Radiologic measurements of tumor response to treatment: practical approaches and limitations

[Advanced NSCLC first pass perfusion at 64-slice CT: reproducibility of volume-based quantitative measurement]

背景与目的

本研究旨在探讨进展期非小细胞肺癌（non-small cell lung cancer, NSCLC）首过法CT灌注（CT perfusion, CTP）的可重复性。

方法

在本院行首过法CTP检查（8×5 mm层厚），且经病理证实的进展期NSCLC患者14例，肿瘤最大径≤3 cm及>3 cm各7例，均在24 h内行第二次CTP扫描。采用组内相关系数（intraclass correlation coefcient, ICC）及Bland-Altman法评价CTP检查的可重复性。

结果

两组进展期NSCLC的血流速度（blood flow, BF）、血容量（blood volume, BV）及表面通透性（permeability surface area product, PS）值的ICC均>0.75；对比剂的平均通过时间（mean transit time, MT）的ICC均 < 0.75。≤3 cm的进展期NSCLC组的BF、BV、MT及PS的可重复系数（repeatability coefficient, RC）及RC值95%变化区间依次为56%（-39%-53%）、45%（-29%-62%）、114%（-83%-145%）、78%（-57%-98%）；>3 cm组的BF、BV、MTT及PS的RC及RC值95%变化区间依次为46%（-48%-45%）、30%（-33%-26%）、-59%（-54%-64%）、33%（-18%-48%）。

结论

去卷积法首过法CTP参数BF及BV可重复性较好，用于评价进展期NSCLC抗血管生成治疗疗效时，可根据肿瘤大小，应用不同的可重复性标准区别对待。

Chemoembolization follow-up of hepatocellular carcinoma with MR imaging: usefulness of evaluating enhancement features on one-month posttherapy MR imaging for predicting residual disease

PURPOSE

To determine the sensitivity, specificity, and accuracy of contrast-enhanced magnetic resonance (MR) imaging performed 1 month after localized chemotherapy as a measure of tumor response, before detectable changes in size.

MATERIALS AND METHODS

This trial was approved by the authors' institutional review board and was compliant with the Health Insurance Portability and Accountability Act (HIPAA). Inclusion criteria selected patients receiving chemoembolization for hepatocellular carcinoma (HCC) with MR imaging within 2 months before treatment, in addition to MR imaging after treatment at 1 month and 6 months. Pathology was used as a surrogate for 6-month follow-up if the patient underwent interval transplantation. The final population consisted of 23 tumors (occurring within 21 patients). MR imaging studies were evaluated separately by two radiologists. Tumors were scored as showing complete loss of enhancement or as showing some residual tissue enhancement. Changes in T1 and T2 signal and perilesional enhancement were tabulated and recorded. Lesion size was also measured on all MR imaging studies by using a one-dimensional measure of the longest dimension. Increase in tumor size from 1-6 months of 20% or greater was used as confirmation of residual disease. In 5 of 23 tumors, review of pathology served as the surrogate standard. Sensitivity, specificity and accuracy were computed for each rater.

RESULTS

The sensitivity, specificity, and accuracy of 1-month follow-up MR imaging were 71.4-85.7%, 100%, and 91.3-95.7%. There was a high degree of agreement between the two readers for both the 1-month (kappa = 0.88) and 6-month (kappa = 1.0) MR imaging studies.

CONCLUSIONS

This investigation shows high accuracy for using tumor enhancement features on 1-month posttherapy MR imaging to predict residual disease after chemoembolization of HCC.

Rexin-G, a targeted genetic medicine for cancer

IMPORTANCE OF THE FIELD

Rexin-G, a tumor-targeted retrovector bearing a cytocidal cyclin G1 construct, is the first targeted gene therapy vector to gain fast track designation and orphan drug priorities for multiple cancer indications in the US.

AREAS COVERED IN THIS REVIEW

This review describes the major milestones in the clinical development of Rexin-G: from the molecular cloning and characterization of the human cyclin G1 proto-oncogene in 1994, to the design of the first knockout constructs and genetic engineering of the targeted delivery system from 1995 to 1997, through the initial proofs-of-concept, molecular pharmacology and toxicology studies of Rexin-G in preclinical cancer models from 1997 to 2001, to the pioneering clinical studies in humans from 2002 to 2004, which--together with the advancements in bioprocess development of high-potency clinical grade vectors circa 2005 - 2006--led to the accelerated approval of Rexin-G for all solid tumors by the Philippine FDA in 2007 and the rapid progression of clinical studies from 2007 to 2009 to the cusp of pivotal Phase III trials in the US.

WHAT THE READER WILL GAIN

In recording the development of Rexin-G as a novel form of targeted biological therapy, this review also highlights important aspects of vector design engineering which served to overcome the physiological barriers to gene delivery as it addresses the key regulatory issues involved in the development of a targeted gene therapy product.

