THE ROLE OF ADJUVANT RADIOTHERAPY IN THE TREATMENT OF RESECTABLE DESMOID TUMORS

Purpose: Desmoid tumors have a high propensity for local recurrence wi th surgical resection. There are many reports describing good response s of desmoid tumors to irradiation, but none have clearly established the indications for adjuvant radiotherapy in treating resectable desmo id tumors. Methods and Materials: A retrospective analysis was perform ed on 61 patients with resectable desmoid tumor(s) who were treated at our institution from 1965 to February of 1992. Five patients had mult ifocal disease and are analyzed separately. Fifty-six patients had uni focal disease, of which 34 had positive surgical margins. Forty-five o f the 56 patients with unifocal disease were treated with surgery alon e, while 11 were treated with surgery plus adjuvant radiotherapy. Medi an follow-up was 6 years. Local control was measured from the last day of treatment, and all cases were reviewed by our Department of Pathol ogy. Results: Multivariate analysis of the 56 patients with unifocal d isease revealed that positive margins independently predicted for loca l recurrence (p less than or equal to 0.01). Only 3 of 22 patients wit h clear margins experienced a local recurrence, with a 6-year actuaria l local control of 85%. Multivariate analysis of the 34 patients with positive margins revealed that adjuvant radiotherapy independently pre dicted for improved local control (p = 0.01), and patients with recurr ent disease had a slightly higher risk of local recurrence (p = 0.08). The 6-year actuarial local control determined by Kaplan-Meier for pat ients with unifocal disease and positive margins was 32% (+/- 12%) wit h surgery alone, and 78% (+/- 14%) with surgery plus adjuvant radiothe rapy (p = 0.02). Subgroup analysis of the patients with positive margi ns and recurrent disease revealed that those treated with surgery alon e had a 6-year actuarial local control of 0% vs. 80% for those treated with surgery plus radiotherapy (p less than or equal to 0.01). Patien ts with positive margins and primary disease had a trend towards impro ved local control with adjuvant radiotherapy, but this was not statist ically significant. None of the patients treated with radiotherapy dev eloped serious complications or a secondary malignancy. Conclusions: M argin status is the most important predictor of local recurrence for p atients with resectable, unifocal desmoid tumor. Adjuvant radiotherapy is indicated in the treatment of patients with positive margins follo wing wide excision of recurrent disease. The role of adjuvant radiothe rapy in patients with positive margins following resection of primary disease is controversial, and should be based on a balanced discussion of the potential morbidity from radiotherapy compared to the potentia l morbidity of another local recurrence. Adjuvant radiotherapy is less likely to benefit those with clear margins due to the excellent resul ts for these patients treated with surgery alone. The local control of desmoid tumor in the adjuvant setting is excellent with total doses r anging from 50-60 Gy, with acceptable morbidity. Field sizes should be generous to prevent marginal recurrences, and large volume MRIs of pa tients with extremity lesions should be used to identify those patient s with multifocal disease. (C) 1997 Elsevier Science Inc.