Imaging in Therapy Response Assessment and Surveillance of Lung Cancer: Evidenced-based Review With Focus on the Utility of 18F-FDG PET/CT

[18F]FDG-PET/CT atypical response patterns to immunotherapy in non-small cell lung cancer patients: long term prognosis assessment and clinical management proposal

AIM

To determine the long-term prognosis of immune-related response profiles (pseudoprogression and dissociated response), not covered by conventional PERCIST criteria, in patients with non-small-cell lung cancer (NSCLC) treated with immune checkpoint inhibitors (ICPIs).

METHODS

109 patients were prospectively included and underwent [18F]FDG-PET/CT at baseline, after 7 weeks (PETinterim1), and 3 months (PETinterim2) of treatment. On PETinterim1, tumor response was assessed using standard PERCIST criteria. In the event of PERCIST progression at this time-point, the study design provided for continued immunotherapy for 6 more weeks. Additional response patterns were then considered on PETinterim2: pseudo-progression (PsPD, subsequent metabolic response); dissociated response (DR, coexistence of responding and non-responding lesions), and confirmed progressive metabolic disease (cPMD, subsequent homogeneous progression of lesions). Patients were followed up for at least 12 months.

RESULTS

Median follow-up was 21 months. At PETinterim1, PERCIST progression was observed in 60% (66/109) of patients and ICPI was continued in 59/66. At the subsequent PETinterim2, 14% of patients showed PsPD, 11% DR, 35% cPMD, and 28% had a sustained metabolic response. Median overall survival (OS) and progression-free-survival (PFS) did not differ between PsPD and DR (27 vs 29 months, p = 1.0; 17 vs 12 months, p = 0.2, respectively). The OS and PFS of PsPD/DR patients were significantly better than those with cPMD (29 vs 9 months, p < 0.02; 16 vs 2 months, p < 0.001), but worse than those with sustained metabolic response (p < 0.001). This 3-group prognostic stratification enabled better identification of true progressors, outperforming the prognostic value of standard PERCIST criteria (p = 0.03).

CONCLUSION

[18F]FDG-PET/CT enables early assessment of response to immunotherapy. The new wsPERCIST ("wait and see") PET criteria proposed, comprising immune-related atypical response patterns, can refine conventional prognostic stratification based on PERCIST criteria.

TRIAL REGISTRATION

HDH F20230309081206. Registered 20 April 2023. Retrospectively registered.

Feasibility of a deep-inspiration breath-hold [18F]AlF-NOTA-LM3 PET/CT imaging on upper-abdominal lesions in NET patients: in comparison with respiratory-gated PET/CT

PURPOSES

To explore the clinical feasibility and efficacy of a deep inspiration breath-hold (BH) PET/CT using [18F]AlF-NOTA-LM3 on upper abdominal lesions in patients with neuroendocrine tumors (NETs).

METHODS

Twenty-three patients underwent a free-breath (FB) whole-body PET/CT, including a 10 min/bed scan for the upper abdomen with a vital signal monitoring for respiratory gating (RG) followed by a 20-second BH PET/CT covering the same axial range. For the upper abdomen bed, the following PET series was reconstructed: a 2-min FB PET; RG PET (6 bins); a 20-second and 15-second BH PET (BH_15 and BH_20). Semi-quantitative analysis was performed to compare liver SUVmean, lesion SUVmax, MTV, its percentage difference and target-to-background ratio (TBR) between both BH PET and RG PET images. Subgroup analysis considered lesion location, MTV and SUVmax. A 5-point Likert scale was used to perform visual analysis and any missed or additional lesions were identified compared with RG PET.

RESULTS

Quantitative analysis on overall lesions (n = 78) revealed higher SUVmax and TBR, and smaller MTV for both BH PET compared to FB and RG PET, with lesion location-specific variations. Neither significant difference was observed in all metrics between RG and FB PET in larger lesions, nor in MTV in lower-uptake lesions. However, both BH PET significantly enhanced these measurements. In the visual analysis, both BH PET showed noninferior performance to RG PET, and were evaluated clinically acceptable. Additional and missed lesions were observed in FB and both BH PET compared with RG PET, but didn't alter the clinical management. The BH_15 PET showed comparable performance to BH_20 PET in any comparison.

CONCLUSION

The BH PET/CT using [18F]AlF-NOTA-LM3 is effective in detecting upper abdominal lesions, offering more accurate quantitative measurements. Using a novel PET/CT scanner, a 15-second BH PET can provide comparable and superior performance to RG PET, indicating potential feasibility in clinical routines.

