CT Colonography vs Optical Colonoscopy - Equivalent or Complementary Techniques?
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
ACTA RADIOLÓGICA PORTUGUESA
Maio-Agosto 2017 Vol 29 nº2 7-12
Artigo Original/ Original Article
CT Colonography vs Optical Colonoscopy – Equivalent or
Complementary Techniques?
Colonografia por TC vs. Colonoscopia Óptica – Técnicas Equivalentes ou Técnicas
Complementares?
Carlos Oliveira, Luís Amaral Ferreira, Amélia Estêvão, José Ilharco, Luísa Teixeira,
Filipe Caseiro-Alves
Medical Image Department, Centro Hospitalar e Abstract Resumo
Universitário de Coimbra, Faculdade de
Medicina da Universidade de Coimbra, Coimbra, Purpose Objetivos
Portugal Review the CT Colonography (CTC) Caracterizar os exames de Colonografia por TC
examinations of our institution. (CTC) da nossa instituição.
Compare the results of CTC with the results of Comparar os resultados da CTC com a
optical colonoscopy (OC) studies to access the Colonoscopia óptica (CO) de forma a avaliar a
efficacy of the former in a screening setting. sua eficácia num contexto de rastreio.
Introduction Introdução
Colorectal cancer is a malign neoplasm with a O carcinoma coloretal é uma das neoplasias
Correspondência high incidence worldwide. Mortality rate has malignas com maior incidência a nível global.
been decreasing in the past decades, mostly due A taxa de mortalidade tem vindo a diminuir
Carlos Oliveira to better screening programs and diagnostic nas últimas décadas, devido essencialmente a
Serviço de Imagem Médica techniques. Two techniques are used for melhores planos de rastreio e à evolução das
Centro Hospitalar e Universitário de Coimbra this purpose: CT Colonography and Optical técnicas de diagnóstico. Para o diagnóstico desta
Av. Bissaya-Barreto Colonoscopy, being the latter considered the patologia há duas técnicas que são comummente
3000-075 Coimbra gold-standard. However, as CT Colonography usadas: a colonoscopia óptica e a Colonografia
Portugal continues to evolve, it is of utmost importance por TC, sendo a primeira destas considerada o
e-mail: carlosmigoliveira@gmail.com that these two techniques get compared. gold-standard. Contudo, com a rápida evolução
Methods tecnológica que a TC sofreu nos últimos anos,
Retrospective study with a consecutive sample of torna-se relevante comparar estas duas técnicas.
202 CTC studies (131F:71M, mean age 67±12 Métodos
years), where it was recorded the study indication, Estudo retrospetivo com amostra consecutiva
image findings, C-RADS and extra-colic findings. de 202 exames de CTC (131M:71H, idade média
CTC and OC results were compared. Statistical 67±12 anos), tendo sido registados a indicação
analysis was performed using descriptive do exame, resultados, C-RADS e achados extra-
methods, chi-square tests and Student’s t test cólicos. Foram comparados os resultados da CTC
using a confidence interval of 95%. com os da CO. Estudo estatístico com métodos
Results/Discussion descritivos, qui-quadrado e teste t de Student para
Seventeen (8%) of the CTC studies were um intervalo de confiança de 95%.
inconclusive and 37 (18%) showed neoplasia. Resultados
Only 58 (29%) cases did not have a previous OC. Dezassete (8%) das CTC foram inconclusivas
No immediate complications were recorded in e 37 (18%) mostraram patologia neoplásica.
any of the CTC examinations. Apenas 58 (29%) casos não tinham realizado CO
From the 202 CTC studies evaluated, 73 had an antes. Sem complicações imediatas em nenhum
accessible previous OC result, where 75% of dos exames de CTC.
them were concordant. Most discrepancies were Dos 202 exames de CTC, 73 dos casos tinham
due to intestinal mucosal inflammation. No CTC resultado da CO acessível, havendo concordância
false negatives were recorded in the diagnosis of em 75% deles, sendo que as discordâncias se
potentially neoplastic polyps or masses. deviam principalmente a alterações da mucosa
Conclusion intestinal. Não se registaram casos de falsos
CTC is similar to OC when performed in negativos da CTC no diagnóstico de pólipos ou
a colorectal screening setting. Although it massas potencialmente neoplásicas.
lacks therapeutic capabilities, CTC have other Conclusão
features that can empower itself to be used as a A CTC é semelhante à CO quando a indicação
complementary technique or even an equivalent clínica incide sobre o rastreio de carcinoma colo-
one in a colorectal screening setting, when rectal. Embora sem capacidades terapêuticas,
compared to OC. não evitando o uso da CO se uma lesão for
encontrada, apresenta outras características
Keywords que podem tornar esta técnica complementar à
CO ou mesmo equivalente em cenários clínicos
CT Colonography; Optical colonoscopy; CT; específicos, nomeadamente em contexto de
Post-processing; Colo-rectal cancer screening rastreio populacional.
