Journal of Cancer Research and Therapeutics Medknow Publications on behalf of the Association of Radiation Oncologists of India (AROI) ISSN: 0973-1482 EISSN: 1998-4138 Vol. 6, Num. 3, 2010, pp. 263-266

Journal of Cancer Research and Therapeutics, Vol. 6, No. 3, July-September, 2010, pp. 263-266

Original Article

Estimation and comparative study of serum total sialic acid levels as tumor markers in oral cancer and precancer

Manjiri Joshi¹, Ranjitkumar Patil²

¹ Department of Oral Medicine and Radiology, Pravara Institute of Medical Sciences, Loni, Maharashtra, India
² Department of Oral Medicine and Radiology, K M Shah Dental College, Piparia, Vadodara, Gujarat, India

Correspondence Address:Manjiri Joshi, Niranjan Niwas, Opp Anjali Theatre, Aurangabad - 431 001, Maharashtra, India, manjudentist@yahoo.co.in

Code Number: cr10060

PMID: 21119250

DOI: 10.4103/0973-1482.73339

Abstract

Keywords: Oral cancer, oral precancer, serum sialic acid

Introduction

Despite half century of intensive efforts throughout the world, cancer still remains an enigma. The incidence of head and neck cancer accounts for 30-40% of all malignant tumors in India. ^[1] In this, oral cavity is fourth common site for carcinoma after lungs, stomach and liver in males and fifth common site in females after cervix, breast, stomach and liver. ^[2] The etiological factors attributed to this are tobacco and lime chewing and tobacco related habits, smoking, alcohol consumption, nutritional deficiencies, sunlight and other miscellaneous factors. ^[3],[4]

Substances changing quantitatively in the serum during tumor development are collectively called tumor marker or biochemical serum markers. Classically, a marker is synthesized by the tumor and released into circulation or expressed at the cell surface in large quantities by malignant cells, than by their counterparts. ^[5] The tumor marker/substance can be classified as tumor specific and tumor associated. Tumor specific substances are considered as a direct result of oncogenesis, while tumor associated markers are various proteins and enzymes, hormones, immunoglobulins which occur in the blood and are mediated by tumor itself or by the influence of the tumor on the involved tissues.

From over 30 acetylated derivatives of neuraminic acid, N-acetyl neuraminic acid (NANA) referred to as sialic acid, is the most common in humans. Sialic acids (SAs) are acetylated derivatives of neuraminic acid. They are attached to the non-reducing residue of the carbohydrate chains of glycoproteins and glycolipids.

Materials and Methods

The present study was conducted on 90 subjects after approval by local ethical committee. By obtaining an informed consent, the patients were examined thoroughly and detailed case history proforma was recorded. Then 5 ml venous blood was withdrawn for evaluation of serum total sialic acid. The study conducted on 90 subjects was with age range from 21 to 65 and were grouped as follows:

1. Group I: 30 healthy individuals without any systemic disease with age and sex match with that of Group II and Group III.
2. Group II: 30 subjects with clinically and histopathologically diagnosed oral precancer without any other underlying systemic disease.
3. Group III: 30 subjects with clinically and histopathologically diagnosed oral cancer without any other underlying systemic disease.

The estimation of serum total sialic acid level was done according to Plucinsky et al by resorcinol reagent method. The N-acetyl neuraminic acid (NANA) as standard was obtained from Sisco Research Laboratories Ltd for standardization of the procedure.

Statistical analysis

The statistical analysis was carried out by using SPSS 10.0 software. The statistical analysis included mean values, standard deviation, standard error, 95% confidence interval. Student′s t-test, ANOVA test were applied for significance and variability of the values.

Results

Total subjects in the study included 80% males and 20% females. The mean age of males was 36.84 ± 13.05 years while that of females was 47.50 ± 13.96 years. The above values indicate that the individuals above 40 years are at high risk for oral cancer. The sex ratio was evaluated by Chi-square test, which was significant (P<0.05) showing the male predominance in oral pre cancer and oral cancer, this could be because the habits like tobacco chewing, smoking alcohol consumption are more common in males.

