Treatment of Experimental Tumors with a Combination of a Pulsing Magnetic Field and an Antitumor Drug

We investigated the effects of a combination treatment involving a pulsing magnetic field (PMF) and an antitumor drug, mitomycin C (MMC), on two experimental tumors (fibrosarcoma KMT‐17 and hepatocellular carcinoma KDH‐8) in WKA rats, paying attention to possible potentiation of the therapeutic effect of the antitumor drug. PMF was obtained using a system generating a pulsed current in a solenoid coil. On day 7 after tumor implantation into the right thighs of rats, the region of the tumor was exposed to PMF (frequency 200 Hz, mean magnetic flux density 40 gauss) for 1 h immediately after iv injection of MMC at a dose of 1 mg/kg. Survival rates at day 90 of KMT‐17 implanted rats were 0% (0/10) in the non‐treated group, 34% (4/12) in the MMC‐treated group, 47% (6/13) in the PMF‐treated group and 77% (10/13) in the MMC/PMF combination group. The increase of life span (ILS) of KDH‐8‐implanted rats in the combination therapy group was significantly prolonged (%ILS 17.6%) compared with that in the MMC‐treated (%ILS 3.4%) and PMF‐treated (%ILS 7.6%) groups. By using cultured cells of the above two lines of tumor, the therapeutic effects of MMC and PMF were also determined from the cell colony‐forming efficiency in soft agar. The colony‐forming efficiencies of both cell lines were significantly suppressed in the combination therapy group compared with those in the other single therapy groups. The present results indicate that PMF exhibited a potentiation of the antitumor effect of mitomycin C.