Palavras-chave
Clonografia por TC; Colonoscopia óptica; TC;
Pós processamento; Rastreio cancro colorectal.
7
Introduction of suspected malignancy or premalignant pathology.10 It
depends on the emission of ionizing radiation unlike OC,
Colorectal carcinoma (CRC) is one of the most common although in a smaller amount than in a regular abdominal
malignant neoplasms worldwide, particularly in Western CT without compromising its diagnostic acuity.14 It allows
countries, ranking third in Portugal and second in the USA.1,2 the evaluation of other abdominal organs or even the staging
The mortality rate of this disease has been decreasing of a neoplasm found in the examination itself. There is also
in the last decades, mainly due to the prevention with the a lower risk of complications in OC and it is associated with
implementation of screening plans at the population level a higher degree of patient satisfaction.14
as well as to the development of diagnostic and treatment
techniques.2 There have already been several attempts to compare the
Being a sporadic disease that affects mainly individuals older two techniques or even attempt to show CTC superiority
than 50, the population-based opportunistic screening was in specific clinical settings.5,12 One of the flaws that these
implemented in Portugal, which is defined by guidelines studies point to the methodology used is that most of the
issued by the Portuguese Health Authority.3 This includes time the CTC is compared to the OC and not to the true
a colonoscopy every 10 years from the age of 50 in gold standard (inducing a bias, in which OC is used to
asymptomatic individuals.3 However, these guidelines do evaluate its own sensitivity and specificity). On the other
not include the use of Virtual Colonoscopy by CT (CTC) hand, a polyp referenced in a colonography that was not
as a screening technique, despite the literature supporting found in a subsequent OC was considered a false positive
this possibility, referring as an example the recommendation colonography.10
to perform CTC every 5 years as an effective method of The purpose of this study was to characterize the CT
screening by the American Cancer Society.1,4-9 colonography exams of our Institution as well as, in a
Conventional radiology with contrast has fallen out of use second part, to compare the results of the CTC with optic
since the 90s and the optic colonoscopy (OC) has gained colonoscopy, in order to assess its ability to replace OC in a
widespread use, which allows not only the detection of screening context.
lesions but also the diagnosis with more invasive techniques
such as the biopsy.10 Recently with the technological advances
of computerized tomography and the reduction of radiation
dose by examination, CTC became an alternative technique
to OC, allowing not only the diagnosis of colonic lesions
but also of extracolic findings (Fig. 1).11 The effectiveness of
MR colonography has been evaluated by several randomized
studies and appears to have a diagnostic accuracy comparable
to that of CTC.12,13 However, it is expensive, time-consuming,
and not performed in most of the centers (including the
authors’) and therefore will not be the subject of comparison
in this study.13
OC and CTC are the two most commonly used techniques
for CRC diagnosis, each with its advantages and
disadvantages.10,11 OC has a lower proportion of cases in
which the entire colon is properly studied and a higher risk Figure 2 – OC image showing a tumor lesion growing in the lumen whose
biopsy revealed to be CRC.
of perforation, often requiring anesthetic sedation (with an
associated increased risk).14 It has the advantage of being
a technique used for treatment, as it allows the removal
Methods
of polyps, biopsy of lesions (Fig 2) or local hemostasis.
A retrospective study was carried out at our institution,
The CTC does not have therapeutic capabilities and does
covering all the CTC examinations carried out in a period of
not avoid performing the endoscopic technique in cases
one year (January 1 to December 31, 2015), corresponding
to a consecutive sample of 202 examinations. Demographic
data (sex and age), indicated in each study, C-RADS
classification, presence of findings that required follow-up
by OC, and immediate complications after the examination
were recorded for each of these exams.
