Assessment of early treatment response after CT-guided radiofrequency ablation of unresectable lung tumours by diffusion-weighted MRI: a pilot study

Magnetic Resonance Imaging for Guidance and Follow-up of Thoracic Needle Biopsies and Thermal Ablations

Magnetic resonance imaging (MRI) is used for the guidance and follow-up of percutaneous minimally invasive interventions in many body parts. In the thorax, computed tomography (CT) is currently the most used imaging modality for the guidance and follow-up of needle biopsies and thermal ablations. Compared with CT, MRI provides excellent soft tissue contrast, lacks ionizing radiation, and allows functional imaging. The role of MRI is limited in the thorax due to the low hydrogen proton density and many air-tissue interfaces of the lung, as well as respiratory and cardiac motion. Here, we review the current experience of MR-guided thoracic needle biopsies and of MR-guided thermal ablations targeting lesions in the lung, mediastinum, and the chest wall. We provide an overview of MR-compatible biopsy needles and ablation devices. We detail relevant MRI sequences and their relative advantages and disadvantages for procedural guidance, assessment of complications, and long-term follow-up. We compare the advantages and disadvantages of CT and MR for thoracic interventions and identify areas in need of improvement and additional research.

Feasibility of diffusion-weighted magnetic resonance imaging in evaluation of early therapeutic response after CT-guided microwave ablation of inoperable lung neoplasms

Objective

To determine the early treatment response after microwave ablation (MWA) of inoperable lung neoplasms using the apparent diffusion coefficient (ADC) value calculated 24 h after the ablation.

Materials and methods

This retrospective study included 47 patients with 68 lung lesions, who underwent percutaneous MWA from January 2008 to December 2017. Evaluation of the lesions was done using MRI including DWI sequence with ADC value calculation pre-ablation and 24 h post-ablation. DWI-MR was performed with b values (50, 400, 800 mm²/s). The post-ablation follow-up was performed using chest CT and/or MRI within 24 h following the procedure; after 3, 6, 9, and 12 months; and every 6 months onwards to determine the local tumor response. The post-ablation ADC value changes were compared to the end response of the lesions.

Results

Forty-seven patients (mean age: 63.8 ± 14.2 years, 25 women) with 68 lesions having a mean tumor size of 1.5 ± 0.9 cm (range: 0.7–5 cm) were evaluated. Sixty-one lesions (89.7%) showed a complete treatment response, and the remaining 7 lesions (10.3%) showed a local progression (residual activity). There was a statistically significant difference regarding the ADC value measured 24 h after the ablation between the responding (1.7 ± 0.3 × 10⁻³ mm²/s) and non-responding groups (1.4 ± 0.3 × 10⁻³ mm²/s) with significantly higher values in the responding group (p = 0.001). A suggested ADC cut-off value of 1.42 could be used as a reference point for the post-ablation response prediction (sensitivity: 66.67%, specificity: 84.21%, PPV: 66.7%, and NPV: 84.2%). No significant difference was reported regarding the ADC value performed before the ablation as a factor for the prognosis of treatment response (p = 0.86).

Conclusion

ADC value assessment following ablation may allow the early prediction of treatment efficacy after MWA of inoperable lung neoplasms.

Key Points

• ADC value calculated 24 h post-treatment may allow the early prediction of MWA efficacy as a treatment of pulmonary tumors and can be used in the early immediate post-ablation imaging follow-up.

• The pre-treatment ADC value of lung neoplasms is not different between the responding and non-responding tumors.

Adverse events of hyperthermic intravesical chemotherapy for non-muscle invasive bladder cancer patients

INTRODUCTION

Non-muscle invasive bladder cancer (NMIBC) is one of the most frequent neoplasms in Denmark. Treatment of high-risk NMIBC usually consists of transurethral resection of bladder (TUR-B) followed by intravesical Bacillus Calmette-Guérin (BCG) instillations. Unfortunately, some patients are BCG-unresponsive and will relapse over time. Radical cystectomy is the recommended salvage treatment following BCG-failure or BCG-intolerance. However, not all patients are candidates for surgery and thus, in need of other treatment. This study investigates the adverse events of Hyperthermic Intravesical Chemotherapy (HIVEC) treatment.

METHODS

Twenty-three high-risk NMIBC patients, who were BCG-unresponsive or had contraindications for BCG, received HIVEC with Mitomycin C. Prior to each instillation, patients were interviewed by a nurse, using a systematic questionnaire regarding the adverse events. Patients were followed with cytology and cystoscopy every fourth month. The primary outcome was adverse event related to the HIVEC treatment.

RESULTS

In general, the adverse events were mild to moderate and often self-limiting. The most common adverse events were urinary frequency (23.6%), incontinence (19.4%) and urinary tract pain (12.2%).

CONCLUSION

In the current study, we found that HIVEC was a well-tolerated treatment. HIVEC might be a feasible option for patients, who experienced BCG-failure or BCG-intolerance and could potentially postpone or avoid radical cystectomy.

Follow-up after radiological intervention in oncology: ECIO-ESOI evidence and consensus-based recommendations for clinical practice

Interventional radiology plays an important and increasing role in cancer treatment. Follow-up is important to be able to assess treatment success and detect locoregional and distant recurrence and recommendations for follow-up are needed. At ECIO 2018, a joint ECIO-ESOI session was organized to establish follow-up recommendations for oncologic intervention in liver, renal, and lung cancer. Treatments included thermal ablation, TACE, and TARE. In total five topics were evaluated: ablation in colorectal liver metastases (CRLM), TARE in CRLM, TACE and TARE in HCC, ablation in renal cancer, and ablation in lung cancer. Evaluated modalities were FDG-PET-CT, CT, MRI, and (contrast-enhanced) ultrasound. Prior to the session, five experts were selected and performed a systematic review and presented statements, which were voted on in a telephone conference prior to the meeting by all panelists. These statements were presented and discussed at the ECIO-ESOI session at ECIO 2018. This paper presents the recommendations that followed from these initiatives. Based on expert opinions and the available evidence, follow-up schedules were proposed for liver cancer, renal cancer, and lung cancer. FDG-PET-CT, CT, and MRI are the recommended modalities, but one should beware of false-positive signs of residual tumor or recurrence due to inflammation early after the intervention. There is a need for prospective preferably multicenter studies to validate new techniques and new response criteria. This paper presents recommendations that can be used in clinical practice to perform the follow-up of patients with liver, lung, and renal cancer who were treated with interventional locoregional therapies.

