Guidelines of the French Society of Otorhinolaryngology-Head and Neck Surgery (SFORL), part II: Management of recurrent pleomorphic adenoma of the parotid gland

[Radiotherapy of rare head and neck tumors]

Management of head and neck tumors is complex because of multiple anatomical locations and histologies possibilities. Rare tumors must be managed in a specialized center and be registered in the French network of expertise on ENT Cancers (Refcor). Despite heterogeneous levels of evidence, radiotherapy plays an essential role in their treatment. Radiation therapy is generally indicated in the adjuvant setting, or in case of non-operability. Dose and target volumes depend on histology, location and extensions of the tumor, and the quality of the excision if applicable. We present here a review of the literature and available guidelines for the management by radiotherapy of rare upper aerodigestive tract tumors.

Clinical parameters predictors of malignant transformation of recurrent parotid pleomorphic adenoma

Malignant transformation (MT) in recurrent parotid pleomorphic adenomas (PAs) is rare; therefore its occurrence lacks reliable predictive factors. Our goal was to clarify the predictors for MT of recurrent parotid PAs based on preoperative clinical parameters. Patients with a clinical diagnosis of recurrent parotid PA were retrospectively enrolled. The association between clinicopathologic variables and MT of PA was assessed using univariate and multivariate analyses. MT occurred in 11.8% of the 467 patients. In univariate analysis, three or more previous recurrences, newly developed facial nerve paralysis, difficulty in mouth opening, tumors with the largest tumor diameter ≥ 2.4 cm, and abnormal neck lymph node enlargement were associated with MT occurrence. Further, multivariate analysis showed that three or more previous recurrences, newly developed facial nerve paralysis, difficulty in mouth opening, and abnormal neck lymph node enlargement were independently related to MT. MT of recurrent PA was not uncommon. Clinical signs of malignancy included newly developed facial nerve paralysis, difficulty in mouth opening, three or more previous recurrences, and abnormal neck lymph node enlargement.

Recurrent pleomorphic adenoma of the parotid gland: A population-based study with emphasis on re-recurrence and malignant transformation

BACKGROUND

This study aimed to analyze the prognostic determinants for re-recurrence and malignant transformation of parotid recurrent pleomorphic adenoma (RPA).

METHODS

Between January 2011 and December 2020, all the cases of RPA of the parotid gland at our single institution were reviewed.

RESULTS

A total of 168 patients were included in this study, with a median age of 41.5 years, and 20 (11.9%) patients developed re-recurrence during follow-up. It has been evidenced that recurrence times (single or multiple) was an independent prognostic factor for recurrence-free survival (p = 0.0264). A total of 26 (15.48%) patients experienced malignant transformation of parotid RPA, and older age (>45 year old), male sex, and higher clinical tumor staging (T3-T4) were significantly associated with malignant transformation of parotid RPA.

CONCLUSIONS

Recurrence times was an independent prognostic factor for re-recurrence of parotid RPA, and older male with high T-stage may more easily develop malignant transformation.

Histopathological Aspects of the Prognostic Factors for Salivary Gland Cancers

Salivary gland cancers (SGCs) are diagnosed using histopathological examination, which significantly contributes to their progression, including lymph node/distant metastasis or local recurrence. In the current World Health Organization (WHO) Classification of Head and Neck Tumors: Salivary Glands (5th edition), malignant and benign epithelial tumors are classified into 21 and 15 tumor types, respectively. All malignant tumors have the potential for lymph node/distant metastasis or local recurrence. In particular, mucoepidermoid carcinoma (MEC), adenoid cystic carcinoma (AdCC), salivary duct carcinoma, salivary carcinoma, not otherwise specified (NOS, formerly known as adenocarcinoma, NOS), myoepithelial carcinoma, epithelial-myoepithelial carcinoma, and carcinoma ex pleomorphic adenoma (PA) are relatively prevalent. High-grade transformation is an important aspect of tumor progression in SGCs. MEC, AdCC, salivary carcinoma, and NOS have a distinct grading system; however, a universal histological grading system for SGCs has not yet been recommended. Conversely, PA is considered benign; nonetheless, it should be cautiously treated to avoid the development of metastasizing/recurrent PA. The aim of this review is to describe the current histopathological aspects of the prognostic factors for SGCs and discuss the genes or molecules used as diagnostic tools that might have treatment target potential in the future.

