The impact of actual body weight-based chemotherapy dosing and body size on adverse events and outcome in older patients with breast cancer: Results from Cancer and Leukemia Group B (CALGB) trial 49907 (Alliance A151436).

OBJECTIVE

Actual weight-based (AWB) chemotherapy dosing is recommended for obese patients in the 2012 ASCO Clinical Practice Guideline. CALGB 49907, which utilized ABW-based adjuvant chemotherapy dosing, was a phase 3 trial in women age≥65years with early stage breast cancer, providing the opportunity to examine impact of such dosing on toxicities and outcome in older patients with breast cancer.

MATERIALS AND METHODS

Adverse event data were available for 615 of 633 enrolled patients. Objectives were to assess grade≥3 hematologic/non-hematologic toxicities by treatment arm, age, study entry BSA/BMI, and relapse-free (RFS) and overall survival (OS) by BSA/BMI.

RESULTS

The 615 patients were sub-grouped by BSA (quartiles) and standard BMI categories, with BMI underweight/normal weight categories combined. Overall, grade≥3 non-hematologic and hematologic toxicities occurred in 39.8% and 28.3% of patients, respectively. There were no significant differences in grade≥3 toxicities among BSA quartiles. However, more grade≥3 hematologic toxicities occurred in the underweight/normal weight BMI subgroup compared to overweight/obese subgroups (p=0.048). Type of chemotherapy and age had no impact on toxicity occurrence by BSA/BMI categories. RFS was superior in the 25th-50th BSA percentile patients in univariate analysis (p=0.042), as was OS in both univariate and multivariate analyses (p=0.007, p=0.009, respectively). No differences in RFS or OS were found by BMI categories.

CONCLUSION

Obesity was not correlated with adverse relapse or survival outcome, and grade≥3 toxicities were not greater with ABW-based dosing. This supports safety and efficacy of ABW-based dosing as per the 2012 ASCO clinical practice guideline. ClinicalTrials.gov Identifier: NCT00024102 (49907).