Clinical Topics & News

Accuracy of Endoscopic Ultrasound in Staging of Early Rectal Cancer

Endoscopic ultrasound can be highly accurate for the staging of neoplasms in early rectal cancer.

Fed Pract. 2019 August;36(5):S26-S29

Author(s):

Claudio Roberto Tombazzi, MD

Parker Loy

Victor Bondar, MD

Jose I. Ruiz, MD

Bradford Waters, MD

Claudio Ruben Tombazzi, MD

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References

1. Harewood GC, Wiersema MJ, Nelson H, et al. A prospective, blinded assessment of the impact of preoperative staging on the management of rectal cancer. Gastroenterology. 2002;123(1):24-32.

2. Siegel RL, Miller KD, Jemal A. Cancer statistics, 2015. CA Cancer J Clin. 2015;65(1):5-29.

3. Ahuja NK, Sauer BG, Wang AY, et al. Performance of endoscopic ultrasound in staging rectal adenocarcinoma appropriate for primary surgical resection. Clin Gastroenterol Hepatol. 2015;13:339-44.

4. Doornebosch PG, Bronkhorst PJ, Hop WC, Bode WA, Sing AK, de Graaf EJ. The role of endorectal ultrasound in therapeutic decision-making for local vs. transabdominal resection of rectal tumors. Dis Colon Rectum. 2008;51(1):38-42.

5. Santoro GA, Gizzi G, Pellegrini L, Battistella G, Di Falco G. The value of high-resolution three-dimensional endorectal ultrasonography in the management of submucosal invasive rectal tumors. Dis Colon Rectum. 2009;52(11):1837-1843.

6. National Comprehensive Cancer Network. NCCN clinical practice guidelines in oncology: rectal cancer, version 2.2019. https://www.nccn.org/professionals/physician_gls/pdf/rectal.pdf. Published May 15, 2019. Accessed July 19, 2019.

7. Bipat S, Glas AS, Slors FJ, Zwinderman AH, Bossuyt PM, Stoker J. Rectal cancer: local staging and assessment of lymph node involvement with endoluminal US, CT, and MR imaging—a meta-analysis. Radiology. 2004;232(3):773-783.

8. Puli SR, Bechtold ML, Reddy JB, Choudhary A, Antillon MR, Brugge WR. How good is endoscopic ultrasound in differentiating various T stages of rectal cancer? Meta-analysis and systematic review. Ann Surg Oncol. 2009;16(2):254-265.

9. MERCURY Study Group. Diagnostic accuracy of preoperative magnetic resonance imaging in predicting curative resection of rectal cancer: prospective observational study. BMJ. 2006;333(7572):779.

10. Balyasnikova S, Read J, Wotherspoon A, et al. Diagnostic accuracy of high-resolution MRI as a method to predict potentially safe endoscopic and surgical planes in patient with early rectal cancer. BMJ Open Gastroenterol. 2017;4(1):e000151.

11. Frasson M, Garcia-Granero E, Roda D, et al. Preoperative chemoradiation may not always be needed for patients with T3 and T2N+ rectal cancer. Cancer. 2011;117(14):3118-3125.

12. Rafaelsen SR, Sørensen T, Jakobsen A, Bisgaard C, Lindebjerg J. Transrectal ultrasonography and magnetic resonance imaging in the staging of rectal cancer. Effect of experience. Scand J Gastroenterol. 2008;43(4):440-446.

13. Marusch F, Ptok H, Sahm M, et al. Endorectal ultrasound in rectal carcinoma – do the literature results really correspond to the realities of routine clinical care? Endoscopy. 2011;43(5):425-431.

14. Marusch F, Koch A, Schmidt U, et al. Routine use of transrectal ultrasound in rectal carcinoma: results of a prospective multicenter study. Endoscopy. 2002;34(5):385-390.

15. Ashraf S, Hompes R, Slater A, et al; Association of Coloproctology of Great Britain and Ireland Transanal Endoscopic Microsurgery (TEM) Collaboration. A critical appraisal of endorectal ultrasound and transanal endoscopic microsurgery and decision-making in early rectal cancer. Colorectal Dis. 2012;14(7):821-826.