Superficial versus total parotidectomy for recurrent pleomorphic adenoma in the parotid gland

Recurrent pleomorphic adenoma (RPA) is a challenging disease because of difficulty in reoperation, a high rate of postoperative facial palsy, and potential malignant transformation. The optimal management of RPA is still arguable regarding the surgical extent and the necessity of radiotherapy. Therefore, this study compared the complication and re-recurrence rates of superficial versus total parotidectomy in a prospective cohort of 29 patients with RPA. Two surgical techniques were allocated to consecutive patients without randomization and blinding processes. Total parotidectomy was applied to lesions in deep or both lobes. Most early and late complication rates were statistically comparable between the two groups (P > 0.05). Transient and permanent facial nerve paralysis frequently occurred in 55 % and 14 % of all cases, respectively, without statistical difference between the two groups (P > 0.5). Only one patient (3 %) had re-recurrence after superficial parotidectomy during the mean follow-up of 89 months. Superficial or total parotidectomy is recommended to reduce the risk of further recurrence in patients with RPA.

Radiotherapy of salivary gland tumours

Primary tumours of the salivary glands account for about 5 to 10% of tumours of the head and neck. These tumours represent a multitude of situations and histologies, where surgery is the mainstay of treatment and radiotherapy is frequently needed for malignant tumours (in case of stage T3-T4, nodal involvement, extraparotid invasion, positive or close resection margins, histological high-grade tumour, lymphovascular or perineural invasion, bone involvement postoperatively, or unresectable tumours). The diagnosis relies on anatomic and functional MRI and ultrasound-guided fine-needle aspiration for the diagnostic of benign or malignant tumors. In addition to patient characteristics, the determination of primary and nodal target volumes depends on tumor extensions and stage, histology and grade. Therefore, radiotherapy of salivary gland tumors requires a certain degree of personalization, which has been codified in the recommendations of the French multidisciplinary network of expertise for rare ENT cancers (Refcor) and may justify a specialised multidisciplinary discussion. Although radiotherapy is usually recommended for malignant tumours only, recurrent pleomorphic adenomas may sometimes require radiotherapy based on multidisciplinary discussion. An update of indications and recommendations for radiotherapy for salivary gland tumours in terms of techniques, doses, target volumes and dose constraints to organs at risk of the French society for radiotherapy and oncology (SFRO) was reported in this article.

Supporting the use of adjuvant radiotherapy in recurrent pleomorphic adenoma of the parotid

BACKGROUND

The use of adjuvant radiotherapy remains controversial in the treatment of recurrent pleomorphic adenomas.

AIMS/OBJECTIVES

The aim of this study was to provide the highest level of evidence possible by performing a systematic review and meta-analysis of the literature.

MATERIAL AND METHODS

We searched the English-language literature between 1985 and 2019.Inclusion criteria included any study on the treatment and outcome of recurrent pleomorphic adenomas. Exclusion criteria included the use of radiotherapy for residual tumors, case reports, and pleomorphic adenomas not arising from the parotid.

RESULTS

A total of 522 abstracts were studied, data analyzed from 14 studies, on a total of 697 patients. When the data werepooled, the overall risk of further recurrence was 21%. In studies where surgery alone was undertaken this increased to 26% and decreased to 10% in those receiving adjuvant radiotherapy (p = .000). There were 21 recurrences in 159 patients in the radiotherapy group, and 151 recurrences out of 538 patients in the surgery group (p < .0001).

CONCLUSIONS

These data support the use of radiotherapy to decrease the risk of re-recurrence in recurrent pleomorphic adenoma.

SIGNIFICANCE

This study is the highest level of evidence currently available in guiding management of recurrent pleomorphic adenoma.