of them are very important. Various imaging modalities have been employed in the setting of diagnosis of bone metastasis, from plain radiography and bone scintigraphy to SPECT, SPECT/CT, PET/CT, MRI. However, each modality showed its own limitation providing accurate diagnostic performance. In this regard, various tumor-targeted radiotracers have been introduced for molecular imaging of bone metastases using modern hybrid modalities. In this article we review the strength of different cancer-specific radiopharmaceuticals in the detection of bone metastases. As shown in the literature, among various tumor-targeted tracers, 68Ga DOTA-conjugated-peptides, 68Ga PSMA, 18F DOPA, 18F galacto-RGD integrin, 18F FDG, 11C/18F acetate, 11C/18F choline, 111In octreotide, 123/131I MIBG, 99mTc MIBI, and 201Tl have acceptable capabilities in detecting bone metastases depending on the cancer type. However, different study designs and gold standards among reviewed articles should be taken into consideration.

FLT-PET-CT for the Detection of Disease Recurrence After Stereotactic Ablative Radiotherapy or Hyperfractionation for Thoracic Malignancy: A Prospective Pilot Study

Differentiating local recurrence from post-treatment changes on PET scans following stereotactic ablative radiotherapy (SABR) or hyperfractionation for lung tumors is challenging. We performed a prospective pilot study of 3-deoxy-3-[¹⁸F]-fluorothymidine (FLT)-PET-CT in patients with equivocal post-radiation FDG-PET-CT to assess disease recurrence.

Methods: We prospectively enrolled 10 patients, 9 treated with SABR and 1 with hyperfractionated external beam radiotherapy for thoracic malignancy with subsequent equivocal follow-up FDG-PET-CT, to undergo FLT-PET-CT prior to biopsy or serial imaging. FLT-PET scans were interpreted by a radiologist with experience in reading FLT-PET-CT and blinded to the results of any subsequent biopsy or imaging.

Results: Of the 10 patients enrolled, 8 were evaluable after FLT-PET-CT. Based on the FLT-PET-CT, a blinded radiologist accurately predicted disease recurrence vs. inflammatory changes in 7 patients (87.5%). The combination of higher lesion SUV_max and higher ratio of lesion SUV_max to SUV_max of mediastinal blood pool was indicative of recurrence. Qualitative assessment of increased degree of focality of the lesion also appears to be indicative of disease recurrence.

Conclusion: Adjunctive FLT-PET-CT imaging can complement FDG-PET-CT scan in distinguishing post-treatment radiation changes from disease recurrence in thoracic malignancies. These findings support the investigation of FLT-PET-CT in a larger prospective study.

[Application of Metabolic Parameters Measured by ¹⁸F-FDG PET/CT in the Evaluation of the Prognosis of Non-small Cell Lung Cancer]

基于肺癌肿瘤-淋巴结-转移（tumor-node-metastasis, TNM）分期的治疗方案制定和预后评价是目前国内外肺癌指南中的基本原则。18氟代脱氧葡萄糖正电子发射计算机断层显像（¹⁸F-deoxyglucose positron emission tomography/computed tomography, ¹⁸F-FDG PET/CT）代谢参数如标准摄取值（standardized uptake value, SUV）、肿瘤代谢体积（metabolic tumor volume, MTV）、病灶糖酵解总量（total lesion glycolysis, TLG）可以反映肿瘤侵袭性的信息，提供额外的预后信息。将量化的肿瘤代谢负荷MTV、TLG联合传统的TNM分期对患者进行危险分层，作为一种新的分期方式可以辅助临床医师制定更为合适的治疗方案。¹⁸F-FDG PET/CT图像纹理分析作为一种新兴研究方法，可以量化肿瘤内放射性摄取的空间分布异质性，进而了解肿瘤的生物学特征。本文对¹⁸F-FDG PET/CT代谢参数在非小细胞肺癌患者预后评估的应用进行阐述。

18F-FDG and 11C-4DST PET/CT for evaluating response to platinum-based doublet chemotherapy in advanced non-small cell lung cancer: a prospective study

Background

4′-[Methyl-¹¹C] thiothymidine (4DST) PET/CT provides DNA synthesis imaging, which represented a higher correlation with the proliferation in advanced non-small cell lung cancer (NSCLC) than that from imaging with FDG. The aim of this prospective study was to evaluate the potential of 4DST in early therapy monitoring for advanced NSCLC, and to compare the results with those from CT and FDG PET/CT.