The role of device-assisted therapies in the management of non-muscle invasive bladder cancer: A systematic review

OBJECTIVE

Despite optimal treatment, patients affected by non-muscle invasive bladder cancer (NMIBC) suffer from high risk of recurrence and progression. Intravescical device assisted therapies such as radiofrequency induced thermochemotherapeutic effect (RITE) and electromotive drug administration (EMDA) have shown promising effect in enhancing the effect of intravescical chemotherapies. The aim of the study was to assess clinical outcomes of these two devices in non-muscle invasive bladder cancer.

METHODS

A systematic literature review was performed in December 2019 using the Medline, Embase, and Web of Science databases. Only articles published in the last 10 years were considered (2009-2019). The articles were selected using the following keywords association: "bladder cancer" AND "EMDA' AND "synergo" AND "hyperchemotherapy" AND "electromotive drug administration", AND "radiofrequency induced thermochemotherapeutic" AND "RITE".

RESULTS

We found 16 studies published in the last ten years regarding the efficacy of RITE (12 studies) and EMDA (4 studies) in the treatment of NMIBC. Both RITE and EMDA showed promising results in the treatment of intermediate and high risk NMIBC as well as in patients affected by recurrent BCa after BCG failure. In high-risk BCG naïve NMIBC patients treated with EMDA recurrence and progression rates were 68% and 95%, respectively. Considering RITE, recurrence and progression range rates were 43%-88% and 62%-97%, respectively. Discordance results were reported regarding its effect on patients with carcinoma in situ. However, only few studies could be compared since differences exist regarding inclusion criteria with high patients' heterogeneity. Considering recurrence after BCG, recurrence and progression range rates were 29%-29.2% and 62%-83% for RITE and 25% and 75% for EMDA, respectively.

CONCLUSION

Delivery of intravescical hyperthermia seems to enhance the normal effect of intravescical chemotherapy instillation. Although prospective trials supported its effect on both BCG naïve and BCG failure patients, data are urgently required to validate these findings and to understand its effect on patients with carcinoma in situ.

LEVEL OF PROOF

3.

Intravesical device-assisted therapies for non-muscle-invasive bladder cancer

Non-muscle-invasive bladder cancer (NMIBC), the most prevalent type of bladder cancer, accounts for ~75% of bladder cancer diagnoses. This disease has a 50% risk of recurrence and 20% risk of progression within 5 years, despite the use of intravesical adjuvant treatments (such as BCG or mitomycin C) that are recommended by clinical guidelines. Intravesical device-assisted therapies, such as radiofrequency-induced thermochemotherapeutic effect (RITE), conductive hyperthermic chemotherapy, and electromotive drug administration (EMDA), have shown promising efficacy. These device-assisted treatments are an attractive alternative to BCG, as issues with supply have been a problem in some countries. RITE might be an effective treatment option for some patients who have experienced BCG failure and are not candidates for radical cystectomy. Data from trials using EMDA suggest that it is effective in high-risk disease but requires further validation, and results of randomized trials are eagerly awaited for conductive hyperthermic chemotherapy. Considerable heterogeneity in patient cohorts, treatment sessions, use of maintenance regimens, and single-arm study design makes it difficult to draw solid conclusions, although randomized controlled trials have been reported for RITE and EMDA.

Evaluation of diffusion-weighted MRI and (18F) fluorothymidine-PET biomarkers for early response assessment in patients with operable non-small cell lung cancer treated with neoadjuvant chemotherapy

Objective:

To correlate changes in the apparent diffusion coefficient (ADC) from diffusion-weighted (DW)-MRI and standardised uptake value (SUV) from fluorothymidine (¹⁸FLT)-PET/CT with histopathological estimates of response in patients with non-small cell lung cancer (NSCLC) treated with neoadjuvant chemotherapy and track longitudinal changes in these biomarkers in a multicentre, multivendor setting.

Methods:

14 patients with operable NSCLC recruited to a prospective, multicentre imaging trial (EORTC-1217) were treated with platinum-based neoadjuvant chemotherapy. 13 patients had DW-MRI and FLT-PET/CT at baseline (10 had both), 12 were re-imaged at Day 14 (eight dual-modality) and nine after completing chemotherapy, immediately before surgery (six dual-modality). Surgical specimens (haematoxylin-eosin and Ki67 stained) estimated the percentage of residual viable tumour/necrosis and proliferation index.

Results:

Despite the small numbers,significant findings were possible. ADC_median increased (p < 0.001) and SUV_mean decreased (p < 0.001) significantly between baseline and Day 14; changes between Day 14 and surgery were less marked. All responding tumours (>30% reduction in unidimensional measurement pre-surgery), showed an increase at Day 14 in ADC75^th centile and reduction in total lesion proliferation (SUV_mean x proliferative volume) greater than established measurement variability. Change in imaging biomarkers did not correlate with histological response (residual viable tumour, necrosis).

Conclusion:

Changes in ADC and FLT-SUV following neoadjuvant chemotherapy in NSCLC were measurable by Day 14 and preceded changes in unidimensional size but did not correlate with histopathological response. However, the magnitude of the changes and their utility in predicting (non-) response (tumour size/clinical outcome) remains to be established.

Advances in knowledge:

During treatment, ADC increase precedes size reductions, but does not reflect histopathological necrosis.

Local control and vertebral compression fractures following stereotactic body radiotherapy for spine metastases

•

SBRT provides a satisfying local control rate of 88% in patients with spMets.

