Short summary

Salivary gland carcinoma is rare. Furthermore, it is a heterogeneous disease covering 24 histological subtypes with very different biological behavior, malignant potential and prognosis. To reach sufficient data for research, collection over many years is necessary. This PhD focus on the time interval 1990-2015 and will result in the largest national study worldwide on salivary gland carcinoma. The long study period enables to estimate Danish salivary gland carcinoma epidemiology, diagnostics, treatment and outcome and to establish guidelines on the surgical treatment of cervical lymph nodes.

Rationale

Carcinoma of the salivary glands is rare and represents only 3-5 % of all head and neck cancers. The incidence of primary salivary gland carcinoma is in average 62 per year in Denmark accounting for only 1.1/100.000/year. Furthermore, primary salivary gland carcinomas are a heterogeneous group of cancers, consisting of 24 histological subtypes with very different biological behavior, malignant potential and prognosis. The wide variety of histologic subtypes combined with relatively few patients in all ages makes it difficult to reach sufficient data on epidemiology, histopathology, treatment and prognosis. 

National registries and the individual social security number of all inhabitants in Denmark create unique opportunities to investigate patients with salivary gland carcinoma. An earlier Ph.D. project established a national database in the structure of the Danish Head and Neck Cancer Group (DAHANCA) with registration of all patients with primary salivary gland carcinoma in the period 1990-2005. Up to 146 possible variables were recorded in 952 patients. It is the world largest unselected study group of salivary gland carcinoma patients.

This study will conduct a follow up on all existing patients in the database as well as update the database with patients diagnosed with a primary salivary gland carcinoma in Denmark in the period 2005 to 2015. The long time-period enables to update epidemiology, patient and tumor characteristics, diagnostics, treatment and outcome in salivary gland carcinoma patients over a period of 25 years.

According to the Danish salivary gland carcinoma guidelines, the treatment of choice is surgery with the aim to obtain free microscopic margins. Postoperative radiotherapy might be administered in patients with positive resection margins, stage T3/T4 disease, perineural invasion, lymph node metastases, recurrence and high grade histology. 

No international consensus on the surgical treatment of the neck has been established. It is difficult to establish recommendations on the surgical treatment of the neck because of the relatively small number of patients, the many histological subtypes with different malignant potential and the lack of long follow up.  Analyzation of data from the updated national database enables to compare characteristics and location of the cervical lymph node metastases to the surgical treatment of the neck and the outcome (recurrence rate and overall survival). Based on the location of neck lymph node metastases at primary surgery and regional recurrences, recommendations concerning surgical strategy will be proposed. Endpoints will be disease-specific survival and locoregional control correlated with nodal metastases and extent of neck dissection.  

Description of the cohort

All patients diagnosed with primary salivary gland carcinomas in major or minor salivary glands in Denmark in the period of 1990-2015 will be included. The patients will be identified from three Danish national registries: The Danish Cancer Registry, The Danish Pathology Registry and DAHANCA (a clinical database administered by Danish Head and Neck Cancer Group). The search criteria will be based on ICD-10 coding as well as combinations of topography and morphology codes. 

Histologic revision will be performed on all available specimens. If the revision changes the diagnosis to another than salivary gland carcinoma (for example carcinoma in situ, benign tumor or another malignant tumor) the patient will be excluded. The revision will be performed by a specialist in salivary gland pathology. 

Data and biological material

A complete follow up on existing patients in the database in the period 1990-2005 will be conducted, and the database will be extended with all patients diagnosed with primary salivary gland carcinoma in the period 2005-2015. Clinical data will be gathered from medical records and pathological reports.

Medical reports will be retrieved from the four Danish head and neck cancer centers and from local departments of ENT Head and Neck Surgery. Relevant data will be extracted according to the variables in the national database using a registration form in five parts (onstudy, surgery, histology, oncology and follow-up). Endpoints are incidence over time, frequency of histological subtypes over time, over-all survival, cause-specific survival and recurrence-free survival. 

Data on surgical treatment of the neck will be implemented in the database. There will be registration of TNM stage prior to treatment, extent of neck dissection, histopathologic diagnosis, locoregional recurrence and most recent disease status.

Collaborating researchers and departments

Department of Otorhinolaryngology, Odense University Hospital

• Consultant Kristine Bjørndal, PhD
• Professor and Consultant Christian Godballe, PhD

Department of Oncology, Aarhus University Hospital

• Professor and Consultant Jesper Grau Eriksen, PhD

Department of Pathology, Odense University Hospital

• Consultant Stine Rosenkilde Larsen

Publications associated with the project