Effect of cyclophosphamide or x-rays on spontaneously occurring metastases from tumors transplanted into the tails of mice.

A spontaneous metastases model in mice is being used to test the efficiency of various treatments in eliminating metastases. Solid tumors were transplanted into the tails of mice and removed by tail transection when they had grown to a 4- to 5- or 6- to 7-mm mean diameter. Subsequently, 70 to 95% of mice not given other treatment developed metastases in the lungs or in regional lymph nodes (lumbar sacral region), or in both sites. The present paper reports the effects of whole-body or partial-body treatment on these metastases. The treatments, which started at the time of surgical transection of the tail, included a range of single or fractionated doses of cyclophosphamide (CTX) or X-rays given either to the whole body or locally to the lungs only. CTX reduced the incidence of metastases in both sites although the incidence of lung metastases was reduced by smaller doses of CTX than that of the lumbar sacral metastases. Whole-body irradiation of 6 grays (600 rads) had no effect on the incidence of metastases, whereas local irradiation of the lungs with single doses of 14.5 or 20 grays reduced the number substantially, as did 95 mg or more of CTX per kg. Thus, CTX or radiation reduced the incidence of lung metastases in a system where metastases developed from cells seeded from a primary tumor rather than from a cell suspension injected into the tail vein.