Preliminary retrospective investigation of FDG-PET/CT timing in follow-up of ablated lung tumor

Imaging of the thorax after percutaneous thermal ablation of lung malignancies

Image-guided thermal ablation is a minimally invasive treatment option for patients with early stage non-small cell lung cancer or metastatic disease to the lungs. Percutaneous ablation treats malignant tumours in situ, which precludes histopathological evaluation of the ablated tumours. Imaging studies are used as surrogates to assess technical and clinical success. Although it is not universally accepted, a common protocol for surveillance imaging includes contrast-enhanced computed tomography (CT) at 1, 3, 6, 9, 12, 18, 24 months, and yearly thereafter. Integrated 2-[¹⁸F]-fluoro-2-deoxy-d-glucose positron-emission tomography (PET)/CT imaging is recommended at 3 and 12 months and when recurrent disease is suspected. There is a complex evolution of the ablation zone on CT and PET imaging studies. The zone of ablation, initially larger than the ablated tumour, undergoes gradual involution. In the process, it may cavitate and resemble a lung abscess. Different contrast-enhancement and radionuclide uptake patterns in and around the ablation zone may indicate a wide range of diagnostic possibilities from a normal physiological response to local progression. Ultimately, the zone of ablation may be replaced by a variety of findings including linear bands of density, pleural thickening, or residual necrotic tumour. Diagnostic and interventional radiologists interpreting post-ablation imaging studies must have a clear understanding of the ablation process and imaging findings on surveillance studies. Accurate and timely recognition of complications and/or local recurrence is necessary to guide further therapy. The purpose of this article is to review imaging protocols and salient imaging findings after thermal ablation of lung malignancies.

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.

Role of dual-energy computed tomography in detecting early recurrences of lung tumours treated with radiofrequency ablation

PURPOSE

Detecting a recurrence after lung radiofrequency ablation (RFA) is based on a group of arguments that include CT, positron emission tomography (PET-CT) at 3 months and clinical patient follow-up. There is no one examination that is absolutely reliable. Recurrences are diagnosed tardily, when the cancers are locally extended, or when the patients are metastatic. The purpose of this article is to investigate the utility of dual-energy computed tomography (DECT) in order to assess therapeutic responses to RFA for lung neoplasia.

MATERIALS AND METHODS

This institutional review board-approved study enroled 70 patients with lung tumours who underwent DECT after RFA. All patients provided a written informed consent for the study.

RESULTS

The study included 70 consecutive patients, and 191 DECT measures were performed. We collected the enhancement values of all scars without establishing a prior threshold of positivity. The optimal threshold value areas appeared to be located between 20 and 35 Hounsfield unit (HU) with sensitivity between 70% and 82%; specificity between 72% and 90%; a negative predictive value (NPV) between 96% and 97% and a diagnostic accuracy index between 73% and 87%. At the one month follow-up, 53 nodules were analysed with DECT and four nodules had recurred, all of which were detected by DECT. The sensitivity, which was calculated at 100%, was excellent; the NPV was at 100% (CI: 91.62, 100) and the specificity was at 85.71% (CI: 73.33, 92.9). The diagnostic accuracy index was 86.79% (CI: 75.16, 93.45) and the average DECT acquisitions dosimetry was 106 mGy.cm (33mGy.cm 245mGy.cm).

CONCLUSION

DECT could be a conceivable alternative for detecting early recurrence after lung RFA. Key points After lung RFA, a PET CT has a high rate of false positives in the initial phase; The study of enhancement in the follow-up of lung lesions treated with RFA, and especially by DECT, can be relevant; Dual Energy CT has a good efficiency for a threshold between 20 and 35 HU, especially in the first month after RFA; DECT could be a conceivable alternative for detecting early recurrence.

