Why is there a "five-day work schedule and two-day rest" in radiotherapy?

Radiotherapy, also known as radiotherapy, has been used for more than 100 years and is one of the three major means of tumor treatment, along with surgery and chemotherapy. Radiotherapy is the use of radiation (X-rays, gamma rays, electron beams, heavy ion beams and proton beams) to kill cancer cells and shrink or eliminate tumors to treat tumors. According to statistics, more than 70% of tumor patients have received radiotherapy during their treatment, and radiotherapy contributes 40% to the cure rate of malignant tumors. Therefore, radiotherapy has long been one of the main means of treating malignant tumors.

The process of radiotherapy generally includes 7 steps: "body membrane production - simulation positioning - target area delineation - plan design - plan evaluation - plan verification - plan execution". These 7 steps are indispensable for accurate and effective treatment. At present, most chemotherapy cycles are set to 21 days (3 weeks), mainly based on the half-life of chemotherapy drugs, the duration of toxic side effects, the recovery time of the human body and the doubling time of tumors; then why is radiotherapy adopted in the mode of 5 days on and 2 days off?

Optimizing the effect of radiotherapy

First, tumor cells in different states have different sensitivities to radiotherapy. The cell cycle of mammals can be divided into four phases: G1 phase (pre-DNA synthesis phase), S phase (DNA synthesis phase), G2 phase (late DNA synthesis phase), and M phase (mitosis phase). Generally, cells are most radiosensitive in the M phase (mitosis phase), while cells in the "quiescent phase" are the least sensitive. Tumor cells, like normal tissue cells, have a cell cycle. After being irradiated, tumor tissues will selectively kill cells in the sensitive phase first, while those insensitive cells will still survive.

The advantage of five days of radiotherapy and two days of rest is that during the interval between fractionated radiotherapy, some tumor cells that were originally insensitive to radiotherapy will enter the radiosensitive period and be killed. After repeated treatment, the goal of shrinking and eliminating the tumor can be achieved. This principle is the cell cycle redistribution principle in radiation biology.

Secondly, the response of tumor cells to ionizing radiation also depends on oxygen. Hypoxic cells are less sensitive to radiation than well-oxygenated cells. Therefore, during treatment, sensitive cells with high oxygen content are more likely to be killed by radiation, while cells with low oxygen content still survive. There is a principle in radiation biology called the reoxygenation principle, which means that as oxygenated cells are killed, hypoxic cells will gradually turn into well-oxygenated cells, which will then be more easily killed by radiation.

Therefore, the model of radiotherapy for five days and rest for two days is similar to the principle mentioned above, that is, to allow more cells to be transformed into highly radiation-sensitive cells, and ultimately achieve the goal of improving the effect of radiotherapy.

2. Protect normal cells

Secondly, during the radiotherapy process, radiotherapy rays will inevitably damage the normal cells of the human body, affect other functions of the human body and bring serious side effects, such as being lethal to normal cells, decreased immune function, decreased bone marrow hematopoietic function, and even causing adverse side effects such as nausea, vomiting, and physical fatigue.

The "radiotherapy for five days and rest for two days" split-second irradiation not only kills cancer cells, but also gives normal cells time to repair, thus reducing the damage of radiotherapy to normal tissues.

Three precise radiotherapy, patients are assured

In recent years, with the continuous development and progress of medical science and technology, radiotherapy has entered the era of precision. As an efficient, individualized and precise tumor treatment method, precision radiotherapy is considered to be a new era in tumor treatment.

Radiotherapy has developed to a point where it is no longer just about the selection of radiotherapy cycles. It also includes the calculation of radiotherapy doses, the size of the target area, the range relationship, and the selection of sub-target areas, all of which are related to the local control, survival, and quality of life of tumor patients. It can even use a variety of imaging techniques to accurately determine the range of the target area of ​​the primary cancer lesion, so that even the smallest one will not be missed!

Therefore, during the entire radiotherapy period, the overall error can be less than 5 mm, and the damage is within a controllable range. Moreover, with the application of 5G technology, it can even provide remote delineation and remote planning for grassroots hospitals, truly realizing the "Internet + radiotherapy" model, so that grassroots patients can enjoy high-level radiotherapy.

In short, radiotherapy has long had two major problems: one is that it cannot kill all tumor cells; the other is that it damages normal tissue. Now, with the advancement of the era of precision radiotherapy and the application of 5G technology, we can continuously achieve high precision, high efficacy, high popularity, and low damage, which will gradually change patients' views on radiotherapy.