The mean serum total sialic acid (TSA) level in control group was 58.59 ± 5.81mg/dl, whereas it was 66.95 ± 4.61mg/dl and 84.44 ± 8.26mg/dl in oral precancer and oral cancer group respectively and when compared was statistically significant (P<0.05).

The mean serum total sialic acid levels of the subgroups in oral precancer group was compared by Students unpaired t- test. The t-value (Table value) between OSMF group and control group was found to be 4.97, whereas it was 4.81 between leukoplakia and control group; and was statistically significant (P<0.05). But the t value between OSMF and leukoplakia was 1.32 and thus statistically found to be not significant (P>0.05).

Histopathologically, when the mean serum total sialic acid levels in precancerous group between no dysplasia, mild dysplasia and moderate dysplasia were compared it was statistically not significant although the mean TSA level in moderate dysplasia was slightly higher (72.70mg/dl) as compared to mild (66.98mg/dl) or no dysplasia (66.48mg/dl).

The oral cancer group was divided clinically into four sub groups according to TNM staging by American Joint Committee of Cancer (AJCC). The mean TSA level in stage I was 71.24 mg/dl whereas it was 73.36±4.65 mg/dl, 84.61±6.40 mg/dl, and 89.34±4.68 mg/dl in stage II, stage III and stage IV respectively. These were compared by Students unpaired t-test which showed marked increase in the serum total sialic acid as the stage of tumor advances and suggested that TSA level is directly proportional to tumor burden. The values in stage III and stage IV were markedly increased as compared to stage I and stage II. Thus when stage I and stage II were compared with stage III and stage IV, it was statistically significant.

Histopathologically, oral cancer was divided by Broder′s classification into three groups: well differentiated squamous cell carcinoma (WDSCC), moderately differentiated squamous cell carcinoma (MDSCC) and poorly differentiated squamous cell carcinoma (PDSCC). The mean TSA level in WDSCC was 83.84 ± 8.99 mg/dl, while it was 82.73 ± 6.82 mg/dl in MDSCC and 95.02 ± 3.42 mg/dl in PDSCC. The mean serum total sialic acid levels between these when compared by Students unpaired t-test were found to be statistically not significant (P>0.05). The t-value between WDSCC and PDSCC was 2.07 which was statistically significant (P<0.05). Out of the 3 patients with PDSCC, 2 were diagnosed clinically as stage IV of oral cancer, which again signifies that it might be related to the clinical staging rather than histopathologic grading, as it is of subjective variability.

Comparison of the serum TSA levels within the oral cancer group of patients with habits of tobacco chewing / betel nut chewing /smoking or alcohol consumption (WHT) and the patients without any habit (NHT) was also performed which was statistically not significant (P>0.05) suggesting that the serum TSA levels are independent of tobacco and related values, and have positive correlation with tumor burden.

Discussion

Recently, tumor markers are receiving more attention in early detection as well as predicting prognosis of the lesion. In the last few decades, considerable research efforts have been focused on defining the changes in cell surface membrane molecule in neoplastic transformation, particularly the cell surface glycoproteins which contributes for malignant transformation of a cell. Among these glyco conjugates, sialic acid is present up to 30% in various glycoproteins. The serum sialic acid levels in healthy individuals remain approximately same throughout life. They might increase slightly with advancing age. The values of serum total sialic acid levels in healthy individuals carried out by various investigators and the present study are shown [Table - 1].

The possible reasons for such difference in values of serum sialic acid can be attributed to high carbohydrate content in diet, anemia and hypoproteinemia in Indian population. It might also be slightly attributed to the difference in method applied and the procedure followed.