•

Post-SBRT vertebral compression rate of 4% corresponds to the current literature.

•

>6 months of bisphosphonates use is associated with lower fracture-free survival.

Purpose

We aimed to retrospectively assess the incidence of vertebral compression fractures (VCF), examine clinicopathologic factors potentially associated with VCF, and evaluate treatment response in patients who received stereotactic body radiotherapy (SBRT) for spine metastases (spMets).

Methods and Materials

We identified 78 patients with 125 spMets at baseline and subsequent assessments. Patients received SBRT doses of 16 or 18 Gy. Patients with pre-existing VCF and co-existing local progression were excluded. Spine instability neoplastic score (SINS) was used for spMets categorization. Response to SBRT and VCF were assessed according to the Positron Emission tomography Response Criteria In Solid Tumors (PERCIST) and Genant scores, respectively. Kaplan–Meier analyses were used to assess local control of disease and vertebral compression fracture-free survival (FFS).

Results

We treated 103 cases with single spMets and 11 cases involving double spMets with SBRT. Progressive disease was reported in 3.2% and 8.2% of the cases in the first and last PET/CT reports, respectively. The distribution of treatment response in the remaining patients was: complete response in 30.6% of patients, partial response in 47.1% of patients, and stable disease in 22.3% of patients in the first PET/CT; complete response in 62.3% of patients, partial response in 16.7% of patients, and stable disease in 21% of patients at the last monitoring. Local failures were observed in 15 (12%) of cases. Median SINS was 5 (range: 1−13); majority of patients in our cohort (70.4%) were categorized as stable according to SINS, five (4%) patients had Grade 3 VCF at a median time of 16 months after SBRT (range: 2−22 months), and 60% of VCF occurred after an interval of at least 12 months after SBRT. No bisphosphonate usage was significantly associated with VCF (r = −0.204; p = 0.022). Median FFS was 21 months. Univariate analyses indicated that female gender (p < 0.001), bisphosphonate use (p = 0.005), >6 months of bisphosphonates use (p = 0.002), and the lowest vertebral body collapse score (p = 0.023) were associated with higher FFS. Female gender (p = 0.007), >6 months of bisphosphonates usage (p = 0.018), and the lowest vertebral body collapse score (p = 0.044) retained independent significance.

Conclusions

This study demonstrated that spine SBRT with doses of 16–18 Gy promises good local control of disease with acceptable VCF rates. Lowest vertebral body collapse score, female gender, and >6 months of bisphosphonate use were significantly associated with longer FFS.

Optimizing diffusion-weighted magnetic resonance imaging for evaluation of lung tumors: A comparison of respiratory triggered and free breathing techniques

Purpose

The aim of this study was to compare respiratory-triggered (RT) and free breathing (FB) diffusion weighted imaging (DWI) techniques regarding apparent diffusion coefficient (ADC) measurements and repeatability in non-squamous non-small cell lung cancer (NSCLC) measuring the total tumor volume.

Material and Methods

A total of 57 magnetic resonance imaging (MRI) examinations were analyzed. DWI was obtained by a single-shot spin-echo echo-planar imaging sequence, and for each MRI examination 2 consecutive RT and 2 consecutive FB DWI sequences were performed. Two radiologists independently read the images and made measurements. For each tumor the mean ADC value of the whole tumor volume was calculated. The difference in mean ADCs between FB and RT DWI was evaluated using the paired-sample t-test. The repeatability of ADC measurements related to imaging method was evaluated by intra class correlations (ICC) for each of the FB and RT DWI pairs.

Results

There were no significant differences in mean ADCs between FB and RT (Reader 1 p = 0.346, Reader 2 p = 0.583). The overall repeatability of ADC measurement was good for both acquisition methods, with ICCs > 0.9. Subgroup analysis showed somewhat poorer repeatability in small tumors (50 ml or less) and tumors in the lower lung zones for the RT acquisition, with ICC as low as 0.72.

Conclusions

No difference in ADC measurement or repeatability between FB and RT DWI in whole lesion ADC measurements of adenocarcinomas in the lung was demonstrated. The results imply that in this setting the FB acquisition method is accurate and possibly more robust than the RT acquisition technique.

Diffusion-weighted (DW) MRI in lung cancers: ADC test-retest repeatability

PURPOSE

To determine the test-retest repeatability of Apparent Diffusion Coefficient (ADC) measurements across institutions and MRI vendors, plus investigate the effect of post-processing methodology on measurement precision.

METHODS

Thirty malignant lung lesions >2 cm in size (23 patients) were scanned on two occasions, using echo-planar-Diffusion-Weighted (DW)-MRI to derive whole-tumour ADC (b = 100, 500 and 800smm-2). Scanning was performed at 4 institutions (3 MRI vendors). Whole-tumour volumes-of-interest were copied from first visit onto second visit images and from one post-processing platform to an open-source platform, to assess ADC repeatability and cross-platform reproducibility.

RESULTS

Whole-tumour ADC values ranged from 0.66-1.94x10-3mm2s-1 (mean = 1.14). Within-patient coefficient-of-variation (wCV) was 7.1% (95% CI 5.7-9.6%), limits-of-agreement (LoA) -18.0 to 21.9%. Lesions >3 cm had improved repeatability: wCV 3.9% (95% CI 2.9-5.9%); and LoA -10.2 to 11.4%. Variability for lesions <3 cm was 2.46 times higher. ADC reproducibility across different post-processing platforms was excellent: Pearson's R2 = 0.99; CoV 2.8% (95% CI 2.3-3.4%); and LoA -7.4 to 8.0%.

CONCLUSION

A free-breathing DW-MRI protocol for imaging malignant lung tumours achieved satisfactory within-patient repeatability and was robust to changes in post-processing software, justifying its use in multi-centre trials. For response evaluation in individual patients, a change in ADC >21.9% will reflect treatment-related change.

