Background: Fearing increased myelotoxicity, many practitioners adjust the body surface area (BSA)-calculated doses in obese patients. Regarding temozolomide (TMZ), a prior study suggested men with a BSA >2 m2 may experience increased toxicity; however, surprisingly, the inverse observation was noted in women, ie, BSA <2 m2 was associated with higher toxicity. To further clarify this issue, data derived from a large clinical trial were analyzed.
Methods: The incidence of grade 3 and 4 myelotoxicity in a newly diagnosed glioblastoma phase 3 trial (RTOG 0525) was statistically correlated with BMI and separately with BSA. All patients received radiation and TMZ followed by adjuvant standard dose TMZ vs dose-dense TMZ; dosing regimen-associated myelotoxicity and BMI/BSA were analyzed separately. Obesity was defined as a BMI ≥30.
Results: There was no statistically significant correlation between gender and BSA and the occurrence of myotoxicities. For the standard arm, surprisingly the incidence of grade 3/4 myotoxicities in patients with a BMI <30 was significantly higher than in patients with a BMI ≥30 (12% vs 1%, odds ratio [OR] 12.5, P < .001). There was no significant difference between obese and nonobese patients (BMI "cut-point" of 30) in the dose-dense arm (OR = 0.9, 95% confidence interval: 0.4-1.6). The grade hematological 3/4 toxicity rate was significantly higher in women vs men (14% vs 8%) P = .009 in spite of the lack of association between gender and BSA or BMI.
Conclusion: TMZ dosing based on actual BSA is recommended with the caveat that woman are likely at higher toxicity risk.
Keywords: body mass index; surface area; temozolomide toxicity.
© The Author(s) 2019. Published by Oxford University Press on behalf of the Society for Neuro-Oncology and the European Association of Neuro-Oncology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.