Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_28_2663 - Treatment Outcomes of Whole-Field vs. Split-Field Intensity-Modulated Radiation Therapy for Nasopharyngeal Carcinoma Patients

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Treatment Outcomes of Whole-Field vs. Split-Field Intensity-Modulated Radiation Therapy for Nasopharyngeal Carcinoma Patients
C. S. Lin1,2, Y. W. Chen3, S. C. Liu4, C. C. Tsao1, K. T. Lin1, S. P. H. Lee5, C. Y. Fan1, M. Y. Liu1, P. C. Shen1, and Y. M. Jen1,6; 1Department of Radiation Oncology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, 2Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan, 3Department of Oral and Maxillofacial Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, 4Department of Otolaryngology-Head and Neck Surgery, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, 5VA Long Beach Healthcare System, Long Beach, CA, 6Yee-Ren Hospital, Tao Yuan City, Taiwan

Purpose/Objective(s): To compare the clinical outcome of nasopharyngeal carcinoma (NPC) patients treated with whole-field intensity-modulated radiation therapy (WF-IMRT) or split-field (SF-IMRT). Our study analyzes the clinical results of using a similar total dose but a low fractional dose to the supraclavicular area compared with the conventional 1.8 Gy/fraction.

Materials/Methods: Between Nov. 1999 and Dec. 2014, 388 histologically proven M0 NPC patients treated with WF-IMRT or SF-IMRT were retrospectively studied. Patients in both groups received 70 Gy (range, 68-74 Gy) to planning target volume 1 (PTV1) with a fractional dose of 2 Gy, and 60 Gy (range, 56-70 Gy) to PTV2 and 50 Gy (range, 45-60 Gy) to PTV3. Of the 240 patients receiving WF-IMRT, the median lower neck dose was 50 Gy in 1.35 Gy/fraction. Of the 148 patients receiving SF-IMRT, the median lower neck dose was 50.4 Gy in 1.8-2.0 Gy/fraction.

Results: At the time of analysis in July 2017, the median follow-up time was 58.7 months (range 2-176 months) for patients alive. For the whole cohort, the 5-year overall survival (OS) and locoregional control (LRC) were 76.2% and 83.1%, respectively. IMRT technique did not affect the OS (p=0.077) and LRC (p=0.231). However, the SF-IMRT group had more locoregional recurrences at the whole neck (p=0.005), but not at the nasopharynx (p=0.968) or the lower neck (p=0.485). Patients in the WF-IMRT had lower incidences of grade 3 neck fibrosis (p<0.001).
Table. Recurrent patterns of the 388 nasopharyngeal carcinoma patients by IMRT technique
Factors (No. of patients, %) WF-IMRT (n) SF-IMRT (n) p-value
Locoregional recurrent subsites
Nasopharynx No (351, 90.5%) 217 134 0.968
Yes (37, 9.5%) 23 14
Whole neck No (355, 91.5%) 227 128 0.005
Yes (33, 8.5%) 13 20
Lower neck No (380, 97.9%) 236 144 0.485
Yes (8, 2.1%) 4 4
Abbreviations: WF, whole-field; SF, split-field; IMRT, intensity-modulated radiation therapy

Conclusion: To our knowledge, this is the first study comparing the treatment outcomes of NPC patients using WF-IMRT vs. SF-IMRT. Our study shows that WF-IMRT using a lower dose/fraction for the low neck results in at least comparable control to conventional fraction with SF-IMRT and less fibrosis. WF-IMRT using a fractional dose of around 1.35 Gy and a total dose of 50 Gy can efficiently eradicate potentially existing microscopic disease at the lower neck region. Since the SF-IMRT used higher dose/fraction, the fibrosis may not be from split-field itself but rather the higher dose/fraction. Radiation dose of 2.0 Gy to PTV1 with WF-IMRT and SIB technique produced very low incidence of temporal lobe necrosis.

Author Disclosure: C. Lin: None. Y. Chen: None. S.P. Lee: None.

Chun-Shu Lin, MD

Biography:
Chun-Shu Lin
Associate Professor
Director, Department of Radiation Oncology, Tri-Service General Hospital, National Defense Medical Center
Deputy Secretary General, Taiwan Society of Cancer Palliative Medicine
Chief, Hospice Ward, Penghu Branch of Tri-Service General Hospital, 2007 Aug. to 2008 July.
Visiting Scholar at Department of Radiation Oncology, University of California, Los Angeles, U.S.A. 2008 Aug. to 2009 Aug.
Attending Doctor, Department of Radiation Oncology, Tri-Service General Hospital, Taipei, 2006 Aug. ~

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