Malignant tumours of the minor salivary glands: a survival analysis of 17 years from a tertiary referral cancer centre.M Pandey, S Thomas, A Mathew, MK Nair
Department of Surgical Oncology, Regional Cancer Centre, Medical College P.O. Thiruvananthapuram - 695 011, India. , India
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0022-3859.932
Source of Support: None, Conflict of Interest: None
BACKGROUND: Malignant tumours of the minor salivary glands are rare and constitute less than 0.5% of all malignant neoplasms. AIM: This study was carried out to evaluate the clinical presentation, site distribution, treatment, survival and predictors of survival in malignant minor salivary gland tumours. SETTING: A tertiary care, superspeciality referral hospital. DESIGN: Retrospective analysis. PATIENTS AND METHOD: Forty-two cases of minor salivary gland tumours treated over a period of 17 years were reviewed for clinical presentation, histopathology, stage distribution, treatment and treatment outcome. STATISTICAL ANALYSIS: Survival by Kaplan Meier Method and the outcomes were compared using log-rank test. RESULTS: The mean age of the patients was 46.9 years with a male to female ratio of 1.4:1. Majority of the patients presented with a painless progressive swelling, with 13 (31%) of them in T2 stage. About one-third of the patients had palpable lymph nodes at presentation, while none had distant metastasis. Palate was the commonest site and mucoepidermoid carcinoma was the commonest hispathological type. About 1/3 of the patients were treated with primary surgery and were followed up by adjuvant radiotherapy. Seven patients underwent palliative treatment alone. Over a mean follow-up of 30 months, 5 patients failed. The disease free survival was 72% at 5-year, none of the factors studied were found to significantly influence survival. CONCLUSIONS: Results of the present study suggest that minor salivary gland tumours should be treated with primary surgery irrespective of site and histological type to achieve best loco-regional control and survival.
Keywords: Adolescent, Adult, Aged, Carcinoma, diagnosis,pathology,therapy,Disease-Free Survival, Female, Human, Male, Middle Age, Neoplasm Staging, Palate, pathology,Retrospective Studies, Salivary Gland Neoplasms, diagnosis,pathology,therapy,Survival Analysis, Treatment Outcome,
Tumours of salivary gland constitute a heterogeneous group of neoplasms originating from the proliferation of different precursor cells. They represent about 3-5% of all head and neck neoplasms with incidence of malignancy varying with primary site of origin.,,, Most of these tumours arise in major salivary glands. Malignant neoplasm of minor salivary glands constitutes 9-20% in various series.,,,,, Malignant tumors of minor salivary glands are rare and constitute less than 0.5% of all malignant neoplasms. Majority of the earlier series concentrated on histopathological type and epidemiological distribution of the disease. Due to the rarity of the disease, and cases in series being treated over many years by differing modalities of treatment there is no consensus on what should be the optimal treatment. A few studies concentrating on prognostic factors have found the histological type, tumour grade, localisation of tumour and stage as important prognostic factors.,, In the present study we describe our experience with 42 cases of malignant tumours of minor salivary gland treated at our centre.
All cases of malignant tumours minor salivary gland treated at our centre between 1982-1999 were extracted from the electronic database of Regional Cancer Centre, Trivandrum, India, maintained on Ingress software (Ingress corp., California USA) by using International Classification of Diseases- Oncology (ICD-O) (1st edition) codes for histology and sites. A total of 42 patients were identified. The case records of these patients were reviewed for history, clinical findings, pathological types, treatment and outcome details. All the patients were staged using International Union Against Cancer (UICC), Tumour, Node, and Metastasis (TNM) classification (1997).14 Survival analysis was carried out using Kaplan-Meier method and the curves were compared using long-rank test.
A total of 42 patients treated between 1982-1999 were included, this constituted about 0.001% of all head and neck cancers seen during the same period. The mean age of the patients was 46.9 years [standard deviation (SD) + 16.7] ranging from 14 years to 76 years, with a male to female ratio of 1.4:1. There were 14 (33.3%) Christians, 21 (50%) Hindus and 6 (14.3%) Muslims. Past history of chewing tobacco was present in one (2.4%), alcoholism in two (4.8%), and smoking in 2 (4.8%) patients. None of the patients had a family history of tumours of salivary gland and only one (2.4%) had a family history of other cancers.
