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Objectives: Locally advanced cancers of the head and neck require aggressive treatment, often with limited effectiveness and significant toxicity and morbidity. This pilot study was designed to assess tolerance using combined hyperfractionated radiotherapy and the halogenated pyrimidine radiosensitizer 5'-iododeoxyuridine (IdUrd)., Study Design: This was a prospective single-arm study open to patients with advanced head and neck cancers that had a poor chance of control with conventional radiation therapy. Patients were treated with hyperfractionated radiation therapy at standard doses in combination with an IdUrd infusion and observed for tumor response and normal tissue tolerances., Methods: Radiation therapy was delivered in fractions of 1.2 Gy or 1.5 Gy twice daily to a total dose in the range of 70 to 76 Gy. IdUrd was delivered as an intravenous infusion (1000 mg/m2 per day) for a maximum of 14 days at the beginning and then again during the middle of the radiotherapy., Results: Twelve patients with advanced squamous cell lesions were enrolled and 11 were observed to have complete clinical remissions. Seven patients remained clinically free of local disease at the time of death or most recent follow-up. Acute toxicities, usually hematologic or mucosal, were severe and all patients required treatment modifications and considerable supportive care., Conclusions: Although a high rate of response was achieved using this regimen, the toxicities are prohibitive. The kinetic profile of IdUrd incorporation suggests the need for future studies using repetitive short courses of IdUrd.

Background: The halogenated pyrimidines 5'-iododeoxyuridine (IdUrd) and 5'-bromodeoxyuridine (BrdUrd) are under active study as radiation sensitizers for a variety of malignancies. Head and neck neoplasms may also be suitable for halogenated pyrimidine-mediated sensitization; previous regimens using intra-arterial BrdUrd delivery, however, were poorly tolerated., Purpose: A pilot study was undertaken with the use of intravenous IdUrd with hyperfractionated radiotherapy to assess tolerance. In addition, serial tumor biopsy specimens were obtained to determine the kinetics of IdUrd labeling and incorporation., Methods: Twelve patients with squamous cell carcinomas of the head and neck (one patient had stage II cancer, one had stage III, and 10 had stage IV) were treated with hyperfractionated radiation therapy at a dose of 1.2 or 1.5 Gy twice a day, to a total dose in the range of 70-76 Gy. IdUrd (1000 mg/m2 per day) was infused for a maximum of 14 days at the beginning and then again during the middle of the radiotherapy. A tumor biopsy specimen was obtained from 11 patients following initiation of treatment with IdUrd. Eight patients consented to serial biopsy to allow the study of IdUrd-labeling indices and thymidine replacement over time. Incorporation of IdUrd into tumor DNA was determined by high-performance liquid chromatography, and cell labeling was determined with the use of an anti-BrdUrd/IdUrd monoclonal antibody in conjunction with flow cytometry. Patients continue to be followed to assess local control., Results: A plot of corrected IdUrd replacement as a function of infusion time suggests the possibility of a plateau after 5-7 days of infusion at 7.5%-8%. The average rate of replacement from days 1 to 5 was 1.3% per day and was determined by linear regression analysis. Acute toxic effects, especially mucositis, were severe enough to require delays in the radiation therapy. Eleven of 12 patients treated had complete clinical remissions. Seven of these patients remain clinically free of local disease at the time of death or most recent follow-up., Conclusions: The level of IdUrd incorporation and cell labeling should be adequate to produce sensitization. However, the treatment as prescribed in this study (two 14-day infusions of IdUrd during radical radiotherapy with only one planned split) was not completed in a single patient because of either dose-limiting hematologic toxicity or severe mucositis necessitating treatment break. Since this particular regimen is not tolerable, future protocols will have shorter exposures to IdUrd., Implications: Previous regimens using halogenated pyrimidine radiosensitizers have generally used protracted drug delivery schedules. In this study, a high level of IdUrd labeling was measured after 5-7 days of drug infusion. The halogenated pyrimidines deserve further study with the use of repetitive short courses to reduce toxicity and possibly improve efficacy.

PDT and IUdR-sensitized radiation therapy represent potential advances in the treatment of tumors of the head and neck. Light-activated photosensitizers have definite antitumor activity in both in vitro and in vivo experimental systems. Much of the early clinical work in head and neck cancer involved treatment of patients with advanced, recurrent disease who had not responded to conventional therapy. Because of the limited light penetration in tissue and infiltrative nature of most recurrent lesions, little effective palliation was seen in these advanced cases. More success has been achieved in the treatment of earlier, more superficial lesions, and active investigation continues in this area. Current research is aimed at defining the most appropriate sites and applications for the technique. HpD and DHE are currently only approved for use as investigational compounds in clinical studies. If ongoing trials of PDT in the treatment of superficial bladder cancer, obstructing esophageal cancer, and non-small cell lung cancer show encouraging results, an application will be made to the Food and Drug Administration for approval of DHE as a photosensitizer for general clinical use for these indications. Laboratory work to better understand the mechanism of action of HpD also continues, as well as investigations into alternative photosensitizers with improved tumor localization, less cutaneous photosensitivity, and absorption peaks at deeper penetrating wavelengths of light. A pilot program evaluating IUdR-sensitized radiation therapy for treatment of advanced head and neck cancer is in progress. If encouraging early results continue to be observed, a randomized trial comparing IUdR-sensitized radiation therapy with conventional radiation therapy can be conducted. Hopefully, these developments in the field will improve the therapy for patients with head and neck cancers.

Based upon the radiation sensitization properties of the halogenated pyrimidines, 5-iododeoxyuridine (IdUrd) and 5-bromodeoxyuridine, long term i.v. infusions of halogenated pyrimidines in conjunction with fractionated radiation therapy have been evaluated in the treatment of a variety of human malignancies. While clinical studies have attempted to measure the halogenated pyrimidine incorporation, few have successfully related tumor response to the incorporation of IdUrd by the tumor. The present study reports the continuous IdUrd labeling index (number of cells labeled) and the IdUrd corrected replacement (percentage of thymidine replacement in the labeled cells of the population) from the tumors of 17 patients who received continuous infusions of IdUrd (1000 mg/m2/24 h). The tumors treated included four high grade gliomas, five head and neck tumors, four high grade sarcomas, and five other tumors of varying types. Less than 25% of the cells in three of four gliomas incorporated IdUrd after 5-7-day IdUrd infusion time. Corrected replacement for the gliomas ranged from 0 to 4%. In contrast, 63-85% of the cells in the head and neck biopsies were labeled with IdUrd after 3-7-day IdUrd infusions suggesting that these large tumors (3-12 cm diameter) have a high fraction of dividing cells. Corrected replacements values for the head and neck tumor patients ranged from 2.9 to 26.3%. The high grade sarcomas also demonstrated a high percentage of IdUrd labeled cells (57-79%) with three patients having corrected replacements of 7.5-14.2%. The continuous labeling and thymidine replacement data for four patients from whom serial biopsies were taken during IdUrd infusion demonstrated both an increasing IdUrd replacement and continuous labeling index with an increasing duration of IdUrd infusion. The clinical response of both the high grade glioma and head and neck tumor patients indicate that the IdUrd replacement and labeling data may provide some important predictive information with regard to the successful use of the halogenated pyrimidines in clinical radiation trials.