Objective: To explore the methods of detecting and defining the biological boosting target volume (BBTV) in patients with locally advanced nasopharyngeal carcinoma (NPC).
Methods: Ten patients with locally advanced NPC treated at our center during September to December 2010 were enrolled. The following factors were used to define and contour BBTV, including dose-deficient area locating at skull-base of gross tumor volume in conventional irradiation, hypoxia area detected by (99m)Tc-HL91 Single-photon emission computed tomography/computed tomography (SPET/CT) imaging and tumor-burdened area evaluated by comparing the pre-treatment and 36 Gy irradiation's CT images scanning at the same treatment position.
Results: The volume of BBTV was (17 ± 7) cm(3), accounting for 51% ± 19% of gross tumor volume. In BBTV, the volumes and proportion of skull base dose-deficient, hypoxia and tumor-burdened area were (5.8 ± 2.5) cm(3), (7.7 ± 3.6) cm(3), (9.0 ± 5.8) cm(3) and 34.4%, 45.7% and 53.3% respectively. However, the proportion of overlapping volume between three areas was only 33.1%.
Conclusion: BBTV may be composed of skull base dose-deficient, hypoxia and tumor-burdened volume. It provides a new reference for individualized radiotherapy in locally advanced NPC.