Obesity and carboplatin dosing in gynecologic oncology patients

Purpose: This retrospective study illustrates the relationship between body weight, dose of carboplatin and treatment outcomes for patients with gynecologic malignancies.

Methods: A retrospective chart review of 100 patients who received carboplatin from the University of Kansas Hospital for the treatment of gynecologic malignancies between July 1, 2009 and June 30, 2011 was performed.  Medical records were reviewed for indication, dosing weight, stage, performance status, dose modifications, concurrent chemotherapy, granulocyte colony stimulating factor (GCSF) use, platelet count, serum albumin, serum creatinine, cancer antigen 125 (CA-125) levels, robotic versus open surgery, and adjuvant versus neoadjuvant therapy.  Outcomes were evaluated by a student t-test.

Results: After evaluating 100 patients, a statistically significant difference in platelet response was discovered when actual vs. adjusted body weight was used for carboplatin calculations (38.7% vs. 44.0%; p=0.009).  When stratifying by GCSF utilization, a more robust platelet response was seen when GFR was calculated by actual body weight and GCSF was utilized (45.6% vs. 40.3%; p=0.022), but not if GCSF was excluded (41.1% vs. 32.9%; p=0.053).  A significant difference was also found in patients with a serum albumin less than 3.5 g/dL (45.1% vs. 40.2%, p=0.019) and a trend was observed when comparing intensity of therapy in obese compared to non-obese patients.  No difference in progression-free interval was encountered when evaluating CA-125 levels.

Conclusions: Using adjusted body weight when calculating the dose of carboplatin in patients with gynecologic malignancies significantly diminished platelet response in patients receiving GCSF as well as the combined group.  A trend towards significance was seen in the non-GCSF group.  Serum albumin concentrations and obesity also influence the extent of hematologic toxicity.