Multivariate Analysis Of The Risk Factors Influencing Re-recurrencein The Patients With Recurrent Parotid Pleomorphic Adenoma

Background:Pleomorphic adenoma(PA) is the most common neoplasm of the salivary gland. It is a benign tumor composed of epithelial and myoepithelial cells arranged in various morphological patterns. It is a slow-growing benign salivary tumour, most commonly arising in the parotid. It accounts for 60-70% of all neoplasms in the parotid. The incidence is approximately 2.40-3.05 per 100,000 population annually, of which about 80% occurs in the parotid. Although PA is usually a benign slow-growing adenoma, a relative high postoperative recurrence rate and malignant change tendency are the reasons for concern. The treatment of recurrent pleomorphic adenoma (RPA) could cause facial nerve injury, and there is a very high rate of re-recurrence. Many researchers believe that the possibility of recurrence, especially in the form of multiple foci or malignant change tendency, may depend not only on the presence of incomplete surgical removal, but also on the intrinsic biological properties of each pleomorphic adenoma. However, it has not been reached at present to establish a correlation between the intrinsic biological properties and clinical outcome. The purpose of this study is to estimate re-recurrent rate of recurrent pleomorphic adenoma (RPA) of the parotid and analyze the risk factors for re-recurrence.Methods:A retrospective analysis of 46 patients with RPA arising in the parotid was performed to examine the clinical and histologic features. Immunohistochemical S-P method was used to detect the expression of PCNA, Mucl, Bcl-2 and Bax proteins both in recurrence group and re-recurrence group. The expression between the two groups was compared by the x2 test. Tumor re-recurrent rate was estimated by the life table method. In univariate analysis of the factors examined, the variables was tested by Kaplan-Meier method. In multivariate analysis, the COX proportional hazard model was used to screen the risk factors for recurrence. Statistical analysis was performed using the SPSS 13.0 statistical package.Results:1,In this study, there were 20 males(43.48%) and 26 females (56.52%), with a median age of 37.5 years, ranging from 15 to 74 years. A local excision was performed in 13 cases, there were 7 second recurrences(53.85%); a superficial parotidectomy in 21 cases,9 with second recurrences (42.86%); a total parotidectomy in 12 cases,2 with second recurrences (16.67%). The estimated tumor re-recurrent rates were (28.38+ 7.71)% at 5 years, (65.57±11.02)% at 10 years, and (74.18±11.13)% at 15 years, respectively. The re-recurrent rate was significantly incresse with the time extend.2,Immunohistochemical result showed that the difference of Mucl expressive level in recurrence group and re-recurrence group had statistical significance (P<0.05). The high expression of Mucl might be a risk factor affecting the re-recurrence of the parotid RPA.3,In univariate analysis of the factors examined, there were three variables tested by Kaplan-Meier method had statistical significance, which included the operative pattern, the number of tumor nodules and the expressive level of Mucl protein. The patients with RPA of the parotid underwent total parotidectomy had a lower re-recurrent rate than that underwent superficial parotidectomy and local excision patients. The re-recurrent rate of the patients with multinodular was significantly higher than that with uninodular. The tumor with high-espression of Mucl protein had a high postoperative re-recurrent rate. In multivariate analysis, three variables had statistically significant by the COX proportional hazard model, which were the operative pattern, the number of tumor nodules and the expressive level of Mucl protein. Presence of a multinodular lesion, the surgical method and the expressive level of Mucl protein were significantly associated with a higher probability of re-recurrence.Conclusions:As the risk of re-recurrence appears to increase with time, for the patients with RPA of the parotid, a long-term follow-up may be appropriate. To reduce the re-recurrent rate and the incidence of postoperative facial paresis, a total parotidectomy together with preservation of the facial nerve seems to be suitable for RPA arising from the parotid, especially for the patients with multinodular lesion or high-expression of Mucl protein.