TAKE HOME MESSAGE

Progressive clinical development of Rexin-G demonstrates the potential safety and efficacy of targeted genetic medicine, while validating the design engineering of the molecular biotechnology platform.

Evaluation of a method of computer-aided detection (CAD) of pulmonary nodules with computed tomography

PURPOSE

The authors sought to compare the sensitivity and reading time obtained using computer-aided detection (CAD) software as second reader (SR) or concurrent reader (CR) in the identification of pulmonary nodules.

MATERIALS AND METHODS

Unenhanced CT scans of 100 consecutive cancer patients were retrospectively reviewed by four readers to identify all solid, noncalcified pulmonary nodules ranging from 3 to 30 mm in diameter. The sensitivity and reading time of each reader and of CAD alone were calculated at 3-mm and 5-mm thresholds with respect to the reference standard, consisting of a consensus reading by the four radiologists involved in the study. The McNemar test was used to compare the sensitivities obtained by reading without CAD (readers 1 and 2), with CAD as SR (readers 1 and 2 with a 2-month delay), and with CAD as CR (readers 3 and 4). The paired Student's t test was used to compare reading times. A value of p<0.05 was considered statistically significant.

RESULTS

A total of 258 and 224 nodules were identified at 3-mm and 5-mm thresholds, respectively. The sensitivity of CAD alone was 62.79% and 67.41% at the 3-mm and 5-mm threshold values respectively, with 4.15 and 2.96 false-positive findings per examination. CAD as SR produced a significant increase in sensitivity (p<0.001) in nodule detection with respect to reading without CAD both at 3 mm (12.01%) and 5 mm (10.04%); the average increase in sensitivity obtained when comparing CAD as SR to CAD as CR was statistically significant (p<0.025) both at the 3-mm (5.35%) and 5-mm (4.68%) thresholds. CAD as CR produced a nonsignificant increase in sensitivity compared with reading without CAD (p>0.05). Mean reading time using CAD as SR (330 s) was significantly longer than reading without CAD (135 s, p<0.001) and reading with CAD as CR (195 s, p<0.025).

CONCLUSIONS

The use of CAD as CR, without any significant increase in reading time, produces no significant increase in sensitivity in pulmonary nodule detection when compared with reading without CAD (p>0.05); CAD as SR, at the cost of longer reading times, increases sensitivity when compared with reading without CAD (p<0.001) or with CAD as CR (p<0.025).

Does multidetector CT attenuation change in colon cancer liver metastases treated with 90Y help predict metabolic activity at FDG PET?

PURPOSE

To evaluate the correlation between change in attenuation and tumor metabolic activity assessed by using fluorodeoxyglucose (FDG) positron emission tomography (PET) in colon cancer liver metastases treated with yttrium 90 ((90)Y) radioembolization.

MATERIALS AND METHODS

This Health Insurance Portability and Accountability Act-compliant retrospective study was approved by the institutional review board; patient informed consent was waived. Unresectable chemorefractory colon cancer liver metastases treated with (90)Y radioembolization in 28 patients were evaluated at pre- and posttreatment multidetector computed tomographic (CT) and FDG PET scans. Maximum cross-sectional diameter, volume, and overall attenuation of target lesions were calculated. The percentage change (%Delta) in these parameters after treatment was calculated and correlated with the standardized uptake value (SUV) analysis at FDG PET. The accuracy of the radiologic parameters in helping predict response to treatment at FDG PET was assessed. Data were analyzed by using the Student t, Wilcoxon matched pair, Mann-Whitney, Spearman rank correlation, and chi(2) tests. The significance level was set at .05.

RESULTS

Seventy-four metastatic lesions in 10 women and 18 men (mean age, 61.5 years +/- 14.3 [standard deviation]) were evaluated. Mean follow-up interval for multidetector CT after treatment was 30 days. A significant reduction in maximum cross-sectional diameter, volume, and attenuation was observed from pre- to posttreatment multidetector CT (P < .05). The %Delta in attenuation had higher correlation with %Delta in SUV (r = 0.61) than diameter (r = 0.39) or volume (r = 0.49) and also predicted the metabolic activity at FDG PET with higher sensitivity (P < .001). By using a threshold level of a reduction in attenuation of 15% or greater, attenuation showed 84.2% sensitivity and 83.3% specificity in predicting response at FDG PET evaluation.

CONCLUSION

Changes in attenuation of colon cancer liver metastases treated with (90)Y radioembolization correlate highly with metabolic activity at FDG PET and may be useful as an early surrogate marker for assessing treatment response.

A differential response to sunitinib: sustained systemic response paralleled by intra-dural progression in the spine. Should standard response criteria be reviewed?

