In January 2019, the Health Institute Carlos III published a report titled Diagnostic effectiveness and safety of elastography in oncology. An overview of systematic reviews and meta-analysis.
Elastography includes a set of techniques that allow the study of one of the physical properties of tissues: elasticity. This property may be altered by different pathological processes, either due to inflammation, fibrosis or tumors. Since its inception at the end of the previous century, the elastography has experienced great technological advances. In clinical practice, there are two main types of elastography. On the one hand, qualitative modalities, which measure strain, and, on the other hand, quantitative modalities that measure the elasticity by calculating the propagation speed of cutting waves. They can also be classified according to whether the force exerted to study the tissue elasticity is a force of compression or a force of acoustic radiation.
This report has had two objectives: to review the different ultrasound-based elastography techniques (technologies, their classification and clinical indications) and study the diagnostic effectiveness and safety of ultrasound-based elastography in the characterization of lesions in pancreas, prostate, breast, and thyroid.
A literature review was carried out. Consensus documents, recommendations or clinical practice guidelines and Health Technology Assessment (HTA) reports on elastography were reviewed. To study the effectiveness and safety of elastography, a systematic review including systematic reviews (SR) and meta-analysis (MA) was performed. A search was made systematically and exhaustively of scientific literature in different sources of information to identify the available evidence between 2010 and December of 2017. The main databases screened were Medline, Cochrane Database of Systematic Reviews, Centre for Review and Dissemination (CRD) and NIHR (National Institute for Health Research) Dissemination Centre.
For the literature review, after reading the title and abstract of the 380 identified references, 31 duplicates were discarded, and another 281 references were not eligible. The remaining 56 were reviewed to assess whether they met the established inclusion and exclusion criteria. The inclusion criteria were RS and/or MA that study the effectiveness and safety of elastography in patients of any age and both sexes, with suspicious lesions of pancreatic, prostate, breast or thyroid cancer. Finally, 34 articles in total were selected; 15 articles about the diagnosis of elastography in the differential diagnosis of benign/malignant thyroid nodules, 8 MA of solid mammary lesions, 6 MA of solid pancreatic lesions and 5 MA of prostatic lesions. Furthermore, 1 HTA report and 14 consensus documents or clinical practice guidelines and recommendations from different medical societies or entities were identified.
For solid pancreatic lesions, in all the MA elastography by endoscopic ultrasound had been used. The number of patients collected in the total MA ranged between 752-1537 and 893-1544 injuries reported by the authors. The reference test used was a biopsy or clinical follow-up by a minimum time of 6 months. The cumulative sensitivity in these MA varied between 0.95 and 0.98, and the cumulative specificity was between 0.67 and 0.76. It was considered very useful to rule out malignant disease, and it was recommended to use it together with the conventional ultrasound or with contrast.
The five MAs on elastography in prostate cancer showed a wide heterogeneity between studies. The cumulative sensitivity ranged between 0.62 and 0.85, and the specificity was between 0.79 and 0.87. Overall, the diagnostic results seemed better with the SWE.
To study the effectiveness of elastography in mammary lesions, 8 MA were included, in which various quality and quantitative technologies have been used. A great heterogeneity was detected between studies. The diagnostic parameters were calculated for the different qualitative and quantitative techniques and depending on the way of interpreting the test (color pattern, SR, length ratio) and ranged from 0.83 to 0.94 for the cumulative sensitivity, and between 0.81 and 0.93 for the cumulative specificity. In general, no significant differences were found between the diagnostic capacity of the different elastographic techniques.
The 15 MAs on elastography in the study of thyroid nodules included between 469 and 16,624 patients, and between 639 and 5,942 nodules. The reference test used was cytology, biopsy or histological samples of surgery. A high negative predictive value was found which allowed concluding that qualitative elastography is of great value to rule out malignancy when the result is negative, leading to reduce the number of biopsies. Besides, it would be useful in monitoring nodules that have not been biopsied, helping to detect whether or not they are malignant.
- There is enough scientific evidence to consider elastography as a technique with good diagnostic capacity for detection of malignancy in prostate, breast, pancreas and thyroid lesions. The elastography should always be done as a complementary test or together with the ultrasound in B-mode. Besides, it would be indicated to reduce the number of unnecessary biopsies
- Most of the scientific evidence found is based on studies of diagnostic accuracy compared to a reference test (generally, biopsy), while few works include impact evaluation in clinical practice
- For pancreatic lesions, the elastography associated with endoscopic ultrasound can be considered a good diagnostic technique, especially to exclude malignancy. It does not replace the biopsy, but its combined use with conventional or contrast ultrasound would be recommended. It would also be indicated to guide the procedure of biopsy, helping to choose the most suspicious area of malignancy. The usefulness of elastography has not been proven to detect malignant tumors when the lesion develops within the framework of a chronic pancreatitis
- Elastography in prostate cancer could add information in the early stages of the disease, compared to other diagnostic tests, and would also be useful to guide the taking of prostate biopsies, in addition to contributing to reducing the number of unnecessary biopsies
- It should be considered as an additional tool in the study of mammary lesions, complementary to B-mode ultrasound, with a special diagnostic utility for BI-RADS 3 or 4a lesions so that it would contribute to clinical decision making. It could also be used to guide the taking of biopsy samples. Its usefulness has not been demonstrated in mucinous carcinomas or in situ ductal carcinomas
- In the study of thyroid nodules, it seems that elastography could be very useful if used together with conventional ultrasound, achieving greater specificity and allowing the exclusion of malignancy, with greater probability that the ultrasound, if the elastography study is negative. There are not enough published studies to establish the diagnostic role and in the clinical practice of elastography in diffuse thyroid pathology or after received surgical or radioiodine treatment. It is also not proven its diagnostic capacity in follicular carcinoma and calcified cystic nodules
- It would be convenient to design future clinical studies with a rigorous methodology, to avoid or minimize biases results
- Studies are needed with which to determine some aspects that still need to be specified like the best diagnostic cut-off points, the most appropriate period of time for the repetition of the test, what change in the measurement of elastography involves a significant change in the progression of the pathology or a change in response to treatment
- Studies are needed to compare the effectiveness between qualitative and quantitative elastography, with its different diagnostic parameters, to determine the value of each one in different pathologies, both oncological and non-oncological
See the full report in Spanish here
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