[A Theory to Achieve Cure for Peritoneal Metastases from Low Grade Appendiceal Mucinous Carcinoma Peritonei]

A comprehensive treatment(COMPT)composed of macroscopic complete removal of peritoneal metastasis(PM)and perioperative chemotherapy has been performed to cure patients with PM. The present article shows the theoretical basis to cure patients with low grade mucinous carcinoma peritonei(LGMCP)from appendiceal mucinous neoplasm(AMN)by COMPT. When the micrometastasis(MM)does not exist outside the surgical field, complete cytoreductive surgery/complete cytoreduction(CRS, CCR-0)alone can cure the patients(Scenario A). If the MM burden left after CCR-0 resection(Scenario C)or neoadjuvant chemotherapy(NAC)+CCR-0(Scenario D)is less than the threshold level that could be completely eliminated by IOHIPEC, patients will be cured by CRS+IOHIPEC. Scenario F shows the status where MM can be completely eliminated by NAC, resulting in cure by NAC+CRS without IOHIPEC. In trying to cure patients with PM, our aim is to induce patients to follow Scenarios A, C, D or F. Between 2009 and 2023, 509 patients with LGMCP from AMN received CCR-0. Of these patients, 142 patients were treated with neoadjuvant laparoscopic(NLHIPEC)and CRS, neoadjuvant intraperitoneal chemotherapy(NIPC), and 101 patients were treated with neoadjuvant systemic chemotherapy(NSC)NIPC was performed 5 cycles, before CRS. Five-year, and 10-year overall survival rates of these patients after CCR-0 resection were 88.7%, and 77.6%, respectively. Recurrence was found in 158 patients, and peritoneal, pleural, and lung recurrence were found in 143, 6 and 3 patients. Treatment options related to the cure were inspected. To define cure, patients who survived without recurrence longer than 5 years were cured(n=202), and 43.2%(19/44)of patients were cured after CCR-0 alone(Scenario A). Patients treated with CRS+IOHIPEC were cured in 54.3%(132/243), and those treated by NIPC+CCR-0 were cured in 53.5%(38/71). Cured rates after treatment by NIPC and NSC were 53.5%(38/71), and 38.5%(35/91)(p=0.056, χ2 =3.65). Cure rate after non NIPC+CCR-0+IOHIPEC(68/117; 58.1%), and NIPC+CCR-0+IOHIPEC(34/54; 63.0%) were significantly higher than those after CRS alone(19/44; 43.2%). The PCI scores of patients treated with IOHIPEC and non IOHIPEC were 15.1±10.4 and 13.7±9.7(NS). In contrast, PCI scores for patients treated with NIPC and with NSC were 10.7±8.2 and 16.8±10.6(p<0.0001). Grade 3, 4 and 5 postoperative complications after CRS were encountered in 43 (9.2%), 43(9.2%)and 5(0.9%)patients, respectively. Conclusions: CCR-0 with IOHIPEC and NIPC may improve the cure rate of patients with LGMCP. According to our theory, this improvement is due to the elimination of MM by IOHIPEC and reduction of MM burden within threshold levels, that can be completely eliminated by IOHIPEC. We await more effective options for the elimination of MM.