Hypofractionated Radiotherapy for Nasopharyngeal Carcinoma

Nasopharyngeal carcinoma (NPC) is a type of head and neck malignancies with uneven geographic distribution. According to the World Health Organization, about 40 percent of nasopharyngeal cancer cases occur in China, especially in southern China. Because of the anatomical location, pathological type and biological behavior of nasopharyngeal carcinoma, radiotherapy is the most important treatment method for nasopharyngeal carcinoma. There are four main factors that affect the effect of radiotherapy: (1) repair of radiation damage, (2) repopulation or reproliferation of tumor cells, (3) reoxygenation of hypoxic tumor cells, and (4) redistribution of cell cycle. Reproliferation of surviving tumor cells is one of the important reasons for local failure of conventional frit radiotherapy. The key to improve local control of tumor cells is to overcome the accelerated reproliferation of tumor cells.

Under the conditions of conventional radiotherapy techniques, the organs can be exposed to a large range of radiation, serious damage, difficult to achieve the target dose, and lead to some acute and late toxicity, which may have a negative impact on the patient's quality-of-life (QoL). The conventional segmentation course is too long and the treatment time is too long, thus creating conditions for the accelerated reproliferation of tumor cells, which is not conducive to local control, and has a certain impact on patients in physiological, psychological and economic aspects.

Clinical studies have shown that a variety of human tumors have accelerated reproliferation after conventional radiotherapy, and this reproliferation is closely related to the potential doubling time of tumors. Hypofractionated radiotherapy , also known as low segmentation radiotherapy, refers to the dose segmentation mode with a single radiotherapy dose >2Gy. It can shorten radiotherapy on the premise that the biological effect dose of conventional dose segmentation radiotherapy is equivalent to or increased. It has been widely used in the treatment of a variety of tumors, and is a safe, effective and short course of radiotherapy mode. This method can increase the single dose and shorten the course of treatment, considering the reproliferation of tumor cells and the protection of normal tissues, which is in line with the principle of radiobiology. When the time factor of doubling time days was added, the large segmentation radiotherapy was higher than that of conventional radiotherapy and was consistent with clinical results. Recently, many scholars have made clinical exploration on the technique of Hypofractionated radiotherapy, which provides a new model for radiotherapy. Compared with conventional segmentation, Hypofractionated radiotherapy can give a higher bioeffective dose to the tumor, effectively improve the tumor control rate, shorten the average radiotherapy time by one week, and reduce the reproliferation of tumor cells.

In recent years, with the increasingly detailed optimization of precision radiotherapy technology and the development of radiobiology, Hypofractionated radiotherapy has achieved good therapeutic effects in prostate cancer, lung cancer, liver cancer and breast cancer. Long Bin et al. found that in patients with recurrent nasopharyngeal carcinoma, the duration of Hypofractionated radiotherapy is significantly shorter than that of conventional fractionated radiotherapy, which reduces part of the radiation damage reaction, increases the equivalent biological dose, and can significantly increase the Tumor Control Probability (TCP), with good short-term and long-term efficacy. High gain ratio and good safety were obtained. At present, there is no research on Hypofractionated radiotherapy in nasopharyngeal carcinoma patients at home and abroad. At present, conventional segmentation is still advocated, and the conventional mode is 70Gy/35F/7W. However, this dose segmentation mode has negative factors such as multiple patient trips and high medical costs. Radiobiology and a large number of clinical studies have shown that there is accelerated proliferation of tumor cells after radiotherapy, and this accelerated reproliferation is the main reason for radiotherapy failure, thus challenging whether conventional fractionated radiotherapy is the best scheme. A variety of unconventional fractionated radiotherapy schemes such as hyperfractionation, Hypofractionated radiotherapy and late accelerated fractionation have been proposed to improve the therapeutic effect of cancer.

Therefore, we initiated a non-inferior, non-randomized controlled clinical trial to evaluate whether mafrit is comparable to conventional radiotherapy in nasopharyngeal carcinoma patients with a view to further improving the prognosis and quality of life of nasopharyngeal carcinoma patients.