Progressive painless swelling was the commonest presenting feature in 22 (52.4%) patients, five (11.9%) patients had pain while 4 (9.5%) presented with ulcerated lesion. There were 8 (19%) cases of T1, 13 (31%) of T2, 7 (16.7%) of T3 and 3 (7.1%) cases of T4 tumour. The T stage of primary tumour was not known (Tx) in 11 (26.2%) patients [Table - 1].
Clinically palpable nodes were present in 14 (33.3%) patients, this was N1 in 9 (21.4%), N2 in 4 (9.5%) and N3 in 1 (2.4%). Majority of the lesions (7; 16.7%) were present on hard palate followed by tongue and nasopharynx (5 each; 11.9%) [Table - 1]. Almost half of the tumours were mucoepidermoid carcinoma (19; 45.2%) followed by adenoid cystic carcinoma in 9 (21.4%), adenocarcinoma not otherwise specified in 7 (16.7%) and mucin producing adenocarcinoma in 5 (11.9%).
Majority of the patients were treated by surgery as primary modality and were followed by radiotherapy (13; 31%). Nine (21.4%) were treated by surgery alone while 7 (16.7%) underwent radiotherapy alone. Seventeen patients underwent neck dissection, of these one underwent radical neck dissection; 3 underwent modified radical neck dissection; 4 underwent selective neck dissection while 9 underwent bilateral neck dissection, which was modified radical on ipsilateral side and selective on contra lateral side. The intention of treatment was palliative in 7 patients. The details of treatment are given in [Table - 2]. Of the 11 patients treated by primary radiotherapy only 4 had complete response while 4 (9.6%) had residual disease in primary and 3 (7.2%) had residual disease in both primary and neck. One patient treated by radiotherapy and chemotherapy had complete response. All patients with partial or no response were managed by salvage surgery. After a mean follow-up of 30 months (median follow-up of 19 months; range 1-144 months), five patients failed the pattern of treatment failure is detailed in [Table - 2]. Of these, one patient was salvaged by surgery, two by radiotherapy while one patient received palliative treatment alone. The disease free survival at 5-years was 72% (median 72 months) [Figure - 1]. None of the factors studied were found to have a significant effect on survival [Table - 3] [Figures:2] & [Figure - 3].
Tumours arising in the minor salivary gland are rare. They occur at almost all age with slight female preponderance and preferred location being palate., However, the present study showed a slight male preponderance. The tumours have diverse histopathology and are classified as epithelial, non-epithelial, lymphomas and unclassified tumours. Malignant epithelial tumours are further classified in about 18 sub types. This paper describes our experience with malignant tumours of salivary gland of epithelial origin. Two of the patients undergoing primary surgery elsewhere remained unclassified.
Like various other series,,,,, this study too is plagued by absence of a definite treatment protocol, the cases being treated over a long period of time. Seven patients were offered no treatment or palliative treatment alone at our centre. Cure rate were near 100% for those treated by surgery as primary modality with or without adjuvant radiotherapy. Results of primary radiotherapy were however poor with only 4/11 having a complete response to radiotherapy, two of these subsequently failed. On the other hand 2 out of 9 patients undergoing primary surgery and 1/13 patient undergoing surgery with adjuvant radiotherapy failed. A lower failure rate and higher survival in these neoplasms has also been reported by Lopes et al (1998). Recent studies using fast neutron therapy in adenoid cystic carcinoma however have shown a higher response to primary radiotherapy (5 year survival of 72%) which is similar to the present series. A even higher survival is however achieved by using radiotherapy as adjuvant after complete removal of tumour surgically. Similar results were observed in the present study as well.
Survival rates were better among males (88.9% vs. 39.4%), and in low or intermediate grade tumours (80-100% vs. 50%). Survival was also better in Tx tumours (patients with previous surgical excision) (100% vs. 66.6%) and in node-negative patients (100% vs. 58.7%). None of these differences were however statistically significant. Similarly, none of the parameters studied in univariate analysis were found to be statistically significant.
Results of the present study shows that all patients with tumours of minor salivary gland should be treated by surgery primarily with adjuvant radiotherapy irrespective of site, or histopathological type to achieve good local control and overall survival.
[Figure - 1], [Figure - 2], [Figure - 3][Table - 1], [Table - 2], [Table - 3]