The role of cytoreductive surgery and hyperthermic intraperitoneal chemytherapy in the treatment of rare histological subtypes of ovarian cancer

Malignant ovarian tumor is the eighth most common malignant tumor in the female population with an incidence rate of 6.6 and a mortality rate of 4.2 per 100,000 in the world. The initial diagnosis is most frequently made at an advanced stage of the disease with peritoneal dissemination when the five-year survival rate is 29%. Rare histological subtypes of malignant ovarian tumors have a worse prognosis than high-grade serous adenocarcinoma of the ovary. Rare malignant ovarian tumours include: mucinous, clear cell, granulosa-cell tumours, low-grade serous ovarian carcinoma, endometrioid cancer. The worse prognosis for these subtypes is most likely related to their resistance to systemic chemotherapy. The aim of this study is a literary review to evaluate the role of cytoreductive surgery and HIPEC in the treatment of rare malignant tumors of the ovary. Patients with rare malignant ovarian tumors with peritoneal dissemination have traditionally been considered as poor prognosis cases and treated with palliative surgery or chemotherapy. Over the last three decades, the survival of patients with peritoneal dissemination has improved significantly with the development of cytoreductive surgery with intraperitoneal heated chemotherapy. Cytoreductive surgery involves a series of intraperitoneal procedures to achieve complete cytoreduction and is combined with heated intraperitoneal chemotherapy (HIPEC, open or closed technique) to reduce residual microscopic disease. Rare ovarian cancers are prone to peritoneal dissemination and limited spread to the peritoneal cavity at an advanced stage and in the form of recurrence, without systemic and visceral spread, and therefore require cytoreductive surgery for optimal disease control. Due to the limited data available and the rare frequency of these tumors, therapy is still a challenge with no clear guidelines for their treatment. After cytoreductive surgery and HIPEC, the 5-year survival rate was 69.6% for the mucinous subtype, 41.9% for the endometrioid subtype and 61.5% for granulomatous tumors, while the 5-year survival rate for teratomas and germinal tumors was 72.9%. The overall survival of patients with the clear cell subtype is 59.2 months, while for the low-grade subtype it is 130 months. It is recommended to use cytoreductive surgery and HIPEC in the treatment of rare subtypes of ovarian cancer with peritoneal dissemination. Complete cytoreduction without macroscopic residual disease is considered the only independent prognostic factor.