For each of the exams included in the study, the existence
of OC performed in an interval of less than 6 months,
either before or after the CTC study, was investigated in
the respective clinical records. All CTCs that did not allow a
comparative study with OCs were excluded, for a total of 58
exams. Of the 144 remaining, only 72 had OC examination
available for consultation through the clinical file, and the
remaining ones were excluded (n = 72). The sample for
comparative statistical study between the two techniques
comprised 72 CTC exams, and there was concern in reducing
Figure 1 – Scanning is prone position with evidence of concentric parietal possible biases due to therapeutic procedures in OC that
thickening in the descending colon, compatible with CRC neoplasia. could alter the results of colonography. Whenever available,
8
the anatomopathological result was used as a gold standard Table 1 - Demographic distribution of the study (sex)
for comparison. CTC exams were performed on 64-detector Sex n (%)
CT equipment, with rectal CO2 administration until adequate
Female 131 (64,9)
distension of the entire colon was achieved. The technical
protocol used at our institution includes two abdominal- Male 71 (35,1)
pelvic volumetric acquisitions, one supine and one prone, Total 202 (100%)
reconstructed with a slice thickness of 0.6 mm and evaluated
in an advanced postprocessing station (GE® Advanced
Workstation 4.3) (Fig. 3). Routine intravenous iodine contrast
is not given. The statistical study was performed using SPSS
23 software, using descriptive methods, chi-square test and
Student t-test, for a 95% confidence interval.
Figure 3 – Example of visualization of
the post-processing station, with division
of the work area into several quadrants,
for concomitant and synchronized
visualization of the two acquisitions
performed and reconstruction with
“endoscopic view”..
Results Table 2 - Distribution of the exams regarding the C-RADS result
C-RADS
The descriptive analysis of the 202 exams included in the first
Colic findings n (%)
part of the study, regarding age, sex and C-RADS respectively,
are shown in Tables 1 and 2 and Chart 1. The mean age of C0 – Inconclusive 17 (8.4)
patients undergoing CTC was 67 years. About 78.6% of the C0 – Inconclusive 148 (73.3)
women who underwent CTC had a C1 result, contrasting with C2 – Polyp 6-9mm 13 (6.4)
only 63.4% of the men with this result. The C4 result was C3 – Polyp >10mm 9 (4.5)
more prevalent in men (11.3% to 5.3%).
C4 – Mass 15 (7.4)
Table 3 shows the indications for performing the tests, sorted
in descending order of frequency. Of the 202 CTC exams Extra-colic findings n (%)
performed, subsequent OC for therapeutic and / or diagnostic E0 – Inappropriate examination 1 (0.5)
purposes was required in 39 (19.3%), and subsequent OC E1 – Normal or variant from normality 52 (25.7)
testing was not required in 163 CTC (80.7%). E2 – Findings not clinically relevant 76 (37.6)
No immediate complications were observed in any of the
E3 – Probably not important or uncharacteristic 52 (25.7)
examinations performed.
In the second part of the study, a comparison was made E4 – Potentially important, to follow up 21 (10.4)
between these two techniques, and they were concordant in
75% of the exams (n = 55). In the remaining 25% of the cases Discussion
(n = 18) we observed a disagreement among the techniques,
which we explain below. Neither the sex nor the age of the There is an increasing number of CT Colonography exams
patients showed a statistically significant relationship with performed in the female population, although it does not
the number of non-concordant tests (p = 0.96 and p = 0.88 seem to correspond to a higher incidence of pathology in
respectively, obtained with the chi-square and Student’s t tests). this population. The majority of the exams was performed in
Table 5 shows the pathology detected by each technique when patients in the seventh and eighth decades of life. This fact
the other one does not show it. becomes expected as we are dealing with the age group where
9
Graph 1 - Demographic distribution of the study (age) the colorectal carcinoma is more prevalent, corresponding to
the period where screening is recommended. A parallelism
of these results is made with Table 3, where it stands out that
the majority of the exams were performed in context of CRC
screening or where OC did not allow to visualize the entire
colon. Effectively, when patients were referred for CTC after
inconclusive OC with specific symptoms/diagnoses, they
have been properly registered as such in the data collection
process (neoplasm bleeding, bleeding from the digestive
tract, intestinal transit), assuming that all patients who were
submitted to CTC because of “OC’s inability to go through
all the colon” had as basis the performance and screening
of CRC. All patients with this indication were within the
screening criteria, so we consider that 58.6% of the CTC
were carried out in a context of CRC screening, becoming
the most frequent indication of this examination.
