evidence: Americans have benefited from huge leaps in breast cancer treatment over the last two decades, but diagnoses are becoming more common, especially among younger women, according to a report published Tuesday by the American Cancer Society. [...] The reason why more women younger than 50 are getting breast cancer is not clear, but Reid said it’s likely due to modifiable risk factors such as environmental exposures in food, air or water, rising rates of obesity and sedentary lifestyles — the same risk factors thought to be causing higher rates of colorectal cancer in younger people. [...] Compared to white women, Asian American and Pacific Islanders, American Indian and Alaska Natives, Black and Hispanic women are all more likely to develop breast cancer at a younger age, the report found. However, AAPI and Hispanic women have similar mortality rates to white women.