KEY POINTS

• In lung cancer, free-breathing DWI-MRI produces acceptable images with evaluable ADC measurement. • ADC repeatability coefficient-of-variation is 7.1% for lung tumours >2 cm. • ADC repeatability coefficient-of-variation is 3.9% for lung tumours >3 cm. • ADC measurement precision is unaffected by the post-processing software used. • In multicentre trials, 22% increase in ADC indicates positive treatment response.

Diffusion MRI in early cancer therapeutic response assessment

Imaging biomarkers for the predictive assessment of treatment response in patients with cancer earlier than standard tumor volumetric metrics would provide new opportunities to individualize therapy. Diffusion-weighted MRI (DW-MRI), highly sensitive to microenvironmental alterations at the cellular level, has been evaluated extensively as a technique for the generation of quantitative and early imaging biomarkers of therapeutic response and clinical outcome. First demonstrated in a rodent tumor model, subsequent studies have shown that DW-MRI can be applied to many different solid tumors for the detection of changes in cellularity as measured indirectly by an increase in the apparent diffusion coefficient (ADC) of water molecules within the lesion. The introduction of quantitative DW-MRI into the treatment management of patients with cancer may aid physicians to individualize therapy, thereby minimizing unnecessary systemic toxicity associated with ineffective therapies, saving valuable time, reducing patient care costs and ultimately improving clinical outcome. This review covers the theoretical basis behind the application of DW-MRI to monitor therapeutic response in cancer, the analytical techniques used and the results obtained from various clinical studies that have demonstrated the efficacy of DW-MRI for the prediction of cancer treatment response. Copyright © 2016 John Wiley & Sons, Ltd.

Prospective pilot study of CT-guided microwave ablation in the treatment of osteoid osteomas

PURPOSE

The aims of this work were to assess the feasibility and efficacy of CT-guided microwave ablation (MWA) in the treatment of osteoid osteomas (OOs).

MATERIALS AND METHODS

Thirteen consecutive patients (range 11-31 years old) presenting with OO were prospectively included and treated by CT-guided MWA. Power and duration of MWA were both recorded. The patient's pain was assessed using a numeric pain rating scale (NRS), and side effects were recorded during procedures, after 1 day, 7 days and 1 month. The nidus vascularization and the volume of necrosis induced by MWA were assessed using contrast-enhanced MRI. Success was defined as the complete relief of the patient's pain 1 month after the first procedure, associated with necrosis of the nidus on follow-up MRI.

RESULTS

The success rate was up to 92.3% (12/13). At 1 day, 7 days and 1 month, the median NRSs were respectively 5 [interquartile range (IQR) 2-5], 0 (IQR 0-1) and 0 (IQR 0-0). Side effects observed were one partial and self-resolving lesion of a sensory branch of the radial nerve and two skin burns. The median power of the MWA used was 60 W (IQR 50-60) with a 1.5-min duration (IQR 1-2), leading to MWA-induced necrosis measuring on average 23 × 15 × 16 mm.

CONCLUSION

CT-guided MWA of OO has a success rate that appears to be almost similar to that of laser or radiofrequency ablation, but care must be taken to prevent nerve or skin lesions.

Evaluation of the efficacy of chemoradiotherapy in cervical cancer using diffusion-weighted imaging and apparent diffusion coefficient

Objective

This study aims to evaluate the efficacy of chemoradiotherapy (CRT) in cervical cancer using diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) values.

Methods

A total of 71 patients with cervical cancer were enrolled in this study. All patients underwent conventional magnetic resonance imaging and DWI scanning before CRT and at 7, 14, 21 days, and 6 months after CRT. These patients were divided into the complete response (CR) and non-CR groups according to the response evaluation criteria in solid tumors criteria. Receiver operating characteristic (ROC) curve was used to evaluate the accuracy of ADC values in predicting the efficacy of CRT in cervical cancer.

Results

Compared with before-CRT treatment, tumor volumes were reduced and ADC values were elevated in both CR and non-CR groups after CRT treatment. At 21 days after CRT, tumor volumes in the CR group were smaller than those in the non-CR group. During the period of 21 days to 6 months after CRT, tumor regression rate and the increased rate of ADC values in the CR group were higher than those in the non-CR group. ROC curves revealed that the increased rate of ADC values at 21 days after CRT was the optimal time point for the prediction of CRT efficacy in cervical cancer, with the area under the curve, sensitivity, and specificity of 0.775, 92.7%, and 62.5%, respectively.

Conclusion

Our study provides evidence that the increased rate of ADC at 21 days after CRT might be a promising tool for predicting the efficacy of CRT in cervical cancer.

Therapy Monitoring with Functional and Molecular MR Imaging

Cancer therapy is mainly based on different combinations of surgery, radiotherapy, and chemotherapy. Additionally, targeted therapies (designed to disrupt specific tumor hallmarks, such as angiogenesis, metabolism, proliferation, invasiveness, and immune evasion), hormonotherapy, immunotherapy, and interventional techniques have emerged as alternative oncologic treatments. Conventional imaging techniques and current response criteria do not always provide the necessary information regarding therapy success particularly to targeted therapies. In this setting, MR imaging offers an attractive combination of anatomic, physiologic, and molecular information, which may surpass these limitations, and is being increasingly used for therapy response assessment.

Inter- and intraobserver agreement of ADC measurements of lung cancer in free breathing, breath-hold and respiratory triggered diffusion-weighted MRI

OBJECTIVE

To prospectively evaluate the inter- and intraobserver agreement of apparent diffusion coefficient (ADC) measurements in free breathing, breath-hold, and respiratory triggered diffusion-weighted imaging (DWI) of lung cancer.

METHODS

Twenty-two patients with lung cancer (tumor size >2cm) underwent DWIs (3.0T) in three imaging methods. Lesion ADCs were measured twice by both of the two independent observers and compared.

RESULTS

No statistical significance was found among methods, though respiratory-triggered DWI tended to have higher ADCs than breath-hold DWI. Great inter- and intraobserver agreement was shown.

CONCLUSION

ADCs had good inter- and intraobserver agreement in all three DWI methods.

