R Ramer

Purpose: To utilize Data Envelopment Analysis (DEA) as a novel method of comparison between treatment options for prostate cancer patients. Method and Materials: There are many options available for the treatment of prostate cancer. For example, a prostate patient could be treated using low dose rate (LDR) brachytherapy permanent implants, external beam radiotherapy (EBRT), or surgery, among others. Data Envelopment Analysis (DEA) is a tool designed to compare the relative performance of peer entities. It has the potential to be an invaluable tool in radiation therapy in the comparison between various treatment options. DEA handles multiple objectives, including those with different units. It provides a single score for ranking in terms of efficiency, by calculating a weighted sum of the inputs divided by a weighted sum of the outputs. These ranks are normalized so that an efficiency score of 1.0 is the most efficient. These inputs and outputs can be anything; in terms of radiotherapy, one option is for the inputs to be patient cases and the outputs to be the objectives considered clinically, such as the five year biochemical failure free survival rate and the impotence rate. Data was taken from the literature, and analyzed using in-house MATLAB 7.5.0. For homogeneity, only favorable (Gleason score < 6, a PSA of < 10 μg/L, and stage T1c or T2) patients were considered. Results: Implant I-125 seeds had an efficiency score of E = 1.000, indicating it was most efficient with respect to the objectives considered. This was followed by surgery and EBRT, with efficiencies of 0.975 and 0.914 respectively. Conclusion: Based on the data included in the analysis, LDR brachytherapy permanent implant I-125 seeds gave the best outcome. Both prostatectomy surgery and external beam radiotherapy showed inefficient scores of less than one.

Purpose: To determine what effect allowing the patient to wear various articles of clothing might have on the dose delivered to the patient during 6 MeV high dose rate total skin electron therapy. Method and Materials: Total skin electron (TSE) radiotherapy delivers a dose of radiation to the total body using electrons to treat the shallow region affected by mycosis fungoides, a cutaneous T‐cell lymphoma, while sparing deeper tissues. A Rando phantom was placed in the treatment position. Thermoluminescent dosimeters (TLDs) were placed at strategic locations on the phantom. The phantom was dressed in various outfits and surface dose measurements were made. These outfits included (1) fully dressed: t‐shirt, sweatpants, underwear and bra, (2) underwear and bra, (3) bra with underwire, (4) hospital gown, and (5) no clothing. Results: When compared with the measurements taken with no clothing, the fully dressed phantom results in a maximum difference of 22.0 cGy at the sternum, and a minimum difference of 0.1 cGy at the center back. Dressed in underwear and bra, the maximum difference from the unclothed measurements was 13.9 cGy at the underwear tag on the waistband and the minimum was 2.7 cGy at the sternum. The underwire bra resulted in a decreased dose of 12.3 cGy. Finally the hospital gown showed only 1 cGy of maximum difference at the stomach center, a difference of 0.2 cGy at the center back, and no difference in measurement under the tied knot. Conclusion: The hospital gown, made of thin cotton, had a minimal impact to the surface dose received. A patient could wear a similar garment during treatment without significant therapeutical impact. All other outfits tested resulted in a greater difference in skin dose, which may make such outfits undesirable for wear during treatment.

Purpose: To evaluate and compare the expected effectiveness of the planned and delivered dose distributions in prostate cancer radiotherapy. The average setup uncertainties were determined by using the on‐board megavoltage computed tomography (MVCT) capabilities of the tomotherapy HiArt unit. Method and Materials: Co‐registrations between daily MVCT and planning CT were used. Before the delivery of each treatment an MVCT image was acquired. The therapists registered the MVCT image with the planning kilovoltage computed tomography (kVCT) images. The registration criteria were based on bony anatomy and contoured regions of interest. For a typical prostate cancer patient the dose distributions of the Helical Tomotherapy plan and that of the average shifted delivery registration were used. The dose distributions were compared based on dosimetric criteria and the biologically effective uniform dose (BEUD) together with the complication‐free tumor control probability ( P + ). Results: The average shifts that were observed are 10.7 mm for the vertical, 4.0 mm for the longitudinal and 0.5 mm for the lateral directions, respectively. At the optimum dose levels of the planned and delivered dose distributions, the P + values are 84.7% and 84.0%, respectively. The total control probabilities, P B are 93.0% and 92.9%, whereas the total complication probabilities, P I are 8.3% and 8.9%. More specifically, the response probabilities of the different tissues are 95.6% and 95.5% for the GTV, 97.4% and 97.3% for the seminal vesicles, 0.8% and 0.7% for bladder and 7.6% and 8.3% for rectum. Conclusion: It is shown that the intra‐fraction movement of tumors can be reduced by using the MVCT co‐registration. This appears to be a powerful tool, which can result in improved sparing of critical structures, while delivering high doses to the target. The use of P + — BEUD diagrams to compare similar treatment plans may show that in radiobiological terms they may be quite different.