Results

Patients who had been pathologically diagnosed with advanced NSCLC and were scheduled to receive platinum-doublet chemotherapy (PT-DC) were eligible. PET/CT imaging with 4DST and with FDG, and CT were performed at baseline and after 2 cycles of PT-DC (interim). Patients were evaluated semi-quantitatively after the 2 cycles of PT-DC using several PET parameters, response evaluation criteria in solid tumors (RECIST) 1.1 based on CT measurements, European Organization for Research and Treatment of Cancer (EORTC) criteria and PET Response Criteria in Solid Tumors (PERCIST) 1.0 based on PET/CT measurements. Baseline measurement data and metabolic response were compared between patients with progression-free survival (PFS) > 4 months and ≤ 4 months, and PFS and overall survival (OS) were compared between patients with and without metabolic response measured with each of the different parameters, using Kaplan-Meier statistics and log-rank testing. A total of 22 patients were included in this study. For predicting PFS > 4 months and ≤ 4 months, metabolic tumor volume (MTV) of baseline 4DST showed the highest area under the curve (0.73), positive predictive value (80.0%), negative predictive value (66.7%), and accuracy (72.7%) among baseline measurement data and metabolic responses from 4DST PET/CT, FDG PET/CT, and CT. Kaplan-Meier curves and log-rank tests for PFS with MTV of baseline FDG and baseline 4DST, and for OS with MTV of baseline FDG and baseline TLG, and MTV of baseline 4DST revealed significant results.

Conclusions

MTV of baseline 4DST PET/CT along with MTV of baseline FDG PET/CT represent promising predictors of PFS, and MTV of baseline 4DST PET/CT along with MTV and TLG of baseline FDG PET/CT are possible predictors of OS in patients with advanced NSCLC.

Noninvasive evaluation of 18F-FDG/18F-FMISO-based Micro PET in monitoring hepatic metastasis of colorectal cancer

This study aimed to explore the application of two radiotracers (¹⁸F-fluorodeoxyglucose (FDG) and ¹⁸F-fluoromisonidazole (FMISO)) in monitoring hepatic metastases of human colorectal cancer (CRC). Mouse models of CRC hepatic metastases were established by implantation of the human CRC cell lines LoVo and HT29 by intrasplenic injection. Wound healing and Transwell assays were performed to examine cell migration and invasion abilities. Radiotracer-based cellular uptake in vitro and micro-positron emission tomography imaging of liver metastases in vivo were performed. The incidence of liver metastases in LoVo-xenografted mice was significantly higher than that in HT29-xenografted ones. The SUVmax/mean values of ¹⁸F-FMISO, but not ¹⁸F-FDG, in LoVo xenografts were significantly greater than in HT29 xenografts. In vitro, LoVo cells exhibited stronger metastatic potential and higher radiotracer uptake than HT29 cells. Mechanistically, the expression of HIF-1α and GLUT-1 in LoVo cells and LoVo tumor tissues was remarkably higher than in HT29 cells and tissues. Linear regression analysis demonstrated correlations between cellular ¹⁸F-FDG/¹⁸F-FMISO uptake and HIF-1α/GLUT-1 expression in vitro, as well as between ¹⁸F-FMISO SUVmax and GLUT-1 expression in vivo. ¹⁸F-FMISO uptake may serve as a potential biomarker for the detection of liver metastases in CRC, whereas its clinical use warrants validation.

The developing role of FDG PET imaging for prognostication and radiotherapy target volume delineation in non-small cell lung cancer

Advancements in functional imaging technology have allowed new possibilities in contouring of target volumes, monitoring therapy, and predicting treatment outcome in non-small cell lung cancer (NSCLC). Consequently, the role of ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG PET) has expanded in the last decades from a stand-alone diagnostic tool to a versatile instrument integrated with computed tomography (CT), with a prominent role in lung cancer radiotherapy. This review outlines the most recent literature on developments in FDG PET imaging for prognostication and radiotherapy target volume delineation (TVD) in NSCLC. We also describe the challenges facing the clinical implementation of these developments and present new ideas for future research.