In the present study, statistical analysis showed male predominance, which was correlated well with the previous studies. Also the mean age found in the oral cancer group was 48.90 years, which suggested that oral cancer usually affects individuals more than 40 years of age as depicted previously. ^[14]

The oral pre cancer group included 70% patients with oral submucous fibrosis and 30% patients with leukoplakia. The mean serum total sialic acid levels when compared mutually were not statistically significant, but was comparable with control group. This was again consistent with the findings by Rajpura et al., ^[13] and Baxi et al. ^[9]

The present study also includes correlation of histopathologic grading of these oral pre cancerous lesion and condition with that of mean serum total sialic acid levels. The histopathologic grading is done according to no dysplasia, mild dysplasia, moderate dysplasia and severe dysplasia. The mean serum sialic acid level in patients with no dysplasia was 66.48 ± 4.47 mg/dl, whereas 66.98 ± 4.70 mg/dl, 72.70 ± 3.05 mg/dl in mild dysplasia and moderate dysplasia, respectively. It was found to be statistically not significant when compared mutually. It suggests that serum sialic acid levels are independent of histopathologic grading for oral precancer.

With reference to oral squamous cell carcinoma, various investigators found a statistically significant rise in serum sialic acid levels as compared to healthy subjects. They also noticed the increased levels of sialic acid when correlated with the clinical staging of oral squamous cell carcinoma. Present study has also shown the comparison of total serum sialic acid levels with that of clinical staging of cancer. Various investigators compared the serum total sialic acid level with clinical staging [Table - 2].

Above table shows significant rise with the advancing stage of tumor. This means that TSA level is directly proportional to the tumor burden. The values we found were closely related to those of Vallikanthan et al., ^[11] Shashikant and Balajirao, ^[12] Rajpura et al. ^[13] with the only difference that the values of TSA were toward lower side in initial stages of tumor in the study by Rajpura et al. ^[13] and Vallikanthan et al. ^[11]

The present study also includes correlation of TSA level with histopathologic grading of tumor. Histopathologic grading of oral squamous cell carcinoma (OSCC) was done according to the degree of differentiation as per Broder′s classification. ^[15] The TSA levels according to histopathologic grading by some authors and present study is also evaluated [Table - 3].

The values when compared mutually in the study by Rajpura et al., ^[13] it was statistically not significant (P=0.155). When the TSA levels were mutually compared in our study between WDSCC and MDSCC it was not statistically significant, but when TSA levels were compared between MDSCC and PDSCC it was statistically significant. Not any previous study has given such correlation. The possible reason could be subjective variation between histopathologic grading and only three cases of PDSCC were studied. Also if we consider the clinical staging of these histopathologically diagnosed PDSCC, two patients out of three were of stage IV with one case of recurrence and the third one is of stage III. So tumor burden might be the cause of higher values of serum TSA level in PDSCC. Again we found slightly lower value in MDSCC as compared to the WDSCC, this could be attributed to subjective variation.

The present study also suggested that no correlation exists between habit of tobacco chewing / betel nut chewing / smoking or alcohol consumption with that of serum total sialic acid levels. This finding was consistent with Baxi et al. ^[9]

Conclusion

In the present study, it can be observed that no positive correlation exists between tobacco and tobacco related habits with serum TSA level. Increase in serum TSA levels in oral precancer may help in differentiating the early precancerous state of patients. The level of serum TSA increases with degree of dysplasia in oral precancer, suggesting its association with malignant transformation. Increased sialic acid levels is dominant in oral cancer patients which is imparted due to release of sialic acid in to circulation due to increased turn over, secretion and or shedding from malignant cells. There is progressive elevation in serum TSA level in oral squamous cell carcinoma, showing positive correlation of TSA level and stage of malignancy, specifically with the tumor burden. Serum total sialic acid levels can be used as an adjunctive diagnostic marker in head and neck cancer.

Acknowledgement

I express my deep gratitude to Dr. SS Degwekar (Prof and Head) and Dr. R Bhowate from Department of Oral Medicine and Radiology DMIMS Wardha for their incredible support and guidance.

References

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