New bone foci after starting endocrine therapy
History
64-year-old woman with ER-positive, HER2-negative breast cancer and bone metastases at diagnosis (T8, right ilium, left 7th rib). She started letrozole with a CDK4/6 inhibitor. At 3 months her back pain is better and CA 15-3 has fallen from 88 to 51 kU/L. Restaging bone scan requested by the oncologist: 'Progression? Two new areas reported on a CT elsewhere.'
Step 1 · Restaging scan at 3 months
Compared with baseline on the same display scale, the known T8, right iliac and left 7th rib lesions are brighter, and there are two foci not seen at baseline. How should the 3-month scan be interpreted?