R. Ash

Analysis of a Novel Protocol of Combined Induction Chemotherapy and Concurrent Chemoradiation in Unresected Non-Small- Cell Lung Cancer: A Ten-Year Experience With Vinblastine, Cisplatin, and Radiation Therapy

BACKGROUND The London Regional Cancer Program (LRCP) uses a unique schedule of induction plus concurrent chemoradiation, termed VCRT (vinblastine, cisplatin, and radiation therapy), for the treatment of a subset of unresectable stage IIIA and IIIB non-small-cell lung cancer (NSCLC). This analysis was conducted to better understand the outcomes in VCRT-treated patients. PATIENTS AND METHODS We report a retrospective analysis of a large cohort of patients who underwent VCRT at the LRCP over a 10-year period, from 1996 to 2006. The analysis focused on OS, toxicities, and the outcomes from completion surgery in a small subset of patients. RESULTS A total of 294 patients were included and 5-year OS, determined using Kaplan-Meier methodology, was 19.8% with a MST of 18.2 months. Reported grade 3-4 toxicities included neutropenia (39%), anemia (10%), pneumonitis (1%), and esophagitis (3%). Significant differences in survival between groups of patients were demonstrated with log-rank tests for completion surgery, use of radiation therapy, and cisplatin dose. Similarly, Univariate Cox regression showed that completion surgery, use of radiation therapy, cisplatin dose, and vinblastine dose were associated with increased survival. CONCLUSION This retrospective analysis of a large cohort of patients reveals an OS for VCRT comparable to that reported in the literature for other current combined chemoradiation protocols. The success of this protocol seems to be dose dependent and the outcomes in those who underwent completion surgery suggests that pathologic complete remission is possible for IIIA and IIIB NSCLC.

Impact of urethrography on geometric uncertainty in prostate cancer radiotherapy

Results: The average systematic displacement (and standard deviation) of the prostate on treatment as measured from the position at the time of simulation/urethrography was 0.02cm (0.24), 0.00cm (0.39), and 0.32cm (0.38) in the x (left:, right:), y(anterior:, posterior:) and z(cephalad:, caudad:) directions, respectively (Figure). The average threedimensional vector of 0.32cm was in an anterior-cephalad direction; consistent with the urethrography induced prostate motion noted by Malone (1). Using our measurements and the Monte Carlo geometric error equations from van Herk (2), a required planning target margin (PTV) of 0.87cm was needed in order to give 90% of patients an equivalent uniform dose (EUD) of at least 98% of the prescription dose. For coverage of the prostate for 95% of the treatment fractions, PTV margins of 1.0cm and 0.6cm were necessary with and without the inclusion of the systematic error attributed to the urethrogram. Conclusions: Using a combination of implanted markers and weekly CT scans we detected a systematic shift of the prostate apex and centre of mass superiorly/cephalad at the time of simulation/urethrography compared to during treatment. While our current 1cm PTV margins are sufficient to compensate for geometric uncertainties including this shift, reduced margins in the context of dose or fraction escalation may require methods other than urethrography to help localize the apex of the prostate.

TH‐C‐ValB‐01: Prostate Contouring Uncertainty in Mega‐Voltage Computed Tomography (MVCT) Images Acquired with a Helical Tomotherapy Unit During Image‐Guided Radiation Therapy (IGRT)

Purpose: To evaluate the image guidance capabilities of helical tomotherapy‐based MVCT, this work compares the inter‐ and intra‐observer contouring uncertainty in KVCT used for radiotherapy planning with MVCT acquired with a tomotherapy unit. Methods and Materials: Five prostate cancer patients who underwent tomotherapy treatment (with daily MVCT) at our institution were selected. One planning KVCT and one randomly selected MVCT from each patient were used. Slice spacings for KVCT and MVCT were 3 mm and 6 mm, respectively. Retrograde urethrography was performed on the KVCT studies only. For inter‐observer study, seven observers contoured the prostate on the 10 CT studies. For intra‐observer study, the same seven observers repeat‐contoured one patients KVCT and MVCT studies. Quantitative analysis of contour variations was performed using volumes and radial distances. F‐test was performed to detect statistically significant differences between KVCT and MVCT. Results: The inter‐ and intra‐observer contouring variability was larger in MVCT than KVCT. The largest variability was mainly found in the prostate apex and base regions. Up to 1 cm (SD) was found in MVCT. In the prostate apex region, interestingly, large but similar variability between KVCT and MVCT was observed. This suggest that the use of urethrography during KVCT simulation was not very helpful. For F‐test, generally, the regions with significant differences were patient‐dependent and uniformly distributed in all directions. In terms of prostate volume, observers consistenly contoured larger prostate in MVCT (by 10 %). This reflects the poorer soft‐tissue contrast in MVCT than KVCT since observers tend to over‐estimate or over‐draw target volumes under less visible conditions. Conclusions: Based on our data, the application of MVCT for estimating daily organ motion and deformation during image‐guidedradiotherapy(IGRT) is somewhat discouraging. Optimization of slice thickness and dose utilization may result in better imaging performance for prostate delineation and adaptive tomotherapy.