Delaying chemotherapy after breast cancer surgery increases the risk of recurrence and death, according to research presented at the 2018 San Antonio Breast Cancer Symposium in December.

Treatment for localized breast cancer typically includes surgery followed by radiation therapy or chemotherapy—known as adjuvant therapy—to kill off any remaining cancer cells and reduce the risk of relapse.

In a study of nearly 700 women with mostly Stage II or III triple-negative breast cancer, those who waited more than a month after surgery to start chemotherapy had worse outcomes. The 10-year overall survival rate was 82 percent for those who started within a month but fell to 67 percent for those who waited longer.

“After this period of time, the benefit of the chemotherapy is significantly diminished,” says Zaida Morante, MD, of Instituto Nacional de Enfermedades Neoplásicas in Lima, Peru.

Another study found that Kadcyla, an antibody-drug conjugate, reduces the risk of breast cancer recurring and spreading after surgery. The KATHERINE trial enrolled nearly 1,500 people with HER2-positive breast cancer who took Herceptin (trastuzumab) before surgery but still had some residual cancer at the time of the operation. After surgery, they were randomly assigned to receive Herceptin or Kadcyla, which combines the trastuzumab antibody with a chemotherapy drug.

At three years postsurgery, 88 percent of those in the Kadcyla group and 77 percent in the Herceptin group were still alive without invasive disease—a 50 percent reduction in the risk of cancer recurrence or death.