Role of Precursor Lesions in Diagnosis and Prognosis of Oral Squamous Cell Carcinoma
Amna Noor, Bsc
Oral squamous cell carcinoma (OSCC) is the most common form of oral cancer, contributing to both a high rate of severe illness and mortality in affected patients. The severity of OSCC is strongly associated with the stage of disease at the time of diagnosis, where stage of disease refers to the spread and size of tumour when it is first found. For example, a small tumour in only one spot would be considered Stage I. However, if a tumour is large and has spread to other parts of the body, then it is said to be Stage IV.
Early detection of oral cancer usually results from monitoring early signs of abnormal cell growth, known as precursor lesions. The most common examples of these lesions appear as white or white-red patches in the mouth. The goal of managing OSCC is to prevent further development of cancerous tumours, which makes early diagnosis an utmost priority.
In a recent study, researchers from Western University in collaboration with the University of Toronto, conducted a series of experiments to see if identifying precursor lesions helps diagnose OSCC at earlier stages and lower the mortality rate in comparison to OSCC cases not associated with a precursor lesion. Using the Ontario Cancer Registry, the researchers obtained records of oral cancer cases in Ontario from the year 2005 to 2015. Additionally, cases of precursor lesions were obtained through Oral Pathology Diagnostic Services from the University of Toronto and Western University.
It was found that the average age of diagnosis was 63.5, and that the cancer was about twice as likely to be diagnosed in males than females. Cancer was most often diagnosed on the tongue, tonsil, base of the tongue, lip, and floor of the mouth, which could be due to the ease of access to those sites. For example, a lesion on the tongue is more easily identifiable than a lesion deep inside the throat. The researchers also found that cases in females were twice as likely to be associated with a precursor lesion. Lastly, patients living in the Central region (Greater Toronto Area and surrounding cities) had a greater number of OSCC cases associated with a precursor lesion, which might be due to more accessible care in the larger cities.
The researchers then studied the relationship between precursor lesions and the diagnosis and severity of OSCC. It was found that cancers diagnosed at Stage I had a much higher frequency of precursor lesions than cancers diagnosed at later stages. As for the severity of the disease, the analyses demonstrated that OSCC associated with precursor lesions had a lower mortality rate than OSCC not associated with a precursor lesion. Additionally, those patients whose diagnosis was associated with a precursor lesion were more likely to have died of other causes and not OSCC, likely attributable to better treatment plans and an earlier diagnosis.
It is important to highlight some considerations and limitations of the study. Firstly, most precursor lesions are identified during opportunistic screening. This means that finding these lesions is mainly reliant on either the patient telling their dental-care provider about strange patches in their mouth, or the provider identifying it themselves. This process relies heavily on access to dental care, making socioeconomically advantaged, health-conscious groups who live in an urban setting the most likely to be diagnosed early. Furthermore, biopsies of precursor lesions may be done by surgeons who have not been included in this study, which may have resulted in an underestimate of the number of OSCC associated with precursor lesions. The Ontario Cancer Registry database also does not keep track of patients’ lifestyle choices, such as alcohol consumption and smoking, or of treatment plans. This made it difficult to study the interactions and impacts of factors other than precursor lesions on OSCC.
This research suggests that recognition of precursor lesions can have beneficial effects for diagnosis and treatment of OSCC, and is associated with significantly lower rates of mortality, especially for slow-progressing cancers. Future research into the development of precursor lesions may help patients and healthcare professionals more quickly identify them, leading to an earlier diagnosis. The study also makes a case for the importance of a database linking cases of OSCC to precursor lesions, in an effort to improve long-term management of lesions and allow for better outcomes of oral cancer treatments.
 McCord C, Kiss A, Magalhaes MA, Leong IT, Jorden T, Bradley G. Oral Squamous Cell Carcinoma Associated with Precursor Lesions. Cancer Prev Res (Phila). 2021 Sep;14(9):873-884. doi: 10.1158/1940-6207.CAPR-21-0047. Epub 2021 Jun 30. PMID: 34193432.