Prognostic impact of [18F]fluorothymidine and [18F]fluoro-D-glucose baseline uptakes in patients with lung cancer treated first-line with erlotinib

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.

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.

18F-FLT PET/CT as a Prognostic Imaging Biomarker of Disease-Specific Survival in Patients with Primary Soft-Tissue Sarcoma

The purpose of this study was to evaluate ¹⁸F-FLT PET/CT as an early prognostic imaging biomarker of long-term overall survival and disease-specific survival (DSS) in soft-tissue sarcoma (STS) patients treated with neoadjuvant therapy (NAT) and surgical resection. Methods: This was a 10-y follow-up of a previous single-center, single-arm prospective clinical trial. Patients underwent ¹⁸F-FLT PET/CT before treatment (PET1) and after NAT (PET2). Posttreatment pathology specimens were assessed for tumor necrosis or fibrosis and for Ki-67 and thymidine kinase 1 expression. Maximally selected cutoffs for PET and histopathologic factors were applied. Survival was calculated from the date of subject consent to the date of death or last follow-up. Results: The study population consisted of 26 patients who underwent PET1; 16 of the 26 with primary STS underwent PET2. Thirteen deaths occurred during a median follow-up of 104 mo. In the overall cohort, overall survival was longer in patients with a low than a high PET1 tumor SUV_max (dichotomized by an SUV_max of ≥8.5 vs. <8.5: not yet reached vs. 49.7 mo; P = 0.0064). DSS showed a trend toward significance (P = 0.096). In a subanalysis of primary STS, DSS was significantly longer in patients with a low PET1 tumor SUV_max (dichotomized by an SUV_max of ≥8 vs. <8; P = 0.034). There were no significant ¹⁸F-FLT PET response thresholds corresponding to DSS or overall survival after NAT at PET2. Conclusion:¹⁸F-FLT PET may serve as a prognostic baseline imaging biomarker for DSS in patients with primary STS.

Post-chemotherapy and targeted therapy imaging of the chest in lung cancer

Non-small-cell lung cancer (NSCLC) is frequently diagnosed when it is not amenable to local therapies; therefore, systemic agents are the mainstay of therapy for many patients. In recent years, treatment of advanced NSCLC has evolved from a general approach primarily involving chemotherapy to a more personalised strategy in which biomarkers such as the presence of genomic tumour aberrations and the expression of immune proteins such as programmed death-ligand 1 (PD-L1), in combination with other elements of clinical information such as histology and clinical stage, guide management. For instance, pathways resulting in uncontrolled growth and proliferation of tumour cells due to epidermal growth factor receptor (EGFR) mutations and anaplastic lymphoma kinase (ALK) rearrangements may be targeted by tyrosine kinase inhibitors (TKIs). In this article, we review the current state of medical oncology, imaging characteristics of mutations, pitfalls in response assessments and the imaging of complications.

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.

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.

Sorafenib and everolimus in patients with advanced solid tumors and KRAS-mutated NSCLC: A phase I trial with early pharmacodynamic FDG-PET assessment

BACKGROUND

Treatment of patients with solid tumors and KRAS mutations remains disappointing. One option is the combined inhibition of pathways involved in RAF-MEK-ERK and PI3K-AKT-mTOR.

METHODS

Patients with relapsed solid tumors were treated with escalating doses of everolimus (E) 2.5-10.0 mg/d in a 14-day run-in phase followed by combination therapy with sorafenib (S) 800 mg/d from day 15. KRAS mutational status was assessed retrospectively in the escalation phase. Extension phase included KRAS-mutated non-small-cell lung cancer (NSCLC) only. Pharmacokinetic analyses were accompanied by pharmacodynamics assessment of E by FDG-PET. Efficacy was assessed by CT scans every 6 weeks of combination.

RESULTS

Of 31 evaluable patients, 15 had KRAS mutation, 4 patients were negative for KRAS mutation, and the KRAS status remained unknown in 12 patients. Dose-limiting toxicity (DLT) was not reached. The maximum tolerated dose (MTD) was defined as 7.5 mg/d E + 800 mg/d S due to toxicities at previous dose level (10 mg/d E + 800 mg/d S) including leucopenia/thrombopenia III° and pneumonia III° occurring after the DLT interval. The metabolic response rate in FDG-PET was 17% on day 5 and 20% on day 14. No patient reached partial response in CT scan. Median progression free survival (PFS) and overall survival (OS) were 3.25 and 5.85 months, respectively.