Image-guided adaptive radiotherapy in patients with locally advanced non-small cell lung cancer: the art of PET

With a worldwide annual incidence of 1.8 million cases, lung cancer is the most diagnosed form of cancer in men and the third most diagnosed form of cancer in women. Histologically, 80-85% of all lung cancers can be categorized as non-small cell lung cancer (NSCLC). For patients with locally advanced NSCLC, standard of care is fractionated radiotherapy combined with chemotherapy. With the aim of improving clinical outcome of patients with locally advanced NSCLC, combined and intensified treatment approaches are increasingly being used. However, given the heterogeneity of this patient group with respect to tumor biology and subsequent treatment response, a personalized treatment approach is required to optimize therapeutic effect and minimize treatment induced toxicity. Medical imaging, in particular positron emission tomography (PET), before and during the course radiotherapy is increasingly being used to personalize radiotherapy. In this setting, PET imaging can be used to improve delineation of target volumes, employ molecularly-guided dose painting strategies, early response monitoring, prediction and monitoring of treatment-related toxicity. The concept of PET image-guided adaptive radiotherapy (IGART) is an interesting approach to personalize radiotherapy for patients with locally advanced NSCLC, which might ultimately contribute to improved clinical outcomes and reductions in frequency of treatment-related adverse events in this patient group. In this review, we provide a comprehensive overview of available clinical data supporting the use of PET imaging for IGART in patients with locally advanced NSCLC.

Positron emission tomography/magnetic resonance imaging (PET/MRI): An update and initial experience at HC-FMUSP

The new technology of PET/MRI is a prototype of hybrid imaging, allowing for the combination of molecular data from PET scanning and morphofunctional information derived from MRI scanning. Recent advances regarding the technical aspects of this device, especially after the development of MRI-compatible silicon photomultipliers of PET, permitted an increase in the diagnostic performance of PET/MRI translated into dose reduction and higher imaging quality. Among several clinical applications, PET/MRI gains ground initially in oncology, where MRI per se plays an essential role in the assessment of primary tumors (which is limited in the case of PET/CT), including prostate, rectal and gynecological tumors. On the other hand, the evaluation of the lungs remains an enigma although new MRI sequences are being designed to overcome this. More clinical indications of PET/MRI are seen in the fields of neurology, cardiology and inflammatory processes, and the use of PET/MRI also opens perspectives for pediatric populations as it involves very low radiation exposure. Our review aimed to highlight the current indications of PET/MRI and discuss the challenges and perspectives of PET/MRI at HC-FMUSP.

ESTRO ACROP guidelines for target volume definition in the treatment of locally advanced non-small cell lung cancer

Radiotherapy (RT) plays a major role in the curative treatment of locally advanced non-small cell lung cancer (NSCLC). Therefore, the ACROP committee was asked by the ESTRO to provide recommendations on target volume delineation for standard clinical scenarios in definitive (chemo)radiotherapy (RT) and adjuvant RT for locally advanced NSCLC. The guidelines given here are a result of the evaluation of a structured questionnaire followed by a consensus discussion, voting and writing procedure within the committee. Hence, we provide advice for methods and time-points of diagnostics and imaging before the start of treatment planning and for the mandatory and optional imaging to be used for planning itself. Concerning target volumes, recommendations are given for GTV delineation of primary tumour and lymph nodes followed by issues related to the delineation of CTVs for definitive and adjuvant radiotherapy. In the context of PTV delineation, recommendations about the management of geometric uncertainties and target motion are given. We further provide our opinions on normal tissue delineation and organisational and responsibility questions in the process of target volume delineation. This guideline intends to contribute to the standardisation and optimisation of the process of RT treatment planning for clinical practice and prospective studies.

