Intensity of immunosuppressive therapy and the incidence of Pneumocystis carinii pneumonitis

A series of 149 children with acute lymphocytic leukemia treated according to a prospective protocol was randomized after induction of remission and central nervous system (CNS) irradiation to receive maintenance chemotherapy with 1, 2, 3, or 4 chemotherapy agents. The incidence of P. carinii pneumonitis (PCP) was 5.0, 2.3, 2.2, and 22.4%, respectively, during the period of maintenance therapy. An additional 31 patients enrolled in the same study were placed in special categories to receive three drugs for maintenance plus supplemental chemotherapy or irradiation because of CNS leukemia on admission, remission failure, mediastinal mass, or generalized lymphosarcoma without bone marrow involvement. The incidences of PCP in these groups were 16.7, 30.0, 35.7, and 0%, respectively, during the period of maintenance therapy.