Three-dimensional conformal radiotherapy versus intracavitary brachytherapy for salvage treatment of locally persistent nasopharyngeal carcinoma

Abstract

Purpose To compare the outcomes of three-dimensional conformal radiotherapy (3D-CRT) and intracavitary brachytherapy (ICBT) as salvage treatment for locally persistent nasopharyngeal carcinoma. Methods and materials Between March 1994 and November 2001, a total of 117 patients with locally persistent nasopharyngeal carcinoma received salvage treatment for 2–8 weeks (median, 4 weeks) after a full course of conventional external beam RT. Of the 117 patients, 54 were salvaged with 3D-CRT (3D group) and 63 with ICBT (BT group). No statistically significant differences were found in the patient characteristics between the two groups ( p >0.05). In the 3D group, the planning target volume for 3D-CRT was defined as the persistent disease plus a 5-mm margin; three to seven static conformal coplanar or noncoplanar portals were delivered for each fraction. The median salvage dose was 24 Gy (range, 18–38 Gy), with fraction size of 2.0 Gy/d. In the BT group, a median salvage dose of 20 Gy (range, 15–30 Gy) was delivered with a 192Ir source, at 5 Gy/fraction, twice weekly. The brachytherapy dose was prescribed at a distance of 1 cm from the center of the surface as defined by the sources, irrespective of the extent of persistent disease. The actuarial rates of survival were estimated using the Kaplan-Meier method. Potential differences in the actuarial outcomes between groups were evaluated using the Mantel log–rank test. Multivariate analyses were performed with the Cox regression proportional hazards model. Results The 5-year actuarial rates of overall survival, disease-specific survival, and local failure-free survival for the 3D group and BT group were 64.50% vs. 55.78% ( p = 0.33), 70.03% vs. 59.56% ( p = 0.11), and 88.93% vs. 76.28% ( p = 0.07), respectively. Subgroup analysis showed that the 5-year actuarial local failure-free survival rate of patients with initially diagnosed T3-T4 disease for the 3D group and BT group was 84.01% vs. 60.50% ( p = 0.03). The incidence of Grade 3-4 late complications was comparable between the two groups. Multivariate analyses performed in the whole group showed that T stage at initial diagnosis and the salvage technique (3D-CRT or ICBT) were the statistically significant, independent prognostic factors for local failure-free survival ( p = 0.00 and p = 0.02, respectively). Conclusion 3D-CRT seemed to provide better local control than ICBT as a salvage treatment for locally persistent nasopharyngeal carcinoma, especially in patients with initially diagnosed T3-T4 disease. CT/MRI evaluation of the extent of persistent disease is recommended for technique selection of salvage RT. Patients should be cautioned about the potentially increased complications. The optional time for salvage treatment remains controversial.