BACKGROUND: Occult metastasis varies widely from 12 to 48% among patients with cN0, high-grade parotid carcinoma. Current treatment paradigms include adjuvant radiation to the ipsilateral neck regardless of cN0 or pN0 staging. Controversy arises as surgeons decide whether or not to perform ipsilateral elective neck dissection (END) in cN0 patients as it is unclear if neck dissection improves survival. Moreover, occult metastasis is much higher than regional recurrence would predict implying that radiotherapy is an effective method of managing regional metastasis. Thus, we sought to evaluate the association between neck dissection and survival among cN0 patients with high-grade parotid cancer.
METHODS: This is a retrospective study of the National Cancer Database that included adult patients with clinically N0, high-grade (ICD-O-3 grade 3 or 4), parotid carcinoma diagnosed between 2004 and 2013. Survival analysis was used to compare neck dissection versus no neck dissection when controlling for additional covariates.
RESULTS: After exclusion criteria, 1,547 patients remained. The median follow-up time among all patients was 36 months. A total of 578 patients died and 795 were alive at the conclusion of the study interval with 174 lost to follow-up. A total of 1,094 patients underwent neck dissection and 453 did not. Among patients who underwent neck dissection, <1% yielded 0 nodes, 62% yielded 1-17 nodes, and 38% yielded 18 or more nodes. Occult metastasis was identified in 28% of patients. After adjusting for confounders, we found evidence suggesting that END may have an effect on survival in the first two-to-four years following surgery, but that its effect on survival wanes by five years following surgery. When controlling for confounding, we found that 67.3% of patients would survive three years were all patients to receive END (CI: 64.4, 70.2), while 62.7% of patients would survive three years were no patients to receive END (CI: 58.2, 67.2; Figure 1). The difference in these survival probabilities is 4.6% (CI: -0.5, 9.6; p=0.072). On the other hand, 51.8% of patients would survive five years were all patients to receive END (CI: 48.6, 55.0) compared to 51. 5% of patients that would survive five years were no patients to receive END (CI: 46.9, 56.2; Figure 1). There was no significant difference in five-year survival probabilities.
CONCLUSIONS: Elective neck dissection may have an effect on survival in the first two-to-four years following surgery while this effect wanes by 5 years among cN0 high-grade parotid cancer patients undergoing neck dissection when controlling for confounding. In patients with cN0 high-grade parotid carcinoma, neck dissection should be reserved for select cases.