Local recurrence of soft tissue sarcoma following brachytherapy

Twenty-five patients with soft tissue sarcomas were treated with Ir192 implants following wide local excision at our institution between 1982 and 1987. External beam radiotherapy was given in addition to the implant in a majority of patients. The median follow-up in these 25 patients is 36 months (12 to 75 months). Twenty patients have had no evidence of local recurrence following their primary treatment (FFR = 80%). A multivariate analysis using stepwise logistic regression was used to predict failure in 3 years or less. Potential predictors examined included age, sex, tumor location, primary versus recurrent disease, grade, histology, surgical margins, implant only versus implant plus external beam, and a ratio of the volume of tissue which received 65 Gy (TV65) to the tumor volume (TV), that is (TV65/TV). The single variable which was significantly associated with local failure by 3 years was a TV65/TV of less than one. Once this variable was entered into the analysis, no other factor proved statistically significant. Our data suggest that when attempting local control of soft tissue sarcomas with brachytherapy, the volume of tissue receiving 65 Gy (TV65) from both implant and external beam must exceed the volume of the excised lesion (TV). Since the volume of a tumor can be readily determined prior to surgical excision either by CT or MRI scanning, pre-planning of the implant volume could potentially reduce the rate of local failure.