SPONTANEOUS REGRESSION OF LUNG METASTASES FROM OSTEOSARCOMA

Background. Spontaneous regression of malignancy is infrequent, but in osteosarcoma, such occurrence is extremely rare. Through a survey of many university hospitals and cancer centers in Japan, two patients wi th such regression were found. Methods. In both patients, radiograms o f the primary sites and histologic specimens were studied carefully fo r accurate diagnosis. The clinical records, serum alkaline phosphatase values, and changes in the pulmonary metastasis on chest radiograms w ere followed for 26 years and 13 years, respectively. In the second pa tient, metastatic lesions were studied histologically. Results. The pa tients, a 19-year-old man and an 11-year-old boy each with osteosarcom a in the distal femur. Each was treated by amputation. Pulmonary metas tases were found on routine checkup 5 months and 12 months after the s urgery, respectively, despite adjuvant chemotherapy. The metastatic no dules of both patients became denser and smaller 12 and 5 months, resp ectively, after detection, and the alkaline phosphatase concentration returned to normal, without special treatment. To date, the patients a re alive and well. In the second patient, histologic examination of th e metastatic nodules showed no remarkable infiltration of lymphocytes that would suggest an immunologic response; however there was florid b one formation indicating maturation of the tumor cells. Conclusion. Ca ses that have been reported as spontaneous regression of pulmonary met astases from osteosarcoma often show equivocal pathologic or clinical signs, and some have shown only temporary regression of the lesions. T he two patients presented here are unique, however, because they had a definite diagnosis of osteosarcoma and showed extraordinarily long-la sting regression, which presumably occurred spontaneously, not as a di rect effect of chemotherapy.