Correlations of 18F-FDG and 18F-FLT uptake on PET with Ki-67 expression in patients with lung cancer: a meta-analysis

Background Positron emission tomography (PET) imaging using the radiotracers 18F-fluorodeoxyglucose (FDG) or 18F-fluorothymidine (FLT) has been proposed as imaging biomarkers of cell proliferation. Purpose To explore the correlations of FDG and FLT uptake with the Ki-67 labeling index in patients with lung cancer. Material and Methods Major databases were systematically searched for all relevant literature published in English. The correlation coefficient (rho) and its 95% confidence interval (CI) of individual studies were meta-analyzed using a random-effects model. The sources of heterogeneity were explored by subgroup analyses. Results Twenty-seven articles involving 1213 patients were included in this meta-analysis, comprising 22 studies for FDG uptake/Ki-67 expression correlation and eight for FLT uptake/Ki-67 expression correlation. The pooled rho values for 18F-FDG/Ki-67 correlation and 18F-FLT/Ki-67 correlation were 0.45 (95% CI, 0.41-0.50) and 0.65 (95% CI, 0.56-0.73), respectively, which indicated a moderate correlation for the former and a significant one for the latter. Although the subgroup analyses based on study design, scanner, sample method, and Ki-67 labeling method did not significantly explain the heterogeneity, these factors were potential sources of heterogeneity. In lung cancer, the pooled SUVmax of FDG uptake was significantly higher than that of FLT uptake (7.59 versus 3.86, P < 0.05). In addition, compared to FDG, FLT showed higher specificity yet lower sensitivity for the diagnosis of pulmonary lesions. Conclusion Both 18F-FDG and 18F-FLT correlate significantly with the Ki-67 labeling index in pulmonary lesions, and the latter, with a stronger correlation, may be more reliable for assessing tumor cell proliferation in lung cancer.

Anatomic, functional and molecular imaging in lung cancer precision radiation therapy: treatment response assessment and radiation therapy personalization

This article reviews key imaging modalities for lung cancer patients treated with radiation therapy (RT) and considers their actual or potential contributions to critical decision-making. An international group of researchers with expertise in imaging in lung cancer patients treated with RT considered the relevant literature on modalities, including computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). These perspectives were coordinated to summarize the current status of imaging in lung cancer and flag developments with future implications. Although there are no useful randomized trials of different imaging modalities in lung cancer, multiple prospective studies indicate that management decisions are frequently impacted by the use of complementary imaging modalities, leading both to more appropriate treatments and better outcomes. This is especially true of ¹⁸F-fluoro-deoxyglucose (FDG)-PET/CT which is widely accepted to be the standard imaging modality for staging of lung cancer patients, for selection for potentially curative RT and for treatment planning. PET is also more accurate than CT for predicting survival after RT. PET imaging during RT is also correlated with survival and makes response-adapted therapies possible. PET tracers other than FDG have potential for imaging important biological process in tumors, including hypoxia and proliferation. MRI has superior accuracy in soft tissue imaging and the MRI Linac is a rapidly developing technology with great potential for online monitoring and modification of treatment. The role of imaging in RT-treated lung cancer patients is evolving rapidly and will allow increasing personalization of therapy according to the biology of both the tumor and dose limiting normal tissues.

Non-Small-Cell Lung Cancer PET Imaging Beyond F18 Fluorodeoxyglucose

F18 Flurodeoxyglucose (FDG) is a nonspecific PET tracer representing tumor energy metabolism, with common false-positive and false-negative findings in clinical practice. Non-small cell lung cancer is highly heterogeneous histologically, biologically, and molecularly. Novel PET tracers designed to characterize a specific aspect of tumor biology or a pathway-specific molecular target have the potential to provide noninvasive key information in tumor heterogeneity for patient stratification and in the assessment of treatment response. Non-FDG PET tracers, including ⁶⁸Ga-somatostatin analogs, and some PET tracers targeting tumor proliferation, hypoxia, angiogenesis, and pathway-specific targets are briefly reviewed in this article.

Prospective Study of Serial Imaging Comparing Fluorodeoxyglucose Positron Emission Tomography (PET) and Fluorothymidine PET During Radical Chemoradiation for Non-Small Cell Lung Cancer: Reduction of Detectable Proliferation Associated With Worse Survival

PURPOSE

To investigate the associations between interim tumor responses on ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and ¹⁸F-fluorothymidine (¹⁸F-FLT) PET and patient outcomes, especially progression-free survival (PFS) and overall survival (OS), in non-small cell lung cancer (NSCLC) patients.

