Tumor response assessment in locally advanced colon cancer after neoadjuvant chemotherapy.

Background: Preoperative chemotherapy followed by radical surgery is a novel therapeutic approach for locally advanced colon cancer (LACC). Neoadjuvant strategies require highly accurate diagnostic tests for a proper selection of candidate patients, allowing a low risk of overtreatment. This paper assesses the radiological, metabolic and pathological findings induced by preoperative oxaliplatin and fluoropyrimidines-based chemotherapy in LACC.

Methods: Forty-four consecutive patients with a confirmed diagnosis of LACC who received neoadjuvant chemotherapy and colon surgery were included. All patients were staged at baseline and before surgery. Clinical diagnosis consisted of physical examination, endoscopy with biopsy and computed tomography (CT) scan. In selected cases, a positron emission tomography/CT (PET/CT) scan was also performed. Accuracy and correlations between CT scan findings and pathologic report was assayed for T stage, N stage and TN stage. This study is retrospective in design.

Results: After chemotherapy, a statistical significant tumor volume reduction of 62.5% was achieved by CT-scan (P<0.001; Wilcoxon test) and a 38.9% decrease of standard uptake value (SUVmax) was observed on PET/CT (P=0.004). No progressive disease was reported during neoadjuvant treatment. Accuracy for T and N classification was 62% and 87%, respectively. Accuracy for TN stage was 77%, with 13.6% and 9.1% of the patients being under or overstaged, respectively. Pathologic stage II and III disease was observed in 29/44 (65.9%) and 15/44 (34.1%) of the patients, respectively. Pathologic complete response was achieved in three patients.

Conclusions: Oxaliplatin/fluorpyrimidine neoadjuvant chemotherapy induces major tumour shrinkage at both the pathological and radiological levels. The CT scan shows a high accuracy and a low overstaged rate in LACC patients treated by means of a neoadjuvant approach.