RT-PCR of peritoneal washings predicts peritoneal pancreatic cancer recurrence

Peritoneal recurrence of pancreatic cancer is a frequent and lethal outcome after R0 resection. A method to predict peritoneal recurrence could be helpful in its prevention.

Peritoneal washings were prospectively obtained from 29 patients in whom R0 resection was performed. Cytological examination (CY) and real-time reverse transcription polymerase chain reaction (RT-PCR) of the peritoneal washing for the detection of cancer-related genes, CEACAM5, KRT7, KRAS, and MUC1, were performed. Clinicopathological characteristics and real-time RT-PCR results of the peritoneal washing were compared between patients whose pancreatic cancer recurred peritoneally (n = 7) and those patients who it did not recur (n = 22).

Only one CY-positive (CY⁺) case was detected, and that patient recurred. MUC1 mRNA expression was significantly higher in the recurrence group (P = 0.015). Cumulative incidence-function analysis demonstrated that peritoneal recurrence rate was significantly higher in MUC1-positive (MUC1⁺) patients (P = 0.044). MUC1⁺ patients had significantly decreased disease-free survival (P = 0.009) and disease-specific survival (P = 0.031). MUC1 protein was detected in the primary tumor in 18 of 29 patients. However, no significant difference was observed in the expression of MUC1 protein in peritoneal washings from the primary tumor (P = 0.579).

High expression of MUC1 mRNA in peritoneal washings is a significant risk factor for peritoneal recurrence of pancreatic cancer after R0 resection along with poor disease-specific survival. RT-PCR of MUC1 mRNA in peritoneal washing may be useful for individualization of adjuvant chemotherapy.