TREATMENT FAILURE FOLLOWING SEQUENTIAL THERMORADIOTHERAPY OF LOCALLY ADVANCED BREAST-CARCINOMA OCCURS PRIMARILY IN POORLY VASCULARIZED TUMORS

Sequential thermoradiotherapy was given to 24 patients with locally ad vanced breast carcinoma. The outcome of treatment was analyzed in rela tion to the thermal dose as well as clinical stage, tumor volume, vasc ular density and necrotic fraction prior to treatment. Complete or par tial response was seen in all patients. Three of the patients showed l ocal recurrence following treatment. One of the recurrences was due to a geographic miss of the radiation therapy whereas the other two recu rrences were 'true' local treatment failures. Local treatment failure could not be attributed to an advanced clinical stage, large tumor mas ses or poor tumor heating. The recurrent tumors had a low vascular den sity and significant necrotic fraction prior to treatment, suggesting that treatment failure was due to the presence of chronic hypoxia. The radiotherapeutic problem of treatment resistance caused by chronicall y hypoxic cells is probably not eliminated with sequential thermoradio therapy.