METHODS AND MATERIALS

Patients with FDG-PET/computed tomography stage I-III NSCLC were prescribed concurrent chemotherapy and radiation therapy (60 Gy in 30 fractions). Scans were acquired at baseline (FDG-PET/computed tomography [FDG_BL] for radiation therapy planning and FLT-PET [FLT_BL]), week 2 (FDG_wk2 and FLT_wk2), and week 4 (FDG_wk4 and FLT_wk4) of chemoradiation therapy. Tumor responses were categorized as complete or partial responses or stable or progressive disease (SD, PD) using European Organization for Research and Treatment of Cancer criteria. Associations between response, OS, and PFS were analyzed with univariate Cox regressions and plotted using Kaplan-Meier curves.

RESULTS

Between 2009 and 2013, 60 patients were recruited. Thirty-seven (62%) were male, and the median age was 66 years (range, 31-86 years). Two-year OS and PFS were 0.51 and 0.26, respectively. Unexpectedly, SD on FLT_wk2 compared with complete response/partial response was associated with longer OS (hazard ratio [95% confidence interval] 2.01 [0.87-4.65], P=.082) and PFS (2.01 [0.92-4.36], P=.061). Weeks 2 and 4 FDG PET/CT were not significantly associated with survival. Study scans provided additional information to FDG_BL in 21 patients (35%). Distant metastases detected in 3 patients on FLT_BL and in 2 patients on FDG/FLT_wk2 changed treatment intent from curative to palliative. Locoregional progression during radiation therapy was observed in 5 (8%) patients, prompting larger radiation therapy fields.

CONCLUSIONS

Stable uptake of ¹⁸F-FLT at week 2 was paradoxically associated with longer OS and PFS. This suggests that suppression of tumor cell proliferation may protect against radiation-induced tumor cell killing. Baseline FLT, FLT_wk2, and FDG_wk2 detected rapid distant and locoregional progression in 10 patients (17%), prompting changes in management.

[Quantitative Imaging Assessment of Tumor Response to Chemoradiation in Lung Cancer]

精准医疗的实施要求及时准确地对治疗疗效进行评估，以便于治疗方案的调整和优化，从而进一步提高疗效，改善预后。以定量评估为基础的影像组学以其无创、直观和可重复的特点在临床疗效评估方面具有不可替代的作用。本文将综述定量影像学在肺癌放化疗疗效评估中的应用现状及其相关进展。

The Value of FDG PET/CT in Treatment Response Assessment, Follow-Up, and Surveillance of Lung Cancer

OBJECTIVE

The purpose of this article is to summarize the evidence regarding the role of FDG PET/CT in treatment response assessment and surveillance of lung cancer and to provide suggested best practices.

CONCLUSION

FDG PET/CT is a valuable imaging tool for assessing treatment response for patients with lung cancer, though evidence for its comparative effectiveness with chest CT is still evolving. FDG PET/CT is most useful when there is clinical suspicion or other evidence for disease recurrence or metastases. The sequencing, cost analysis, and comparative effectiveness of FDG PET/CT and conventional imaging modalities in the follow-up setting need to be investigated.

Late-Course Adaptive Adjustment Based on Metabolic Tumor Volume Changes during Radiotherapy May Reduce Radiation Toxicity in Patients with Non-Small Cell Lung Cancer

