Use of an electron beam for post-mastectomy radiotherapy: 5-year follow-up of 500 cases.

Since 1982, the standard method of postmastectomy regional radiotherapy at the Christie Hospital has been to use a single electron field of fixed energy (8 MeV) to irradiate the chest wall, matched to a single megavoltage field (4 or 8 MV) irradiating the nodal areas in the axilla and supraclavicular fossa. (A separate parasternal field was not used.) All 500 cases treated in 1982 and 1983 with this method were reviewed (median follow-up 59 months). Four hundred and twenty-two were referred directly post-mastectomy and 78 for local recurrence after previous mastectomy. Of these, 42 were treated palliatively, and 458 with radical intent. In radical cases the given dose in both fields was 40 Gy in 15 fractions in 3 weeks. The overall survival (n = 458) was 51% (actuarial) at 5 years. At 5 years the local recurrence rate by site and UICC stage were as follows: chest wall - all Stages 17%, Stage I 4%, Stage II 13%, Stage III 26%, recurrent cases 21%; axillary recurrence - all Stages 20%, Stage I 4%, Stage II 10%, Stage III 22%, recurrent cases 39%; supraclavicular recurrences - all Stages 9%. Only one patient of the 500 treated had a parasternal recurrence. Late effects included mild telangiectasia in the electron field and asymptomatic apical lung fibrosis in the photon field. There was no match line fibrosis.