Mechanism and non-mechanism based imaging biomarkers for assessing biological response to treatment in non-small cell lung cancer

Therapeutic options in locally advanced non-small cell lung cancer (NSCLC) have expanded in the past decade to include a palate of targeted interventions such as high dose targeted thermal ablations, radiotherapy and growing platform of antibody and small molecule therapies and immunotherapies. Although these therapies have varied mechanisms of action, they often induce changes in tumour architecture and microenvironment such that response is not always accompanied by early reduction in tumour mass, and evaluation by criteria other than size is needed to report more effectively on response. Functional imaging techniques, which probe the tumour and its microenvironment through novel positron emission tomography and magnetic resonance imaging techniques, offer more detailed insights into and quantitation of tumour response than is available on anatomical imaging alone. Use of these biomarkers, or other rational combinations as readouts of pathological response in NSCLC have potential to provide more accurate predictors of treatment outcomes. In this article, the robustness of the more commonly available positron emission tomography and magnetic resonance imaging biomarker indices is examined and the evidence for their application in NSCLC is reviewed.

Dual time-point (18)F-FDG PET/CT to assess response to radiofrequency ablation of lung metastases

AIM

To establish the usefulness of dual time-point PET/CT imaging in determining the response to radiofrequency ablation (RFA) of solitary lung metastases from gastrointestinal cancer.

MATERIALS AND METHODS

This prospective study included 18 cases (3 female, 15 male, mean age 71±15 yrs) with solitary lung metastases from malignant digestive tract tumors candidates for RFA. PET/CT images 1h after injection of 4.07MBq/kg of (18)F-FDG (standard images) were performed at baseline, 1 month, and 3 months after RFA. PET/CT images 2h after injection centered in the thorax at 1 month after RFA were also performed (delayed images). A retention index (RI) of dual time-point images was calculated as follows: RI=(SUVmax delayed image-SUVmax standard image/SUVmax standard image)*100. Pathological confirmation of residual tumor by histology of the treated lesion was considered as local recurrence. A negative imaging follow-up was considered as complete response.

RESULTS

Local recurrence was found in 6/18 lesions, and complete response in the remaining 12. The mean percentage change in SUVmax at 1 month and at 3 months showed a sensitivity and specificity for PET/CT of 50% and 33%, and 67% and 92%, respectively. The RI at 1 month after RFA showed a sensitivity and specificity of 83% and 92%, respectively.

CONCLUSIONS

Dual time point PET/CT can predict the outcome at one month after RFA in lung metastases from digestive tract cancers. The RI can be used to indicate the need for further procedures to rule out persistent tumor due to incomplete RFA.

Radiofrequency ablation of advanced lung tumors: imaging features, local control, and follow-up protocol

To prospectively observe imaging features and local control of advanced lung tumors after radiofrequency ablation (RFA), and to propose a follow-up protocol post-ablation. 58 stage IV malignant lung tumor patients were enrolled in our study. One hundred of lung lesions were performed 77 sessions of RFA. Enhanced computed tomographic (CT) images of pre-ablation, 1-month, and 3-month post-ablation and thereafter every 3 months were obtained. Positron emission tomographic/CT (PET/CT) was performed pre-ablation, 3-month post-ablation and thereafter every 6 months. The CT size, shape, enhancement, and PET/CT metabolic activity of the ablated zone were analyzed to assess local lesion control. There was significant difference in lesion size between pre-ablation and 1-month post-ablation (P=0.000), 1 and 3-month post-ablation (P=0.000), 3 and 6-month post-ablation (P=0.006). Metabolic activity of the ablated zone after 3 months decreased markedly as compared with pre-ablation (p=0.001). Local control rate was 88%, and forms of definite recurrence or residual included increased size, nodular enhancement, and central enhancement. Time to local progression (TTLP), progression-free survival (PFS), and overall survival (OS) were 15.4±7.5, 9.6±5.8 and 18.0±7.0 months respectively. No death related to operation occurred, and the main complication rate was 29%, of which 9% needed clinical management. RFA is a safe and effective approach for local control of lung tumors even if in advanced patients. To obtain definite CT evaluation, lesion size at 1-month post-ablation as the baseline is appropriate, with efficacy assessment 6-month post-ablation. PET/CT is a useful tool to predict recurrence or residual at least 3 months post-ablation.

Intravoxel Incoherent Motion Diffusion Weighted MR Imaging for Monitoring the Instantly Therapeutic Efficacy of Radiofrequency Ablation in Rabbit VX2 Tumors without Evident Links between Conventional Perfusion Weighted Images

OBJECTIVE

To investigate the intravoxel incoherent motion diffusion weighted imaging (IVIM-DWI) as a potential valuable marker to monitor the therapy responses of VX2 to radiofrequency ablation (RF Ablation).

METHODS

The institutional animal care and use committee approved this study. In 10 VX2 tumor-bearing rabbits, IVIM-DWI examinations were performed with a 3.0T imaging unit by using 16 b values from 0 to 800 sec/mm2. The true diffusion coefficient (D), pseudodiffusion coefficient (D*) and perfusion fraction (f) of tumors were compared between before and instantly after RF Ablation treatment. The differences of D, D* and f and conventional perfusion parameters (from perfusion CT and dynamic enhanced magnetic resonance imaging, DCE-MRI) in the coagulation necrosis area, residual unablated area, untreated area, and normal control had been calculated by compared t-test. The correlation between f or D* with perfusion weighted CT including blood flow, BF (milliliter per 100 mL/min), blood volume, BV (milliliter per 100 mL/min), and capillary permeability-surface area, PMB (as a fraction) or from DCE-MRI: transfer constant (Ktrans), extra-vascular extra-cellular volume fraction (Ve) and reflux constant (Kep) values had been analyzed by region-of-interest (ROI) methods to calculate Pearson's correlation coefficients.