CONCLUSIONS

Treatment of patients with relapsed solid tumors with 7.5 mg/d E and 800 mg/d S is safe and feasible. Early metabolic response in FDG-PET was not confirmed in CT scan several weeks later. The combination of S and E is obviously not sufficient to induce durable responses in patients with KRAS-mutant solid tumors.

Imaging of Novel Oncologic Treatments in Lung Cancer Part 1: Systemic Therapies

Thoracic tumors are a leading cause of cancer-related morbidity and mortality. In recent years, developments in oncologic treatments for these tumors have ushered in an era of targeted therapy, and, in many cases, these novel treatments have replaced conventional strategies to become standard therapeutic options, particularly in those with lung cancer. Targeted medical therapies for lung cancer now include angiogenesis inhibitors, tyrosine kinase inhibitors, and immunotherapeutic agents. Several novel ablative therapies have also gained widespread acceptance as alternatives to conventional surgical options in appropriately selected patients. Tumors treated with targeted medical therapies can respond to treatment differently when compared with conventional therapies. For example, pseudoprogression is a well-described phenomenon in patients receiving checkpoint inhibitor immunotherapy in which an initial increase in tumor burden is followed by a decrease in tumor burden and sometimes partial or complete response, while the frequent cavitating responses seen when antiangiogenic agents are used can be difficult to quantify using existing response assessment criteria. In some cases, novel response assessment criteria are needed to adequately capture response. In addition, numerous treatment-related side effects have been described, which are important to recognize, both to ensure appropriate treatment and to avoid misclassification as worsening tumor. Imaging plays a vital role in the assessment of patients receiving targeted medical therapy, and it is essential that thoracic radiologists are familiar with the rationale underpinning these treatments and the expected posttherapy findings.

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.

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.

c-RAF Ablation Induces Regression of Advanced Kras/Trp53 Mutant Lung Adenocarcinomas by a Mechanism Independent of MAPK Signaling

A quarter of all solid tumors harbor KRAS oncogenes. Yet, no selective drugs have been approved to treat these malignancies. Genetic interrogation of the MAPK pathway revealed that systemic ablation of MEK or ERK kinases in adult mice prevent tumor development but are unacceptably toxic. Here, we demonstrate that ablation of c-RAF expression in advanced tumors driven by Kras^G12V/Trp53 mutations leads to significant tumor regression with no detectable appearance of resistance mechanisms. Tumor regression results from massive apoptosis. Importantly, systemic abrogation of c-RAF expression does not inhibit canonical MAPK signaling, hence, resulting in limited toxicities. These results are of significant relevance for the design of therapeutic strategies to treat K-RAS mutant cancers.

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.

The prognostic value of CT radiomic features for patients with pulmonary adenocarcinoma treated with EGFR tyrosine kinase inhibitors

PURPOSE

To determine if the radiomic features on CT can predict progression-free survival (PFS) in epidermal growth factor receptor (EGFR) mutant adenocarcinoma patients treated with first-line EGFR tyrosine kinase inhibitors (TKIs) and to identify the incremental value of radiomic features over conventional clinical factors in PFS prediction.

METHODS

In this institutional review board-approved retrospective study, pretreatment contrast-enhanced CT and first follow-up CT after initiation of TKIs were analyzed in 48 patients (M:F = 23:25; median age: 61 years). Radiomic features at baseline, at 1st first follow-up, and the percentage change between the two were determined. A Cox regression model was used to predict PFS with nonredundant radiomic features and clinical factors, respectively. The incremental value of radiomic features over the clinical factors in PFS prediction was also assessed by way of a concordance index.

RESULTS

Roundness (HR: 3.91; 95% CI: 1.72, 8.90; P = 0.001) and grey-level nonuniformity (HR: 3.60; 95% CI: 1.80, 7.18; P<0.001) were independent predictors of PFS. For clinical factors, patient age (HR: 2.11; 95% CI: 1.01, 4.39; P = 0.046), baseline tumor diameter (HR: 1.03; 95% CI: 1.01, 1.05; P = 0.002), and treatment response (HR: 0.46; 95% CI: 0.24, 0.87; P = 0.017) were independent predictors. The addition of radiomic features to clinical factors significantly improved predictive performance (concordance index; combined model = 0.77, clinical-only model = 0.69, P<0.001).

CONCLUSIONS

Radiomic features enable PFS estimation in EGFR mutant adenocarcinoma patients treated with first-line EGFR TKIs. Radiomic features combined with clinical factors provide significant improvement in prognostic performance compared with using only clinical factors.

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.