Short-term effect analysis of radiofrequency ablation combined chemotherapy on middle and late period non-small cell lung cancer

In this study, we investigated the effect of radiofrequency ablation (RFA) combined chemotherapy on middle and late period non-small cell lung cancer (NSCLC). In total, 85 cases of middle and late period NSCLC patients were selected, and were randomly divided into the RFA combined chemotherapy group, RFA treatment group and chemotherapy group. After treatment, the three groups were followed up for computed tomography (CT) scan, and were analyzed for the effect of RFA combined chemotherapy on middle and late period NSCLC. It was found that CT value of RFA combined chemotherapy group decreased significantly compared to before surgery (P<0.05). The CT value of the RFA group decreased significantly compared to before surgery (P<0.05). The CT value of chemotherapy group was not significantly changed compared to before surgery (P>0.05). The postoperative CT value of the RFA combined chemotherapy group and RFA group was smaller compared to that of the chemotherapy group (P<0.05). Effective rate [complete response (CR) + partial response (PR)] of RFA combined chemotherapy group was significantly higher than that of the EFA and chemotherapy groups (P<0.05). Effective rate (CR+PR) of the RFA group was significantly higher than that of the chemotherapy group (P<0.05). By contrast, the progressive rate (P) of RFA combined chemotherapy group was significantly lower than that of the RFA and chemotherapy groups (P<0.05). In conclusion, RFA combined chemotherapy has obvious effect on middle and late period NSCLC, and is safe and feasible.

FDG-PET in the evaluation of response to nivolumab in recurrent non-small-cell lung cancer

BACKGROUND

Nivolumab, an immune checkpoint inhibitor, is recently clinically applied to non-small cell lung cancer (NSCLC) treatment, and this causes T cell activation and T cell infiltration to tumor tissue through the blockade of the interaction between programmed cell death 1 (PD-1) and programmed cell death ligand 1 (PD-L1). 18F-fluorodeoxyglucose-positron emission tomography (FDG-PET) sometimes shows false positive because of the recruitment of neutrophils, lymphocytes, and macrophages. To date, there is only one report except our case, which described the correlation between FDG-PET and nivolumab.

CASE PRESENTATION

We report on a 75-year-old man on nivolumab treatment for metastatic non-small cell lung cancer. He had undergone right lower lobectomy for lung adenocarcinoma in the right S8 segment 10 months prior to recurrence. Pathological findings revealed invasive adenocarcinoma, pT1bN2M0 stage IIIA. Epidermal growth factor receptor (EGFR) mutation was positive for de novo T790M and anaplastic lymphoma kinase (ALK) rearrangement was negative. Immunohistochemistry was negative for PD-L1. He underwent chemotherapy with a combination of cisplatin and pemetrexed for four cycles but developed progressive disease involving the right hemithorax, multiple lymph nodes, and multiple osseous sites. Nivolumab was instituted as a second-line chemotherapy. After six courses of this immunotherapy, FDG-PET scan showed decreased FDG uptake in each recurrent lesion despite T lymphocyte activation by nivolumab. Serum carcinoembryonic antigen (CEA) level was also remarkably decreased.

CONCLUSIONS

Nivolumab's effect on recurrent NSCLC may be monitored by PET; larger studies are needed.

Utilizing gemstone spectral CT imaging to evaluate the therapeutic efficacy of radiofrequency ablation in lung cancer

PURPOSE

To evaluate the therapeutic efficacy of radiofrequency ablation (RFA), quantitative water-based, and iodine-based images of gemstone spectral computed tomography (CT) were analyzed.

PATIENTS AND METHODS

30 patients underwent lung RFAs from March 2012 to March 2013. Through enhanced chest scans, we obtained the tumor size values by conventional CT images, and quantitatively analyzed the densities of iodine and water in lung tumors from water-based and iodine-based material decomposition images.

RESULTS

Tumors in 22 cases increased in size after RFA while there was no detectable change in the remaining 8 cases. Through water-based material decomposition images, the water content in the tumors increased from (1014.76 ± 6.83 mg/mL) to (1022.71 ± 10.16 mg/mL) after RFA, and this difference was significant (t = -2.329, p < 0.05). Through iodine-based material decomposition images, the iodine content in the tumors was 2.49 ± 0.74 mg/mL before RFA. The tumors were mostly or completely necrotized after RFA and the iodine content in the area of necrosis reduced to 0.45 ± 0.29 mg/m (t = 11.072, p = 0.000).

CONCLUSION

By comparing the tumor size, water content and iodine content before and after RFA, we can visualize the morphology and metabolic states of the tumors and evaluate the therapeutic efficiency.

