This has actually been going on since 1998. Here is a more accurate description of the program:
The U.S. Postal Service currently has three 45-cent fundraising or "semipostal" stamps available for purchase at Post Offices, online at The Postal Store, and by toll-free phone order at 1 800 STAMP-24: the Breast Cancer Research stamp, the Heroes of 2001 stamp, and the Stop Family Violence stamp.
The price of a semipostal pays for the First-Class single-piece postage rate in effect at the time of purchase plus an amount to fund causes that the Postal Service determines to be in the national public interest and appropriate. By law, revenue from sales (minus postage and the reasonable costs of the Postal Service) is to be transferred to a selected executive agency or agencies.
The Breast Cancer Research semipostal was issued on July 29, 1998, at a first day ceremony held in the White House. It was the first semipostal in U.S. history.
To date, the stamp has raised more than $40 million for breast cancer research. By law, 70 percent of the net amount raised is given to the National Institutes of Health and 30 percent is given to the Medical Research Program at the Department of Defense.
Designed by Ethel Kessler of Bethesda, MD, the stamp features the phrases, "Fund the Fight" and "Find a Cure" and an illustration of a mythical "goddess of the hunt" by Whitney Sherman of Baltimore.