Radiation for synovial cell sarcoma

Amit Maity, MD, PhD
Last Modified: February 24, 2002

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Question

Dear OncoLink "Ask The Experts,"

My son is 9 years old and was diagnosed with synovial cell sarcoma in the right rear shoulder area in September 2001. He received 3 chemo treatments (doxorubin on ifosfamide) in September, October and November each 3 weeks apart. December 17th, 2001 the tumor was removed. The pathology showed the tumor still contained live cancer cells but the margins were "good". The current discussion for further treatment is whether to do radiation therapy. The debate centers on the negative side effects of radiating the growth plates in the shoulder area. Several doctors (our oncologist and the oncology surgeon) have said that radiating the growth plates will result in the right shoulder getting no larger than it is right now. A local radiology oncologist said he did not believe that radiating the growth plates would cause a "major" problem. I haven't been able to find any information on my own about the effects of radiating growth plates.

Also, the option is being discussed of possibly forgoing radiation due to his age and doing additional chemo.

Any advice or comments?  


Answer

Amit Maity, MD, PhD, Assistant Professor of Radiation Oncology at the Hospital of the University of Pennsylvania, responds:

The treatment of synovial cell sarcomas in children is controversial, especially the role of radiation therapy. There is at least one single institution study that found a high rate of local relapse in children who did not receive radiation therapy, leading the authors to recommend radiation therapy in all patients with this disease, even those with negative margins. Margins can be very difficult to interpret in sarcomas and sampling error can occur because the pathologist only really looks at some sample areas of the tumor to assess margins. Furthermore, in this case, the surgery was performed after several rounds of chemotherapy; therefore, it is even less clear how to interpret the "good" margin status.

The purpose of radiation therapy is to increase the likelihood of local control in the event that there is some microscopic disease left behind. For this disease, the dose that most radiation oncologists would use is fairly high (as childhood cancer goes); on the order of 5000 - 6000 cGy the downside is the potential late effects, particularly on soft tissue and bone growth. It is impossible to predict precisely what would happen with this dose, especially since I have not seen the films and do not know how much area would need to be treated. However, the likely scenario is somewhere in between what you have been told by the surgeon and your radiation oncologist. There would undoubtedly be significant hypoplasia (failure of growth) of the tissues in the treated field; however, I don't think that all growth of the shoulder region would cease. The scapula (shoulder blade) has more that one growth center, and I doubt that all of them would need to be treated with radiation. The humerus (long bone of the upper arm) has two growth plates, one near the shoulder and one near the elbow. The one near the shoulder would stop growing; however, my assumption is that the one near the elbow would not need to be irradiated. Most of the growth of the upper arm actually comes from this growth plate, so in all likelihood there would still be significant growth of the arm in spite of radiation. However, the treated arm might still end up a little shorter that the untreated arm.

The other late effect that we always inform parents about is the possibility of a second cancer following radiation. I cannot give you specific numbers for synovial cell sarcoma because of its rarity. For rhabdomyosarcoma it is approximately a 1-2% risk at 10-15 years, but for Ewing's sarcoma it is higher, 5-10% at 15 years. These second cancers don't usually start until 8-10 years after radiation; however, unfortunately there is probably a lifetime risk for developing them. In other words, as a long as a patient is alive, they must be vigilant about the possibility of a second cancer and have appropriate follow up with an oncologist familiar with this problem.

Although the risks of radiation therapy may seem high, you should keep in mind the dire consequences should this tumor recur locally. Based on its location, there may be no surgical option or the option may be terribly disfiguring. As with all pediatric cases, the choice of whether to give radiation is based on a balancing of the risks of treatment versus the risks of a higher chance of the tumor coming back.

Although this does not give a specific answer to your question regarding the necessity of radiation, I hope it does provide you with some information you can use to make a decision. The fact that you are getting conflicting messages from different physicians tells you that there is no universally agreed upon answer to this question.