A feasibility study using three-dimensional conformal boost technique in locally advanced carcinoma of the nasopharynx

To investigate the feasibility and efficacy of dose escalation using three- dimensional (3-D) conformal boost technique, 21 patients with stage III or IV nasopharyngeal cancer were enrolled in a prospective protocol. All patie nts with node metastases initially received external radiotherapy by conven tional technique up to 70.2 Gy, followed by 3-D conformal radiotherapy (3-D CRT) to the boost part up to 79.2 Gy with 9 Gy increments (daily fraction of 1.8 Gy for 5 days). A modified technique with the same dose escalation o f 9 Gy using 3-D CRT was applied to 7 patients without node metastases, who were treated by conventional technique up to 54 Gy, followed by 3-D CRT to boost up to a basic dose of 70.2 Gy, and then finally with dose escalation of 9 Gy. The protocol was relatively well tolerated by the majority of pat ients. Acute complications during the dose escalation schedule was low, wit h rare occurrences of grade 3 or 4 toxicity. Although late radiation-induce d complications also appeared limited, 1 patient developed a temporal lobe necrosis and 2 patients suffered from sensory-neural hearing loss. There we re no radiation-induced fatal complications. At a median follow-up of 48 mo nths, only 3 patients experienced local failure and 2 patients developed di stant metastases. The 5-year overall actuarial survival rate and recurrence -free survival rate for all patients were 68% and 85%, respectively. On the basis of acceptable morbidity and encouraging treatment results, we conclu de that the dose escalation in 9 Gy increments using a 3-D conformal boost technique is relatively safe and efficacious, enough to be used routinely f or locally advanced nasopharyngeal cancers.