Second malignant tumors in childrenStudies were made on the appearance of second malignant tumors (SMT) in children followed in a pediatric hospital at metropolitan Santiago, Chile, between years 1968 and1987. A retrospective analysis identified SMT in 7 of 430 patients who survived a childhood cancer (incidence 1.62%). An 8 tn patient was added, whose first neoplasm was treated in another hospital. The initial diagnosis in the afected children were meduloblastoma, neuroblastoma, Wilrn's tumor retinoblastoma, Ewing's sarcoma, Hodgkin's disease and, in two cases, acute lymphocytic leukemias. The age range was 6 months to 11 years. Treatment was done by surgery in 5/8, chemotherapy in 7/8 and radiotherapy in all patients. The latent period between the diagnosis of the first cancer and the diagnosis of the SMT was 3.5 to 12 years (median 8.5 years). Osteosarcomas were the most frecuent SMT (5/8). The other SMT were a rhabdomyosarcoma, a non Hodgkin lymphoma and an astrocytoma. The majority of SMT were located in the area of prior radiotherapy (6/8). In the other two cases, one had an osteosarcoma, after a bilateral retinoblastoma, which grew outside the previously treated area, and the last one consisted of a lymphoma which was identified 9 years after an acute lymphocytic leukemia. Only 3/8 SMT patients are alive after 14.21 and 34 months follow up. The other children died between 11 and 20 months after diagnosis of SMT. Notwithstanding these kinds of outcome, benefits of therapy for patients with primary tumors greatly outweight the later risk of cancer induction in a small proportion of them. (Key words: second cancer, radiotherapy, chemotherapy.) El pronostico de los pacientes con cancer infantil ha mejorado considerablemente en los ultimos arios. En la actualidad es posible la curacion de mas del 50% de ellos, debido fundamentalmente a los adelantos en los tratamientos de cirugfa, radioterapia y quimioterapia multiple 1 ' 7 .Sin embargo, estos tratamientos tienen complicaciones a corto plazo, por efectos toxicos sobre las celulas normales del organismo y, a largo plazo, por su potencial accion oncogenica 1 ' 3 ' ^ 9 .Los segundos canceres (SC) han aumentado debido a mayores sobrevidas y tiempos de seguimiento de los pacientes pediatricos oncologicos. Ademas, existe cierta predisposicion genetica a desarrollar mas de un cancer, lo que se ha hecho, tambien, mas manifiesto en las ultimas decadas, como resultado del tratamiento del primer cancer.El objetivo de este trabajo es describir los SC observados en nuestro servicio y sus relaciones con el tipo de cancer inicial y el tratamiento efectuado. 1. Servicio de Oncologia, Hospital Luis Calvo Mackenna. MATERIAL Y PACIENTESSe revise la estadistica del servicio de oncologi'a del Hospital Luis Calvo Mackenna desde 1968 a 1987. En este pen'odo fueron atendidos 1.580 pacientes, de los cuales 430 terminaron su tiatamiento sin mostrar evidencias de la enfermedad inicial hasta la fecha. En siete de ellos se presento un SC histologicamente diferente del primario. Se registra...