Table 3 - Distribution of CTC indications However, more than one third of the CTCs (37.8%) were
performed due to unsatisfactory OC response, making
Indication for CT Colonography CTC a 2nd line exam, fact already extensively studied in the
Indication n (%) literature.
Inability to travel throughout the whole colon in OC 68 (33.7) With regard to the diagnostic result of CTCs, given by
Screening for neoplasia 42 (20.8)
C-RADS classification, it is observed that about 8% of
those were inconclusive and that about 1/5 of the cases had
Changes in intestinal transit 31 (15.3)
malignant or premalignant pathology (Fig 4 and 5).
Anemia / Hematochezia / Positive occult blood test 27 (13.4) These results are described in the literature. Regarding
Abdominal pain 13 (6.4) the extracolic findings, only 25.7% of the patients had no
Neoplasia insurmountable in OC 10 (5.0) changes to register, whether they were clinically relevant or
Refusal of OC 7 (3.5)
not. The other 3/4 of the exams showed extracolic changes,
which is a plus of CTC against OC. The proportion of
Contraindication for OC 4 (2.0) potentially relevant extracolic pathology diagnosed by CTC
Total 202 (100) was 10.4%, gaining relevance in a potential CRC population
screening scenario. This aspect should be better evaluated
Figure 4 – Polyp with 9 mm iden-
tified in the transverse colon, with
correspondence in the axial images
and “endoscopic view”.
10Table 4 - Comparison of results of the two techniques - Χ2 test
(p = 0,313)
Findings only Findings only
detected at OC detected at CTC
Diverticula 1 3
Polyps 2 2
Adenopathies NA 1
Inflammatory alterations 5 2
of mucosa
Blood 1 NA
Mass 1 0
Figure 5 – Polyp by OC corresponding to the polyp shown in the previous
figure (3).
by studies designed for this purpose, since there is a bias of
patient selection inherent to the current study.
About 80% of patients undergoing CTC had no need
to perform a subsequent OC for diagnostic and / or
therapeutic purposes. Knowing a priori the limitation of CTC
in the possibility of performing therapeutic procedures, this
number reinforces the weight that the technique has in a
context of population screening, where it is expected that
the incidence of alterations requiring subsequent OC will be
lower than in other contexts (eg in the symptomatic patient
or with other changes that increase the suspicion of the
presence of a CRC).
Figure 6 – Image of the colorectal anastomosis performed after sigmoi-
In the direct comparison between the results of the two dectomy, correctly identified in CT colonography, corresponding to false
techniques, we obtained a concordance of 75%. positive of Optic Colonoscopy.
The 18 non-concordant exams will be discussed from the
descriptive point of view, without statistical analysis tools that Conclusion
support this evaluation due to the sample size. There was a
higher rate of detection of diverticula and adenopathy in the CTC is similar to OC when the clinical indication focuses on
CTC, explained by the differences between an endoscopic the screening of colorectal carcinoma. The CTC technique has
technique and a sectional technique. Likewise, the presence important advantages over OC, namely a better visualization
of inflammatory changes of the mucosa and the presence of the entire colon, a lower risk of complications for the
of blood was more easily observed in OC. Both techniques patient and the possibility of detecting extracolic findings.
presented two false negatives in the detection of polyps, This study showed similar levels of diagnostic accuracy
suggesting similar levels of sensitivity in the detection of this between the two techniques in the context of population
pathology. screening. CTC is a noninvasive technique that the patient
As shown in table 4, there was a case detected in the OC that prefers to undergo than OC and that, because of its sensitivity
was not evidenced in the CTC and could be a major problem and specificity, it may be an alternative technique to OC for
for the CTC assertion in the screening context. A more the CRC screening.
careful analysis of this particular case revealed that it was a
70-year-old patient with previous surgery for resection of
colon neoplasia, whose OC recorded the presence of mass
at the anastomosis level and CTC showed only anastomosis
thickening, without evidence of mass (Fig. 6). The histological
examination of the fragments collected during OC set aside
the hypothesis of tumor recurrence, allowing to characterize
this case as a false positive of the OC.
The authors note the following limitations of the study: a
retrospective study with a small sample and based largely on
radiological and endoscopic examination reports. There is
also an inability to calculate the true sensitivity and specificity
of the CTC because it was compared with the OC and not
with the gold standard.