Multidisciplinary approach for locally advanced non-small cell lung cancer (NSCLC): 2023 expert consensus of the Spanish Lung Cancer Group GECP

INTRODUCTION

Recent advances in the treatment of locally advanced NSCLC have led to changes in the standard of care for this disease. For the selection of the best approach strategy for each patient, it is necessary the homogenization of diagnostic and therapeutic interventions, as well as the promotion of the evaluation of patients by a multidisciplinary oncology team.

OBJECTIVE

Development of an expert consensus document with suggestions for the approach and treatment of locally advanced NSCLC leaded by Spanish Lung Cancer Group GECP.

METHODS

Between March and July 2023, a panel of 28 experts was formed. Using a mixed technique (Delphi/nominal group) under the guidance of a coordinating group, consensus was reached in 4 phases: 1. Literature review and definition of discussion topics 2. First round of voting 3. Communicating the results and second round of voting 4. Definition of conclusions in nominal group meeting. Responses were consolidated using medians and interquartile ranges. The threshold for agreement was defined as 85% of the votes.

RESULTS

New and controversial situations regarding the diagnosis and management of locally advanced NSCLC were analyzed and reconciled based on evidence and clinical experience. Discussion issues included: molecular diagnosis and biomarkers, radiologic and surgical diagnosis, mediastinal staging, role of the multidisciplinary thoracic committee, neoadjuvant treatment indications, evaluation of response to neoadjuvant treatment, postoperative evaluation, and follow-up.

CONCLUSIONS

Consensus clinical suggestions were generated on the most relevant scenarios such as diagnosis, staging and treatment of locally advanced lung cancer, which will serve to support decision-making in daily practice.

Imaging Follow-Up of Nonsurgical Therapies for Lung Cancer: AJR Expert Panel Narrative Review

Lung cancer continues to be the most common cause of cancer-related death worldwide. In the past decade, with the implementation of lung cancer screening programs and advances in surgical and nonsurgical therapies, the survival of patients with lung cancer has increased, as has the number of imaging studies that these patients undergo. However, most patients with lung cancer do not undergo surgical re-section, because they have comorbid disease or lung cancer in an advanced stage at diagnosis. Nonsurgical therapies have continued to evolve with a growing range of systemic and targeted therapies, and there has been an associated evolution in the imaging findings encountered at follow-up examinations after such therapies (e.g., with respect to posttreatment changes, treatment complications, and recurrent tumor). This AJR Expert Panel Narrative Review describes the current status of nonsurgical therapies for lung cancer and their expected and unexpected imaging manifestations. The goal is to provide guidance to radiologists regarding imaging assessment after such therapies, focusing mainly on non-small cell lung cancer. Covered therapies include systemic therapy (conventional chemotherapy, targeted therapy, and immunotherapy), radiotherapy, and thermal ablation.

Nested multi-scale transform fusion model: The response evaluation of chemoradiotherapy for patients with lung tumors

BACKGROUND AND OBJECTIVE

The response evaluation of chemoradiotherapy is an important method of precision treatment for patients with malignant lung tumors. In view of the existing evaluation criteria for chemoradiotherapy, it is difficult to synthesize the geometric and shape characteristics of lung tumors. In the present, the response evaluation of chemoradiotherapy is limited. Therefore, this paper constructs a response evaluation system of chemoradiotherapy based on PET/CT images.

METHODS

There are two parts in the system: a nested multi-scale fusion model and an attribute sets for the Response evaluation of chemoradiotherapy (AS-REC). In the first part, a new nested multi-scale transform method, i.e., latent low-rank representation (LATLRR) and non-subsampled contourlet transform (NSCT), is proposed. Then, the average gradient self-adaptive weighting is used for the low-frequency fusion rule, and the regional energy fusion rule is used for the high-frequency fusion rule. Further, the low-rank part fusion image is obtained by the inverse NSCT, and the fusion image is generated by adding the low-rank part fusion image and the significant part fusion image. In the second part, AS-REC is constructed to evaluate the growth direction of the tumor, the degree of tumor metabolic activity, and the tumor growth state.

RESULTS

the numerical results clearly show that the performance of our proposed method outperforms in comparison with several existing methods, among them, the value of Qabf increased by up to 69%.

CONCLUSIONS

Through the experiment of three reexamination patients, the effectiveness of the evaluation system of radiotherapy and chemotherapy are proved.

Deep learning-based dynamic PET parametric Ki image generation from lung static PET

OBJECTIVES

PET/CT is a first-line tool for the diagnosis of lung cancer. The accuracy of quantification may suffer from various factors throughout the acquisition process. The dynamic PET parametric K_i provides better quantification and improve specificity for cancer detection. However, parametric imaging is difficult to implement clinically due to the long acquisition time (~ 1 h). We propose a dynamic parametric imaging method based on conventional static PET using deep learning.

