• Measuring response in bone lesions takes longer and is more difficult because most metastatic breast cancers
produce a softening or dissolving of the bone with the appearance of a "lytic" spot that looks like a hole. If
treatment is successful, the lytic lesion will fill in with new bone, but this takes many months.
For determining the response to chemotherapy or hormonal therapy, a bone lesion that has not received radiation therapy has to be chosen as a marker. Obviously, if a lesion given radiation heals and hormone therapy or chemotherapy is also being given, it would be impossible to know which treatment brought about the healing.
Bone lesions require that an x-ray be done before treatment and another as soon as the treatment has been given an adequate trial.
Following bone scans for evidence of response to treatment may not be as useful as conventional x-rays of lytic bone lesions. Scans may show "hot spots" in any abnormal area, and these spots may also indicate healing. They may also be produced by inflammation , metabolic diseases or severe arthritis. The area could remain positive for months or a few years with successful therapy.
In a few patients with positive bone scans but without any lesions on x-rays, response may be signified by no new lesions developing. If the bone scan is unchanged after six months, especially if pain lessens, the positive areas can be presumed to indicate healing.
