Magnetic Resonance Imaging Assessment of Squamous Cell Carcinoma of the Anal Canal Before and After Chemoradiation: Can MRI Predict for Eventual Clinical Outcome?

The assessment of local response using magnetic resonance imaging at 3- and 6-month post chemoradiotherapy in patients with anal cancer

“…A study from the London Royal Marsden investigators of 15 patients suggested that size involution is most evident at 6 months post-treatment compared with the immediate post-treatment stage where inflammation is superimposed on treated disease [18]. A study of 35 patients, from the London Mount Vernon investigators, showed that early assessment of response by MRI at 6–8 weeks was unhelpful in predicting future clinical outcome [13]. The present study similarly found a lack of association between imaging characteristics and DFS.…”

“…Previous studies have shown that tumour size change and signal intensity change post-CRT are not predictive of clinical outcome [13]. Tumour regression grading (TRG) is known to be a better predictor of outcome after treatment than T stage in rectal cancers [31].…”

“…The ESMO guidelines endorse a ‘watchful wait’ approach, stating that “partial regression can be managed by close follow-up, to confirm that (a delayed) complete regression takes place, which may take 6 months”. The US National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines make no specific reference to the role of MRI in post-CRT surveillance [16], and the American Society of Colon and Rectal Surgeons guidance [17] does not endorse a role for MRI post-CRT surveillance, citing evidence that MRI is not a predictor of clinical response in early (6–8 weeks) follow-up of CRT [13] and that longer term (6–12 months) MRI evaluation can demonstrate changes in tumour size and a reduction/stabilisation of signal intensity, but correlates only modestly with outcome [13]. However, both cited series supporting this recommendation were limited to small sample sizes (35 [13] and 15 [18] patients, respectively) and optimal timing of MRI post-CRT remains unclear [19].…”

Anal cancer: ESMO–ESSO–ESTRO clinical practice guidelines for diagnosis, treatment and follow-up

“…Distant metastases can be assessed with computed tomography (CT) of the thorax and abdomen. MRI provides excellent contrast and spatial resolution, providing information on tumour size, local extent and spread, and invasion of adjacent organs and more accurate nodal involvement [3].…”

“…Assessment and treatment should be carried out in specialised centres treating a high number of patients as early as possible in the clinical diagnosis. To date, the limited evidence from only 6 randomised trials [1,2,3,4,5,6,7], the rarity of the cancer, and the different behaviour/natural history depending on the predominant site of origin, (the anal margin, anal canal or above the dentate line) provide scanty direction for any individual oncologist. Here we aim to provide guidelines which can assist medical, radiation and surgical oncologists in the practical management of this unusual cancer.…”