Resectable T3 rectal carcinoma with limited mesorectal infiltration (<=50%: T3a): is neoadjuvant chemoradiotherapy mandatory? Impact on local recurrence and survival

Rectal cancer accounts for approximately 30% of all colorectal malignancies. Standardization of surgical technique with the introduction of total mesorectal excision (TME) has led to improved outcome. The mesorectum is a thin enveloping fascial layer that encloses perirectal fat along with blood vessels, lymph nodes, and the rectum. TME surgery has been repeatedly associated with a reduction in the local recurrence rate from 30-40% to 5-15% with the feeling that surgical technique is the key factor. There is universal agreement that surgery alone can cure localized rectal cancer: tumors within the bowel wall (T1-2) and some T3 tumors with adequate circumferential resection margins (CRM) should have a good prognosis with an accurate surgical technique with TME. Most treatment include in the indication to neoadjuvant therapy also T3 tumors (tumors which infiltrates full thickness of the rectal wall invading the perirectal fat). While there is no doubt in our opinion too that T3 with massive mesorectal infiltration (e.g. >50% of mesorectal thickness at that particular point) demand neadjuvant treatment, there is ongoing controversy as to whether also the patients with a limited T3 (<=50%) should be submitted to this treatment protocol. The reason of this controversial indication is in the fact that the routine use of neoadjuvant therapy in all T3 rectal cancer patients could lead to overtreat a large group of patients, exposing them to unnecessary risks and delay of therapy. There is no clear classification of T3 tumors: some papers on the matter gives a division according to the millimeters of infiltration of the mesorectal fat. In our opinion, millimeters are not sufficiently precise if they are not related to the thickness of the mesorectum in that particular slice. We thus propose a classification in T3a and T3b according to the infiltration rate of the mesorectal fat (T3a <=50%; T3b >50%) and consequently we propose a study protocol to assess whether T3a (T3 tumors with minimal infiltration of the mesorectal fat) have to be submitted to neoadjuvant treatment. Patients with cT3a tumor will be subdivided in two groups: the first group will be treated by surgery alone, and the second group will be treated by neoadjuvant therapy and surgery. Patients with cT3b tumor will be treated by neoadjuvant therapy and surgery. Both high resolution MRI and EUS will be performed preoperatively, subdividing T3 tumors in T3a and T3b, and after neoadjuvant therapy to define the tumor shrinkage. This study is designated to: establish if a cT3a rectal carcinoma has lower risk of recurrence and adverse outcome rather than a cT3b (by means of determination of local recurrence - recurrence free survival at 24 and 60 months); identify if patients with a cT3a tumor submitted to surgery alone have good prognosis, comparable to those submitted to neoadjuvant treatment and surgery, and to use these results to reevaluate the indication to neoadjuvant therapy.