Dr Johnson on Trastuzumab Plus Paclitaxel in HER2+ Breast Cancer

Kai Conrad Cecil Johnson, MD, medical oncologist, The Ohio State University Comprehensive Cancer Center–James, discusses key invasive disease-free survival (IDFS) findings from the final 10-year analysis of the phase 2 APT trial (NCT00542451) and HER2DX exploratory analyses in patients with HER2-positive breast cancer.

The APT trial investigated the long-term outcomes of patients with HER2-positive breast cancer with small disease, defined as tumors measuring less than 3 cm, who were node negative at the time of surgery, Johnson says. Patients received weekly adjuvant paclitaxel plus trastuzumab (Herceptin) for 12 weeks followed by 40 additional weeks of trastuzumab. This trial’s primary end point was IDFS.

Initial results from this trial showed that at a median follow-up of 4.0 years, the 3-year IDFS rate was 98.7% (95% CI, 97.6%-99.8%). At a median follow-up of 10.8 years (interquartile range, 7.1-11.4), the 10-year IDFS rate was 91.3% (95% CI, 88.3%-94.4%), and the 10-year recurrence-free interval was 96.3% (95% CI, 94.3%-98.3%). In addition, the 10-year overall survival and 10-year breast cancer–specific survival rates were 94.3% (95% CI, 91.8%-96.8%) and 98.8% (95% CI, 97.6%-100%), respectively.

Since APT was a single-arm trial, outcomes with no therapy or trastuzumab alone in this population are unknown, Johnson says. However, trastuzumab plus paclitaxel was well tolerated in this trial, and the efficacy findings support the use of trastuzumab plus paclitaxel in this population, Johnson emphasizes.

APT also used the HER2DX genomic assay to stratify patients by recurrence risk to determine which patients were at high risk of recurrence and should receive additional treatment, according to Johnson. The association between HER2DX risk score and IDFS was statistically significant, with a hazard ratio (HR) per 10-unit increment of 1.24 (95% CI, 1.00-1.52). There was also a significant association between HER2DX risk score and recurrence-free interval, with an HR of 1.45 (95% CI, 1.09-1.93).