Orally available tyrosine kinases have revolutionized the treatment of renal cell carcinoma. These agents have impressive response rates compared with interferon and also have a cytostatic effect. We describe a case of a patient treated predominantly with continuous sunitinib who had a good partial response to sunitinib in the lungs, liver, adrenal gland, and lymph nodes but dural progression. We describe prolonged sustained response achieved by continuing sunitinib despite dural progression. This case demonstrates that standard treatment criteria may need reviewing.

Prognostic nomogram for overall survival in stage IIB-IVA cervical cancer patients treated with concurrent chemoradiotherapy

OBJECTIVE

On the basis of outcome data from concurrent chemoradiotherapy (CCRT) for locally advanced cervical squamous cell carcinoma, the authors developed a nomogram for predicting survival outcome.

STUDY DESIGN

Two hundred fifty-one eligible patients with International Federation of Gynecology and Obstetrics stage IIB-IVA squamous cell carcinoma of the uterine cervix who underwent CCRT were included for the construction of the nomogram. Predictor variables included age, serum squamous cell carcinoma antigen, tumor size, parametrium invasion, hydronephrosis, bladder/rectum invasion, and lymph node metastases. Internal validation of the nomogram was performed.

RESULTS

A nomogram for predicting the 5 year overall survival for these patients was constructed on the basis of a Cox regression model from 7 parameters. The concordance index was 0.69.

CONCLUSION

This nomogram is a predictive tool, upon external validation, that can be used to counsel patients in predicting outcomes. The discriminatory ability of the nomogram indicates that this population should not be considered homogeneous with respect to risk of death.

Trial design for evaluation of novel targeted therapies

OBJECTIVES

The vast number of novel targeted therapies available for testing in the United States dictates that a more efficient system aimed at identifying promising agents for phase III testing needs to be developed. Alternatives to traditional phase II trial design including alternative end points, randomized designs, biomarkers, and imaging tools are discussed.

METHODS

Novel techniques for phase II trials were researched in the literature. Incorporation of surrogate endpoints and novel approaches were identified.

RESULTS

Phase II trials are traditionally designed evaluating response rates compared to historical controls. In addition to identifying surrogates, novel approaches to phase II study design need to be tested. Incorporation of biomarkers into phase II trial design could allow for more accurate identification of patients who will benefit from targeted therapies. Tumor response as measured by anatomic imaging has been used to measure therapeutic efficacy in the era of cytotoxic drugs. Fluorodeoxyglucose (FDG)-positron emission tomography (PET) however, has been used increasingly in the evaluation of biologic responses.

CONCLUSIONS

Alternatives to traditional phase II trial design including alternative end points, randomized designs, biomarkers, and imaging tools should allow ineffective agents to be discarded and promising agents to undergo further investigation.

Diffusion-weighted MRI of advanced hepatocellular carcinoma during sorafenib treatment: initial results

OBJECTIVE

The objective of our study was to evaluate signal changes of advanced hepatocellular carcinoma in diffusion-weighted MRI in the early-response monitoring of oral therapy with the multikinase inhibitor sorafenib.

CONCLUSION

Hepatocellular carcinoma lesions exhibit characteristic but unusual apparent diffusion coefficient (ADC) changes during sorafenib therapy, consisting of early decrease in ADC after therapy onset followed by a reincrease. The ADC changes seem to reflect the underlying pathophysiologic mechanisms in tumor necrosis (most probably hemorrhagic) induced by this novel targeted agent early after therapy onset and may indicate tumor reactivation in the later follow-up period.

Morphological analysis of pancreatic adenocarcinoma on multidetector row computed tomography: implications for treatment response evaluation

OBJECTIVES

Response Evaluation Criteria in Solid Tumors (RECIST) guidelines assume spherical shape of tumors. Morphology of pancreatic adenocarcinoma (PAC) on multidetector row computed tomography was investigated to evaluate the applicability of RECIST guidelines.

METHODS

Study population comprised 16 patients with histologically confirmed localized PAC enrolled in a phase II clinical trial of chemoradiation. Pancreatic adenocarcinomas were segmented on baseline and follow-up multidetector row computed tomography with commercially available software. Tumor volumes (mL), RECIST diameter (mm), volume equivalent sphere diameter (VESD, mm), maximum 3-dimensional diameter (M3DD, mm), and elongation value were obtained. RECIST diameter, VESD and M3DD of the tumors at baseline and follow-up were compared to determine differences. Elongation values were analyzed. The significance level was set at P less than 0.05.

RESULTS

Mean volume, RECIST diameter, VESD, M3DD, and elongation for baseline versus follow-up studies were 23.12 mL versus 19.43 mL (P > 0.05), 41.86 mm versus 39.35 mm (P > 0.05), 33.14 mm versus 32.1 mm (P > 0.05), 51.76 mm versus 51.73 mm (P > 0.05), and 0.67 versus 0.76 (P > 0.05), respectively. There was a significant difference at baseline and follow-up between RECIST diameter, VESD, and M3DD (P < 0.05, in all instances).

