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Long Term Effects of Radiation to the Head and Neck

Long Term Effects of Radiation to the Head and Neck

Question

Dear OncoLink "Ask The Experts,"

I'm two treatments away from being done with 5 weeks of radiation treatments for head and neck cancer. I am wondering what the long-term effects of the radiation therapy to the head and neck area might be?

Answer

Harry Quon, MD, MS (CRM), Assistant Professor of Radiation Oncology at the Abramson Cancer Center of the University of Pennsylvania, responds:

The long-term effects of radiation depend on the technique of irradiation, the dose and the location that was irradiated.

Typically, most head and neck squamous cell cancers are locoregionally advanced, requiring treatment of both sides of the neck. In the past, this was accomplished with two large radiation fields on both sides of the neck, matched with a third field coming from the front to treat the lower neck. This resulted in a larger volume of normal tissues being irradiated and accounted for many long-term side effects. It is helpful to summarize the long-term side effects by considering the normal tissues in the head and neck that were included in the treatment field. This is also helpful to understand how newer techniques, such as IMRT, can reduce the side effects of head and neck irradiation.

Among these side effects is injury to the parotid glands (salivary gland) on both sides of the neck, which can lead to xerostomia, or dry mouth. Dry mouth is a concern because it makes swallowing difficult when you can't properly lubricate food. The absence of saliva and change in composition of any remaining saliva increases the risk of dental complications, because saliva helps to kill bacteria on the teeth.

Most patients receive a dose of radiation to the mandible (lower jaw bone), which raises concerns for most dentists that subsequent dental extractions may lead to problems with wound healing over the jaw bone. This is why most dentists want to evaluate patients before they start radiation therapy.

Radiation, particularly when combined with concurrent chemotherapy, can result in edema (swelling) of the tissues in the mouth and throat. This can be further complicated if neck surgery is done after chemoradiation, as surgery further impairs the normal lymphatic fluid drainage of the neck. This persistent edema can make swallowing more difficult.

Lastly, there can be fibrosis (scarring) that can affect various normal functions, depending on where it is located. If it is in the soft tissues of the neck, particularly if surgery is performed, then the range of motion of the neck can be limited, such as when looking over the shoulder while driving. If it is in the back of the tongue and upper voice box, then the ability to move food from the mouth into the throat can be limited, and patients can feel that they can't "get the food back" when swallowing. If the cancer was in the throat area beside the voice box, then patients can often describe food sticking and not passing a point in their throat. Sometimes, a procedure that stretches the throat can help with this, but if the muscle of the swallowing tube has been scarred down, it may not be reversible.

Newer radiation techniques such as IMRT are improving the side effect profile of head and neck irradiation. Since this is a new technique, we have limited experience and publications describing improvements in the long term side effects, such as xerostomia. By being able to reduce the volume of the parotid glands that are radiated, as well as the dose that they receive, it is clear that there can be recovery of saliva, whereas in the past, this was not possible. The ability for IMRT techniques to reduce other causes of swallowing problems is being actively studied and is too premature to generalize at this time.