RESULTS

In the ablated necrosis areas, f and D* significantly decreased and D significantly increased, compared with residual unblazed areas or untreated control groups and normal control groups (P < 0.001). The IVIM-DWI derived f parameters showed significant increases in the residual unablated tumor area. There was no significant correlations between f or D* and conventional perfusion parameters.

CONCLUSIONS

The IVIM-DW derived f, D and D* parameters have the potential to indicate therapy response immediately after RF Ablation treatment, while no significant correlations with classical tumor perfusion metrics were derived from DCE-MRI and perfusion-CT measurements.

Diffusion-weighted magnetic resonance imaging for assessment of lung lesions: repeatability of the apparent diffusion coefficient measurement

PURPOSE

To establish repeatability of apparent diffusion coefficients (ADCs) acquired from free-breathing diffusion-weighted magnetic resonance imaging (DW-MRI) in malignant lung lesions and investigate effects of lesion size, location and respiratory motion.

METHODS

Thirty-six malignant lung lesions (eight patients) were examined twice (1- to 5-h interval) using T1-weighted, T2-weighted and axial single-shot echo-planar DW-MRI (b = 100, 500, 800 s/mm(2)) during free-breathing. Regions of interest around target lesions on computed b = 800 s/mm(2) images by two independent observers yielded ADC values from maps (pixel-by-pixel fitting using all b values and a mono-exponential decay model). Intra- and inter-observer repeatability was assessed per lesion, per patient and by lesion size (> or <2 cm) or location.

RESULTS

ADCs were similar between observers (mean ± SD, 1.15 ± 0.28 × 10(-3) mm(2)/s, observer 1; 1.15 ± 0.29 × 10(-3) mm(2)/s, observer 2). Intra-observer coefficients of variation of the mean [median] ADC per lesion and per patient were 11% [11.4%], 5.7% [5.7%] for observer 1 and 9.2% [9.5%], 3.9% [4.7%] for observer 2 respectively; inter-observer values were 8.9% [9.3%] (per lesion) and 3.0% [3.7%] (per patient). Inter-observer coefficient of variation (CoV) was greater for lesions <2 cm (n = 20) compared with >2 cm (n = 16) (10.8% vs 6.5% ADCmean, 11.3% vs 6.7% ADCmedian) and for mid (n = 14) vs apical (n = 9) or lower zone (n = 13) lesions (13.9%, 2.7%, 3.8% respectively ADCmean; 14.2%, 2.8%, 4.7% respectively ADCmedian).

CONCLUSION

Free-breathing DW-MRI of whole lung achieves good intra- and inter-observer repeatability of ADC measurements in malignant lung tumours.

KEY POINTS

• Diffusion-weighted MRI of the lung can be satisfactorily acquired during free-breathing • DW-MRI demonstrates high contrast between primary and metastatic lesions and normal lung • Apparent diffusion coefficient (ADC) measurements in lung tumours are repeatable and reliable • ADC offers potential in assessing response in lung metastases in clinical trials.

Functional imaging biomarkers for assessing response to treatment in liver and lung metastases

Management of patients with metastatic cancer and development of new treatments rely on imaging to provide non-invasive biomarkers of tumour response and progression. The widely used size-based criteria have increasingly become inadequate where early measures of response are required to avoid toxicity of ineffective treatments, as biological, physiologic, and molecular modifications in tumours occur before changes in gross tumour size. A multiparametric approach with the current range of imaging techniques allows functional aspects of tumours to be simultaneously interrogated. Appropriate use of these imaging techniques and their timing in relation to the treatment schedule, particularly in the context of clinical trials, is fundamental. There is a lack of consensus regarding which imaging parameters are most informative for a particular disease site and the best time to image so that, despite an increasing body of literature, open questions on these aspects remain. In addition, standardization of these new parameters is required. This review summarizes the published literature over the last decade on functional and molecular imaging techniques in assessing treatment response in liver and lung metastases.

Increase in fluorodeoxyglucose positron emission tomography activity following complete radiofrequency ablation of lung tumors

OBJECTIVE

The objective of this study was to evaluate the F-fluorodeoxyglucose positron emission tomography (F-FDG-PET) findings following complete radiofrequency ablation (RFA) treatment of malignant lung tumors.

METHODS

Follow-up PET and computed tomography examinations in 18 patients (mean age, 67 ± 16 years [range, 30-91 years]; 10 males, 8 females) who underwent 19 RFA sessions for the treatment of primary (n = 14) and metastatic (n = 5) lung tumors with mean follow-up of 18 months (range, 12-24 months) were retrospectively reviewed by 2 thoracic radiologists. All tumors were completely ablated. The maximum standardized uptake value (SUV) of the tumor and surrounding lung at baseline and at 1, 6, 12 and 24 months after RFA was measured. In addition, the size, histology, location of the tumor, presence of underlying emphysema, electrode type, and complications from RFA were recorded. Data were analyzed using Fisher exact test.

RESULTS

Baseline tumor SUV was variable (mean, 1.8 ± 1.5 [range, 0.7-7]). The post-RFA F-FDG-PET appearances could be divided into 2 groups. A ring of peripheral activity and central photopenia was seen following 13 (68%) of 19 of ablations, and no ring was noted following 6 (32%) of 19 of ablations. The ring of F-FDG-PET activity was present at 1 month in 62%, at 6 months in 69% and at both 1 and 6 months in 31%. In all cases, central photopenia at 1 or 6 months was replaced by increased activity as the ring resolved at 6 or 12 months, mimicking local tumor progression. The presence of a ring of activity was associated with the use of a cluster electrode (P = 0.01). Lesion size, histology, location, baseline SUV, electrode type, or development of cavitation following RFA were not significantly associated with a post-RFA ring (P > 0.05) on PET scans. At 12 or 24 months, the SUV in the center of the lesion was equal to or greater than the SUV at baseline in 9 (47%) of 19 cases.

CONCLUSIONS

Recognition of the normal FDG-PET appearances after RFA is important to prevent misdiagnosis of local tumor progression.