Characteristic CT Findings After Percutaneous Cryoablation Treatment of Malignant Lung Nodules

Assess computed tomography (CT) imaging characteristics after percutaneous cryotherapy for lung cancer.A retrospective IRB-approved analysis of 40 patients who underwent nonsurgical treatment for primary stage 1 lung cancer performed from January 2007 to March 2011 was included in this study. All procedures were performed using general anesthesia and CT guidance. Follow-up imaging with CT of the chest was obtained at 1 month, 3 months, 6 months, and 12 months postprocedure to evaluate the ablated lung nodule. Nodule surface area, density (in Hounsfield units), and presence or absence of cavitations were recorded. In addition, the degree of nodule enhancement was also recorded. Patients who were unable to obtain the aforementioned follow-up were excluded from the study.Thirty-six patients underwent percutaneous cryoablation with men to women ratio of 75% with mean age for men 74.6 and mean age for women 74.3 years of age. The average nodule surface area preablation and postcryoablation at 1-, 3-, 6-, and 12-month follow-ups were 2.99, 7.86, 3.89, 3.18 and 3.07[REPLACEMENT CHARACTER]cm, respectively. The average precontrast nodule density before cryoablation was 8.9 and average precontrast nodule density postprocedure at 1, 3, 6, and 12 months follow-ups were 8.5, -5.9, -9.4, and -3.8 HU, respectively. There is increased attenuation of lung nodules over time with an average postcontrast enhancement of 11.4, 18.5, 16.1, and 25.7 HU at the aforementioned time intervals. Cavitations occurred in the cryoablation zone in 53% (19/36) of patients. 80.6% (29/36) of the cavitations in the cryoablation zone resolved within 12 months. Four patients (11%) had recurrence of tumor at the site of cryoablation and none of the patients had satellite or distant metastasis.Our study shows that patients who underwent cryotherapy for lung nodules treatment had characteristic changes on follow-up CT including. The surface area of the nodule increases at the 1-month follow-up with subsequent gradual decrease in the surface area. Decreased nodule density (Hounsfield units) at each interval follow-up is associated with complete ablation of the lung cancer whereas increasing nodule density was suggestive of recurrence. Cavity formation within the region of the ablated nodule, most of which typically resolved within the first 3 to 6 months. Nodule enhancement is difficult to assess because of the limited data sets that are available.

Role of PET/Computed Tomography in Radiofrequency Ablation for Malignant Pulmonary Tumors

Radiofrequency ablation (RFA) is a useful tool for local control of unresectable pulmonary neoplastic lesions. However, RFA is limited to tumors smaller than 4 cm and peripheral lesions. The sensitivity and specificity of FDG-PET are higher than those of computed tomography. FDG-PET at 3 to 6 months after RFA is important for predicting recurrence. Complications associated with RFA, such as infection and abscess formation, which concentrate glucose in the ablation area, can cause false-positive findings in PET examination. Knowledge of the morphologic imaging features of these complications is important in avoiding these potential pitfalls.

Lung radiofrequency and microwave ablation: a review of indications, techniques and post-procedural imaging appearances

Lung ablation can be used to treat both primary and secondary thoracic malignancies. Evidence to support its use, particularly for metastases from colonic primary tumours, is now strong, with survival data in selected cases approaching that seen after surgery. Because of this, the use of ablative techniques (particularly thermal ablation) is growing and the Royal College of Radiologists predict that the number of patients who could benefit from such treatment may reach in excess of 5000 per year in the UK. Treatment is often limited to larger regional centres, and general radiologists often have limited awareness of the current indications and the techniques involved. Furthermore, radiologists without any prior experience are frequently expected to interpret post-treatment imaging, often performed in the context of acute complications, which have occurred after discharge. This review aims to provide an overview of the current indications for pulmonary ablation, together with the techniques involved and the range of post-procedural appearances.

A phase II study of radiofrequency ablation therapy for thoracic malignancies with evaluation by FDG-PET

PURPOSE

Computed tomography (CT)-guided radiofrequency ablation (RFA) is safe and effective for patients with unresectable primary, recurrent, or metastatic thoracic malignancies. Several studies have shown the benefit of employing 18-fluoro-deoxyglucose positron-emission tomography (FDG-PET) to follow thoracic malignancies treated with RFA. In this prospective study, we show the safety and therapeutic efficacy of RFA and the utility of FDG-PET as tool for early detection of local recurrence.

