The woman, who is in her 60s, also received radiation and cortisone, The Local.se reported. Doctors say the needless treatment caused permanent brain damage, leaving her with less ability to control her hands.
"It's extremely regrettable," Lars-Goran Holtby, chief doctor at the Gavle hospital, told Arbetarbladet.
The woman had previously been successfully treated for breast cancer.
The case was reported to the National Board of Health and Welfare.