To conclude, the authors consider that the study of the
lower rectum should not be performed by CTC, since it is
a known limitation of the technique, and the importance
of clinical evaluation (namely rectal examination) and
rectosigmoidoscopy should not be neglected in the study of
the pathology of the rectum and anal canal.
11Recebido / Received 05/03/2017 5. Devir C, Kebapci M, Temel T, Ozakyol A. Comparison of 64-detector CT
Aceite / Acceptance 25/05/2017 colonography and conventional colonoscopy in the cetection of colorectal
cesions. Iran J Radiol. 2016;13:e19518.
6. Rex DK, Johnson DA, Anderson JC, et al. American College of
Divulgações Éticas / Ethical disclosures Gastroenterology guidelines for colorectal cancer screening 2009 [corrected].
Conflitos de interesse: Os autores declaram não possuir conflitos de interesse. Am J Gastroenterol. 2009;104:739-50.
Conflicts of interest: The authors have no conflicts of interest to declare. 7. Halligan S, Altman DG, Taylor SA, et al. CT colonography in the
Suporte financeiro: O presente trabalho não foi suportado por nenhum detection of colorectal polyps and cancer: systematic review, meta-analysis,
subsídio ou bolsa. and proposed minimum data set for study level reporting. Radiology.
Financing Support: This work has not received any contribution, grant or 2005;237:893-904.
scholarship. 8. Robinson C, Halligan S, Taylor SA, Mallett S, Altman DG. CT
Confidencialidade dos dados: Os autores declaram ter seguido os protocolos do colonography: a systematic review of standard of reporting for studies of
seu centro de trabalho acerca da publicação dos dados de doentes. computer-aided detection. Radiology. 2008;246:426-33.
Confidentiality of data: The authors declare that they have followed the pro- 9. Levin B, Lieberman DA, McFarland B, et al. Screening and surveillance
tocols of their work center on the publication of data from patients. for the early detection of colorectal cancer and adenomatous polyps, 2008:
Protecção de pessoas e animais: Os autores declaram que os procedimentos a joint guideline from the American Cancer Society, the US multi-society
seguidos estavam de acordo com os regulamentos estabelecidos pelos task force on colorectal cancer, and the American College of Radiology. CA
responsáveis da Comissão de Investigação Clínica e Ética e de acordo com Cancer J Clin. 2008;58:130-60.
a Declaração de Helsínquia da Associação Médica Mundial 10. Spada C, Stoker J, Alarcon O, et al. Clinical indications for computed
Protection of human and animal subjects: The authors declare that the procedu- tomographic colonography: European Society of Gastrointestinal
res followed were in accordance with the regulations of the relevant clinical Endoscopy (ESGE) and European Society of Gastrointestinal and
research ethics committee and with those of the Code of Ethics of the Abdominal Radiology (ESGAR) Guideline. Eur Radiol. 2015;25:331-45.
World Medical Association (Declaration of Helsinki). 11. Laghi A. Computed tomography colonography in 2014: an update on
technique and indications. World J Gastroenterol. 2014;20:16858-67.
Referências 12. Pooler BD, Kim DH, Weiss JM, Matkowskyj KA, Pickhardt PJ. Colorectal
1. Patel JD, Chang KJ. The role of virtual colonoscopy in colorectal polyps missed with optical colonoscopy despite previous detection and
screening. Clin Imaging. 2016;40:315-20. localization with CT colonography. Radiology. 2016;278:422-9.
2. Doenças oncológicas em números. Programa Nacional para as Doenças 13. Pickhardt PJ, Hassan C, Halligan S, Marmo R. Colorectal cancer: CT
Oncológicas. Direção-Geral da Saúde 2013. colonography and colonoscopy for detection--systematic review and meta-
3. Rastreio oportunístico do cancro do cólon e reto. Direção-Geral da Saúde analysis. Radiology. 2011;259:393-405.
2014;(003/2014). 14. Berrington de Gonzalez A, Kim KP, Yee J. CT colonography:
4. Schmidt SA, Ernst AS, Beer M, Juchems MS. 3D detection of colonic perforation rates and potential radiation risks. Gastrointest Endosc Clin N
polyps by CT colonography: accuracy, pitfalls, and solutions by adjunct 2D Am. 2010;20:279-91.
workup. Clin Radiol. 2015;70:1144-51.
12You can also read
