CT findings at the primary site of oropharyngeal squamous cell carcinoma within 6–8 weeks after definitive radiotherapy as predictors of primary site control

Abstract

Purpose : To determine whether findings on CT studies, done 6 weeks after radiotherapy (RT), can predict the likelihood of ultimate control at the primary site in oropharyngeal carcinoma. Methods and Materials : Forty-six patients with oropharyngeal squamous cell carcinoma underwent RT with curative intent. A minimal 2-year clinical follow-up after RT was required. The primary site CT findings were graded for risk of recurrence on a modified 3-point scale as follows: Grade 0, no detectable focal abnormalities; Grade 1, anatomic asymmetry or focal mass <1 cm; Grade 2, focal mass >10 mm (2a) or <50% shrinkage of the mass as seen on pretreatment studies (2b). Results : No patients with CT findings of Grade 0 ( n = 26) or Grade 1 ( n = 5) had a primary site recurrence. One of the 13 patients with CT findings of Grade 2a had a primary site recurrence 1 year after completion of RT. None of the 2 patients with CT findings of Grade 2b had a primary site recurrence. Ultimately, 45 of the 46 patients in this study group had disease control at the primary site. Conclusion : In the evaluation of oropharyngeal squamous cell carcinoma on post-RT CT studies, diffuse and symmetric post-RT changes of the soft tissue or asymmetry without detectable mass or a discrete mass ≤10 mm always indicated ultimate control at the primary site. Even when post-RT CT shows a discrete mass >10 mm at the primary site, the likelihood of local control is high (93%). The study results indicate that CT findings, based on this relatively small series, may not add incremental information beyond that of clinical examination for predicting local control but may be useful as a baseline if imaging surveillance is contemplated.