Head and Neck Cancer

PD 10 - H&N 2 - Head and Neck Poster Discussion

1082 - Incidence of Radiographically Occult Nodal Metastases in HPV-Driven Oropharyngeal Carcinoma: Implications for Reducing Elective Nodal Coverage

Tuesday, October 23
1:06 PM - 1:12 PM
Location: Room 217 A/B

Incidence of Radiographically Occult Nodal Metastases in HPV-Driven Oropharyngeal Carcinoma: Implications for Reducing Elective Nodal Coverage
J. R. Kelly1, G. Loganadane V1, N. C. J. Lee1, B. H. Kann1, A. Mahajan2, J. E. Hansen1, Y. Belkacemi3, W. Yarbrough4, and Z. A. Husain1; 1Department of Therapeutic Radiology, Yale School of Medicine, New Haven, CT, 2Yale University School of Medicine, Department of Radiology & Biomedical Imaging, New Haven, CT, 3Department of Radiation Oncology and Henri Mondor Breast Center, Henri Mondor University Hospital, AP-HP, Creteil, France, Creteil, France, 4Department of Surgery, Section of Otolaryngology, Yale School of Medicine, New Haven, CT

Purpose/Objective(s): Initial de-escalation studies for HPV-associated oropharyngeal squamous cell carcinomas (HPV-A OPC) altered radiation therapy dose or the systemic agent used. Newer trials examine the disease control achieved with a decreased elective nodal field. We examined patterns of nodal involvement in patients with HPV-A OPC with a focus on implications for radiation field design for treatment de-escalation.

Materials/Methods: Records of patients with HPV-A OPC with preoperative imaging (CT or FDG-PET/CT) who underwent neck dissection without neoadjuvant therapy from 2010 to 2017 were retrospectively reviewed. The number and location of clinically positive lymph nodes on preoperative imaging were compared with those documented on pathology. These data were then used to establish the probability of omitting nodal disease in three modified radiation field designs. Univariable and multivariable logistic regression analyses were performed to explore the impact of delay between imaging and surgery and the utilization of PET/CT scans on the sensitivity of preoperative imaging.

Results: One hundred patients were included. The median time between imaging and surgery was 22 days. The most common clinical N stage was cN2a (35%), while the most common pathologic N stage was pN2b (45%). The median number of radiographically and pathologically involved nodes was 1 (range 0-6) and 2 (range 0-11), respectively. 43% of patients had more pathologically involved nodes than predicted on imaging, while 21% had pathologic involvement at an additional nodal level not predicted on imaging. Of the 21 patients with additional pathologically involved nodal levels, 14 had involvement of a directly adjacent station, four were patients with a cN0 hemineck with pathologically positive level II disease, and three had pathologic involvement of a level two echelons removed from that predicted on imaging. On multivariable regression analysis, neither delay between imaging and surgery (OR=1.65; 95% CI 0.58-4.75, p=0.35) nor the use of PET/CT imaging (OR=0.43; 95%CI 0.13-1.4, p=0.16) was significantly associated with an improvement in the detection of subclinical metastases to lymph nodes.

Conclusion: Our study suggests that radiation fields encompassing only clinically involved nodes or levels has an unacceptably high likelihood of missing subclinical disease in HPV-A OPC. Alternatively, treating the first uninvolved echelon nodes in addition would cover pathologic sites of disease in 97% of patients. This approach merits further study in prospective trials.

Author Disclosure: J.R. Kelly: None. G. Loganadane: None. N.C. Lee: None. B.H. Kann: None. J.E. Hansen: Patent/License Fees/Copyright; Yale School of Medicine. Y. Belkacemi: None. Z.A. Husain: Independent Contractor; RadOncQuestions LLC.

Jacqueline Kelly, MD, MS

Yale School of Medicine

Disclosure:
No relationships to disclose.

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