Retention Rate of Electromagnetic Navigation Bronchoscopic Placed Fiducial Markers for Lung Radiosurgery.

BACKGROUND: Radiosurgery is becoming an increasingly used modality for the medically inoperable early stage lung cancer patient. The optimal fiducial marker with respect to retention rate has yet to be identified. METHODS: We retrospectively reviewed our experience with electromagnetic navigational bronchoscopic fiducial marker placement in preparation for stereotactic radiosurgery. RESULTS: Forty-eight patients, treated between 2010 and January 2013, were retrospectively reviewed. All patients had a diagnosis of early stage lung cancer. Comparison of initial fiducial placement procedure data with imaging at the time of treatment was accomplished for all patients in this data set. Fiducial retention rates were as follow: VortX coil fiducials were retained in 59 of 61 (96.7%) cases; two-band fiducials were retained in 24 of 33 (72.7%) of instances; and gold seed fiducials were retained in 23 of 33 (69.7%) of cases. Retention was statistically superior when comparing the VortX coil with the two-band fiducial or the gold seed (p = 0.004 and p = 0.0001). Anatomic location by lobe was analyzed, but no statistically significant differences were observed. CONCLUSIONS: The VortX coil fiducial marker showed a statistically significant increase in retention rate compared with gold seeds or two-band fiducials. This may translate to cost savings through placing fewer markers per patient as retention is high.

Optimal planning target volume margins for elective pelvic lymphatic radiotherapy in high-risk prostate cancer patients.

Purpose. High-risk prostate cancer patients often receive radiotherapy (RT) to pelvic lymphatics (PLs). The aim of this study was to determine the safety margin around clinical target volume for PL (PL-CTV) to construct planning target volume for PL (PL-PTV) and for planning elective PL irradiation. Methods and Materials. Six patients who received RT to PL as part of prostate cancer treatment were identified. To determine average daily shifts of PL, the right and left IVs were contoured at 3 predetermined slices on the daily MV scans and their daily shifts were measured at these 3 levels using a measuring tool. Results. A total of 1,932 observations were made. Daily shifts of IV were random in distribution, and the largest observed shift was 13.6 mm in lateral and 15.4 mm in AP directions. The mean lateral and AP shifts of IV were 2.1 mm (±2.2) and 3.5 mm (±2.7), respectively. The data suggest that AP and lateral margins of 8.9 mm and 6.5 mm are necessary. Conclusions. With daily alignment to the prostate, we recommend an additional PL-CTV to PL-PTV conversion margin of 9 mm (AP) and 7 mm (lateral) to account for daily displacement of PL relative to the prostate.