Spontaneous regression of lung metastases from osteosarcoma

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 with such regression were found.

In both patients, radiograms of the primary sites and histologic specimens were studied carefully for accurate diagnosis. The clinical records, serum alkaline phosphatase values, and changes in the pulmonary metastasis on chest radiograms were followed for 26 years and 13 years, respectively. In the second patient, metastatic lesions were studied histologically.

The patients, a 19-year-old man and an 11-year-old boy each with osteosarcoma in the distal femur. Each was treated by amputation. Pulmonary metastases were found on routine checkup 5 months and 12 months after the surgery, respectively, despite adjuvant chemotherapy. The metastatic nodules of both patients became denser and smaller 12 and 5 months, respectively, after detection, and the alkaline phosphatase concentration returned to normal, without special treatment. To date, the patients are alive and well. In the second patient, histologic examination of the metastatic nodules showed no remarkable infiltration of lymphocytes that would suggest an immunologic response; however there was florid bone formation indicating maturation of the tumor cells.

Cases that have been reported as spontaneous regression of pulmonary metastases from osteosarcoma often show equivocal pathologic or clinical signs, and some have shown only temporary regression of the lesions. The two patients presented here are unique, however, because they had a definite diagnosis of osteosarcoma and showed extraordinarily long-lasting regression, which presumably occurred spontaneously, not as a direct effect of chemotherapy.