William Rehnquist is the Chief Justice of the United States. He is also a cancer patient, who has been able to continue working with accomodations, which have presumably included time off for chemotherapy and radiation treatment, and the ability to keep his government job at will.
Patricia Garrett is the former Director of OB/GYN/Neonatal Services at Cooper Green Hospital, an Alabama state hospital. She was also a cancer patient, took no time off for chemotherapy and radiation treatment, and did not request any accomodations, but was nonetheless fired by her government employer.
Why did the firing of Patricia Garrett stand? Because Chief Justice Rehnquist wrote an opinion in her Supreme Court case, arguing that it was legitimate for state employers to undermine the ADA by conserving “scarce financial resources by hiring employees who are able to use existing facilities.”