Prognostic value of early response assessment using (18F)FDG-PET in patients with advanced non-small cell lung cancer treated with tyrosine-kinase inhibitors

The purpose of this meta-analysis was to determine the prognostic value of early response assessment using (18F)fluorodeoxyglucose (FDG)-positron emission thermography (PET) in patients with advanced non-small cell lung cancer (NSCLC) treated with tyrosine-kinase inhibitors (TKIs). MEDLINE, PubMed, Cochrane, EMBASE, and Google Scholar databases were searched until August 1, 2016 using the keywords non-small cell lung carcinoma, positron-emission tomography, fluorodeoxyglucose, prognosis, disease progression, survival, erlotinib, gefitinib, and afatinib. Inclusion criteria were studies of patients with stage III or IV NSCLC treated with a TKI and had response assessed by FDG-PET. Outcome measures were overall survival (OS) and progression-free survival (PFS). Of the 167 articles identified, 10 studies including 302 patients were included in the analysis. In 8 studies, patients were treated with erlotinib, and in 2 they were treated with gefitinib. The overall analysis revealed that early metabolic response was statistically associated with improved OS (HR=0.54; 95% CI 0.46 to 0.63; p<0.001), and with longer PFS (HR=0.23; 95% CI 0.17 to 0.33; p<0.001). Early response of patients with NSCLC treated with TKIs identified on FDG-PET is associated with improved OS and PFS.

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.

PET Imaging-Based Phenotyping as a Predictive Biomarker of Response to Tyrosine Kinase Inhibitor Therapy in Non-small Cell Lung Cancer: Are We There Yet?

The increased understanding of the molecular pathology of different malignancies, especially lung cancer, has directed investigational efforts to center on the identification of different molecular targets and on the development of targeted therapies against these targets. A good representative is the epidermal growth factor receptor (EGFR); a major driver of non-small cell lung cancer tumorigenesis. Today, tumor growth inhibition is possible after treating lung tumors expressing somatic mutations of the EGFR gene with tyrosine kinase inhibitors (TKI). This opened the doors to biomarker-directed precision or personalized treatments for lung cancer patients. The success of these targeted anticancer therapies depends in part on being able to identify biomarkers and their patho-molecular make-up in order to select patients that could respond to specific therapeutic agents. While the identification of reliable biomarkers is crucial to predict response to treatment before it begins, it is also essential to be able to monitor treatment early during therapy to avoid the toxicity and morbidity of futile treatment in non-responding patients. In this context, we share our perspective on the role of PET imaging-based phenotyping in the personalized care of lung cancer patients to non-invasively direct and monitor the treatment efficacy of TKIs in clinical practice.

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.

Prognostic impact of initial maximum standardized uptake value of (18)F-FDG PET/CT on treatment response in patients with metastatic lung adenocarcinoma treated with erlotinib

Purpose

To investigate whether the initial maximum standardized uptake value (SUV_max) on fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) has a prognostic significance in metastatic lung adenocarcinoma.

Patients and methods

Sixty patients (24 females, mean age: 57.9±12 years) with metastatic stage lung adenocarcinoma who used erlotinib and underwent ¹⁸F-FDG PET/CT at the time of diagnosis between May 2010 and May 2014 were enrolled in this retrospective study. The patients were stratified according to the median SUV_max value, which was found as 11. Progression-free survival (PFS) rates for 3, 6, and 12 months were examined for SUV_max values and epidermal growth factor receptor (EGFR) mutation status.

Results

The number of EGFR-sensitizing mutation positive/negative/unknown was 26/17/17, respectively, and the number of patients using erlotinib at first-line, second-line, and third-line therapy was 15, 31, and 14 consecutively. The PFS rates of EGFR mutation positive, negative, and unknown patients for 3 months were 73.1%, 35.3%, and 41.2% (P=0.026, odds ratio [OR]=4.39; 95% confidence interval [CI]: 1.45–13.26), respectively. The PFS rates of EGFR positive, negative, and unknown patients for 6 months were 50%, 29.4%, and 29.4% (P=0.267, OR: 2.4; 95% CI: 0.82–6.96), respectively. The PFS rates of EGFR positive, negative, and unknown patients for 12 months were 42.3%, 29.4%, 23.5% (P=0.408, OR: 2.0; 95% CI: 0.42–5.26), respectively. Thirty-one of 60 patients had SUV_max values ≤11. The PFS rates for 3, 6, and 12 months were 70.5%/28% (P=0.001, OR=9.0; 95% CI: 2.79–29.04), 61.7%/8% (P<0.001, OR=28.35; 95% CI: 5.5–143), and 52.9%/8% (P<0.001, OR=18.69; 95% CI: 3.76–92.9) for low SUV_max (≤11) group/high SUV_max (>11) group, respectively.