Radiofrequency ablation of lung tumors: imaging features of the postablation zone

Radiofrequency ablation (RFA) is used to treat pulmonary malignancies. Although preliminary results are suggestive of a survival benefit, local progression rates are appreciable. Because a patient can undergo repeat treatment if recurrence is detected early, reliable post-RFA imaging follow-up is critical. The purpose of this article is to describe (a) an algorithm for post-RFA imaging surveillance; (b) the computed tomographic (CT) appearance, size, enhancement, and positron emission tomographic (PET) metabolic activity of the ablation zone; and (c) CT, PET, and dual-modality imaging with PET and CT (PET/CT) features suggestive of partial ablation or tumor recurrence and progression. CT is routinely used for post-RFA follow-up. PET and PET/CT have emerged as auxiliary follow-up techniques. CT with nodule densitometry may be used to supplement standard CT. Post-RFA follow-up was divided into three phases: early (immediately after to 1 week after RFA), intermediate (>1 week to 2 months), and late (>2 months). CT and PET imaging features suggestive of residual or recurrent disease include (a) increasing contrast material uptake in the ablation zone (>180 seconds on dynamic images), nodular enhancement measuring more than 10 mm, any central enhancement greater than 15 HU, and enhancement greater than baseline anytime after ablation; (b) growth of the RFA zone after 3 months (compared with baseline) and definitely after 6 months, peripheral nodular growth and change from ground-glass opacity to solid opacity, regional or distant lymph node enlargement, and new intrathoracic or extrathoracic disease; and (c) increased metabolic activity beyond 2 months, residual activity centrally or at the ablated tumor, and development of nodular activity.

Diffusion magnetic resonance imaging of chest tumors

This review provides an overview of the current status of the published data on diffusion magnetic resonance (MR) imaging of chest tumors. Diffusion MR imaging is a non-invasive imaging technique that measures the differences in water mobility in different tissue microstructures and quantifies them based on the apparent diffusion coefficient. Diffusion MR imaging has been used for the characterization, grading and staging of lung cancer as well as for differentiating central tumors from post-obstructive consolidation. In addition, this technique helps in differentiating malignant from benign pulmonary and mediastinal tumors as well as in the characterization of pleural mesothelioma and effusion. Diffusion MR imaging can be incorporated into routine morphological MR imaging to improve radiologist confidence in image interpretation and to provide functional assessments of chest tumors during the same examination. Diffusion MR imaging could be used in the future as a functional imaging technique for tumors of the chest.

Therapy response with diffusion MRI: an update

The efficiency of an oncological treatment regimen is often assessed by morphological criteria such as tumour size evaluated by cross-sectional imaging, or by laboratory measurements of plasma biomarkers. Because these types of measures typically allow for assessment of treatment response several weeks or even months after the start of therapy, earlier response assessment that provides insight into tumour function is needed. This is particularly urgent for the evaluation of newer targeted therapies and for fractionated therapies that are delivered over a period of weeks to allow for a change of treatment in non-responding patients. Diffusion-weighted MRI (DW-MRI) is a non-invasive imaging tool that does not involve radiation or contrast media, and is sensitive to tissue microstructure and function on a cellular level. DW-MRI parameters have shown sensitivity to treatment response in a growing number of tumour types and organ sites, with additional potential as predictive parameters for treatment outcome. A brief overview of DW-MRI principles is provided here, followed by a review of recent literature in which DW-MRI has been used to monitor and predict tumour response to various therapeutic regimens.

Oncologic applications of diffusion-weighted MRI in the body

Diffusion-weighted MRI (DWI) allows the detection of malignancies in the abdomen and pelvis. Lesion detection and characterization using DWI largely depends on the increased cellularity of solid or cystic lesions compared with the surrounding tissue. This increased cellularity leads results in restricted diffusion as indicated by reduction in the apparent diffusion coefficient (ADC). Low pretreatment ADC values of several malignancies have been shown to be predictive of better outcome. DWI can assess response to systemic or regional treatment of cancer at a cellular level and will therefore detect successful treatment earlier than anatomical measures. In this review, we provide a brief technical overview of DWI, discuss quantitative image analysis approaches, and review studies which have used DWI for the purpose of detection and characterization of malignancies as well as the early prediction of treatment response.

Tumour response prediction by diffusion-weighted MR imaging: ready for clinical use?

BACKGROUND

The efficacy of anticancer therapy is usually evaluated by anatomical imaging. However, this method may be suboptimal for the evaluation of novel treatment modalities, such as targeted therapy. Theoretically, functional assessment of tumour response by diffusion weighted imaging (DWI) is an attractive tool for this purpose and may allow an early prediction of response. The optimal use of this method has still to be determined.

METHOD

We reviewed the published literature on clinical DWI in the prediction of response to anticancer therapy, especially targeted therapy. Studies investigating the role of DWI in patients with cancer either for response prediction and/or response monitoring were selected for this analysis.

RESULTS

We identified 24 studies that met our criteria. Most studies showed a significant correlation between (changes in) apparent diffusion coefficient (ADC) values and treatment response. However, in different tumours and studies, both high and low pretreatment ADC were found to be associated with response rate. In the course of treatment, an increase in ADC was associated with response in most cases.

CONCLUSION

The potential of DWI for (early) response monitoring of anticancer therapies has been demonstrated. However, validation is hampered by the lack of reproducibility and standardisation. We recommend that these issues should be properly addressed prior to further testing the clinical use of DWI in the assessment of treatments.

Imaging follow-up of RF ablation of lung tumours

Imaging is important in the decision-making process of how to treat a lung tumour, which ideally should be a multi-disciplinary team decision. Imaging is important during radiofrequency ablation (RFA) treatment with regard to optimal placement of the electrode, the immediate post-treatment criteria and very early detection of complications of the procedure. Imaging is very important in the treatment follow-up. In lung RFA, as in many other interventional procedures, the traditional morphological imaging techniques to evaluate treatment response have difficulties and functional imaging techniques may potentially be more useful. However, larger studies showing this impact have not yet been performed.