METHODS

Based on the imaging data of 203 participants, an improved cycle generative adversarial network incorporated with squeeze-and-excitation attention block was introduced to learn the potential mapping relationship between static PET and K_i parametric images. The image quality of the synthesized images was qualitatively and quantitatively evaluated by using several physical and clinical metrics. Statistical analysis of correlation and consistency was also performed on the synthetic images.

RESULTS

Compared with those of other networks, the images synthesized by our proposed network exhibited superior performance in both qualitative and quantitative evaluation, statistical analysis, and clinical scoring. Our synthesized K_i images had significant correlation (Pearson correlation coefficient, 0.93), consistency, and excellent quantitative evaluation results with the K_i images obtained in standard dynamic PET practice.

CONCLUSIONS

Our proposed deep learning method can be used to synthesize highly correlated and consistent dynamic parametric images obtained from static lung PET.

KEY POINTS

• Compared with conventional static PET, dynamic PET parametric K_i imaging has been shown to provide better quantification and improved specificity for cancer detection. • The purpose of this work was to develop a dynamic parametric imaging method based on static PET images using deep learning. • Our proposed network can synthesize highly correlated and consistent dynamic parametric images, providing an additional quantitative diagnostic reference for clinicians.

Small extracellular vesicles in metabolic remodeling of tumor cells: Cargos and translational application

Warburg effect is characterized by excessive consumption of glucose by the tumor cells under both aerobic and hypoxic conditions. This metabolic reprogramming allows the tumor cells to adapt to the unique microenvironment and proliferate rapidly, and also promotes tumor metastasis and therapy resistance. Metabolic reprogramming of tumor cells is driven by the aberrant expression and activity of metabolic enzymes, which results in the accumulation of oncometabolites, and the hyperactivation of intracellular growth signals. Recent studies suggest that tumor-associated metabolic remodeling also depends on intercellular communication within the tumor microenvironment (TME). Small extracellular vesicles (sEVs), also known as exosomes, are smaller than 200 nm in diameter and are formed by the fusion of multivesicular bodies with the plasma membrane. The sEVs are instrumental in transporting cargoes such as proteins, nucleic acids or metabolites between the tumor, stromal and immune cells of the TME, and are thus involved in reprogramming the glucose metabolism of recipient cells. In this review, we have summarized the biogenesis and functions of sEVs and metabolic cargos, and the mechanisms through they drive the Warburg effect. Furthermore, the potential applications of targeting sEV-mediated metabolic pathways in tumor liquid biopsy, imaging diagnosis and drug development have also been discussed.

Imaging of Cancer Immunotherapy: Response Assessment Methods, Atypical Response Patterns, and Immune-Related Adverse Events, From the AJR Special Series on Imaging of Inflammation

The introduction of immunotherapy with immune-checkpoint inhibitors (ICIs) has revolutionized cancer treatment paradigms. Since FDA approval of the first ICI in 2011, multiple additional ICIs have been approved and granted marketing authorization, and many promising agents are in early clinical adoption. Due to the distinctive biologic mechanisms of ICIs, the patterns of tumor response and progression seen with immunotherapy differ from those observed with cytotoxic chemothera-pies. With increasing clinical adoption of immunotherapy, it is critical for radiologists to recognize different response patterns and common pitfalls to avoid misinterpretation of imaging studies or prompt premature cessation of potentially effective treatment. This review provides an overview of ICIs and their mechanisms of action and discusses anatomic and metabolic immune-related response assessment methods, typical and atypical patterns of immunotherapy response (including pseudoprogression, hyperprogression, dissociated response, and durable response), and common imaging features of immune-related adverse events. Future multicenter trials are needed to validate the proposed immune-related response criteria and identify the functional imaging markers of early treatment response and survival.

"PET/CT Variants and Pitfalls in Lung Cancer and Mesothelioma"

2-deoxy-2-[¹⁸F]fluoro-D-glucose [¹⁸F]FDG-PET/CT represents the metabolic imaging of choice in various cancer types. Used either at diagnosis or during treatment response assessment, the modality allows for a more accurate definition of tumor extent compared to morphological imaging and is able to predict the therapeutic benefit earlier in time. Due to the aspecific uptake property of [¹⁸F]FDG there is an overlap of its distribution in normal and pathological conditions, which can make the interpretation of the imaging challenging. Lung and pleural neoplasia are no exception to this, thus acknowledging of possible pitfalls and artifacts are mandatory for image interpretation. While most pitfalls and artifacts are common for all indications with metabolic imaging with [¹⁸F]FDG-PET/CT, there are specific variants and pitfalls in lung cancer and malignant pleural mesothelioma. The aim of the present article is to shed light on the most frequent and relevant variants and pitfalls in [¹⁸F]FDG-PET/CT imaging in lung cancer and malignant pleural mesothelioma.