This review of the use of brachytherapy (also known as interstitial or intracavitary radiation therapy) in children with soft-tissue sarcomas is well-written and timely. The authors have done an excellent job of summarizing the characteristics of the various types of brachytherapy, including intraoperative treatment, and the table comparing the different types is helpful for the nonradiation oncologist. Dr. Nag and his team are proponents of brachytherapy, and he is one of the leading radiation oncologists contributing to this field in the United States.
Compared to external-beam radiotherapy, brachytherapy has several advantages: (1) It allows for better localization and the possibility of treating a smaller volume around the tumor with less likelihood of late morbidity in surrounding normal tissues. (2) It can be completed in 8 days or less.
Brachytherapy also has several disadvantages. These include the need to involve a surgeon and/or anesthesiologist to place the catheters or applicator(s), and the need to sedate the child when the catheters are removed. Radiation safety is another issue with the low-dose-rate, manually loaded technique using iridium or cesium. Also, the child must be separated from the parents for much of the duration of treatment.
Factors Limiting the Use of Brachytherapy
It is perhaps surprising, then, that this article did not present more basic information about this modality. One of the reasons for the relative lack of popularity of brachytherapy is the somewhat limited availability of centers with personnel familiar with the various techniques involved, as mentioned by the authors. Thus, brachytherapy is not often considered an option for children with soft-tissue sarcoma by members of the multidisciplinary treatment team.
This may reflect, in part, the fact that most of the children with rhabdomyosarcoma in this country are treated based on the guidelines of the Intergroup Rhabdomyosarcoma Study Group (IRSG). These guidelines are quite specific about provisions for external-beam radiotherapy but do not discuss in great detail the indications for and techniques of brachytherapy.
In addition, two other factors may contribute to the limited use of and information on this modality. First, the indications for brachytherapy include the proviso that only a relatively small volume of tumor is to be irradiated. The precise volume in excess of which brachytherapy would not be administered has not been defined, and, thus, volume for each case should be carefully determined on an individual basis. If, for example, a maximum diameter of 5 cm were chosen, the majority of children with rhabdomyosarcoma would probably be excluded.
Also, certain sites, such as the base of the skull, are relatively inaccessible to brachytherapy techniques; external-beam therapy is the preferred way to deliver radiation to these sites. In contrast, the face, neck, trunk, and extremities are generally accessible, and the treatment team should always consider brachytherapy for patients with tumors in these locations, particularly when the tumor volume is not excessive.
Data on Long-Term Effects and Comparative Costs Needed
Another vexing problem associated with brachytherapy is that, because its use is not widespread, there is not much information available regarding its long-term effects. The ability of interstitial/intracavitary to achieve local control is amply described by the authors, but the theoretical advantage for brachytherapy over external-beam radiation relative to late sequelae has not been documented in large numbers of children followed for 10 years or more. There is no comparative trial of brachytherapy vs external-beam radiotherapy in the pediatric age group. Thus, conclusions as to the superiority of one over the other can be suggested but remain unproven.
It would also be helpful to have a cost comparison between brachytherapy and external-beam radiotherapy. While brachytherapy can be accomplished relatively quickly, the need for a surgeon and an anesthesiologist can drive up the cost, as would a special unit for high-dose-rate brachytherapy. On the other hand, time lost from work, transportation costs, and baby-sitters for other children at home over the 5- to 6-week period needed to complete a course of external-beam radiation can strain any familys finances.
Nevertheless, the theoretical and practical advantages of brachytherapy for carefully selected children with soft-tissue sarcoma can outweigh the disadvantages. Members of the Radiation Therapy Subcommittee of the IRSG also support its use in certain circumstances, and guidelines for current and future studies of multimodality treatment of children with rhabdomyosarcoma and undifferentiated sarcoma, which may include brachytherapy, are under development. This article clearly points out the positive and negative aspects of brachytherapy in pediatric patients with soft-tissue sarcoma and is a welcome addition to the literature.