Faculty Bibliography

PURPOSE: To report the local control, survival, and low toxicity observed at the Cooper University Hospital CyberKnife Center post stereotactic body radiation therapy (SBRT) in the treatment of lung tumors near the mediastinum. METHODS AND MATERIALS: Twenty-four medically inoperable lung cancer patients with tumors near the mediastinum were treated using the Accuray CyberKnife system (Accuray, Sunnyvale, CA) with Monte Carlo dose calculations and heterogeneity corrections from July 2008 to May 2010. The prescription dose ranged from 28.5 Gy to 60 Gy in 3-5 fractions. For conventional fractionation schemes, Emami et al(1) organized the dose tolerance limits into a unified format for clinical utility and partitioned them into 2 risk levels (5% and 50%) with preset volumes for most critical structures throughout the body. In contrast, statistical SBRT dose tolerance limits for mediastinal structures have not been established yet. We have sufficient experience at least to begin organizing a unified format with low-risk and high-risk partitions and preset volumes for 1-5 fractions exposing mediastinal structures. With the help of the (dose-volume histogram) DVH Evaluator, a software tool developed by our senior author, each treatment plan was assessed for safety and feasibility prior to treatment. The DVH Evaluator was also used to analyze the follow-up data and to create graphs of risk, called DVH Risk Maps, superimposing clinical data onto the unified SBRT dose tolerance limits. RESULTS: It was not feasible to prescribe the doses of peripheral lung lesions for all tumors near the mediastinum because of known toxicity. The crude local tumor control rate achieved in our series was 92%. Median survival was 26.8 months for the primary lung cases and 9.6 months for the metastatic cases. No patients experienced grade 3 or higher toxicities. CONCLUSIONS: We affirm that SBRT is feasible in the treatment of centrally located lung cancers when the dose tolerance limits of critical structures are diligently respected. The low adverse event rates that we have experienced, combined with a good local tumor control rate, are encouraging.

INTRODUCTION: Brachytherapy plays a key role in the treatment of many gynecologic cancers. However, some patients are unable to tolerate brachytherapy for medical or other reasons. For these patients, stereotactic body radiotherapy (SBRT) offers an alternative form of treatment. METHODS: Retrospective review of patients prospectively collected on SBRT database is conducted. A total of 11 gynecologic patients who could not have brachytherapy received SBRT for treatment of their malignancies. Five patients have been candidates for interstitial brachytherapy, and six have required tandem and ovoid brachytherapy. Median SBRT dose was 25 Gy in five fractions. RESULTS: At last followup, eight patients were alive, and three patients had died of progressive disease. One patient had a local recurrence. Median followup for surviving patients was 420 days (median followup for all patients was 120 days). Two patients had acute toxicity (G2 dysuria and G2 GI), and one patient had late toxicity (G3 GI, rectal bleeding requiring cauterization). CONCLUSIONS: Our data show acceptable toxicity and outcome for gynecologic patients treated with SBRT who were unable to receive a brachytherapy boost. This treatment modality should be further evaluated in a phase II study.