Conclusion

Initial SUV_max value on ¹⁸F-FDG PET/CT is found to be a prognostic factor anticipating the response to erlotinib for 3, 6, and 12-month rates of PFS in both EGFR-sensitizing mutation and wild-type tumor group.

Non-Small Cell Lung Cancer Treated with Erlotinib: Heterogeneity of (18)F-FDG Uptake at PET-Association with Treatment Response and Prognosis

PURPOSE

To determine if first-order and high-order textural features on fluorine 18 ((18)F) fluorodeoxyglucose (FDG) positron emission tomography (PET) images of non-small cell lung cancer (NSCLC) (a) at baseline, (b) at 6 weeks, or (c) the percentage change between baseline and 6 weeks can predict response or survival in patients treated with erlotinib.

MATERIALS AND METHODS

Institutional review board approval was obtained for post hoc analysis of data from a prospective single-center study for which informed consent was obtained. The study included 47 patients with NSCLC who underwent (18)F-FDG PET/computed tomography (CT) at baseline (n = 47) and 6 weeks (n = 40) after commencing treatment with erlotinib. First-order and high-order primary tumor texture features reflecting image heterogeneity, standardized uptake values, metabolic tumor volume, and total lesion glycolysis were measured for all (18)F-FDG PET studies. Response to erlotinib was assessed by using the Response Evaluation Criteria in Solid Tumors (RECIST) on CT images obtained at 12 weeks (n = 32). Associations between PET parameters, overall survival (OS), and RECIST-based treatment response were tested by Cox and logistic regression analyses, respectively.

RESULTS

Median OS was 14.1 months. According to CT RECIST at 12 weeks, there were 21 nonresponders and 11 responders. Response to erlotinib was associated with reduced heterogeneity (first-order standard deviation, P = .01; entropy, P = .001; uniformity, P = .001). At multivariable analysis, high-order contrast at 6 weeks (P = .002) and percentage change in first-order entropy (P = .03) were independently associated with survival. Percentage change in first-order entropy was also independently associated with treatment response (P = .01).

CONCLUSION

Response to erlotinib is associated with reduced heterogeneity at (18)F-FDG PET. Changes in first-order entropy are independently associated with OS and treatment response.

Applications of PET imaging with the proliferation marker [18F]-FLT

[18F]-3'-fluoro-3'-deoxythymidine (FLT) is a nucleoside-analog imaging agent for quantifying cellular proliferation that was first reported in 1998. It accumulates during the S-phase of the cell cycle through the action of cytosolic thymidine kinase, TK1. Since TK1 is primarily expressed in dividing cells, FLT uptake is essentially limited to dividing cells. Thus FLT is an effective measure of cell proliferation. FLT uptake has been shown to correlate with the more classic proliferation marker, the monoclonal antibody to Ki-67. Increased cellular proliferation is known to correlate with worse outcome in many cancers. However, the Ki-67 binding assay is performed on a sampled preparation, ex vivo, whereas FLT can be quantitatively measured in vivo using positron emission tomography (PET). FLT is an effective and quantitative marker of cell proliferation, and therefore a useful prognostic predictor in the setting of neoplastic disease. This review summarizes clinical studies from 2011 forward that used FLT-PET to assess tumor response to therapy. The paper focuses on our recommendations for a standardized clinical trial protocol and components of a report so multi center studies can be effectively conducted, and different studies can be compared. For example, since FLT is glucuronidated by the liver, and the metabolite is not transported into the cell, the plasma fraction of FLT can be significantly changed by treatment with particular drugs that deplete this enzyme, including some chemotherapy agents and pain medications. Therefore, the plasma level of metabolites should be measured to assure FLT uptake kinetics can be accurately calculated. This is important because the flux constant (KFLT) is a more accurate measure of proliferation and, by inference, a better discriminator of tumor recurrence than standardized uptake value (SUVFLT). This will allow FLT imaging to be a specific and clinically relevant prognostic predictor in the treatment of neoplastic disease.

Retrospective quality control review of FDG scans in the imaging sub-study of PALETTE EORTC 62072/VEG110727: a randomized, double-blind, placebo-controlled phase III trial

PURPOSE

(18)F-Labelled fluorodeoxyglucose (FDG) can detect early changes in tumour metabolism and may be a useful quantitative imaging biomarker (QIB) for prediction of disease stabilization, response and duration of progression-free survival (PFS). Standardization of imaging procedures is a prerequisite, especially in multicentre clinical trials. In this study we reviewed the quality of FDG scans and compliance with the imaging guideline (IG) in a phase III clinical trial.

