BCG immunotherapy in a standard regime was administered by scarification to 26 selected patients with controlled malignant disease, 14 with lung cancer and 12 with melanoma. All were followed for 12 months after the first BCG administration or until death. During the first 3 months, when BCC was given weekly, immune reactivity as determined by skin tests and in vitro lymphncytr responses to phytohemagglutinin and recall antigens was enhanced in all 1x1tients except those in whom recurrence or extension of malignancy subsequently occurred. Patients who had received prior radiation therapy for lung cancer also did not manifest significant immunoenhancement. During the following 9 months when BCG was administered a t increasing intervals, immune responses were maintained except in those patients who experienced recurrence of malignancy, and those who discontinued BCG therapy. T h e response to P H A was predictive of a favorable clinical course during the following 9 months, antl was significantly impaired in advance of the clinical recurrence of malignancy.
Tests of cell-mediated immunity, particularly the i n vitro response to PHA, are valuable in assessing the efficacy of BCG immunotherapy, prognosticating clinical progress, and predicting the recurrence of malignancy.