Overall, 29% of the entire study group received adjuvant chemotherapy. The older a woman was, the less likely she was to receive adjuvant chemotherapy. Specifically, 66% of women younger than 45 years of age, 44% of women age 50 to 54 years, 31% of women age 55 to 59 years, 18% of women age 60 to 64 years, 12% of women age 65 to 69 years, and 3% of women older than age 75 years received adjuvant chemotherapy. The researchers could not detect any other factors that explained why older women were less likely than younger women to receive chemotherapy.