METHODS

Forty-four cancer patients were enroled in an imaging sub-study of a randomized international multicentre trial. FDG scan had to be performed at baseline and 10-14 days after treatment start. The image transmittal forms (ITFs) and Digital Imaging and Communications in Medicine (DICOM) [1] standard headers were analysed for compliance with the IG. Mean liver standardized uptake values (LSUVmean) were measured as recommended by positron emission tomography (PET) Response Criteria in Solid Tumors 1.0 (PERCIST) [2].

RESULTS

Of 88 scans, 81 were received (44 patients); 36 were properly anonymized; 77/81 serum glucose values submitted, all but one within the IG. In 35/44 patients both scans were of sufficient visual quality. In 22/70 ITFs the reported UT differed by >1 min from the DICOM headers (max. difference 1 h 4 min). Based on the DICOM, UT compliance for both scans was 31.4%. LSUVmean was fairly constant for the 11 patients with UT compliance: 2.30 ± 0.33 at baseline and 2.27 ± 0.48 at follow-up (FU). Variability substantially increased for the subjects with unacceptable UT (11 patients): 2.27 ± 1.04 at baseline and 2.18 ± 0.83 at FU.

CONCLUSION

The high attrition number of patients due to low compliance with the IG compromised the quantitative assessment of the predictive value for early response monitoring. This emphasizes the need for better regulated procedures in imaging departments, which may be achieved by education of involved personnel or efforts towards regulations. LSUVmean could be monitored to assess quality and compliance in an FDG PET/CT study.

FLT PET-CT in evaluation of treatment response

PURPOSE

Review published studies to investigate the value of clinical 3-deoxy-3-(18)F-fluorothymidine (FLT) positron emission tomography (PET) in predicting response to treatment.

MATERIALS AND METHODS

Interrogate databases to identify suitable publications between 2007 and 2013 with a minimum of five patients. Articles within the inclusion criteria were reviewed with major findings reported leading to a descriptive analysis of FLT PET in therapy response.

RESULTS

Lesions investigated included glioma, head and neck, esophageal, lung, breast, gastric, renal, rectal, sarcomas, germ cell, lymphomas, leukemia, and melanoma resulting in a total of 34 studies analyzed. A variety of therapies were applied and dissimilar PET protocols were widespread making direct comparison between studies challenging. Though baseline, early and late therapy scans were popular particularly in chemotherapy regimes. Most studies investigated showed significantly reduced FLT uptake during or after therapy compared with pretreatment scans.

CONCLUSION

Current evidence suggests FLT PET has a positive role to play in predicting therapy response especially in brain, lung, and breast cancers where good correlation with Ki-67 is observed. However, careful attention must be placed in undertaking larger clinical trials where harmonization of scanning and analysis protocols are strictly adhered to fully assess the true potential of FLT PET in predicting response to treatment.

PET/CT in therapy evaluation of patients with lung cancer

FDG-PET/CT is a well documented and widespread used imaging modality for the diagnosis and staging of patient with lung cancer. FDG-PET/CT is increasingly used for the assessment of treatment effects during and after chemotherapy. However, PET is not an accepted surrogate end-point for assessment of response rate in clinical trials. The aim of this review is to present current evidence on the use of PET in response evaluation of patients with lung cancer and to introduce the pearls and pitfalls of the PET-technology relating to response assessment. Based on this and relating to validation criteria, including stable technology, standardization, reproducibility and broad availability, the review discusses why, despite numerous studies on response assessment indicating a possible role for FDG-PET/CT, PET still has no place in guidelines relating to response evaluation in lung cancer.

New strategy for monitoring targeted therapy: molecular imaging

Targeted therapy is becoming an increasingly important component in the treatment of cancer. How to accurately monitor targeted therapy has been crucial in clinical practice. The traditional approach to monitor treatment through imaging has relied on assessing the change of tumor size by refined World Health Organization criteria, or more recently, by the Response Evaluation Criteria in Solid Tumors. However, these criteria, which are based on the change of tumor size, show some limitations for evaluating targeted therapy. Currently, genetic alterations are identified with prognostic as well as predictive potential concerning the use of molecularly targeted drugs. Conversely, considering the limitations of invasiveness and the issue of expression heterogeneity, molecular imaging is better able to assay in vivo biologic processes noninvasively and quantitatively, and has been a particularly attractive tool for monitoring treatment in clinical cancer practice. This review focuses on the applications of different kinds of molecular imaging including positron emission tomography-, magnetic resonance imaging-, ultrasonography-, and computed tomography-based imaging strategies on monitoring targeted therapy. In addition, the key challenges of molecular imaging are addressed to successfully translate these promising techniques in the future.