To reduce the high risk of radiation toxicity and enhance the quality of life of patients with non-small cell lung cancer (NSCLC), we quantified the metabolic tumor volumes (MTVs) from baseline to the late-course of radiotherapy (RT) by fluorodeoxyglucose positron emission tomography computerized tomography (FDG PET-CT) and discussed the potential benefit of late-course adaptive plans rather than original plans by dose volume histogram (DVH) comparisons. Seventeen patients with stage II-III NSCLC who were treated with definitive conventionally fractionated RT were eligible for this prospective study. FDG PET-CT scans were acquired within 1 week before RT (pre-RT) and at approximately two-thirds of the total dose during-RT (approximately 40 Gy). MTVs were taken as gross tumor volumes (GTVs) that included the primary tumor and any involved hilar or mediastinal lymph nodes. An original plan based on the baseline MTVs and adaptive plans based on observations during-RT MTVs were generated for each patient. The DVHs for lung, heart, esophagus and spinal cord were compared between the original plans and composite plans at 66 Gy. At the time of approximately 40 Gy during-RT, MTVs were significantly reduced in patients with NSCLC (pre-RT 136.2±82.3 ml vs. during-RT 64.7±68.0 ml, p = 0.001). The composite plan of the original plan at 40 Gy plus the adaptive plan at 26 Gy resulted in better DVHs for all the organs at risk that were evaluated compared to the original plan at 66 Gy (p<0.05), including V₅, V₁₀, V₁₅, V₂₀, V₂₅, V₃₀ and the mean dose of total lung, V₁₀, V₂₀, V₃₀, V₄₀, V₅₀, V₆₀ and the mean dose of heart, V₃₅, V₄₀, V₅₀, V_55, V₆₀, the maximum dose and mean dose of the esophagus, and the maximum dose of the spinal-cord. PET-MTVs were reduced significantly at the time of approximately 40 Gy during-RT. Late course adaptive radiotherapy may be an effective way to reduce the dose volume to the organs at risk, thus reducing radiation toxicity in patients with NSCLC.

The Role of PET/CT Molecular Imaging in the Diagnosis of Recurrence and Surveillance of Patients Treated for Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) is the leading cause of cancer mortality worldwide and its prognosis remains poor. Molecular imaging with ¹⁸F-FDG PET/CT can metabolically characterize the nature of lesions as benign or malignant, allowing a better staging at the diagnosis of this kind of patient. This advantage can also be applied in the re-staging due to the suspicion of recurrent disease. Many patients have a recurrence of the disease, including surgically treated patients. In the current context, with new personalized oncological treatments, the surveillance for recurrence and its accurate diagnosis are crucial to improve their survival. In this paper, we revise the current knowledge about the clinical and molecular factors related to the recurrent disease. In the context of new, promising, available personalized treatments, the role of molecular imaging with PET/CT and ¹⁸F-FDG and non-¹⁸F-FDG radiotracers in the follow-up of NSCLC-treated patients is especially attractive and interesting.

Disseminated Skeletal Muscle and Cardiac Metastasis from Squamous Cell Carcinoma of the Lung Detected with FDG and FLT PET/CT

Lung cancer is one of the leading cancers all over the world. Positron emission tomography (PET) using 18F fluorodeoxyglucose (18F FDG) is useful for staging of the disease and decide the appropriate management. 3’-deoxy-3’-18 F-fluorothymidine (18F FLT) is a tracer being extensively evaluated currently and is said to represent tumor proliferation. Common sites of metastases from lung cancer include adrenal glands, bone, and brain. Muscle metastasis and cardiac metastasis are uncommon findings. We report a case of squamous cell carcinoma of the lung with metastases to multiple skeletal muscles and myocardium detected with both FDG and FLT PET/computed tomography (CT).

Biological imaging in clinical oncology: radiation therapy based on functional imaging

Radiation therapy is one of the most effective tools for cancer treatment. In recent years, intensity-modulated radiation therapy has become increasingly popular in that target dose-escalation can be done while sparing adjacent normal tissues. For this reason, the development of measures to pave the way for accurate target delineation is of great interest. With the integration of functional information obtained by biological imaging with radiotherapy, strategies using advanced biological imaging to visualize metabolic pathways and to improve therapeutic index and predict treatment response are discussed in this article.

Evaluation of [(89)Zr]-Oxalate as a PET Tracer in Inflammation, Tumor, and Rheumatoid Arthritis Models

To obtain an additional pharmacological agent for the diagnosis of inflammation, we investigated the medical use of (89)Zr-oxalate as a positron emission tomography (PET) probe for the in vivo imaging of inflammation and compared its efficacy to that of 2-deoxy-2-[(18)F]fluoro-d-glucose ([(18)F]FDG) and sodium [(18)F]fluoride. (89)Zr-oxalate exhibited observable higher uptake in a macrophage cell line than in tumor cells. The inflammatory lesions and tumors were clearly visualized by PET imaging and autoradiography using (89)Zr-oxalate. Compared to [(18)F]FDG and sodium [(18)F]fluoride, (89)Zr-oxalate demonstrated a high selectivity index to the tumor at an early time point after injection and to inflammation at a delayed time point after injection (24 h). Through histological examination, large numbers of macrophages and neutrophils were observed in the tumor lesions with the highest (89)Zr-oxalate uptake. In a rheumatoid arthritis (RA) mouse model, (89)Zr-oxalate demonstrated a high level of accumulation in inflammatory lesions. (89)Zr-oxalate is a new strategic tool for tumor imaging and inflammatory processes.