METHODS

Twenty patients were enrolled in this study, and 24 lesions were ablated. Seven lesions were primary lung cancer, and 17 lesions were recurrent tumors or metastases from extrathoracic sites. Tumor size was in the range of 0.4-3.3 cm in diameter (mean: 1.5 cm). CT and FDG-PET scans were scheduled 7-14 days and 3-6 months after RFA treatment.

RESULTS

There were 17 adverse events (70.8 %) in 24 ablations included 13 pneumothoraces, two cases of chest pain, and two episodes of fever. With a median follow-up of 35.9 months (range 1-62 months), the overall 2-year survival rate was 84.2 %. Local recurrence occurred at four sites (2-year local control rate was 74.3 %). The FDG-PET results 7-14 days after RFA did not predict recurrence, whereas positive findings 3-6 months after RFA significantly correlated with local recurrence (p = 0.0016).

CONCLUSIONS

We confirmed the effectiveness of RFA for unresectable primary and secondary thoracic malignancies. FDG-PET analysis 3-6 months after ablation is a useful tool to assess local control.

Percutaneous strategies for the management of pulmonary parenchymal, chest wall, and pleural metastases

OBJECTIVE

The purposes of this article are to review the indications for and technical aspects of various percutaneous strategies available for the treatment of intrathoracic metastases involving the parenchyma, pleura, and chest wall and to describe the relative merits of one of these strategies over another to determine the best approach to use.

CONCLUSION

The thorax is a common site of metastatic disease with frequent involvement of the lungs, pleura, and osseous structures. A variety of interventional procedures and techniques are available for treatment and for palliative care of patients with this disease. Imaging-guided interventions include thermal ablation of metastatic disease of the lungs and pleura, catheter placement and sclerosis of malignant pleural effusions, and palliative pain management for osseous and soft-tissue metastases.

Case report: Positron emission tomography fails to detect pulmonary adenocarcinoma recurrence after radiofrequency ablation

We describe the case of late recurrence of a focus of invasive mucinous adenocarcinoma (formerly mucinous bronchioloalveolar carcinoma) following radiofrequency ablation, despite a negative positron emission tomography/computed tomography scan at 13 months following the ablation. A computed tomography scan performed at 24 months demonstrated unequivocal recurrence of the lesion. Combined positron emission tomography/computed tomography has been described as an adequate modality for the follow-up of thermally ablated pulmonary lesions. However, its utility in the follow-up of well-differentiated pulmonary adenocarcinoma may be limited. Lesion activity may be underestimated by an inherently low metabolic activity. Small lesions may also be susceptible to partial volume effect. Long-term imaging follow-up of well-differentiated pulmonary adenocarcinoma beyond two years after thermal ablation is prudent to avoid missing late recurrence.

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.

Diagnostic yield of baseline and follow-up PET/CT studies in ablative therapy for non-small cell lung cancer

Although they have proven effectiveness, radiofrequency and microwave ablation techniques have a high rate of partial responses. Diagnostic studies that anticipate the changes in morphology are essential for earlier detection of residual viable tumor tissue or local recurrences to identify patients who will benefit from a new treatment. Our study has determined the diagnostic yield of PET/CT studies at baseline and follow-up and adequate time between them and the ablation intervention. Seven patients with single tumor lesion with a total of 8 ablations were included. CT and PET/CT studies were performed at baseline and follow-up after ablation. Average times between PET studies at baseline and follow-up and the ablative therapy were 1.8 and 3.4 months, respectively. Mean scores in metabolic activities of the PET at baseline and follow-up were 7.6 and 4.3g/ml of SUVmax, respectively. The Dual Time Point technique helped to identify viable tissue after ablation in 3 cases. Follow-up PET/CT studies have conditioned the various treatment strategies adopted by clinical oncologists. The high yield of the PET/CT study including the Dual Time Point technique may be considered as a study replacement of initial and follow-up Contrast-Enhanced CT before and after treatment with RFA and AMO, this achieving considerable reduction in the exposure to high radiation levels. We propose conducting the first PET/CT follow-up study at 3 months of the RFA and AMO.

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.

