Does parasternal irradiation reduce thoracic vertebral metastases in breast cancer?

A review of 197 patients with bone metastases from breast carcinoma was undertaken to assess the effect of adjuvant parasternal irradiation on the distribution of those metastases. A total of 128 patients (Group I) received radiation. The control group consisted of 69 patients (Group II) who did not receive adjuvant radiation. The dose absorbed by the mid-thoracic vertebrae (T3 to T8) varied from 10 Gy in 3 weeks to 20 Gy in 4 weeks. The distribution of bone metastases was analyzed at the initial development in the 197 patients. Repeat assessments (X ray/scans) were available for analysis in 132 patients. Patients in Group I had less metastases from T3 to T8: 37/128 (29%), vs 30/69 (43.5%) for patients in Group II: (chi 2 = 3.62; p less than 0.10). For the 132 patients with serial assessments, the difference at last evaluation was more significant: 45/86 (52%) in Group I, vs 36/46 (78%) in Group II: (chi 2 = 7.44; p less than 0.01). The data shows that patients receiving low-dose exit beam irradiation from the parasternal field have fewer mid-thoracic bone metastases. Potential implications are discussed.