What are the risks of conventional irradiation?
Conventional irradiation of head and neck cancer is one of the most toxic regimens in oncology. The greatest risks are loss of vision, hearing impairment, salivary gland impairment and/or swallowing tract disorders that cause the inability to swallow food, so patients often have to rely on liquid meal replacements. The dose of radiation required for a safe and successful cure is even higher than for brain tumors. This again disproportionately increases the risk of damage to the surrounding tissues when using conventional (photon) radiation. However, these complications can be greatly avoided by proton therapy. If you want to compare the conventional (photon) radiation of healthy tissues, imagine that you would have your skull x-rayed 2400 times. Would you unnecessarily suffer such a burden?
If we treat the following organs by conventional irradiation, the following risks may occur:
|Eye ||Damage to the retina or optic nerve |
|Inner ear ||Hearing impairment |
|Brain ||Impairment of cognitive functions |
|Swallowing tract ||Tube nutrition (PEG) |
|Salivary gland ||Dry mouth |
|Tongue and oral cavity ||Loss of taste |
|Skin and subcutaneous region ||Hardening and tightening of the skin |
When using conventional (photon) radiation, it is necessary to reduce the dose to the high-risk organs to avoid the above risks and complications, which will lower the dose to the tumor and reduce the chance of a cure.
So, what are the risks for a head and neck cancer patient in the case of conventional (photon) radiation?
- Irradiation of the contralateral eye may cause cataract or retinal disease.
- If the tumor is located close to the eye or brainstem, it may be difficult to maintain the tolerance dose. Such tumor location requires a reduced radiation dose, which diminishes the therapeutic effect.
- Moderate- or low-dose irradiation of the brain tissue may lead to cognitive dysfunctions, such as memory problems, attention disorders, impaired speed of thinking, impaired ability to understand information, or speech problems.
- Irradiation of the inner ear structures may cause hearing loss at high frequencies.
- Exceeding the tolerance dose to the pharyngeal constrictors may cause permanent dysfunction of these muscles and long-term swallowing difficulties.
- If it is necessary to irradiate the bilateral cervical lymph nodes, it will be difficult to maintain tolerance doses to the larynx, which may cause swelling, but also dysphonia, affecting the quality of life of the patient.
- If it is not possible to reduce doses to the swallowing tract and the esophagus during the irradiation of cervical lymph nodes, the irradiation may cause inflammation of the esophagus and mucosal damage in the swallowing tract, and it is very likely that PEG tube will be introduced (long-term use of percutaneous endoscopic gastrostomy, a stomach tube needed for feeding).