A systematic review on [(18)F]FLT-PET uptake as a measure of treatment response in cancer patients

Imaging biomarkers have a potential to depict the hallmarks of cancers that characterise cancer cells as compared to normal cells. One pertinent example is 3'-deoxy-3'-(18)F-fluorothymidine positron emission tomography ([(18)F]FLT-PET), which allows non-invasive in vivo assessment of tumour proliferation. Most importantly, [(18)F]FLT does not seem to be accumulating in inflammatory processes, as seen in [(18)F]-fludeoxyglucose, the most commonly used PET tracer for assessment of cell metabolism. [(18)F]FLT could therefore provide additional information about the tumour biology before, during and after treatment. This systematic review focuses on the use of [(18)F]FLT-PET tumour uptake values as a measure of tumour response to therapeutic interventions. The clinical studies which evaluated the role of [(18)F]FLT-PET as a measure of tumour response to treatment are summarised and the evidence linking [(18)F]FLT-PET tumour uptake values with clinical outcome is evaluated.

[(18)F]Fluoro-2-deoxy-2-d-glucose versus 3'-deoxy-3'-[(18)F]fluorothymidine for defining hematopoietically active pelvic bone marrow in gynecologic patients

BACKGROUND AND PURPOSE

We compared [(18)F]fluoro-2-deoxy-2-d-glucose (FDG) versus 3'-deoxy-3'-[(18)F]fluorothymidine (FLT) for the purpose of identifying active pelvic bone marrow (BM), quantifying its locational variation, and determining which technique is likely to be better for BM-sparing radiation planning.

MATERIAL AND METHODS

We sampled 41 patients, of which 25 underwent FDG-PET/CT only, 7 underwent FLT-PET/CT only, and 9 underwent both. Active BM subvolumes were defined as subsets of the pelvic BM with the highest standardized uptake values comprising 40%, 50%, and 60% of the total pelvic BM volume. We used the Dice similarity coefficient to quantify the percent overlap of active BM volumes of equal size. Differences in the spatial distribution of active BM were assessed using a region-growing algorithm.

RESULTS

For patients with both modalities, the mean Dice coefficients for the 40%, 50%, and 60% subvolumes were 0.683, 0.732, and 0.781 respectively. Comparing individual active BM subvolumes to the mean subvolume, Dice coefficients varied from 0.598-0.889 for FDG and 0.739-0.912 for FLT. Region growing analysis showed FLT-PET defined more highly clustered active BM subvolumes.

CONCLUSIONS

Within the limitations of a small sample size, we found significant agreement between FDG-PET and FLT-PET; however, FLT-PET had significantly less individual variation and is likely to be superior to FDG-PET for BM-sparing radiotherapy.

Integration of imaging into clinical practice to assess the delivery and performance of macromolecular and nanotechnology-based oncology therapies

Functional and molecular imaging has become increasingly used to evaluate interpatient and intrapatient tumor heterogeneity. Imaging allows for assessment of microenvironment parameters including tumor hypoxia, perfusion and proliferation, as well as tumor metabolism and the intratumoral distribution of specific molecular markers. Imaging information may be used to stratify patients for targeted therapies, and to define patient populations that may benefit from alternative therapeutic approaches. It also provides a method for non-invasive monitoring of treatment response at earlier time-points than traditional cues, such as tumor shrinkage. Further, companion diagnostic imaging techniques are becoming progressively more important for development and clinical implementation of targeted therapies. Imaging-based companion diagnostics are likely to be essential for the validation and FDA approval of targeted nanotherapies and macromolecular medicines. This review describes recent clinical advances in the use of functional and molecular imaging to evaluate the tumor microenvironment. Additionally, this article focuses on image-based assessment of distribution and anti-tumor effect of nano- and macromolecular systems.