Prognostic Factors Affecting Short- and Long-Term Recurrence-Free Survival of Patients with Rectal Cancer using Cure Models: A Cohort Study.

BACKGROUND

Understanding the prognostic factors affecting the recurrence-free survival (RFS) of patients with rectal cancer (RC) is the mainstay of care. The present study aimed to identify factors affecting both short- and long-term RFS of patients with RC using semiparametric mixture cure models.

METHODS

The data were obtained from the database of the Colorectal Research Center of Shiraz University of Medical Sciences, Shiraz, Iran, which was collected during 2007-2017. To determine the factors affecting recurrence, cure models were applied to short-term and long-term RFS of patients with RC separately. The cure rate was calculated using the smcure package in R 3.5.1 (2018-07-02) software. P<0.05 was considered statistically significant.

RESULTS

Out of the 376 eligible patients with RC, 75.8% of men and 74.5% of women were long-term survivors. The mean age of the patients was 57.0±13.8 years. Lymph node ratio (LNR)≤0.2 increased the probability of short-term RFS. The prominent factors affecting long-term RFS were body mass index (BMI)<25 kg/m (OR=1.98, P=0.047), tumor-node-metastasis (TNM) stage (OR=6.48, P<0.001), abdominal pain (OR=2.15, P=0.007), and computed tomography (CT) scan detected pelvic lymph nodes (OR=3.40, P=0.01). Over a 9-year follow-up period, the empirical and estimated values of cure rates were 75.3% and 83.9%, respectively.

CONCLUSION

The results showed that factors affecting short-term RFS might be different from long-term RFS. A lower BMI was related to a poorer prognosis in patients with RC. Early diagnosis leads to a lower TNM stage and could increase the probability of long-term RFS.