Both progression-free survival (PFS) and overall survival (OS) were similar between the two groups, but patients on the alternative schedule experienced fewer cases of hand-foot syndrome (HFS), diarrhea, and stomatitis, and also had fewer discontinuations and dose modifications.
The Food and Drug Administration–approved dose of capecitabine is 1,250 mg/m2, but 14 days of treatment can lead to significant toxicity, said Qamar Khan, MD, during a presentation of the study at the annual meeting of the American Society of Clinical Oncology. “Mathematical models applied to xenograft [animal model] data suggest that the maximum cytotoxic effect of capecitabine occurs after about 7 days of treatment, beyond which time only toxicity increases,” Dr. Khan said during his talk on the randomized control trial.
The researchers randomized 153 patients to receive a fixed 1,500-mg capecitabine dose twice per day on a 7-day-on, 7-day-off schedule (7/7), or the 1,250–mg/m2 dose twice per day for 14 days followed by 7 days off (14/7). The median age was 60 years, and 85.6% were White, 8.5% were African American, 3.3% were Hispanic, 0.7% were American Indian or Alaskan Native, and 2.0% were other. With respect to disease characteristics, 44% had visceral metastasis, 78% were hormone receptor positive/HER2 negative, and 11% had triple-negative breast cancer. About two-thirds (65%) had received no prior chemotherapy.
Restricted mean survival time (RMST) at 36 months for PFS was 13.9 months in the 7/7 group and 14.6 months in the 14/7 group (difference, 0.7 months; 95.5% CI, –3.14 to 4.57 months). The objective response rate was 8.9% in the 7/7 group and 19.6% in the 14/7 group (P = .11). Median OS was 19.8 months in the 7/7 group and 17.5 months in the 14/7 group (hazard ratio, 0.76; P = .17). The RMST at 47 months for OS was 24.5 months in the 7/7 group and 20.9 months in the 14/7 group (difference, –3.6 months; 95% CI, –8.89 to 1.54 months).
The researchers found no differences in subgroup analyses by visceral metastasis, breast cancer subtype, or number of lines of previous therapy.
The toxicity profile of 7/7 was better with respect to grade 2-4 diarrhea (2.5% vs. 20.5%, P = .0008), grade 2-4 HFS (3.8% vs. 15.1%; P = .0019), and grade 2-4 mucositis (0% vs. 5.5%; P =.0001).
Findings back up clinical practice
“The fixed-dose capecitabine dosing is something that’s been done a lot in practice, because a lot of practitioners recognize that giving the drug for two weeks in a row with a week break is overly toxic, so it’s something we’ve been doing in the community for quite a while,” said Michael Danso, MD, who comoderated the session.
Still, the safety and efficacy data back up that general clinical practice. “There was a randomized trial and colon cancer that didn’t show [equivalent outcomes with the alternate dosing schedule]. So to see that it’s safe and effective in breast cancer is an important [finding],” said Dr. Danso, who is the Research Director at Virginia Oncology Associates, Norfolk.
During the question-and-answer following the talk, Jeffrey Kirshner, MD, a medical oncologist at Hematology-Oncology Associates of Central New York, East Syracuse, noted that his practice has used a similar schedule for years. “I really commend you for doing that study. It really supports what many of us in the real world have been doing for many years. We figured this out empirically, both upfront and when patients can’t tolerate [the 14/7 schedule].”