Addition of mitomycin C to cis-diamminedichloroplatinum(II)/hyperthermia/radiation therapy in the FSaIIC fibrosarcoma

Interstitial hyperthermia and iridium-192 treatment alone vs. interstitial iridium-192 treatment/hyperthermia and low dose cisplatinum infusion in the treatment of locally advanced head and neck malignancies

PURPOSE

To determine whether the addition of low dose platinum infusional chemotherapy adds to the effectiveness of interstitial hyperthermia/iridium-192 management of locally advanced head and neck malignancies.

METHODS AND MATERIALS

From 1987 to 1993, 36 patients with locally advanced head and neck malignancies were treated locally with interstitial hyperthermia and iridium-192 as part or all of their management. Twenty-two of the above-mentioned patients also received low dose infusional cisplatinum chemotherapy at 20 mg/M2 per day during the time of the implant. No patient received greater than 100 mg/M2 total dose. Implant times ranged from 38.5 to 134 h and total doses delivered with the radiation implants ranged from 15 to 39.9 Gy. Average implant volume was 50 cc. Twenty-three patients received external beam irradiation supplementation in a dose range from 25.2 to 64 Gy.

RESULTS

Median follow-up for the entire group was 8, months with 7 months for the chemotherapy group vs. 12 months for the no-chemotherapy group. Freedom from relapse rates for the chemotherapy group vs. the no-chemotherapy group were 70% at 41 months vs. 63% at 60 months, p = not significant (p = NS). Overall survival by Life Table Analysis was 28% for the chemotherapy group at 41 months vs. 31% for the no-chemotherapy group at 60 months (p = NS). Complete response (CR) rates were 93% for the chemotherapy group vs. 86% for the no-chemotherapy group. Seven patients in the chemotherapy group had recurrent disease and four patients in the no-chemotherapy group were being treated for recurrent disease. Complication rates were similar in both groups, with two patients in the chemotherapy arm requiring hyperbaric oxygen treatments and one patient in the no-chemotherapy arm requiring hyperbaric oxygen treatments (for soft tissue necrosis).

CONCLUSION

It appears that low dose platinum infusional chemotherapy can be added safely to patients receiving interstitial iridium-192 implants along with interstitial hyperthermia for head and neck malignancies. Although there appears to be a trend toward better freedom from relapse by adding chemotherapy, a larger trial and longer follow-up will be necessary to prove statistical significance. Further research in these areas is recommended in the form of a randomized prospective study.

Hypoxia and drug resistance

Biologically and therapeutically important hypoxia occurs in many solid tumor masses. Hypoxia can be a direct cause of therapeutic resistance because some drugs and radiation require oxygen to be maximally cytotoxic. Cellular metabolism is altered under hypoxic conditions. Hypoxia can result in drug resistance indirectly if under this condition cells more effectively detoxify the drug molecules. Finally, there is evidence that hypoxia can enhance genetic instability in tumor cells thus allowing more rapid development of drug resistance cells. The current review describes the effects of hypoxia on tumor response to a variety of anti-cancer agents and also describes progress toward therapeutically useful methods of delivering oxygen to tumors in an effort to overcome therapeutic resistance due to hypoxia. Finally, the use of hypoxic cell selective cytotoxic agents as a means of addressing hypoxic 'drug resistance' is discussed.

Addition of a topoisomerase I inhibitor to trimodality therapy [cis-diamminedichloroplatinum(II)/heat/radiation] in a murine tumor

The cytotoxicity of the topoisomerase I inhibitors, camptothecin and topotecan, toward exponentially growing EMT-6 murine mammary carcinoma cells under various conditions of oxygenation, pH and temperature was assessed. Under normal pH (pH 7.40) conditions both camptothecin and topotecan were more cytotoxic toward normally oxygenated cells. Both agents were more cytotoxic under acidic pH (pH 6.45) and the differential in cytotoxicity due to the cellular oxygenation level disappeared. Neither camptothecin nor topotecan was enhanced in cytotoxicity by hyperthermia (42 degrees C or 43 degrees C, 60 min) during drug exposure. Both camptothecin and topotecan killed increasing numbers of FSaIIC tumor cells with increasing dose of the drugs in vivo in a log/linear manner. Local hyperthermia (43 degrees C, 30 min) increased the tumor cell killing of the drugs but decreased the toxicity of these agents to the bone marrow granulocyte/macrophage-colony-forming units. Topotecan was a more effective modulator of cisplatin than was camptothecin, as determined by FSaIIC tumor cell survival assay and by FSaIIC tumor growth delay. Although both camptothecin and topotecan were effective additions to a treatment regimen including cisplatin and daily fractionated radiation (5 x 3Gy), neither of these topoisomerase I inhibitors increased the tumor growth delay produced by the trimodality regimen of cisplatin/hyperthermia/radiation.