Cisplatin with high-dose infusions of hydroxyurea to inhibit DNA repair

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Abstract
A total of 45 patients with locally advanced and/or metastatic non-small-cell lung cancer (NSCLC) were treated in a phase II trial with high-dose i.v. infusions of 24 g hydroxyurea over 24 h, with 50 mg/m2 i.v. cisplatin 8 h after the start of hydroxyurea infusion. Hydroxyurea, a cell-cycle-specific inhibitor of ribonucleotide reductase, inhibits DNA repair by depleting nucleotide pools. We gave hydroxyurea to achieve steady-state levels of ≥1 mM and to potentiate therapy by inhibiting repair of DNA damage produced by cisplatin. Among 21 patients with squamous cell lung cancer, there were 1 complete response (CR), 2 partial responses (PR) and 3 minor responses (MR). Of 13 patients with adenocarcinoma of the lung, 2 had MRs; of 11 patients with large-cell anaplastic lung cancer, none responded. The dominant toxicity was nausea and vomiting, which was manageable and mainly related to cisplatin. The response rate in squamous cell lung cancer was similar to responses obtained with cis-platin alone. The relative ineffectiveness of high-dose 24-h infusions of hydroxyurea in inhibiting repair of DNA damage produced by cisplatin may be due to the low growth fraction of human NSCLC. The high-dose hydroxyurea approach may be more applicable in tumours with a high growth fraction.