| Objective: To assess the feasibility and toxicity of IMRT based on post-induction chemotherapy GTVnx, through comparing the clinical outcomes and adverse effects for delineation GTVnx and implementing IMRT planning based on pre-induction and post-induction chemotherapy image. Methods: A total of 212 patients with stage III–IVB NPC pathologically confirmed between February 2012 and April 2015 at several institutions were enrolled. All the patients were divided into group A and group B at random. Before radiotherapy, all patients received two courses of induction chemotherapy consisting of TP(paclitaxel 175 mg/m2/day on day 1, cisplatin 80 mg/m2/day on days 2) or PF(cisplatin 80 mg/m2/day on days1, and5-fluorouracil 1000 mg/m2/day on days 1). Patients in group A were based on pre-induction chemotherapy image for delineation GTVnx and implementing IMRT planning, while group B were based on post-induction chemotherapy image. The delineation of GTVnd were based on post-induction chemotherapy image for all the patients. All patients were immobilized in the same thermoplastic mask to performed two set of nasopharynx MRI and CT simulation before and after chemotherapy. Pre-chemotherapy MRI was performed to merge with pre-chemotherapy CT, and the same with post-chemotherapy to assist radiotherapy target delineation. It’s need to calculate the gross tumor volume and implement IMRT planning based on group, and observe clinical outcome and adverse events. Results: The volume of GTVnx before and after chemotherapy were 40.03±32.17cm3 and 28.20±23.80cm3( P=0.000) respectively, volume of GTVnd were 29.55±23.91cm3 and 15.74±12.89cm3( P=0.000);Comparison of the GTVnx and GTVnd showed that post-chemotherapy volume was significantly smaller than the pre-chemotherapy volume, with an average reduction of 27.34%±20.56% and 45.28%±30.23%, respectively. Comparison of group A and group B, the average volume of GTVnx were 44.92 ± 40.48cm3 and 25.68 ±22.20cm3(P=0.000); the average volume of V66.5Gy were 194.15±69.43cm3 and 174.45±82.59cm3( P=0.173), the average volume of V63 Gy were 366.52±125.89cm3 and 305.23±100.83cm3( P=0.005), respectively. The mean dose to normal structure in group B was lower than group A, the bilateral optic nerve, bilateral lens, right parotid gland, bilateral temporal lobe and temporomandibular joint, with statistically significant differences(P<0.05). Three months after the completion of radiotherapy, the proportion of patients achieved primary disease complete regression(CR) in group A and group B was 91.8% and 91.3%; and regional lymph nodes CR in group A and group B was 96.9% and 92.2%. A total of 18 patients achieved partial response(PR) in primary disease(8 in group A, 10 in group B), 12 patients achieved partial response(PR) in regional lymph nodes(3 in group A, 9 in group B).With a median follow-up of 21 months(range,8–47), in group A and group B the 3-year estimated overall survival, progression-free survival, disease-free survival, locoregional failure-free survival, distant failure-free survival were 94.7% and 89.0%, 79.8% and 76.8%, 79.8% and 75.7%, 91.6% and 93.9%, 84.5% and 80.4%, respectively(P>0.05). In group A, 7 patients experienced distant metastasis, 4 patients experienced local recurrence, 2 patients occurred both of them. In group B, 14 patients experienced distant metastasis, 3 patients experienced local recurrence, 2 patients occurred both of them, 2 patients got the second primary tumor. Long-term adverse events were similar in two groups. Conclusion: It’s an effective and well-tolerated alternative treatment to delineate GTVnx and implement radiotherapy planning based on post-chemotherapy image for locally advanced NPC, which could reduce the dose of normal tissues and improve the quality of life. |
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