Patterns of failure following treatment of pseudomyxoma peritonei of appendiceal origin

Pseudomyxoma peritonei is a rare disease caused by a perforated adenoma of the appendix. It results in extensive accumulation of mucinous tumour at specific locations within the abdomen and pelvis. The study was undertaken to examine patterns of recurrence in patients with grade I disease treated by cytoreductive surgery and early postoperative intraperitoneal chemotherapy. After a median follow-up of 1.9 years (range 0.5-7.4 years) 42 out of 118 patients had recurred. In 32 patients, detailed information regarding the anatomical location of recurrent tumour from CT-scan and second-look laparotomy were available and these form the basis of this study. The volume of recurrent tumour was recorded at eight abdominal sites, the laparotomy scar and at suture lines. Patient, tumour and treatment factors were analysed for possible relationship with the pattern of recurrence. With recurrence, true metastatic disease was observed in 3 patients and a distinctly higher grade of intraperitoneal tumour in another patient. Pleural spread of pseudomyxoma was found in 6 patients, always related to entering the pleural cavity during cytoreduction (P = 0.000031). Two abdominal sites consistently had an increase in tumour deposits at re-operation as compared to the initial cytoreduction. Small bowel had large deposits at re-operation in 17% versus 3% at initial cytoreduction and retroperitoneal surfaces 10% versus 0%. Recurrences were most frequent in the left subhepatic/lesser omentum area (28%), while the right subdiaphragmatic area (3%) was least involved. Pseudomyxoma peritonei recurrence in the laparotomy scar was found in 15/29 patients (52%), significantly more frequent if tumour had been present at former laparotomy scars during cytoreduction (P = 0.042). In 15/25 (60%) of patients, recurrences were found at suture lines. Differences in the completeness of cytoreduction, inadequate distribution of intraperitoneal chemotherapy to upper abdominal and small bowel surfaces, and entrapment of tumour within suture lines were thought to be causal factors consistent with this pattern of recurrence. Consequences for future treatment strategies are discussed.