A comparative study of dosage strategies in HIPEC: BSA-based vs fixed dose methods.

832 Background: Peritoneal metastases commonly occur in ovarian, gastric, and colorectal cancers, significantly contributing to patient morbidity and mortality. Hyperthermic Intraperitoneal Chemotherapy (HIPEC) is a promising approach for managing peritoneal surface cancers. This procedure involves cytoreductive surgery to remove visible tumors, followed by the perfusion of heated chemotherapy (41-42°C) directly into the peritoneal cavity. HIPEC addresses the limitation of systemic chemotherapy, which often fails to penetrate the peritoneal cavity effectively. HIPEC dosing may either be a flat-fixed dose or be calculated based on Body Surface Area (BSA). BSA can be determined using three methods: actual BSA (based on weight and height), ideal BSA (based on sex and height), and adjusted BSA (considering lean and fat mass). Methods: A retrospective chart review was conducted on 151 metastatic cancer patients at UVMMC. Patient BMI, weight, and height at diagnosis were collected to calculate BSA values (actual, adjusted, and ideal) for estimating a hypothetical chemotherapy dosage. Statistical analysis using SPSS involved linear mixed models and paired t-tests to compare Mitomycin-C dosages between a fixed dose (40 mg) and a BSA-derived dose (30 mg/m²). Results: The average dosage of Mitomycin-C differed significantly depending on whether the dose was calculated using actual, adjusted, or ideal BSA. The largest discrepancy in dosage was observed between the actual BSA method and the flat-fixed dose, with an average difference of 16 mg. The smallest difference in dose was between the adjusted and ideal BSA methods. When stratifying by BMI, the greatest variation in Mitomycin-C dosage was found among overweight and obese patients (BMI ≥ 25). For these patients, the average dosage difference between the flat fixed dose and the actual BSA dose was 20 mg. In comparison, in patients with a BMI under 18.5 (underweight) the actual BSA dose was comparable to the fixed dose. Conclusions: Different institutions utilize a variety of dosing strategies for the HIPEC procedure. Differences in BSA calculation methods and perfusate volumes (literature values of 2, 3 and 4 L is most common) contribute to the complexity of establishing standardized dosing. The significant dosing variations observed, especially in overweight and obese patients, are of concern, as 70% of the U.S. population has a BMI ≥ 25. Our study demonstrates significant variability in HIPEC chemotherapy dosing, especially among patients with higher BMI. The discrepancy between BSA-based methods and flat-fixed doses may impact treatment efficacy and toxicity. Standardizing dosing approaches is important to ensure consistent therapeutic outcomes and patient safety.