Post-irradiation sarcoma after definitive radiation therapy for nasopharyngeal carcinoma.

BACKGROUND AND PURPOSE: Postirradiation sarcoma (PIS) is a rare radiation-induced malignancy after nasopharyngeal carcinoma (NPC) treatment. MATERIALS AND METHODS: We retrospectively screened 9,185 NPC patients between 2000 and 2020 and identified 41 patients with PIS according to the modified Cahan's criteria: (1) the PIS must have arisen within a previous radiation field; (2) a latent period must have existed; (3) histologically proved sarcoma; (4) the tissue in which the PIS arose must have been healthy prior to the radiation. The initial radiation therapy techniques used were 2D (25; 61.0%), 3D (7; 17.1%), and IMRT (9; 22%). RESULTS: The time (year) from radiotherapy (RT) to PIS was longer when using 2D or 3D irradiation techniques (median, 14.2; range, 3.4-28.1; Q1-Q3, 8.6-19.7) than when using IMRT (median, 6.6; range, 3.8-15.7; Q1-Q3, 4.5-11.7; P =.026). The time (year) from RT to PIS diagnosis was significantly longer when using lower radiation energy from cobalt-60 (median, 15.8; range, 10.4-28.4; Q1-Q3, 12.5-23.8) than when using a higher radiation energy of 6 or 10 MV (median, 10.2; range, 3.4-23.3; Q1-Q3, 6.5-16.1; P =.006). The 2-year overall survival rates for patients who underwent surgery, radical radiotherapy, systemic therapy alone and no treatment were 60.7 %, 42.9 %, 0 % and 0 %, respectively (P =.000). Of the 3 retrievable initial RT dosimetry plans for NPC, the D95 values (dose that covers 95 % of the PIS volume) for PIS were 6267, 6344 and 5820 cGy, respectively. CONCLUSION: High radiation energy and modern techniques may shorten NPC PIS latency. Surgery may be associated with improved survival if feasible.