Elective neck irradiation versus observation of the clinically negative neck of patients with oral cancer

Abstract

Purposes: A retrospective study was conducted to determine the efficacy of elective neck irradiation (ENI) versus observation of patients with oral tumors of varying T stages and clinically negative necks, and to statistically evaluate outcome in the two groups with regard to the subsequent development of neck disease. Patients and Methods: Seventy-three patients were treated with surgery of their primary site; 31 received ENI, and 42 of the necks were observed. Of the ENI patients, 3.2% developed neck disease compared with 31% of those observed. When the two groups were evaluated by the T stage of the primary tumor, the results for ENI versus observation were as follows: T1 (0% vs 31 %), T2 (5.9% vs 26.7%), T3 + 4 (0% vs 31%), respectively ( P < .0000, adjusted odds ratio = 13.73, 95% confidence interval). The difference between the two groups was highly statistically significant. One hundred fourteen patients were treated with only radiation therapy alone at the primary site. In this group, 88 received ENI, and 16 necks were observed. Eight percent of the ENI group developed neck disease, compared with 3.8% of the observational group. Further evaluation by T stage of ENI versus observation showed T1 (3% vs 0%); T2 (9.3% vs 7.7%); T3 + 4 (5.6% vs 0%), respectively. The difference between these groups was not found to be statistically significant. Results: The 5-year disease-free survival rate for the surgical group was 90% for patients who received ENI and 40% for those observed. This difference was statistically significant ( P = .0007). No statistical difference was found in 5-year disease-free survival for the radiation group between ENI and observation. Conclusions: When comparing the above data for ENI versus observation, the survival advantages of elective neck irradiation in patients whose primary tumor was treated surgically is striking for all T stages. These results make the decision to observe the neck in such patients difficult to justify. Lack of statistical difference between ENI and observation in the radiation cohort likely reflects selection bias. If radiation therapy is being used to treat the primary disease, only low-risk sites or histologically favorable tumors would not, on a routine basis, have the neck fields treated as well.