Chemotherapy and radiation therapy in locally advanced oropharyngeal cancer

Abstract

Background. About 650,000 new cases of head and neck cancer are diagnosed worldwide each year. About 66 % of these patients already have a common stage of the disease. Mortality up to one year is 38.8-44.4 %. The male/female ratio is 3.4:1. Smoking, alcohol consumption, human papillomavirus (HPV) infection, and herpes viruses are the main risk factors for the developing oropharyngeal cancer (OPC).
 Objective. To identify the features and to describe the treatment of OPC.
 Materials and methods. Analysis of literature data on this issue.
 Results and discussion. HPV-associated OPC is characterized by the favorable survival rates. 60-80 % of patients with such OPC are non-smokers and do not abuse alcohol, the average age is 45-55 years. The main principles of diagnosis and treatment of locally advanced forms of OPC include the use of modern imaging methods, staging depending on HPV status, definitive chemoradiation therapy, dose escalation (66-72 Gray), the use of integrated boosts on the tumor and affected lymph nodes, radiation therapy (RT) without a break, the use of the adaptive RT method. It has been shown that RT split courses reduce local tumor control by 13 %, while increasing the risk of late radiation complications by 18-40 %. RT with modulated dose intensity is accompanied by the reduction in the risk of all-cause mortality by 21 %, as well as the risk of cancer-specific mortality, and by the reduction of the number of aspiration pneumonia cases. Adaptive RT is a modern RT technology that involves adjusting the radiation plan during the course of treatment due to the changes in the anatomy of the tumor and surrounding tissues. The main stages of adaptive RT are obtaining the current data from the megavolt computed tomography, recalculation of the dose distribution, comparison with the plan before treatment, and adaptation of the plan. The results of chemotherapy should be evaluated no earlier than 12 weeks after its completion. Rehabilitation after chemoradiation therapy (prevention of trismus) involves massage and training of the jaw muscles, maintaining proper posture, oral hygiene.
 Conclusions. 1. HPV status is an important parameter in predicting the course of OPC. 2. HPV-associated OPC is characterized by the favorable survival rates. 3. The planned RT must be held without an interruption. 4. RT with modulated dose intensity is accompanied by the reduction in all-cause mortality by 21 %, as well as the risk of cancer-specific mortality. 5. The main area of research in HPV-associated OPC is the de-escalation of treatment regimens.