MRI tumor volume reduction rate vs tumor regression grade in the pre-operative re-staging of locally advanced rectal cancer after chemo-radiotherapy

Objective: To compare tumor volume reduction rate (TVRR) measured by MR volumetry after preoperative chemoradiotherapy(CRT) and pathological tumor regression grade (TRG) in locally advanced rectal cancer (LARC). Material and methods: In total, 20 patients with LARC (cT3-T4) treated with CRT followed by Total Mesorectal Excision (TME) between April 2011 and April 2013 were analyzed retrospectively. Pre- and post- CRT tumor volumes (MR volumetry) were measured on 3D MR sequences. TVRR was determined using the equation TVRR (%) = (pre-CRT tumor volume post-CRT tumor volume) x 100/pre-CRT tumor volume. The downstaging (defined as ypTO-T2) of tumor mass was evaluated and the correlation between TVRR and TRG was calculated with the method proposed by Dworak using the Spearman rank test. Results: The median TVRR was 77.3% (range, 26.4-99.3%); TVRR was >60% in 18 cases (90%) and in 8 of these patients (44.4%) it was >80%. Downstaging of tumor lesions was obtained in 15 patients (75%). In 4 cases there was a complete tumor regression (TRG4) at histological examination and in the same patients there was also a TVRR >80% measured by MR volumetry. A statistically significant correlation between TVRR and TRG = 0.5466, p = 0.0126) was observed. Conclusion: TVRR after preoperative CRT correlates with TRG in LARC. The MR volumetry is a prognostic factor to estimate the tumor response after preoperative CRT. TVRR data may be an useful biomarker for tailoring surgery and postoperative adjuvant chemotherapy. (C) 2015 Published by Elsevier Ireland Ltd.