Does bacillus Calmette-Guérin immunotherapy accelerate growth and cause metastatic spread of second primary malignancy?

ABSTRACT

In our study, 29 of 150 patients with bladder cancer also had other associated primary malignancies, 10 of which were manifested after intravesical treatment with bacillus Calmette-Guérin (BCG). Second primary malignancies developed in 5 of these patients within three months of the start of BCG therapy. All 5 showed acceleration of the second primary tumor, and distant metastatic lesions developed in 4. In the other 5 patients nonbladder primary malignancies developed eight months or more after intravesical BCG therapy started, but did not show acceleration or spread. Twenty patients with other primary malignancies that had developed months to years before intravesical therapy did not show acceleration or spread of those tumors. We have seen enough cases of patients who received intravesical BCG at the time of growth and spread of second primary malignancies to warrant concern. Animal and human studies of BCG use for treatment of malignancy indicate that the temporal relationship between the starting point of tumor development and the starting point of BCG treatment is crucial in determining whether BCG will eradicate or exacerbate the tumor. We have therefore instituted a change in our treatment until the question of whether or not BCG causes the appearance and spread of these second malignancies is answered.