To present a time-to-failure (TTF) analysis for all patients treated with permanent interstitial brachytherapy (PIB) at our institution, with additional analyses to correlate successful reirradiation and to identify the frequency of severe grade 3 to 4 toxicity.

Forty-two previously irradiated patients received curative or palliative intent PIB for a recurrent pelvic malignancy between January 2009 and August 2016. Minimum follow-up was 6 months after the PIB procedure. All patients had a biopsy-proven recurrence and were treated using PIB alone (n=32) or in combination with a short course of additional radiation therapy (n=10). Competing risk analyses were performed to assess the risk of failures in the presence of death without failure. Exploratory analyses were performed for factors related to failure using competing risk analyses and the Gray statistic.

A total of 61 PIB implants were performed among 42 patients with a median follow-up of 16.3 months. Fifty-two implants were performed as the first salvage reirradiation to a solitary recurrence (8 patients had more than 1 lesion); the success rate for initial reirradiation using PIB was 73% (38 cases out of 52), and the median TTF was not reached. Nine patients underwent a second repeat PIB to the same recurrence as a form of salvage; 3 (33%) remain without evidence of recurrence. The median TTF after second salvage was 7.7 months. Even with the limited sample size, prolonged TTF was marginally associated with definitive intent (P=.07) and the extent of disease at the time of PIB (P=.08). Grade 3+ toxicities were seen in 8 patients (16.7%).

Permanent interstitial brachytherapy is a feasible and potentially durable treatment modality that can be used to curatively salvage selected recurrent pelvic malignancies in a previously irradiated field.