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Background Information
Why Use Radiotherapy?
Should Radiotherapy Be Given Before or After Surgery?
What Are the Side Effects of Radiotherapy?
Why Not Just Use Radiotherapy Alone and Avoid Surgery?
Want to know more?
Adenoid cystic carcinomas most commonly arise in either the major (parotid, submandibular, or sublingual) or minor salivary glands. The minor salivary glands consist of clusters of secretory cells scattered throughout the upper aerodigestive tract. Examples of sites where such tumors arise are the palate, nasopharynx, tongue base, mucosal lining of the mouth, larynx, or trachea. Adenoid cystic carcinomas of non-salivary gland origin can arise in the lacrimal (tear) glands of the eye or in the breast. The later are quite rare. Regardless of location, these tumors have the same basic biological behavior in that they tend to spread along nerves (perineural invasion), rarely spread to the lymph nodes (although this does happen in about 5-10% of cases), and have a propensity for hematogenous spread (via the blood stream). The lung is the most common site where these distant metastases occur but they can also occur in the bones, liver, etc. Conventional radiotherapy, using photons/x-rays or electrons, is used both to treat areas of metastatic disease and to treat the primary tumor site following a surgical resection.
Radiation therapy primarily works by damaging the DNA of cancer cells. It is often used as an adjuvant to surgery in the head and neck area to treat areas at high risk for disease spread. It is particularly effective in sterilizing small numbers of tumor cells left behind after surgery. While there have been no randomized trials that directly test how effective this adjuvant treatment is, there is historical data that shows for properly selected patients, it reduces the risk of the tumor recurring. I will first describe the older data for salivary gland tumors in general and then will discuss the newer data relating specifically to adenoid cystic carcinomas.
The following table shows a comparison for the overall local control rates for patients with surgically-resected salivary gland tumors with or without adjuvant radiotherapy [see Molinari R., et al, "Indications and efficacy of postoperative radiation therapy for salivary gland cancer" In Head and Neck Cancer, Vol. III. Eds. Johnson JT, Didolkar MS. Elsevier Press, Amsterdam, 1993, pp. 607 - 617; for a complete list of the references in the table].
For the entire group of patients, the overall local control rate was 76% when adjuvant radiotherapy was used compared to 55% when it was omitted. It is also important to note that the patients who received the radiotherapy generally had more advanced tumors than those who did not. Unfortunately, this improved local control did not translate into improved survival which was about 65% for both patient groups.
Researchers from M.D. Anderson Hospital [ Garden et al, "Postoperative radiotherapy for malignant tumors of the parotid gland". Int J Radiat Oncol Biol Phys 37: 79 - 85, 1997] showed a 90% local control rate at 10 years for patients with adenoid cystic carcinomas treated after a resection producing clear margins. For patients with positive margins (but still microscopic disease) the local control rate was 88% provided a sufficient amount of radiation was given. Note that to obtain good surgical margins, it was sometimes necessary to sacrifice the facial nerve. Researchers from the University of Florida [ Parsons, et al, "Management of minor salivary gland carcinomas". Int J Radiat Oncol Biol Phys 35: 443 - 454, 1996] looked at a group of patients with adenoid cystic carcinomas arising in minor salivary glands and found a local control rate at 10 years of 78% for patients treated with both surgery and radiotherapy.
Should Radiotherapy Be Given Before or After Surgery?
While the adjuvant radiotherapy can be given either before the surgery (preoperative) or after the surgery (postoperative), in the treatment of adenoid cystic carcinomas, it is generally given postoperatively. This is because adenoid cystic carcinomas most often respond slowly to radiotherapy and one would not expect much tumor shrinkage before the surgery (one of the reasons for giving the radiotherapy before the resection is to shrink the tumor and make the surgery easier). Giving the radiotherapy after the surgery allows the Radiation Oncologist to specifically target the high risk sites and many surgeons feel that there is better wound healing if radiotherapy is not given prior to the surgery.
What Are the Side Effects of Radiotherapy?
Unlike chemotherapy which can affect all areas of the body, radiotherapy only affects the tissues in the treatment area. Hence, the symptoms will depend upon the particular part of the body being treated. Assuming that the radiotherapy will be given in the head and neck region, the patient can expect the following side effects:
After a few weeks of treatment, the patient can expect a mucositis reaction (sore mouth and throat) that may make it difficult to swallow. If the parotid glands are in the radiation field, there may be a permanent loss of saliva causing xerostomia (dryness of the mouth),. At the University of Washington we have worked out methods of treatment that often allow us to keep the dose to the parotid gland located on the opposite side of the tumor low enough so that it recovers function. Agents such as Saligen® (pilocarpine)can then stimulate this gland resulting in an acceptable saliva output. We are also studying the use of Amiphostine®(ethyol) to further protect tissues during radiotherapy. Sometimes a facial nerve graft is used to restore function of the facial muscles after a surgical resection. There is often concern that postoperative radiotherapy will damage the nerve graft. This is not the case. Radiotherapy may delay the nerve regeneration but it doesn't prevent it from ultimately happening.
A typical course of postoperative radiotherapy will take about 6-7 weeks to deliver. The use of chemotherapy and radiotherapy together in this setting must be regarded as experimental as there is no data as to whether the increased side effects will be compensated by any improvement in control or survival.
Why Not Just Use Radiotherapy Alone and Avoid Surgery?
Radiotherapy works best when the number of residual tumor cells is small. When conventional radiotherapy alone is used to treat salivary gland tumors, the expected local control rate is only about 25% as can be seen in the following table [see Laramore, In Head and Neck Cancer, Vol. III. Eds. Johnson JT, Didolkar MS. Elsevier Press, Amsterdam, 1993, pp. 599-605]; for a list of the references in the table].
This is considerably less than expected with surgery and adjuvant radiotherapy.
In the case of a patient with a very extensive tumor that cannot be resected or someone with medical problems that
eliminate surgery as an option, fast neutron radiotherapy offers about 2-3 times the local control
rate as that offered by standard photon and/or electron treatments. Read more about neutron radiotherapy and
how it is used in AdCC treatment by viewing our local website page:
Neutron Radiotherapy in the Treatment of AdCC
You may want to research radiotherapy further on the more technical aspects of this treatment option at this University of Washington web pages - Department of Radiation Oncology
Copyright © Sharon Lane,
George Laramore, Ph.D., M.D.
Last modified: July 2, 2005
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