key: cord-0785378-2x1k9maj authors: Borse, Vivek; Konwar, Aditya Narayan; Buragohain, Pronamika title: Oral Cancer Diagnosis and Perspectives in India date: 2020-09-24 journal: Sensors international DOI: 10.1016/j.sintl.2020.100046 sha: 827ef433bc55ada95691ee13affce4bb36a2326f doc_id: 785378 cord_uid: 2x1k9maj Globally, oral cancer is the sixth most common type of cancer with India contributing to almost one-third of the total burden and the second country having the highest number of oral cancer cases. Oral squamous cell carcinoma (OSCC) dominates all the oral cancer cases with potentially malignant disorders, which is also recognized as a detectable pre-clinical phase of oral cancer. Tobacco consumption including smokeless tobacco, betel-quid chewing, excessive alcohol consumption, unhygienic oral condition, and sustained viral infections that include the human papillomavirus are some of the risk aspects for the incidence of oral cancer. Lack of knowledge, variations in exposure to the environment, and behavioral risk factors indicate a wide variation in the global incidence and increases the mortality rate. This review describes various risk factors related to the occurrence of oral cancer, the statistics of the distribution of oral cancer in India by various virtues, and the socio-economic positions. The various conventional diagnostic techniques used routinely for detection of the oral cancer are discussed along with advanced techniques. This review also focusses on the novel techniques developed by Indian researchers that have huge potential for application in oral cancer diagnosis. Oral cancer is an important health issue in India as it is one of the most common types of 90 cancer affecting a large population. The low-income population is at the highest risk due to 91 extensive exposure to various risk factors. Tobacco consumption has been the predominant 92 factor causing oral cancer. The continual use of tobacco in various forms such as gutka, 93 zarda, mawa, kharra, khaini, cigarettes, bidi, hookah, etc. is a major cause of tumor 94 development in the oral cavity in both young as well as the adult Indian population [7] . The 95 distribution of oral cancer across India is shown in Figure 1 . The gender-based distribution 96 of tobacco-related cancer cases and smokers are depicted in Figure 2 . Various factors related 97 to the occurrence of oral cancer in Maharashtra are shown in Figure 3 . Apart from the direct 98 use of tobacco, SLT is also found to be a major reason for oral and pharyngeal cancer with a 99 higher risk in women [8] . A gender-based distinction has been found for oral cancer cases, 100 where males show a high incidence of tobacco-related cancer [9] . 101 In India, epidemiologically, Kerala has the lowest incidence of oral cancer while West 102 Bengal reports the highest. In the western regions of Maharashtra, the highest occurrence of 103 oral malignancy is reported in the age group of ≥60 years, followed by between 40-59 years 104 with a male-female ratio of 2:1 [5]. Several case-control studies, based on age, education, and 105 socio-economic status, have been carried out to assess risk factors, effects, and the prevalence 106 for the occurrence of oral cancer [13] . It is also reported that the nutritional diet is important 114 for oral cancer patients to maintain the oral health-associated quality of life. Table 1 shows a 115 comparative analysis of different sites in the oral cavity that has a high incidence of oral 116 malignancy in the three regions of India, i.e. Kerala, Varanasi, and western Maharashtra. 117 118 Early detection is very important to reduce the mortality rate of patients suffering from oral 120 cancer. Thus, there is a huge demand for oral cancer diagnostic techniques that are non-121 invasive, rapid, and easy-to-use. For oral cancer diagnosis, traces of oral lesions in the mouth 122 are first observed properly by a physician. Upon suspected malignancy, it is further referred 123 to an oral or maxillofacial surgeon who conducts the specific tests. In the case of oral cancer, 124 a dentist plays a pivotal role in the early examination of occurrence. Various routinely 125 practiced techniques for oral cancer detection are shown in Figure 4 and various parameters 126 are compiled in Table 2 . 127 In India, self-examination is considered one of the most effective methods for early diagnosis 128 of oral malignancy. The feasibility of various methodologies such as visual examination, 129 VelScope-aided investigation, and toluidine dye application has been assessed and compared 130 The PET scan is used to determine the spread of tumor cells to the lymph nodes or other parts 240 of the body. A radioactive dye is administered orally or intravenously and the gamma rays 241 emitted from the positron decays are scanned. It is an accurate method that determines the 242 staging of the lymph nodes. It [78] . 265 The biological entities expressed in the serum or saliva that consequently leads to oral cancer 267 may aid as biomarkers for oral cancer detection. Biomarkers in general are components of the 268 cells present in body fluid or tumor cells that are overexpressed during the onset of the 269 disease. Specifically, the advancement of cancer occurs in three major steps that include 270 initiation, promotion, and progression. All the three steps correlate with major changes in the 271 metabolome, transcriptome, and proteome of a cell [79, 80] . These changes are due to 272 alterations in particularly significant genes or proteins that lead to diversification or halting of 273 critical metabolic and structural pathways. In recent years, significant advancements have been reported for the diagnostic techniques 349 that are rapid and specific for the detection of cancer biomarkers. Raman spectroscopy probes 350 the unique vibrational fingerprint of molecules assisting in analyte identification. Using 351 Raman spectra, the differences in protein, amino acid, and beta carotene can be determined, 352 which are excellent biomolecular differences markers for cancer detection [104] . Fourier 353 transform infrared (FTIR) spectroscopy associated with computational systems has been used 354 to distinguish between benign and malignant tumors accurately [105] . In another study from 355 Gujarat, the micronuclei (MN) index, which is a good prognostic indicator or biomarker of 356 the epithelial carcinogenesis, was studied. A step-wise increase in the MN index was 357 observed from the control population to the pre-cancer patients to the cancer patients by 1.14 358 to 2.63 to 4.88, respectively [106] . 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