Applications of molecular imaging

Today molecular imaging technologies play a central role in clinical oncology. The use of imaging techniques in early cancer detection, treatment response, and new therapy development is steadily growing and has already significantly impacted on clinical management of cancer. In this chapter, we overview three different molecular imaging technologies used for the understanding of disease biomarkers, drug development, or monitoring therapeutic outcome. They are (1) optical imaging (bioluminescence and fluorescence imaging), (2) magnetic resonance imaging (MRI), and (3) nuclear imaging (e.g., single-photon emission computed tomography (SPECT) and positron emission tomography (PET)). We review the use of molecular reporters of biological processes (e.g., apoptosis and protein kinase activity) for high-throughput drug screening and new cancer therapies, diffusion MRI as a biomarker for early treatment response and PET and SPECT radioligands in oncology.

Radiofrequency ablation of lung tumours

Pulmonary radiofrequency ablation (RFA) has become an increasingly adopted treatment option for primary and metastatic lung tumours. It is mainly performed in patients with unresectable or medically inoperable lung neoplasms. The immediate technical success rate is over 95%, with a low periprocedural mortality rate and 8–12% major complication rate. Pneumothorax represents the most frequent complication, but requires a chest tube drain in less than 10% of cases. Sustained complete tumour response has been reported in 85–90% of target lesions. Lesion size represents the most important risk factor for local recurrence. Survival data are still scarce, but initial results are very promising. In patients with stage I non-small-cell lung cancer, 1- and 2-year survival rates are within the ranges of 78–95% and 57–84%, respectively, with corresponding cancer-specific survival rates of 92% and 73%. In selected cases, the combination of RFA and radiotherapy could improve these results. In patients with colorectal lung metastasis, initial studies have reported survival data that compare favourably with the results of metastasectomy, with up to a 45% 5-year survival rate. Further studies are needed to understand the potential role of RFA as a palliative treatment in more advanced disease and the possible combination of RFA with other treatment options.

Thermal ablation of lung tumors

The 5-year survival for all stages of nonsmall cell lung cancer (NSCLC) remains bleak, having increased from 13% to just 16% over the past 30 years. Despite promising results in nonoperative patients with NSCLC and pulmonary metastatic disease, thermal ablation appears to be limited by large tumor size and proximity to large vessels. This article discusses the particular challenges of performing thermal ablation in aerated lung tissue and reviews important considerations in performing ablation including treatment complications and imaging follow-up. The article compares and contrasts the three major thermal ablation modalities: radiofrequency ablation, microwave ablation, and cryoablation.

Therapeutic response to radiofrequency ablation of neoplastic lesions: FDG PET/CT findings

Ablation of neoplastic lesions by using radiofrequency energy is gaining popularity in clinical practice because of the minimally invasive nature of radiofrequency ablation (RFA). Primary and secondary tumors of the liver and lung are treated with RFA when surgery is precluded because of comorbidity. Benign bone tumors are also treated with RFA to relieve pain and prevent further tumor growth. Differentiation between postablation tissue changes and residual disease is difficult with morphologic imaging modalities such as ultrasonography, computed tomography (CT), and magnetic resonance (MR) imaging, thus limiting the use of these modalities to detection of residual disease early after RFA. Fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) is a functional imaging modality that can be used to study the effects and efficacy of RFA. Lesions that show increased FDG uptake at PET become completely photopenic immediately after RFA, a finding that is suggestive of the completeness of ablation. Focal areas of increased FDG uptake within the ablated zone are suggestive of residual disease. Reactive tissue changes such as inflammation are depicted in the periphery of the ablated lesion and show a uniform low-grade FDG uptake, which can be differentiated from the focal, nodular intense uptake in areas of residual disease. Use of combined FDG PET/CT to detect residual disease early after RFA allows ablation to be repeated, if necessary, to obtain the maximum therapeutic benefit. Note that FDG uptake in the complications sometimes associated with RFA can be a cause of potential false-positive PET results.

Interventional oncology: the future

Interventional radiology techniques to treat oncological disease have already shown value in adults. The adoption and development of interventional oncology (IO) in children have been more limited and challenging. This relates to the approval process for new devices and agents, oncology group protocol limitations and the inherent hesitation of trying new treatments in children. This paper will discuss how new procedures are developed and approved, and the new therapies that will become available to better treat pediatric malignancies. Bringing the benefits of IO to children will require initiative on the part of pediatric diagnostic and interventional radiologists as well as the cooperation of our clinical colleagues.

Evaluation of treatment response after nonoperative therapy for early-stage non-small cell lung carcinoma

Nonsurgical management of early primary lung cancer has grown tremendously in recent years, and today, available options extend far beyond that of conventional radiation therapy (CRT) to include minimally invasive image-guided delivery of thermal energies, specifically radiofrequency ablation, microwave ablation, and cryoablation, and more conformal stereotactic body radiation therapy. Because the tumor is never resected with these nonoperative interventions, histopathological evaluation of tumor margins for the presence of residual tumor is impossible, and as such, tumor response after each of these therapies is largely based on imaging. To date, computerized tomography and computerized tomography-positron emission tomography remain the most readily available modalities for assessment of therapeutic efficacy, and to this end as detailed within this article, strict imaging survey and familiarity with the expected imaging characteristics of the treated tumor will aid in recognition of unexpected findings, specifically those of incomplete therapy and/or tumor recurrence.

Diffusion-weighted imaging of the chest

Diffusion-weighted imaging (DWI) is feasible in the chest with currently available MR imaging scanners, although it is technically demanding. Although there is scarce clinical experience, the use of DWI has shown promising results in the characterization of pulmonary nodules, in lung cancer characterization and staging, and in the evaluation of mediastinal and pleural pathology. Ongoing research opens a door to noninvasive evaluation of heart fibers by means of diffusion-tensor imaging. Another area under investigation is the use of DWI of hyperpolarized gases as an early biomarker of pulmonary disease.