Effect of neoadjuvant systemic therapy given during window trials on quality metrics in resectable head and neck squamous cell carcinoma.

6033 Background: Quality oncologic care, including negative surgical margin status, adequate lymph node yield and prompt initiation of adjuvant treatment, impacts disease control and overall survival in patients with mucosal head and neck squamous cell carcinoma (HNSCC). The aim of this study was to ascertain the effect of neoadjuvant systemic therapy given during window trials on oncologic quality metrics in patients with delayed definitive surgery for a HNSCC. Methods: Treatment-naïve patients with HNSCC participating in one of two window of opportunity clinical trials at UPMC from 2009-2019 were included. Neoadjuvant regimens consisted of one dose of cetuximab (n = 33) or anti-ErbB3 antibody (n = 9) within 28 days of surgery. Sociodemographic, clinical and tumor staging were recorded. The primary outcome was overall oncologic quality, as defined as a composite measure of negative margin status, adequate lymph node yield, completion of adjuvant therapy (if indicated) and time to initiation of adjuvant therapy within 6 weeks of surgery. Secondary outcomes were difference in clinical and pathologic stages and overall survival (OS). Results: A total of 42 patients with a mean age of 57.1 (±10.2) years and median follow-up of 58 months were analyzed. 29 patients had clinical stage IVA disease with 43% (18/42) oral cavity, 36% (15/42) larynx/hypopharynx and 21% (9/42) oropharynx primaries. All patients underwent surgery following neoadjuvant systemic therapy. In 30 patients (71%), all oncologic quality markers were achieved. Pathological downstaging occurred in 21% (9/42) of patients with 4 patients no longer meeting criteria for adjuvant treatment and were observed. 3 patients showed pathological upstaging. The 3-year OS were 76% (95% CI of 63.6-88.4), respectively. Patients with a pathologic downstage migration (64.9%, 95% CI of 49.9-79.8) had higher 5-year OS compared to those without (57.8%, 95% CI of 40.1-76.4, P = 0.046). Conclusions: Most patients receiving neoadjuvant systemic therapy on window trials prior to surgery met all oncologic quality markers. Importantly, even with brief window trial therapy pathologic downstaging was achieved and associated with significantly better overall survival.