Multicenter Retrospective Study of Adjuvant Therapy for Patients with Pathologically Lymph Node-Positive Oral Squamous Cell Carcinoma: Analysis of Covariance Using Propensity Score.

Background: The presence of pathologically positive lymph nodes (pN+) is a well-known prognostic factor in oral squamous cell carcinoma (OSCC). The aims of this retrospective multicenter study were to assess the prognosis of OSCC patients with pN+ disease; to compare the prognosis of patients with pN+ disease who underwent surgery plus radiotherapy (RT) or concurrent chemoradiotherapy (CCRT) with that of patients who underwent surgery only; and to account for biases associated with treatment selection of adjuvant RT or CCRT.

Methods: The records of 313 OSCC patients with pN+ disease were retrospectively reviewed. The main outcome measures were 5-year disease-specific survival (DSS) and overall survival (OS) rates. To reduce selection biases associated with retrospective data, the treatment groups were evaluated by Cox proportional hazard analysis with propensity score as a covariate.

Results: The 5-year OS and DSS survival rates for the entire patient cohort were 51.8 and 59.2 %, respectively. T3-4 stage, closed (<5 mm) margin distance, ≥4 involved nodes, and extracapsular spread were significant poor prognostic factors for OS and DSS. In the propensity score analysis, postoperative RT/CCRT significantly improved OS and DSS compared to surgery only. However, OS and DSS were not significantly different between patients who received postoperative RT and CCRT.

Conclusion: The addition of cytotoxic chemotherapy to RT does not provide additional survival benefit in OSCC patients with pN+ disease. Alternative strategies, such as molecular targeted therapies, are needed to further improve the survival of high-risk OSCC patients with pN+ disease.