Faculty Bibliography

PURPOSE/OBJECTIVE:Stereotactic body radiotherapy (SBRT) is being used with increasing frequency as definitive treatment of early stage prostate cancer. Much of the justification for its adoption was derived from earlier clinical results using high-dose-rate (HDR) brachytherapy. We determine whether HDR's dosimetry can be achieved by virtual SBRT. METHODS AND MATERIALS/METHODS:Patients with intermediate-risk prostate cancer on a prospective trial evaluating the efficacy of HDR monotherapy treated to dose of 9.5Gy×4 fractions were used for this study. A total of 5 patients were used in this analysis. Virtual SBRT plans were developed to reproduce the planning target volume (PTV) HDR dose distributions. Both normal tissue- and PTV-prioritized plans were generated. RESULTS:From the normal tissue-prioritized plan, HDR and virtual SBRT achieved similar PTV V100 (93.8% vs. 93.1%, p=0.20) and V150 (40.3% vs. 42.9%, p=0.69) coverage. However, the PTV V200 was not attainable with SBRT (15.2% vs. 0.0%, p<0.001). The rectal Dmax was significantly lower with HDR (94.2% vs. 99.42%, p=0.05). The rectal D2 cc was also lower (60.8% vs. 71.1%, p=0.07). Difference in D1 cc urethral dose was not significantly different (87.7% vs. 75.2%, p=0.33). Comparing the PTV-prioritized plans, the rectal Dmax (94.2% vs. 111.1%, p=0.05) and mean dose (27.1% vs. 33.3%, p=0.03) were significantly higher using SBRT, and the rectal D2 cc was higher using SBRT (60.8% vs. 81.8%, p=0.07). CONCLUSIONS:HDR achieves significantly higher intraprostatic doses while achieving a lower maximum rectal dose compared with our virtual SBRT treatment planning. Future studies should compare clinical outcomes and toxicity between these modalities.

PURPOSE/OBJECTIVE:To report long-term outcomes of high-dose-rate (HDR) intraoperative radiotherapy (IORT) at the time of radical resection for recurrent head-and-neck cancer and determine potential prognostic factors. METHODS AND MATERIALS/METHODS:Between 7/1998 and 11/2011, 57 patients with recurrent head-and-neck cancer underwent radical resection with curative intent and single-fraction IORT to 59 sites using a Harrison-Anderson-Mick applicator with remotely after-loaded (192)Ir HDR brachytherapy. RESULTS:One- and 3-year in-field progression-free survival (IFPFS) was 67% and 57%, respectively. In a multivariate model, IORT dose >15Gy (hazard ratio [HR] = 0.11; p = 0.02), and prerecurrence disease-free interval >12 months (HR = 0.29; p = 0.04) independently predicted for superior IFPFS; nodal extracapsular extension (HR = 4.62; p = 0.003) predicted for inferior IFPFS. Three-year overall survival (OS) was 50% vs. 32% in those achieving in-field control vs. those not achieving in-field control (p = 0.04). Grade 3+ toxicity occurred in 37% and was unrelated to IORT dose. CONCLUSIONS:HDR-IORT combined with radical surgical resection is associated with durable IFPFS and long-term overall survival in select patients with acceptable treatment-related morbidity. IORT dose >15Gy should be used to increase the likelihood of disease control. The ability to achieve in-field local control in this poor prognostic cohort was associated with improved survival outcomes.