The impact of BMI extremes on disease-free survival and overall survival following cytoreductive surgery and hyperthermic intraperitoneal chemotherapy.

Background: Cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) are increasingly being offered to patients with peritoneal carcinomatosis (PC). On the other hand, the prevalence of obesity is also increasing and expected to reach unprecedented rates in the upcoming decades. Therefore, managing patients on either extreme of the body mass index (BMI) range is anticipated to become a routine challenge and it becomes imperative to understand the impact of BMI, as a spectrum, on the long-term outcomes of CRS and HIPEC. We aim to study the short and long-term outcomes of CRS and HIPEC in patients on both extremes of the BMI spectrum.

Methods: Patients with PC who underwent CRS and HIPEC over 10 years for ovarian, colorectal, and pseudomyxoma peritonei (PMP), and whose BMI was recorded were retrospectively included. Patients were divided based on their weight strata. The primary outcomes were disease-free survival (DFS) and overall survival (OS).

Results: A total of 126 patients were included. Fifty-seven point one percent were females and mean age was 59.31±1.57 years. No difference was noted between the groups in regards to demographics, perioperative characteristics, and immediate postoperative outcomes. Underweight group had a trend toward a higher peritoneal cancer index and lower rates of complete cytoreduction. Optimum BMI for OS and DFS was in the obesity range in colorectal PC, in the overweight range in ovarian PC, and in borderline obesity in PMP. Regression analysis identified underweight as an independent risk factor for shorter DFS, whereas underweight and morbid obesity were risk factors for shorter OS, after adjustment for other factors such as incomplete cytoreduction, tumor histology, and grade.

Conclusions: OS and DFS vary across the BMI strata. Ovarian PC demonstrates earlier recurrence and shorter survival, whereas colorectal PC demonstrates the "obesity paradox" as patients move into the realm of obesity. BMI extremes, low or high, generally carry a poor prognosis for OS.