Radiological assessment of anal cancer: an overview and update

Abstract

Anal cancer is uncommon neoplasm with an incidence of 2 new cases per 100,000 per year in the USA, accounting approximately 0.4 % of all tumors and 2.5 % of gastrointestinal malignancies. An early detection of the anal cancer is crucial for the patient management, whereas the diagnosis at an early stage allows conservative management with sphincter sparing, on the contrary a delays in diagnosis might lead to an advance cancer stage at presentation with worst survival. According to National Comprehensive Cancer Network (NCCN) Anal Carcinoma guidelines the patients should be subjected to a careful clinical examination, including a digital rectal examination (DRE), an anoscopic examination, and palpation of inguinal nodes. The guidelines recommended for the assessment of T stage, only a clinical examination, while the role of imaging techniques, as Magnetic Resonance imaging (MRI) is limited to the identification of regional nodes. Instead, the endoanal ultrasound (EAUS) is not recommended. This paper presents an overview and some updates about 3D EAUS and MRI in detection, staging and assessment post therapy of anal cancer patients.

Keywords: 3D Endo anal Ultrasound; Anal Cancer; Detection Cancer; Magnetic Resonance Imaging; Post-treatment Imaging Assessment.

Fig. 1

Anatomical scheme of anal canal: levator ani, longitudinal muscle o rectum, anorectal junction, dentate line, anal verge, anal margin, internal sphincter and external sphincter

Fig. 2

3D EAUS: longitudinal plane; external and internal sphincter

Fig. 3

3D EAUS: tridimensional reconstruction

Fig. 4

TSE T2-W in axial plane; (a) anal cancer infiltrating internal and external sphincter on the left; inguinal node. b post treatment assessment: partial response with involvement of internal sphincter; inguinal node disappearances

Fig. 5

Same patient of 4: post contrast sequences; in (a) pre treatment: contrast enhancement of anal cancer infiltrating internal and external sphincter on the left. In (b) post treatment assessment: the lesion shows a lower contrast enhancement

Fig. 6

Same patient of 4 and 5: DWI sequences. In (a) b800 pre-treatment examination: cancer shows hyperintese signal, in (b, a, d, c): the lesion appear hypointhense. In (c) post treatment b800, a lower signal than in A with a higher signal in (a, d, c) than in b