Feasibility and tolerance of pulsed dose rate interstitial brachytherapy

Purpose: Pulsed dose rate (PDR) treatment is a new approach that associates the physical advantages of high-dose-rate (HDR) technology with the potent ial radiobiological advantages of low-dose-rate (LDR) brachytherapy. This r etrospective study analyzes the feasibility, toxicity, and preliminary onco logic results in a series of 43 patients treated with PDR interstitial brac hytherapy. Methods and Materials: Twenty-four patients with pelvic, 17 patients with h ead and neck, and 2 patients with breast cancers were treated. Twenty-eight patients had primary and 15 recurrent tumors; 14 had received prior extern al irradiation to the same site. The doses per pulse at the prescription is odose were 0.4-1 Gy (median 0.5 Gy), delivered using a single cable-driven 0.3-1.0 Ci 192-iridium source (PDR Nucletron Micro-Selectron). Results: The median treated volumes (at the prescribed isodose) were 28 cc for pelvic, 8.33 cc for head and neck, and 40 cc for breast malignancies. O f 14,499 source and 14,499 dummy source transfer procedures, 3 technical ma chine failure events were observed (0.02%). Grade 3 acute toxicities were s een in 5/43 patients (4 oral stomatitis, 1 vaginal mucositis) and grade 4 a cute toxicity in one patient (rectovaginal fistula). Grade 3-4 late complic ations were observed in 4/41 (9.8%) patients: 1 pubic fracture, I rectovagi nal fistula, 1 vesicovaginal fistula and 1 local necrosis. With a median fo llow-up of 18 months, 10/41 patients progressed locoregionally (6 pelvic, 4 head and neck), 3 developed local recurrence and distant metastasis (3 pel vic), 3 only distant metastasis (2 pelvic, 1 head and neck). Two patients a re lost to follow-up. Conclusion: PDR interstitial brachytherapy for pelvic, head and neck, and b reast malignancies is feasible and the acute and late toxicities seem accep table. Although the physical advantages of PDR are clear, further follow-up is required to determine how results compare with those obtained with stan dard LDR brachytherapy. (C) 1999 Elsevier Science Inc.