REIRRADIATION FOR RECURRENT NASOPHARYNGEAL CARCINOMA - FACTORS AFFECTING THE THERAPEUTIC RATIO AND WAYS FOR IMPROVEMENT

Purpose: To identify factors for maximizing local salvage and minimizi ng damages by reirradiation for recurrent nasopharyngeal carcinoma. Me thods and Materials: 654 patients with recurrent nasopharyngeal carcin oma treated by reirradiation during 1976-1992 were retrospectively ana lyzed. Various fractionation schedules had been used during primary tr eatment with the total dose ranging from 45.6-70 Gy, fractional dose ( at different phases) 1.5-4.2 Gy, and overall time 36-101 days, The gap between the two courses ranged from 0.5-10.6 years, Eighty-two percen t of patients were reirradiated with teletherapy, 6% brachytherapy, ad d 12% with both, For those treated with teletherapy alone, the total d ose ranged from 7.5-70 Gy, fractional dose 1.8-5 Gy, and overall time 3-89 days. Results: The 5-year actuarial local salvage and complicatio n-free rates were 23% and 52%, respectively, Multivariate analyses sho wed that the extensiveness of local recurrence was the most significan t factor affecting local salvage, while T-stage of primary tumor also influenced prognosis, Choice of method for reirradiation and fractiona l effect during both courses affected the risk of late complications. For patients treated by teletherapy alone, the hazard of local failure decreased by 1.7% per Biological Effective Dose (assuming alpha/beta ratio = 10) of the second course, while radiation factors during prima ry radiotherapy had no significant effect, On the other hand, the risk of late complications was predominantly affected by the primary treat ment: the hazard increased by 4.2% per Biological Effective Dose (assu ming alpha/beta ratio= 3) of the first course, while the corresponding impact of reirradiation failed to reach Statistical significance. Len gth of the gap between the two courses did not affect the outcome. Con clusion: Early detection of local recurrence and adequate total dose b y reirradiation are crucial for improving the chance of local salvage, Combination of teletherapy and brachytherapy should be considered whe never feasible and large fractional dose avoided to minimize late comp lications, Optimization of biological dose during primary treatment is important. (C) 1997 Elsevier Science Inc.