Abstract
Objective: This study aimed to look into the relationship between intensity-modulated-radiotherapy (IMRT)- or volumetric-modulated-arc-therapy (VMAT)-based dose–volume parameters and 5-year outcome for a consecutive series of non-metastatic nasopharyngeal cancer (NPC) patients (pts) treated in a single institution in a non-endemic area in order to identify potential prognostic factors.Materials and methods: A retrospective analysis of consecutive non-metastatic NPC pts treated curatively with IMRT or VMAT and chemotherapy (CHT) between 2004 and 2014 was conducted. One patient was in stage I (0.7%), and 24 pts (17.5%) were in stage II, 38 pts (27.7%) in stage III, 29 pts (21.2%) in stage IVA, and 45 pts (32.8%) in stage IVB. Five pts (3.6%) received radiotherapy (RT) alone. Of the remaining 132 pts (96.4%), 30 pts (21.9%) received CHT concomitant to RT, and 102 pts (74.4%) were treated with induction CHT followed by RT-CHT. IMRT was given with standard fractionation at a total dose of 70 Gy. Clinical outcomes investigated in the study were local control (LC), disease-free survival (DFS), and overall survival (OS). Kaplan–Meier (KM) analysis was performed for the outcomes considering dose and coverage parameters, staging, and RT technique.Results: Overall, 137 pts were eligible for this retrospective analysis. With a median follow-up of 70 months (range 12–143), actuarial rates at 5 years were LC 90.4, DFS 77.2, and OS 82.8%. For this preliminary study, T stage was dichotomized as T1, T2, T3 vs. T4. At 5 years, the group T1–T2–T3 reported an LC of 93%, a DFS of 79%, and an OS of 88%, whereas T4 pts reported LC, DFS, and OS, respectively, of 56, 50, and 78%. Pts with V95% > 95.5% had better LC (p = 0.006). Pts with D99% > 63.8 Gy had better LC (p = 0.034) and OS (p = 0.005). The threshold value of 43.2 cm3 of GTVT was prognostic for LC (p = 0.016). To predict the risk of local recurrence at 5 years, we constructed a nomogram which combined GTVT with D99% relative to HRPTV.Conclusions: We demonstrated the prognostic value of some dose–volume parameters, although in a retrospective series, this is potentially useful to improve planning procedure. In addition, for the first time in a non-endemic area, a threshold value of GTVT, prognostic for LC, has been confirmed.
Highlights
Intensity modulated radiation therapy (IMRT) is an important milestone in the management of nasopharyngeal carcinoma (NPC), providing lowered frequency of serious radiationinduced late toxicities without compromising local control (LC) and survival compared to previous radiotherapy (RT) techniques [1]
Thirty patients out of 137 received concomitant platinum-based CHT with a median cumulative platinum dose of 225 mg/sm. induction CHT (iCHT) was administered in 102 out of 137 patients followed by concomitant CHT; 100 patients received TP schedule with or without 5FU, and two patients received PF schedule
As for RT parameters, we found that V95, V100, D99, DMean relative to HDPTV and GTVs separately: nasopharyngeal primary tumor (GTVT), and RT technique were significant for LC, and V95% relative to HDPTV and RT technique were significant for Disease-free survival (DFS)
Summary
Intensity modulated radiation therapy (IMRT) is an important milestone in the management of nasopharyngeal carcinoma (NPC), providing lowered frequency of serious radiationinduced late toxicities without compromising local control (LC) and survival compared to previous radiotherapy (RT) techniques [1]. The outcomes after IMRT remain unsatisfactory in T4 tumors, most of all because their proximity to critical neurological structures compromises planning target coverage and undermines LC. Assuming that CHT may make up for coverage defects of the target volume, it is still hard to set a benchmark for dosimetric adequacy. As a matter of fact, data correlating IMRT-based dose parameters and outcome are scanty, making it difficult to identify their potential prognostic role
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