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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 University of Michigan Comprehensive Cancer Center, postoperative irradiation is preferred over preoperative irradiation or brachytherapy if, in the estimation of the surgeon, the tumor can be resected with negative surgical margins. This approach eliminates radiation-induced delays in wound healing that can occur with preoperative irradiation and allows for pathologic evaluation of the entire specimen. This latter point is particularly important, as selected grade I tumors may not need adjuvant radiation therapy. Furthermore, a postoperative approach may allow clinical and pathologic evaluation of response to neoadjuvant induction chemotherapy in those cases where it is applied. However, this strategy requires close cooperation between the surgeon and the radiation oncologist such that the extent of surgical resection can be adequately defined. It is our practice to have the radiation oncologist present at the time of surgical excision so the tumor bed can be viewed as surgical clips are placed to define the volume to be irradiated.

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
Patients with soft tissue sarcomas arising in the head and neck, trunk and retroperitoneum present a challenge that is best met by a multidisciplinary approach. The primary issue is to determine the feasibility of surgical resection. In some cases, a preoperative approach of chemotherapy or chemoradiotherapy is employed in attempt to improve the likelihood of complete surgical excision. More often, postoperative irradiation is delivered as adjuvant therapy in cases where surgical resection has been achieved. The most difficult cases are those in which surgical resection is not feasible at the time of presentation or for a locally recurrent tumor. Doses >55 Gy are required (8). Three-dimensional treatment planning is invaluable in these cases so that the maximum amount of normal tissue can be spared. Two recent cases are shown in Figures 1 and 2 on the next page.

Summary
Although radiation therapy plays a critical role in the management of patients with soft tissue sarcomas, the most important feature of their care is a multi-disciplinary approach. The need for this approach is clear from the perspective of radiation oncology as the treatment options within this discipline can vary widely based on the unique presentation of each patient and the opinions of the surgical and medical oncologists involved. This approach has been pursued at the University of Michigan through a multidisci-plinary Tumor Board and the implementation of a new Multidisciplinary Sarcoma Clinic.

References

  1. Potter DA, Kinsella T, Glatstein E, et al. High-grade soft tissue sarcomas of the extremities. Cancer. 58:190, 1986.
  2. Suit HD, Mankin HJ, Wood WC, et al. Treatment of the patient with stage M0 soft tissue sarcoma. J Clin Oncol. 6:854, 1988.
  3. Pollock RE, Karnell LH, Menck HP, et al. The national cancer data base report on soft tissue sarcoma. Cancer. 78:2247, 1996.
  4. Pisters WT, Harrison LB, Leung DHY, et al. Long-term results of a prospective randomized trial of adjuvant brachytherapy in soft tissue sarcoma. J Clin Oncol. 14:859, 1996.
  5. Karakousis CP, Velez AF, Gerstenbluth R, et al. Resectability and survival in retroperitoneal sarcomas. Ann Surg Oncol. 3:150, 1996.
  6. Singer S, Corson JM, Demetri GD, et al. Prognostic factors predictive of survival for truncal and retroperi-toneal soft-tissue sarcoma. Ann Surg. 221:185, 1995.
  7. Suit H, Spiro I. Radiation as a therapeutic modality in sarcomas of the soft tissue. Hematol Oncol Clin North Am. 9:733, 1995.
  8. Fein DA, Corn BW, et al. Management of retroperi-toneal sarcomas: Does dose escalation impact on locoregional control? Int J Radiat Oncol Biol Phys. 31:129, 1995.

Cornelius J. McGinn, M.D., is a lecturer in the Department of Radiation Oncology.

 

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Please note: The articles listed in the Cancer Center's News Archive are here for historical purposes. The information and links may no longer be up-to-date.