Intravesical thermo-chemotherapy based on conductive heat: a first pharmacokinetic study with Mitomycin C in superficial transitional cell carcinoma patients

PURPOSE: To evaluate, for the first time, the mitomycin C (MMC) pharmacokinetics during intravesical hyperthermia treatment based on conductive heat and the stability and recovery of the drug at the end of the instillation period. METHODS: Eleven patients with recurrent intermediate-risk superficial transitional cell carcinoma of the bladder were treated weekly for six cycles with intravesical MMC (40 mg MMC in 50 ml) in local hyperthermia (45 °C) with Unithermia® system. Each instillation lasted 45 min, with the solution being replaced after the first 22 min. The MMC recovery at the end of the two instillation period and the plasmatic pharmacokinetics of MMC were evaluated by high-pressure liquid chromatography. RESULTS: Nine patients completed all the six planned cycles, whereas two patients missed the last cycle because of allergic reactions. No other systemic toxicity was observed, and the local toxicities were mild. Median MMC concentration in the instillation residual solution decreases from the initial 0.8 to 0.22 mg/ml for the 0-22-min instillation period and to 0.38 mg/ml for the 22-45-min instillation period; the median percentage of MMC recovered after instillation was 66.2 and 99.6, respectively. In all patients, MMC plasmatic C max resulted considerably lower than the toxic threshold (400 ng/ml). CONCLUSIONS: The MMC is stable during the instillation, and its absorption occurs mainly during the first minutes of the treatment. The plasmatic MMC concentration is always well below the threshold level for myelosuppression, as confirmed by the total lack of hematological toxicity evidenced by the patients. In order to evaluate the efficacy of the treatment performed with UniThermia® in reducing the disease recurrence rate in short- and long-term follow-up, we are currently carrying out a clinical multicentric study involving a larger number of patients.