Objective The objective of this study was to develop a predictive model for parametrial involvement (PMI) and to identify low-risk group of PMI in early stages of cervical cancer based on preoperative magnetic resonance imaging (MRI) parameters.

Methods We retrospectively analyzed patients with stages IB1 to IIA2 cervical cancer (N = 1347) who underwent type C radical hysterectomy between 2005 and 2012. Clinical records, preoperative MRI, and its association with pathological data were reviewed. A predictive model for PMI was developed using preoperative MRI parameters for the estimation of its performance.

Results Of 1347 patients, 138 (10.2%) had pathological PMI (p-PMI). Multivariate analysis identified the maximal tumor diameter (odds ratio, 2.0; 95% confidence interval, 1.23–3.40; P < 0.001) and PMI (odds ratio, 7.0; 95% confidence interval, 4.49–11.02; P < 0.001) on preoperative MRI (m-PMI) as independent predictive factors for p-PMI. The rate of p-PMI was 1.3% for low-risk patients identified by the current model (maximal tumor diameter ⩽2.5 cm and no indication of PMI, n = 448). The 5-year progression-free survival rate was significantly greater (96.7%) in low-risk patients than in those with a maximal tumor diameter greater than 2.5 cm and/or indication of m-PMI (90.8%, P = 0.004).

Conclusions A predictive model for p-PMI was developed in which p-PMI exclusion was set as a maximal tumor diameter less than or equal to 2.5 cm and no indication of m-PMI. Patients with a low risk of m-PMI could be identified so that less radical surgery for stages IB1 to IIA2 cervical cancer could be offered.