[Survival after radiofrequency ablation for 100 cases of lung neoplasms]

背景与目的

手术切除是治疗肺部肿瘤的首选治疗手段，而对高龄、肺功能差的患者，射频消融治疗是一个很好的选择。本文总结了射频消融治疗100例肺部肿瘤的远期疗效和并发症。

方法

对不能手术的100例肺部肿瘤患者行射频消融治疗，定期复查胸部增强CT扫描、肿瘤SPECT或PET显像并随访，观察远期疗效及并发症。

结果

100例肺部肿瘤病例的106个病灶接受了射频消融治疗。其中男性62例，女性38例，年龄36岁-91岁，平均66.6岁。原发性肺癌86例，肺转移瘤14例。所有病例完成射频消融治疗，无严重并发症和围手术期死亡。全组总生存时间为13.0个月，1年生存率51.0%，2年生存率32.5%，原发性肺癌与肺转移瘤相比无统计学差异（P=0.922）。早期肺癌的中位生存时间为28个月，2年总生存率为57.7%。

结论

CT引导下射频消融治疗肺癌具有安全、有效、定位准确和微创的优点，是不能耐受手术的早期肺癌患者的选择之一，对中晚期肺癌是一种局部减瘤手段。

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.

Ablation of pulmonary malignancy: current status

Since the first reported use of radiofrequency ablation of the lung in 2000, the field of image-guided lung ablation has received a considerable amount of attention. Survival studies have demonstrated the potential utility of thermal ablation in the treatment of patients with early-stage primary and limited secondary pulmonary tumors with promising results. Diagnostic imaging studies have advanced the understanding of the expected immediate postablation appearance of treated lesions, leading the way for early detection of local tumor progression. These survival studies and the expected imaging follow-up of these patients are reviewed herein.

Role of FDG PET/CT and chest CT in the follow-up of lung lesions treated with radiofrequency ablation

PURPOSE

To compare fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) combined with computed tomography (PET/CT) and chest CT in the evaluation of the effectiveness of lung radiofrequency (RF) ablation.

MATERIALS AND METHODS

Institutional review board approved the study, and all patients gave written informed consent. Thirty-four patients (22 men and 12 women; mean age, 64 years) planned to undergo lung RF ablation were prospectively included and underwent FDG PET/CT and chest CT before (pre-RF ablation PET) and 24 hours, 1 month, and 3 months after RF ablation. Persistent equivocal findings up to 3 months were followed up.

RESULTS

Pre-RF ablation PET led to changes in the treatment strategy in nine patients (26%) by depicting unexpected metastases. Two patients without FDG uptake in lesions to be treated were excluded. Overall, 28 patients (46 lesions: five primary cancer, 41 metastases) were treated and followed up. Within 3 months after RF ablation, incomplete treatment was diagnosed in four of 28 patients (14%, three at 1 month and one at 3 months). Findings of FDG PET/CT were true-positive in four, false-positive in one, and true-negative in 23 patients. Findings of chest CT were true-positive in one, false-positive in one, false-negative in three, and true-negative in 23 patients. Inflammatory FDG uptake in mediastinal lymph nodes and at the needle path puncture site used for RF ablation was observed in 15%, 21%, and 15% of patients and in 19%, 11%, and 15% of patients at 24 hours, 1 month, and 3 months, respectively.

CONCLUSION

FDG PET/CT can be used for the evaluation of the effectiveness of lung RF ablation. Inflammatory FDG uptake in mediastinal lymph nodes or at the needle path site used for RF ablation may occur.

Radiofrequency ablation of non-small-cell carcinoma of the lung under real-time FDG PET CT guidance

Radiofrequency ablation (RFA) is a well-established method in treatment of patients with lung carcinomas who are not candidates for surgical resection. Usually computed tomographic (CT) guidance is used for the procedure, thus enabling needle placement and permitting evaluation of complications such as pneumothorax and bleeding. (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) is generally used for tumor activity assessment and is therefore useful in follow-up after tumor treatment. A method that provides real-time image-based monitoring of RFA to ensure complete tumor ablation would be a valuable tool. In this report, we describe the behavior of preinjected FDG during PET CT-guided RFA of a non-small-cell lung carcinoma and discuss the value of FDG as a tool to provide intraprocedure monitor ablation. The size and the form of the activity changed during ablation. Ablation led to increase of the size and blurring and irregularity of the contour compared to pretreatment imaging. The maximal standardized uptake value decreased only slightly during the procedure. Therefore, before RFA, FDG PET can guide initial needle placement, but it does not serve as a monitoring tool to evaluate residual viable tissue during the procedure.

