Pelvic phased-array MR imaging of anal carcinoma before and after chemoradiation

Abstract

The aim of this study was to evaluate the MR findings of anal carcinoma using an external pelvic phased-array coil before and after chemoradiation treatment. 15 patients with carcinoma of the anal canal underwent T(2) weighted and short-tau inversion recovery (STIR) imaging before and after chemoradiation. Images were reviewed in consensus by two radiologists. At pre-treatment imaging, the tumour size and stage, signal intensity and infiltration of adjacent structures were recorded. MR imaging was repeated immediately after chemoradiation, every 6 months for the first year and then yearly. Tumour response was assessed by recording change in tumour size and signal intensity. Prior to treatment, the mean tumour size was 3.9 cm (range, 1.8-6.4 cm). Tumours appeared mildly hyperintense at T(2) weighted and STIR imaging. There was good agreement in T staging between clinical examination and MR imaging (kappa = 0.68). In 12 responders with long disease remission, a greater percentage reduction in the size of MR signal abnormality in the tumour area was observed at 6 months (mean 54.7%; 46-62%) than immediately after treatment (mean 38.6%; 30-46%) (p = 0.002, t-test). 7/12 showed stabilization of T(2) signal reduction in the tumour area after 1 year, and 5/12 showed complete resolution of signal alterations at 2 years. Pelvic phased-array MR imaging is useful for local staging of anal carcinoma and assessing treatment response. After treatment, a decrease in tumour size accompanied by reduction and stability of the MR T(2) signal characteristics at 1 year after chemoradiation treatment was associated with favourable outcome.

Anal carcinomas: the role of endoanal ultrasound and magnetic resonance imaging in staging, response evaluation and follow-up

“…Studies have shown good agreement in local tumour staging by MRI versus clinical digital examination [15].…”

“…7). Extension laterally into the ischiorectal fat is less common, suggesting that the levators act as a barrier to lateral tumour growth [15].…”

“…11, 12). Stabilisation of T2-weighted signal intensity and size of any residual abnormality more than one year after chemoradiation is associated with a good outcome [15]. Size involution is most evident at 6 months post-treatment compared with the immediate post-treatment stage where inflammation is superimposed on treated disease.…”

“…This does not take into account sphincter muscle involvement which is an important prognostic factor [11]. In the last decade there has been increasing use of endoanal ultrasound (EAUS) and magnetic resonance imaging (MRI) for locoregional staging [12][13][14][15]. There appears to be only one paper to date [16] that directly compares EAUS (using 2-dimensional imaging) with MRI in the primary staging of anal carcinoma.…”

Le point de vue du proctologue sur la prise en charge de formes précoces des carcinomes épidermoïdes du canal anal et des lésions de néoplasie intraépithéliales

“…L'IRM pelvienne est systématique pour certaines équipes. Elle est surtout intéressante pour les tumeurs plus volumineuses car elle est sans doute plus précise que l'échoendoscopie pour préciser les rapports avec les organes et structures de voisinage et pour rechercher des adénopathies à distance [3].…”