Pulse Reduced Dose Rate Re-Irradiation for Recurrent Head and Neck Malignancies: A Single Institution Phase II Pilot Study

Purpose: Treatment options are limited for head and neck cancer patients who develop locoregional recurrence after already having received radiotherapy as part of their initial treatment. Salvage surgery is a potential curative option for these patients, but unfortunately many patients are not suitable candidates. Systemic therapy can improve survival but is not a curative option. Re-irradiation (Re-RT) is a curative treatment option but is associated with significant risk of toxicity. Up to 20% of patients who receive Re-RT for head and neck cancers develop grade 3 toxicity (symptoms that interfere with activities of daily living or that require surgical correction) or higher (hospitalization or death). There has been interest in newer radiation technologies/techniques, including pulse reduced dose rate radiotherapy (PRDR-RT), to reduce toxicity and side effects. PRDR-RT delivers external beam radiotherapy in pulses over a longer time period with the goal of reducing toxicity to normal structures while maintaining (or enhancing) cancer control rates. Previous research has shown encouraging results for Re-RT using PRDR-RT in multiple disease sites outside of the head and neck area.

Methodology: A retrospective case control analysis served as the basis for our proposed trial. In total, 41 consecutive patients with recurrent head and neck malignancies were evaluated for Re-RT. Overall, 15 patients declined or were not candidates for Re-RT. Fifteen patients underwent Re-RT using conventional dose rates (Total Dose ranged from 2500-7000cGy). Ten patients underwent Re-RT usingPRDR-RT; all planned for 6000cGy in 30 daily fractions. Acute and chronic toxicities were collected for all patients.

Results: Of the 10 patients who underwent PRDR-RT, 8 were able to complete it. One patient discontinued treatment early due an unrelated accident and another patient was tolerating treatment but discontinued due to social reasons. There were 2 grade 3 toxicities in the PRDR-RT group; 1 patient had acute radiation dermatitis treated with silver sulfadiazine and 1 patient had late esophageal stenosis requiring dilation. Overall, 6 of 10 patients in the PRDR-RT group underwent systemic therapy. Of the 15 patients who underwent Re-RT using conventional dose rates, all completed treatment. Ten of 15 patients underwent systemic therapy in the standard radiotherapy group. There were 2 grade 3 toxicities in this group, 1 patient with pain and 1 patient with dysphagia. There were no grade 4-5 toxicities in either group.

Conclusions: This single institution case control series directly compared Re-RT using conventional dose rate RT versus PRDR-RT. PRDR-RT may be an effective technique to reduce the toxicity to surrounding organs at risk in the setting of Re-RT. This experience will serve as a basis for a phase II clinical trial at our institution aiming to collect prospective data on toxicity and cancer control outcomes for recurrent head and neck cancer patients receiving Re-RT using PRDR-RT.

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