Is radiation therapy only used to treat malignant tumors?
The radiotherapy acts by damaging the DNA of the cells which in turn dies when trying to multiply with the damaged DNA, says Dr. Mathangi J
Radiotherapy means treatment with ionising radiation, be it gamma rays or X rays or particulate radiation like protons or electrons. Generally, it is used to treat different cancers either all by itself or after surgery or with chemotherapy. But what is less known to the community is that it can be used to treat noncancerous lesions also.
Benign diseases are noncancerous lesions that does not invade surrounding tissues or spread to other places but are locally bothersome by mass effect or by secreting hormones or cosmetically disfiguring or debilitating. They can of different types and hence the treatment can vary from medically controlling them to surgically removing the tumor.
Radiotherapy is indicated in symptomatic or potentially symptomatic patients with a definite therapeutic gain, when other modalities fail.
Most of the non-cancerous lesions treated are from the brain, head and neck region to avoid severe/life threatening symptoms because of pressure and mass effect on critical structures.
Brain tumors: The most common tumors of the brain treated with radiotherapy are meningiomas, pituitary adenomas, craniopharyngiomas, chordomas, paragangliomas (Glomus tumors), vestibular/ trigeminal/ facial schwannomas. Though surgery is the mainstay of treatment in such diseases, radiotherapy is indicated in postoperative residual or recurrence settings or directly for very small schwannomas, where surgery might result in long term side effects.
Head and Neck region: Juvenile Nasopharyngeal Angiofibroma is a condition in young patients which causes recurrent bleeding, blindness or affects the major nerves due to extension into the brain. In such patients, radiotherapy is directly indicated if it is extending into the brain or patient is not fit for surgery. Also, it is indicated if the lesion comes back after surgery.
Vascular disorders: Arteriovenous malformations (AVMs) of the brain and spine that might lead to life threatening bleeding. The lesions that are situated deep inside the brain, in the critical locations and are not accessible to surgery (microvascular decompression) are treated by a single high dose of radiotherapy. This high dose damages the inner lining of the blood vessels resulting in their closure.
Functional disorders: The disorders like Trigeminal neuralgia (Tic Douloureux), Epilepsy, Parkinson’s disease, are generally managed medically or by deep brain stimulation. When such disorders become refractory to all the above managements, radiotherapy can be considered to destroy the relevant causative point in the brain.
Keloids: These are an excessive tissue proliferation scar caused after skin injury from surgery / burns etc. These may be painful or cosmetically disfiguring. Radiotherapy is given when there are repeated recurrences or in unfavourable locations or as a preventive measure after surgery (radiotherapy started within 24 hours of excision of the keloids) to prevent recurrences.
Desmoids: (Aggressive fibromatosis/ deep musculo aponeurotic fibromatosis) are most commonly seen in trunk/ abdominal wall/ inside the abdomen. They are locally aggressive and have a high rate of coming back after surgery. Radiotherapy is considered if the tumor cannot be completely resected or with repeated recurrences.
Eye: Recurrent pterygium, refractory choroidal hemangiomas in the critical locations, Age related Macular degeneration, progressive symptomatic refractory Graves ophthalmopathy, orbital pseudotumor are some of the conditions in the orbit where radiotherapy is considered when all other options are exhausted.
Other benign diseases like Dupuytren contracture, Heterotrophic ossification, pigmented villo nodular synovitis (PVNS) are also considered for radiotherapy if refractory to other managements and in the recurrent setting (when the disease comes back).
Difference between the management of cancerous and noncancerous lesions with radiotherapy:
The lesion alone needs to be treated, as there is no microscopic disease extension into the surrounding tissue.
The dose to the surrounding normal tissues should be kept as low as possible to avoid long term side effects. The patient life expectancy is longer. Hence, high end radiotherapy techniques should be used to minimise the dose to the adjacent structures. This gains special importance when treating lesions in the brain and the head and neck region tumors.
Stereotactic radio surgery (SRS):
It refers to precise and focussed delivery of high dose of radiation to the needed area with as less as possible to the adjacent normal structures. It is usually given in fewer sessions. This was initially done in brain alone and now can be done in any part of the body and hence name stereotactic ablative body radiotherapy (SBRT)
There are different machines that can deliver this treatment like Gamma knife, X knife, Cyber Knife, Novalis Tx and TrueBeam STx.
The radiation is delivered to the tumor from various planes in multiple arcs to cone down to the tumor such that the dose delivered to the normal tissues in the path are divided and reduced to as minimum as possible. The volume of normal brain receiving this extra dose determines the occurrence of long-term complications. Hence excellent imaging systems, CT/MRI/DSA fusion accuracy, good planning systems with experienced staff and a machine with good precision and accuracy are the determinant of good treatment with excellent results.
Post treatment follow-up:
The radiotherapy acts by damaging the DNA of the cells which in turn dies when trying to multiply with the damaged DNA.
So understandably though the DNA is damaged in these benign lesions, the cells are destroyed only when they try to multiply which is very slower compared to a cancerous lesion. So, a change in the shape or size of the lesion or look for a response after such treatments in benign lesions may take months to years. So long term follow-up is needed, and the response is never a magical disappearance.
The patient referred for radiotherapy does not always have cancer. Radiotherapy can be used for treating non- cancerous lesions also. However, it is chosen as a therapy only as a last option for refractory or relapsed or inoperable condition. High end techniques should be taken to reduce the dose to the adjacent normal tissues.
Dr Mathangi J, Senior Consultant & In Charge, Department of Radiation Oncology, BGS Gleneagles Global Hospital, Bengaluru