CONCLUSIONS

Our results suggest that PACs are not spherical in shape. Evaluation of PAC treatment response based on RECIST guidelines may not be accurate.

Interactive modeling and evaluation of tumor growth

This paper addresses the need to quantify tumor growth and detect changes as this information is relevant to manage the patient treatment and to aid biotechnological efforts to cure cancer (Silva et al. 2008). An interactive tumor segmentation technique is used to recover the shape and size of tumors without imposing shape constraints. This segmentation algorithm provides good convergence, is robust to the initialization conditions, and requires simple and intuitive user interactions. A parametric approach to model tumor growth analytically is proposed in this paper. The preliminary experimental results are encouraging. The segmentation method is shown to be robust and simple to use, even in situations where the tumor boundary definition is challenging. Also, the experiments indicate that the proposed model potentially can be used to extrapolate the available data and help predict the tumor size (assuming unconstrained growth). Additionally, the proposed method potentially can provide a quantitative reference to compare the tumor shrinkage rate in cancer treatments.

[Imaging of gastrointestinal stromal tumors]

Gastrointestinal stromal tumors (GIST) arising from interstitial cells of Cajal, represent the first type of solid tumor, which is very sensitive to a specific molecularly targeted tyrosine kinase receptor blocker (i. e., imatinib). On CT, which is considered as the reference technique, GISTs typically present as large, well-delineated, heterogeneous and sometimes exophytic masses. In contrast with the absence of lymph node involvement, hepatic metastasis as well as mesenteric involvement can be observed. MR-enteroclysis is indicated to investigate the local extent of the disease in specific cases whereas MR imaging is used to detect hepatic metastasis. Because of a specific treatment, contrast-enhanced imaging is needed for the follow-up of treated tumors. Evaluation of tumor response to treatment is best assessed with CT which still remains the reference imaging technique whereas FDG-PET imaging is used in specific cases.

The minimum number of target lesions that need to be measured to be representative of the total number of target lesions (according to RECIST)

Response evaluation criteria in solid tumours (RECIST) were introduced as a means to classify tumour response with no definition of the minimum number of lesions. This study was conducted in order to evaluate discrepancies between full assessments based on either all target lesions or fewer lesions. RECIST evaluation was performed on separate occasions based on between one and seven of the target lesions, with simultaneous assessment of non-target lesions. 99 patients were included. 38 patients demonstrated progressive disease, in 61% of whom it was a result of the appearance of new lesions or unequivocal progress in non-target lesions. 32 patients showed stable disease, with 8 having results that differed when 1-3 target lesions were measured. 22 cases were considered as having partial regression, with only 1 case differing when performing 1-3 target lesion assessments. Seven cases demonstrated complete response. The number of discordant cases increased gradually from measuring three lesions to one target lesion. The average number of available target lesions among those with discrepancies was 7.1, which was significantly higher than those demonstrating concordance (4.1 lesions; p<0.05). In conclusion, measuring fewer than four target lesions might cause discrepancies when more than five target lesions are present.

[The imaging aspects of metastases from urological malignancies]

Metastases from cancers in urology do not exhibit specific radiological patterns that would allow identification of the primary site. Their detection relies upon usual imaging techniques, and mainly contrast-enhanced Computed Tomography (CT) that allows the study of the thorax, the abdomen and the pelvis. Ultrasound imaging, and the up-to-date contrast-enhanced ultrasound imaging, as well as Magnetic Resonance Imaging are used in addition to CT in case of contra indication of iodinated contrast agents or for targeted indications (focal liver lesion characterization, MR lymphography for lymph node metastases...). PET CT is playing an increasing role but its performances remain limited for the detection of urological metastases. New anti-angiogenic drugs are questioning the traditional evaluation of the therapeutic response based on RECIST criteria. They require more and more the use of functional imaging techniques, such as MRI or CT dynamic studies as well as contrast-enhanced ultrasound.

Promises and challenges of positron emission tomography for assessment of sarcoma in daily clinical practice

A correct histological diagnosis, careful staging and detection of tumour response to treatment are all crucial in the management of sarcomas. Imaging is important in all of these stages. Sarcomas have distinct biological and treatment-related features posing challenges for imaging. For example, size measurements may not adequately reflect response rates. Techniques which can measure tissue function rather than generate merely anatomical data such as positron emission tomography (PET) are rapidly gaining interest. We discuss the importance of imaging in different stages of patient management, emphasising the unique characteristics of sarcoma. Furthermore, we discuss the potential of PET for the various indications, focussing on therapy evaluation.