Determinants of local progression after computed tomography-guided percutaneous radiofrequency ablation for unresectable lung tumors: 9-year experience in a single institution

The purpose of this study was to retrospectively determine the local control rate and contributing factors to local progression after computed tomography (CT)-guided radiofrequency ablation (RFA) for unresectable lung tumor. This study included 138 lung tumors in 72 patients (56 men and 16 women; age 70.0 +/- 11.6 years (range 31-94); mean tumor size 2.1 +/- 1.2 cm [range 0.2-9]) who underwent lung RFA between June 2000 and May 2009. Mean follow-up periods for patients and tumors were 14 and 12 months, respectively. The local progression-free rate and survival rate were calculated to determine the contributing factors to local progression. During follow-up, 44 of 138 (32%) lung tumors showed local progression. The 1-, 2-, 3-, and 5-year overall local control rates were 61, 57, 57, and 38%, respectively. The risk factors for local progression were age (>or=70 years), tumor size (>or=2 cm), sex (male), and no achievement of roll-off during RFA (P < 0.05). Multivariate analysis identified tumor size >or=2 cm as the only independent factor for local progression (P = 0.003). For tumors <2 cm, 17 of 68 (25%) showed local progression, and the 1-, 2-, and 3-year overall local control rates were 77, 73, and 73%, respectively. Multivariate analysis identified that age >or=70 years was an independent determinant of local progression for tumors <2 cm in diameter (P = 0.011). The present study showed that 32% of lung tumors developed local progression after CT-guided RFA. The significant risk factor for local progression after RFA for lung tumors was tumor size >or=2 cm.

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

The aim of this study was to evaluate prospectively the early treatment response after CT-guided radiofrequency ablation (RFA) of unresectable lung tumours by MRI including diffusion-weighted imaging (DWI). The study protocol was approved by the ethics committee of our hospital and signed consent was obtained from each patient. We studied 17 patients with 20 lung lesions (13 men and 4 women; mean age, 69+/-9.8 years; mean tumour size, 20.8+/-9.0 mm) who underwent RFA using a LeVeen electrode between November 2006 and January 2008. MRI was performed on a 1.5T unit before and 3 days after ablation. We compared changes in the apparent diffusion coefficient (ADC) on DWI and response evaluation based on subsequent follow-up CT. 14 of the 20 treatment sessions showed no local progression on follow-up CT, whereas 6 treatment sessions showed local progression (range, 3-17 months; mean, 6 months). For the no-progression group, the ADC pre- and post-RFA were 1.15+/-0.31 x 10(-3) mm(2) s(-1) and 1.49+/-0.24 x 10(-3) mm(2) s(-1), respectively, while the respective ADC values for those that showed local progression were 1.05+/-0.27 x 10(-3) mm(2) s(-1) and 1.24+/-0.20 x 10(-3) mm(2) s(-1). The ADC of the ablated lesion was significantly higher than before the procedure (p<0.05). There was a significant difference in the ADC post-RFA between no-progression and local progression groups (p<0.05). Our prospective pilot study showed that the ADC without local progression was significantly higher than with local progression after RFA, suggesting that the ADC can predict the response to RFA for lung tumours.

Radiofrequency thermocoagulation of lung tumours. Where we are, where we are headed

Only 25% of all lung cancers are diagnosed in an early stage allowing surgical treatment. Primary tumours usually concerning lung metastasis are breast, colon, kidney, uterus/cervix, prostate, and head and neck tumours. During recent years many publications have confirmed the effectiveness and reliability of lung radiofrequency ablation (RFA) alone or together with other techniques (chemotherapy, radiotherapy...). Results suggest that survival increase and curative rates of lung radiofrequency are similar to those achieved by more aggressive procedures and present lower rates of complications. Pneumothorax, pleural effusion and alveolar haemorrhage are the most frequent complications. Indications for lung RFA must be individually evaluated by lung cancer committees. Percutaneous lung RFA may be useful in patients with pulmonary primary tumours and metastases, especially in those with nodules smaller than 3 cm and a peripheral location (>1 cm from the hilum). PET/CT seems to be the most accurate technique in patient follow up.