When to Consider an Increase in Cyst Size in Patients With Pancreatic Cystic Neoplasms?

Abstract

Introduction: Because of the interobserver variability in radiographic cyst size evaluation, a pancreatic cyst growth rate of ≥ 3mm/year warrants a shorter follow up interval by the current consensus. On the other hand, a 20% increase in the maximum diameter of the cyst size compared to the previous was also considered to be a significant interval change by the existing literature. We aim to determine the significance of an increase in cyst size of ≥ 3mm versus ≥ twenty percent with respect to the initial cyst size in patients with pancreatic cystic neoplasms (PCN). Methods: From the Mayo Clinic, Rochester database, we retrospectively identified 238 subjects with incidentally detected pancreatic cysts. We excluded the patients with inflammatory fluid collections secondary to acute pancreatitis. The study subjects were further classified into three groups according to the initial cyst size of <1cm (99 patients), 1-3 cm (124 patients), and ≥3cm (15 patients) respectively. A difference in 3mm versus twenty percent increase at follow-up from the initial cyst size was compared in each group. Results: Baseline characteristics of the included patients were summarized in the Table. The mean cyst size at baseline was 13.3±9.4 mm which were followed up for a mean duration of 95.5±29.2 months. During the follow up period, out of 238 patients, 104 patients showed ≥3mm cyst growth compared to 110 patients with ≥20% increase in cyst size. In patients with smaller cysts (<1cm), a higher proportion of patients (56.4% versus 47.1%, p < 0.0001) showed a twenty percent difference in cyst size compared to 3mm cyst growth [Figure]. Whereas in patients with cysts size ≥1cm, higher number of patients (48.1% versus 40%; p < 0.0001 for 1-3cm, 4.8% versus 3.6%; p = 0.004 for ≥ 3cm cyst size) showed a cyst growth of 3mm compared to twenty percent increase in cyst size. Conclusion: For any cyst size, an increase in 20% of the maximum diameter of the cyst size is reasonable to consider as a significant change to reduce the effect of measuring error.61_A Figure 1. Baseline characteristics of the patients61_B Figure 2. Proportion of patients with 3mm versus 20% cyst growth with respect to the baseline cyst size