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Michigan Oncology Journal Fall 97
The Current Role of Radiotherapy in the Management of Adults with Soft Tissue Sarcomas
---Cornelius J. McGinn, M.D.
Radiation therapy plays a central role in the management of many adult patients with soft tissue sarcomas. The primary benefit from this modality has been a substantial reduction in the extent of surgical resection required. In most patients with extremity lesions, limb-sparing surgery plus adequate irradiation produces local control and survival rates similar to those achieved with amputation (1, 2). As a result, the incidence of amputation in this setting has now decreased from 30 percent to 10 percent, in the period from 1988 to 1993 (3). The value of adjuvant radiation following limb-sparing surgery has also been demonstrated in a randomized trial of observation versus brachytherapy. The local control rates at five years among patients with high-grade lesions were 66 percent vs. 89 percent, respectively (p=.0025) (4). In several large, single-institution series, preoperative irradiation,postoperative irradiation or brachytherapy have produce remarkably similar and excellent local control rates, which further validates the basic concept that radical treatment can be carried out with limb preservation. In the head and neck, trunk and retroperitoneum, the value of radiotherapy has not been clearly defined considering rarity of these sites of presentation. However, retrospective series reporting encouraging results in terms of local control include the use of radiation in combination with surgery (5, 6).
Treatment Strategies in Patients with Extremity Lesions
At the time of radiation treatment planning, the optimal position of the extremity is determined so as to treat the affected compartment with minimal treatment of uninvolved tissues. Fluoroscopy is utilized to view surgical clips and preoperative imaging is used to confirm the region to be treated. Once an optimal position is achieved, the extremity is immobilized with a custom-made foam cradle or thermoplast cast such that the position can be reproduced for daily treatment. If there is uncertainty regarding the volume to be irradiated (lack of surgical clips or preoperative imaging), a CT scan in a neutral treatment position can be obtained to more clearly define the surgical bed. Three-dimensional treatment planning is then utilized to optimize beam arrangements.
Preoperative radiation therapy has been advocated and practiced by investigators at the Massachusetts General Hospital (7). With this approach, the volume of tissue irradiated is reduced and the risk of local and distant dissemination may be decreased. This strategy may have the greatest advantage in cases where gross total resection cannot be achieved and a reduction of the tumor volume may allow for a more complete excision. The integration of neoadjuvant chemotherapy and preoperative radiation therapy to improve resectability and reduce the risk of distant metastases has been attempted (7) and is currently being considered for investigation at the University of Michigan.
Radiation therapy may also be delivered by brachytherapy. We have reserved the use of this modality for highly selected cases where postoperative irradiation cannot be delivered. These situations include the treatment of recurrence in a previously irradiated field where limb salvage is desired, and in patients for whom logistic factors make the delivery of external beam therapy prohibitively difficult. At the time of surgery, afterloading catheters are placed at approximately 1 cm intervals within the target volume. Surgical clips placed at the margin of the tumor bed permit the target volume to be delineated for planning purposes. Catheters are loaded with 192Ir seeds approximately six days after surgery to permit initial wound healing to occur prior to irradiation. We have routinely delivered doses in the range of 40-45 Gy over four to six days without complication, even in patients who have previously received full-dose external beam irradiation to that site.
Treatment Strategies in Patients with Non-Extremity Lesions
Cornelius J. McGinn, M.D., is a lecturer in the Department of Radiation Oncology.