Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_36_2856 - Radiation Treatment outcome with Reduce clinical target volume (CTV) in patients with oropharynx cancer

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

Radiation Treatment outcome with Reduce clinical target volume (CTV) in patients with oropharynx cancer
A. Vera1, A. I. Urdaneta1, N. D. Mukhopadhyay2, X. Deng1, and S. Song2; 1Virginia Commonwealth University, Richmond, VA, 2Virginia Commonwealth University Health System, Richmond, VA

Purpose/Objective(s): For Head and Neck cancers, there are different ways to delineate CTV also, it varies among institutions and clinical protocols. Usually a 0.5-1.5 cm expansion of gross tumor volume (GTV) is done to create high-risk CTV for a definitive radiation. At our institution, GTV is treated using IMRT to a definitive dose without CTV expansion. The elective neck regions were treated with expanded skin avoidance to reduce skin reaction. Here we report the outcome of oropharynx cancer treatment using reduced CTV volumes.

Materials/Methods: Records of 147 patients with stage I-IVB oropharyngeal cancer treated at our institution from 2005 through 2015 were reviewed. We found 73 patients with reported p16 status. The GTV was contoured including the primary tumor and involved nodes and it is treated to a definitive dose of 68.1-70 Gy in 30-33 fractions without CTV expansion. By adding 1 cm of expansion to the GTV, we create the High-risk CTV minus bones and air (CTV1), which was treated to 60 Gy. The CTV2 or Elective uninvolved nodal regions, including the 1st echelon nodes were treated to 54 Gy. To create the PTV-1, -2 and -3, we added 5 mm from the GTV, CTV1 and CTV2 for uncertainty. To reduce skin toxicity, a 6 mm skin avoidance structure was created, and this was used in the uninvolved neck. Cisplatin was administered either weekly or every 3 weeks during the course of XRT. Of the 147 patients, 107 were treated with chemoradiotherapy, 18 with radiation alone. Toxicities were scored according to CTC Ver. 4. The Overall survival rate was compared in patients with P-16 status, staging and smoking history between treatment groups using the log-rank test.

Results: Median follow-up was 4.6 years. For the entire group, the 5-year overall survival was 69.18% (72.96% for stage I/II and 57.56% for Stage III/IV). Among 73 patients with p16 status known, 48 patients had p16 (+) tumors and 25 had p16 (-) tumors. The 5 year-overall survival was 89.58% vs 68.00% respectively (p= 0.0169). The overall survival in patients with smoking history, less versus more than 10 Pack/years was 82.46% vs 61.90%. Interestingly, we did not detect any difference in survival between p16 (+) smokers and non-smokers. There was no significant difference in acute toxicity between our patients and those reported in the literature, with 30.9% experiencing grade 3 or higher mucositis, and 9.4% patients with grade 3 radiation dermatitis; Permanent feeding tube was needed in 4.06%, which is lower than those reported in the literature.

Conclusion: After reviewing our results, we can conclude that rCTV can be compared favorably with the reported outcomes of oropharyngeal cancer treatment in the literature, both in the patient survival and toxicities. Radiation therapy with reduced CTV expansion is safe. While phase III dose de-escalation trial is being conducted in patients with p16 (+) oropharyngeal cancer and is not considered a standard practice at this time, reduction of CTV volume may be used as an alternative approach for dose de-escalation.

Author Disclosure: A. Vera: None. A.I. Urdaneta: None. N.D. Mukhopadhyay: None.

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