Definitive Radiation Therapy for Locally Advanced Oropharyngeal Carcinoma

Abstract

To report outcomes, patterns of failures, and toxicities in patients treated with definitive radiation therapy for locally advanced squamous cell carcinoma of the oropharynx. Between June 1995 and March 2010, 108 patients with loco-regionally advanced oropharyngeal cancers were treated with radiation therapy (RT) with a curative intent. Of these, 91 (87%) received concurrent systemic therapy with 18 of them also receiving chemotherapy neoadjuvantly. Systemic therapy was Platinum-based in 76/91 patients (83%), Taxane-based in 10/91 (11%) and Cetuximab-based in 5/91 (5%). The median prescribed dose to gross disease was 70 Gy (65.9 -76.0 Gy). Fractionation was conventional in 101 patients and accelerated in 7.IMRT was used in 74 patients and 3D CRT was in 34. The median follow-up was 39 (5-191) months among surviving patients. The 3-year cumulative actuarial rates of local failure (LF), regional failure (RF), and distant metastasis (DM) were 6.5%, 7.9%, and 13.5%, respectively. The 3-year local failure rate was 17.6% (95% CI: 7.0 -32.2%) or 6/34 for those treated using 3DCRT compared with 1.4% (95% CI: 0.1 to 6.5%) or 1/74 for those treated using IMRT. Among the 6 LF treated with 3DCRT, 2 recurred out of RT field and 3 did not receive chemotherapy. The only LR that occurred in the IMRT group was located within the high dose volume. There was no statistically significant difference in RF or DM with respect to the treatment modality. On Univariate analysis, the likelihood of LF correlated with higher T stage (T4-T3 vs. T1-T2 p=0.05), absence of systemic therapy (p=0.02) and use of 3D-CRT technique (p=0.01) whereas the likelihood of DM was associated with an advanced N-stage (N2c-N3 vs.N0-2b p=0.007). On Multivariate analysis, RT technique (3D-CRT) remained a strong predictor for LF (p=0.05), whereas advanced N stage predicted any type of recurrence or death (p=0.02). No statistical difference was found with regards to treatment breaks between the two modalities, However, lower incidence of esophageal stricture and lower rates of PEG tube placement were noted in the IMRT group versus those treated with 3D CRT (1.4% vs 11.8% (p=0.033), and 18.9% vs 24.2% respectively. Our results showed an improvement in outcome with IMRT vs. 3D CRT with respect to local control and the incidence of post-treatment esophageal strictures in patients with locally advanced oropharyngeal cancers. In our series, the extent of nodal involvement was a strong predictor of any recurrence or death. Distant metastases however, remained a major pattern of relapse.