A retrospective study of the prognostic value of MRI-derived residual tumors at the end of intensity-modulated radiotherapy in 358 patients with locally-advanced nasopharyngeal carcinoma

Abstract

ObjectiveTo retrospectively analyze the prognostic value of magnetic resonance imaging (MRI)-derived residual tumors after intensity-modulated radiation therapy (IMRT) in the patients with locally-advanced nasopharyngeal carcinoma.MethodsA total of 358 patients with locally-advanced nasopharyngeal carcinoma who received IMRT were classified as having residual tumors or no residual tumor based on MRI at the end of radiotherapy. The χ2 test, log-rank test, Cox proportional hazards regression model and Kaplan-Meir survival curves were used to investigate the relationship of clinicopathological features and residual tumors and to assess the prognostic value of residual tumors.ResultsThe 3-year overall survival (OS) rate was 73% in the residual tumor group and 90% in the no residual tumor group (HR 2.15, 95% CI 1.21-3.82,, P = 0.007); 3-year local relapse-free survival (LRFS) was 89% in the residual tumor group and 97% in the no residual tumor group (HR 4.46, 95% CI 1.61-12.38, P = 0.002); 3-year disease free survival (DFS) was 67% in the residual tumor group and 82% in the no residual tumor group (HR 2.21, 95% CI 1.40-3.48, P = 0.001). A high prescribed radiation dose (>73.92 Gy) did not increase the percentage volume of the GTVnx receiving 95% of the prescribed dose (GTVnx V95%) or improve any survival outcome.ConclusionThe presence of a residual tumor after IMRT was a significant negative independent prognostic factor for OS, LRFS and DFS. Although IMRT have improved the distribution of radiotherapy doses into the tumors, residual tumors detected by MRI after IMRT are still associated with poor prognosis in patients with advanced nasopharyngeal carcinoma.

Prognostic value of the distance between the primary tumor and brainstem in the patients with locally advanced nasopharyngeal carcinoma

“…The primary tumor (GTVnx) and positive lymph nodes (GTVnd) were defined; the retropharyngeal lymph nodes were included in the GTVnx. Two clinical target volumes (CTVs) were defined, as described in our previous study [ 8 ]. The corresponding planning target volumes (PTVs) were generated by extending each CTV by 3 mm; the prescribed doses for the PGTVnx (GTVnx + 3–5 mm margin) were 66.0–75.9 Gy; GTVnd, 69.96–72.6 Gy; PTV1, 59.4–64.0 Gy, and PTV2, 50.0–54.0 Gy.…”

Prognostic analysis of patients with locally advanced nasopharyngeal carcinoma following intensity modulated radiation therapy

“…Dose limits for the critical tissue structures and the plan evaluation were designed according to the Radiation Therapy Oncology Group 0225 (25). The patients were re-examined by magnetic resonance imaging (MRI) following either the completion of radiotherapy or the radiation dose reaching ~70 Gy (26). All patients were exposed to 6MV beams and 9 fixed-gantry (0, 40, 80, 120, 160, 200, 240, 280 and 320˚) angles were designated.…”

Prognostic value and predictive threshold of tumor volume for patients with locally advanced nasopharyngeal carcinoma receiving intensity-modulated radiotherapy

“…The specific target was defined as described in our previous studies [15]. The prescribed doses were 66.0–75.9 Gy for the PTVnx [the planning target volume (PTV) covering the GTV-P with additional 3–5 mm margin], 70.0–72.6 Gy for the GTV of positive lymph nodes (GTVnd), 59.4–64.0 Gy for PTV1 [the PTV covering the clinical target volume 1 (CTV1, the high-risk area that included a 5–10 mm extension around the GTV-P and other high-risk regions and high-risk lymphatic drainage areas) with additional 3 mm margin], and 50.0–54.0 Gy for PTV2 [the PTV covering the CTV2 (the low-risk lymphatic drainage area, including the cervical lymphatic drainage area that was not covered in CTV1) with additional 3 mm margin].…”