Monitoring immunotherapy with Bacillus Calmette-Guérin by antibody titer.

Antibody titer to Bacillus Calmette-Guérin (BCG) was determined by complement fixation in 111 normal volunteers and 83 melanoma patients. In 43 of these melanoma patients, sequential determination of antibody titer was made and correlated with clinical course. Low titers of antibody to BCG were found frequently in normal volunteers and in melanoma patients prior to BCG immunotherapy. The typical response to BCG immunotherapy was a rapid rise of antibody titer to high levels. Six of 19 patients with recurrence had disappearance of antibody preceding clinical recurrence by up to 5 months. In 13 of 40 patients receiving BCG, serum antibody was a better indicator of the patient's response than measurement of delayed cutaneous hypersensitivity to purified protein derivative. These results suggest that measurement of the antibody response to BCG may be useful in developing an optimum mode of BCG immunotherapy as well as predicting clinical recurrence in patients with melanoma.