Salivary LDH in oral cancer and potentially malignant disorders: A systematic review and meta-analysis

OBJECTIVES

To evaluate whether salivary lactate dehydrogenase (LDH) levels are increased in patients with oral cancer (OC) or oral potentially malignant disorders (OPMD) when compared to a healthy control group (CG).

MATERIAL AND METHODS

We conducted a comprehensive search of specialized databases (PubMed/MEDLINE, The Cochrane Library, Web of Science, Scopus, and OpenGrey), including observational analytical studies evaluating the salivary LDH levels (in UI/L or μ/L) in OC or OPMD patients and compared them with a CG.

RESULTS

Thirteen case-control studies were included. A total of 755 patients were evaluated, including 303 OC cases, 149 OPMD cases, and 303 controls. The meta-analysis showed that LDH levels were higher within the OC group than the CG (SMD 9.49; 95% CI 6.97-12; p = .00001). Patients with oral leucoplakia (SMD 11.67; 95% CI 1.01-22.33; p = .03) and oral submucous fibrosis (SMD 25.83; 95% CI -1.74-53.40; p = .07) also presented higher levels than the CG. In addition, OC patients had higher salivary LDH levels than oral leucoplakia patients (SMD 5.62; 95% CI 2.14-9.11; p = .002). Heterogeneity was high across all the evaluated studies.

CONCLUSIONS

The determination of salivary LDH may be a useful method for screening and tracking OC and OPMD, but new protocolized studies are required to establish precise cutoff values.

Role of Salivary Biomarkers in Oral Cancer Detection

Oral cancers are the sixth most frequent cancer with a high mortality rate. Oral squamous cell carcinoma accounts for more than 90% of all oral cancers. Standard methods used to detect oral cancers remain comprehensive clinical examination, expensive biochemical investigations, and invasive biopsy. The identification of biomarkers from biological fluids (blood, urine, saliva) has the potential of early diagnosis. The use of saliva for early cancer detection in the search for new clinical markers is a promising approach because of its noninvasive sampling and easy collection methods. Human whole-mouth saliva contains proteins, peptides, electrolytes, organic, and inorganic salts secreted by salivary glands and complimentary contributions from gingival crevicular fluids and mucosal transudates. This diagnostic modality in the field of molecular biology has led to the discovery and potential of salivary biomarkers for the detection of oral cancers. Biomarkers are the molecular signatures and indicators of normal biological, pathological process, and pharmacological response to treatment hence may provide useful information for detection, diagnosis, and prognosis of the disease. Saliva's direct contact with oral cancer lesions makes it more specific and potentially sensitive screening tool, whereas more than 100 salivary biomarkers (DNA, RNA, mRNA, protein markers) have already been identified, including cytokines (IL-8, IL-1b, TNF-α), defensin-1, P53, Cyfra 21-1, tissue polypeptide-specific antigen, dual specificity phosphatase, spermidine/spermineN1-acetyltransferase , profilin, cofilin-1, transferrin, and many more. However, further research is still required for the reliability and validation of salivary biomarkers for clinical applications. This chapter provides the latest up-to-date list of known and emerging potential salivary biomarkers for early diagnosis of oral premalignant and cancerous lesions and monitoring of disease activity.

Advances of Salivary Proteomics in Oral Squamous Cell Carcinoma (OSCC) Detection: An Update

Oral cancer refers to malignancies that have higher morbidity and mortality rates due to the late stage diagnosis and no early detection of a reliable diagnostic marker, while oral squamous cell carcinoma (OSCC) is amongst the world’s top ten most common cancers. Diagnosis of cancer requires highly sensitive and specific diagnostic tools which can support untraceable hidden sites of OSCC, yet to be unleashed, for which plenty of biomarkers are identified; the most recommended biomarker detection medium for OSCC includes biological fluids, such as blood and saliva. Saliva holds a promising future in the search for new clinical biomarkers that are easily accessible, less complex, accurate, and cost effective as well as being a non-invasive technique to follow, by analysing the malignant cells’ molecular pathology obtained from saliva through proteomic, genomic and transcriptomic approaches. However, protein biomarkers provide an immense potential for developing novel marker-based assays for oral cancer, hence this current review offers an overall focus on the discovery of a panel of candidates as salivary protein biomarkers, as well as the proteomic tools used for their identification and their significance in early oral cancer detection.