Prognosti̇c impact of tumor volume and magnetic resonance pelvimetry on rectal cancer surgery and oncologic outcomes

Introduction: Aim of this study is to analyze the prognostic importance of pelvic measurements, pelvic cavity index (PCI), and tumor volume determined by magnetic resonance (MR) on the final oncologic outomes and surgical complications of non-metastatic rectal cancer. Patients and Method: Patients who underwent elective potentially curative radical surgery for rectal cancer were analyzedfrom a prospectively collected database. Patients who had peritoneal carcinomatosis, distant metastasis, or emergent surgical interventions were excluded from the study. A total of 125 patients were included in the interim analysis. Preoperative MR imaging data of the patients were re-examined by two radiologists blinded to the design of the study. Relationship between MR-based pelvimetric measurements, tumor volume, tumor volume regression rate(TVRR), final oncologic outcomes, and surgical complications of the patients were investigated. Results: Age(p=0.010), stage(p=0.005), lymphatic invasion(p=0.043), circumferential resectionmargin(CRM)(p<0.001), pelvic depth(b)(p=0.014), interacetabular distance(c) (p=0.026), PCI(p=0.005), tumor volume after chemoradiotherapy(V2)/PCI(V2/PCI)(p=0.028) and local recurrence(p<0.001) were related with 5-year survival in univariate analysis. Age(p=0.03), CRM(p<0.001), PCI(p<0.049), and stage(p=0.027) were found as independent prognostic factors in multivariate analysis. Intertuberous distance(c); the distance from sacral promontorium to S3-S4 space(e); and TVRR were all highly predictive on surgical complications(Logistic RA). While both of the PCI(p<0.001) and pelvic depth(d)(p<0.033) were independent predictive factors on overall blood loss, PCI(p<0.001) was also an independent predictive factor on operation time(Lineer RA). PCI and TVRR showed robust prognostic impact on complications and local recurrence in discriminative analysis. Correct prediction rates of complications and local recurrence were 66% and 88%, respectively. Conclusion: Pelvimetric measurements and tumor volume preoperatively strongly predict the final oncologic outcomes and the surgical complications in treatment of locally advanced rectal cancer. These solid measurements can further help to stratify the patients on controversial prognostic stage(T3N0), whether neoadjuvant chemoradiotherapy has to be given or not.