"Off target", often heard in shooting motion, refers to a target that has not hit or is aimed at. In targeting tumors, the method of irradiation and destruction with radiation is radiation therapy. Since there is a target, there is bound to be a phenomenon of "off-target".
Off-target means losing points for athletes; so, what does it mean for tumor patients in radiation therapy?
Radiation with penetrating nuclear radiation, if irradiated to normal tissues of non-targets, can cause local damage, often in patients in the form of different degrees of side effects, such as gastrointestinal reactions, skin allergies and so on.
However, off-target radiotherapy can cause a more serious problem – damaged tissue increases the risk of metastasis.
A 1973 study reported that exposure to radiation from mouse lung tissue showed colonization of cells prone to cancer metastases;
Early clinical data of the last century: breast cancer patients increased after surgery and radiation therapy.
Recently, a study published in the sub-journal Nature explained the phenomena and mechanisms of radiotherapy off-target and tumor metastasis.
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The tissue repair process can actually promote tumor metastasis
Radiation continues to irradiate tumor tissue, making its damage smaller; damage to normal tissue will also occur, and after radiotherapy, the damaged normal tissue needs to repair itself, but this process has been found to promote tumor metastasis.
In order to simulate lung tissue damage caused by radiation therapy for breast cancer, the researchers exposed the lung tissue of mice to high doses of radiation, causing the mice to develop acute radiation damage to the lungs. A comparison of normal breast cancer mice with radiation-damaged breast cancer mice showed that more cancer cells spread to the lungs in radiation-damaged mice and began to form secondary tumors (i.e., metastases).
The immune system inadvertently helps cancer cells metastasize
Further research found that the occurrence of the above phenomena has a lot to do with neutrophils.
neuter
Granulocytes
The main function is to prevent infection and engulf bacteria. As frontline combatants of the inflammatory response, neutrophils are able to fend off invading pathogens while participating in the repair and healing of tissues and wounds.
During tissue repair, local neutrophils are activated, creating a better environment for metastatic cancer cells and inadvertently promoting the metastasis of tumors.
If the signal transduction of neutrophils in the damaged lungs of mice is blocked in connection with tissue regeneration, the production of secondary tumors in the lungs is greatly reduced. It was further demonstrated that metastasis was associated with tissue repair with neutrophil involvement.
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Can cancer patients still do radiation therapy with confidence?
As one of the troikas of tumor treatment, radiation therapy helps many tumor patients to get their condition well under control and even cure some tumors.
60 to 70% of cancer patients receive radiation therapy because of its irreplaceable role in achieving local tumor control. Radiotherapy is also an indispensable treatment for preoperative and postoperative adjuvant therapy to further improve the effectiveness of surgical treatment.
Therefore, even if radiation therapy will bring mild or severe side effects to patients, and even increase the risk of tumor metastasis, choosing radiation therapy is still a treatment that most tumor patients cannot refuse.
Not only radiation therapy, but also better use of radiation therapy. Then reducing "off-target" and letting radiation accurately shine on the tumor is our constant pursuit.
How to reduce "off-target"
With the advancement of technology and equipment updates, precision treatment techniques such as accurate target delineation, repeated debugging of equipment, and respiratory gating by pre-treatment physicists have greatly reduced the occurrence of "off-target".
In addition, during the treatment process, patients must remain motionless to avoid treatment deviations.
Write at the end
The quality control of radiotherapy of Meizhong Jiahe Group has been recognized by the National Center for Oncology Quality Control and is worthy of the trust of patients.
It is worth mentioning that Meizhong Jiahe Group is the only social medical group among the project undertaking units approved by the radiotherapy quality control guidelines in 2021. At the same time, the shortlisted projects are also from the Cancer Hospital of the Chinese Academy of Medical Sciences, Peking Union Medical College Hospital, the Cancer Prevention and Control Center of Sun Yat-sen University and other institutions.
bibliography
Nolan E, et al. Radiation exposure elicits a neutrophil-driven response in healthy lung tissue that enhances metastatic colonization. Nat Cancer. 2022 Feb;3(2):173-187.