Grading Soft Tissue Involvement in Nasopharyngeal Carcinoma Using Network and Survival Analyses: A Two-Center Retrospective Study.
BACKGROUND
Soft tissue involvement (STI) indicates poor prognosis in nasopharyngeal carcinoma (NPC). However, only a few studies have systematically assessed this extension using network analysis.


PURPOSE
To investigate the prognostic value of STI and to propose an improved STI grading system for NPC therapy.


STUDY TYPE
Retrospective study.


POPULATION
A total of 1225 consecutive patients with pathologically confirmed NPC treated with intensive-modulated radiotherapy from January 2010 to March 2014 were enrolled from two centers.


FIELD STRENGTH/SEQUENCE
T1- and T2-weighted imaging and enhanced T1-weighted imaging with fast spin echo sequence at 1.5 or 3.0 T.


ASSESSMENT
The levator veli palatini and tensor veli palatini involvement were graded "mild," prevertebral muscle involvement, "moderate," medial pterygoid, lateral pterygoid, and the infratemporal fossa involvement, "severe" STI. The above STI sites were evaluated separately by three radiologists using MRI images and graded using network analysis. Overall survival (OS) and progression-free survival (PFS) were assessed.


STATISTICAL TESTS
Kaplan-Meier method, Cox's proportional hazards model, and concordance index (C-index) were used.


RESULTS
Five-year OS and PFS rates between mild and moderate groups (90.5% vs. 81.7%, P < 0.05 and 82.9% vs. 72.5%, P < 0.05, respectively) and between moderate and severe groups (81.7% vs. 70.4%, P < 0.05 and 72.5% vs. 61.2%, P < 0.05, respectively) revealed significant differences. The C-index of the nomogram with STI grading was higher compared with current T-classification (OS 0.641 vs. 0.604, P < 0.05 and PFS 0.605 vs. 0.581, P < 0.05, respectively). Significant OS differences were observed between patients with severe STI who underwent induction chemotherapy (IC) and those who did not (84.5% vs. 70.7%, P < 0.05).


DATA CONCLUSION
STI grading was an independent prognostic factor for OS and PFS in NPC patients and it may be help to improve the accuracy in predicting survival outcomes. Patients with severe STI might benefit from IC to improve OS.


LEVEL OF EVIDENCE
4 TECHNICAL EFFICACY: Stage 2.
['Dong|Annan|A|', 'Huang|Wenjie|W|', 'Ma|Huali|H|0000-0003-1369-2897', 'Cui|Chunyan|C|', 'Zhou|Jian|J|', 'Ruan|Guangying|G|', 'Liang|Shaobo|S|', 'Liu|Lizhi|L|0000-0001-8578-6425', 'Li|Haojiang|H|0000-0001-5854-3989']
D018572:Disease-Free Survival D006801:Humans D000077274:Nasopharyngeal Carcinoma D009303:Nasopharyngeal Neoplasms D009367:Neoplasm Staging D011379:Prognosis D050397:Radiotherapy, Intensity-Modulated D012189:Retrospective Studies
nasopharyngeal carcinoma survival analyses magnetic resonance imaging tumor staging