16. Harewood GC. Assessment of clinical impact of endoscopic ultrasound on rectal cancer. Am J Gastroenterol. 2004;99(4):623-627.

17. Zorcolo L, Fantola G, Cabras F, Marongiu L, D’Alia G, Casula G. Preoperative staging of patients with rectal tumors suitable for transanal endoscopic microsurgery (TEM): comparison of endorectal ultrasound and histopathologic findings. Surg Endosc. 2009;23(6):1384-1389.

18. Akasu T, Kondo H, Moriya Y, et al. Endoscopic ultrasonography and treatment of early stage rectal cancer. World J Surg. 2000;24(9):1061-1068.

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Colorectal cancer is the second most common cause of cancer death in the US, with one-third of all colorectal cancers occurring within the rectum. Each year, an estimated 40000 Americans are diagnosed with rectal cancer (RC).^1,2 The prognosis and treatment of RC depends on both T and N stage at the time of diagnosis.^3-5 According to the most recent National Comprehensive Cancer Network guidelines from May 2019, patients with T1 to T2N0 tumors should undergo transanal or transabdominal surgery upfront, whereas patients with T3 to T4N0 or any TN1 to 2 should start with neoadjuvant therapy for better locoregional control, followed by surgery.⁶ Therefore, the appropriate management of RC requires adequate staging.

Endoscopic ultrasound (EUS), magnetic resonance imaging (MRI), and computed tomography (CT) are the imaging techniques currently used to stage RC. In a meta-analysis of 90 articles published between 1985 and 2002 that compared the 3 radiologic modalities, Bipat and colleagues found that MRI and EUS had a similar sensitivity of 94%, whereas the specificity of EUS (86%) was significantly higher than that of MRI (69%) for muscularis propria invasion.⁷ CT was performed only in a limited number of trials because CT was considered inadequate to assess early T stage. For perirectal tissue invasion, the sensitivity of EUS was statistically higher than that of CT and MRI imaging: 90% compared with 79% and 82%, respectively. The specificity estimates for EUS, CT, and MRI were comparable: 75%, 78%, and 76%, respectively. The respective sensitivity and specificity of the 3 imaging modalities to evaluate lymph nodes were also comparable: EUS, 67% and 78%; CT, 55% and 74%; and MRI, 66% and 76%.

The role of EUS in the diagnosis and treatment of RC has long been validated.^1,2-5 A meta-analysis of 42 studies involving 5039 patients found EUS to be highly accurate for differentiating various T stages.⁸ However, EUS cannot assess iliac and mesenteric lymph nodes or posterior tumor extension beyond endopelvic fascia in advanced RC. Notable heterogeneity was found among the studies in the meta-analyses with regard to the type of equipment used for staging, as well as the criteria used to assess the depth of penetration and nodal status. The recent introduction of phased-array coils and the development of T2-weighted fast spin sequences have improved the resolution of MRI. The MERCURY trial showed that extension of tumor to within 1 mm of the circumferential margin on high-resolution MRI correctly predicted margin involvement at the time of surgery in 92% of the patients.⁹ In the retrospective study by Balyasnikova and colleagues, MRI was found to correctly identify partial submucosal invasion and suitability for local excision in 89% of the cases.¹⁰

Therefore, both EUS and MRI are useful, more so than CT, in assessment of the depth of tumor invasion, nodal staging, and predicting the circumferential resection margin. The use of EUS, however, does not preclude the use of MRI, or vice versa. Rather, the 2 modalities can complement each other in staging and proper patient selection for treatment.¹¹

Despite data supporting the value of EUS in staging RC, its use is limited by a high degree of operator dependence and a substantial learning curve,^12-17 which may explain the low EUS accuracy observed in some reports.^7,13,15 Given the presence of recognized alternatives such as MRI, we decided to reevaluate EUS accuracy for the staging of RC outside high-volume specialized centers and prospective clinical trials.