Effect of Body Mass Factors on Setup Displacement in Gynecologic Tumors and Subsequent Effect on PTV Margins.

Purpose: This study aimed to analyze the effect of body mass factors (BMFs) on setup errors in gynecologic tumors, and whether the planned tumor volumes (PTVs) are adequate for obese patients. Methods: This was a retrospective study of 46 consecutive female patients with gynecologic tumors who were treated with volumetric modulated arc therapy. Setup accuracy was verified using daily cone beam computed tomography. Accuracy was determined for each fraction by testing 2 different PTVs (cutoff I = ≤0.7 cm; cutoff II = ≤1.0 cm). A pooled analysis was conducted to test the association between accuracy levels (within vs beyond PTV) and the mean and variance of body mass index (BMI), umbilical (UC), and hip circumference (HC). A receiver operating characteristics curve analysis was carried out to test the sensitivity of BMI, UC, and HC in predicting inaccurate setup. Results: A significant association between BMFs and level of accuracy was observed in the lateral and vertical directions, but not in the longitudinal direction. In the lateral direction, inaccurate setups were associated with a greater BMI (mean difference: ∼3.50 kg/m2; P = .001), UC (∼10 cm), and HC (∼8 cm) compared with accurate setups (P < .001). With respect to the vertical direction, inaccurate setups (>0.7 cm margin [cutoff I]) were associated with a greater BMI (mean difference = 7.4 kg/m2; P = .001), UC (5.3 cm; P < .001), and HC (16.0 cm; P < .001) with reference to accurate setups. The receiver operating characteristics curve analysis showed that a BMI >31.4 kg/m2 was predictive for inaccurate setup in the vertical direction with 90.0% sensitivity with respect to cutoff I. Furthermore, a BMI >30.3 kg/m2 was predictive for inaccurate setup in the lateral direction with 92.5% sensitivity with respect to cutoff II. Conclusions: The accuracy of radiation therapy setups for gynecologic tumors is highly sensitive to patients' BMI, notably in the lateral and vertical directions. We suggest that daily cone beam computed tomography should be applied on patients with a BMI >30.3 kg/m2, using customized protocols that are lower in dose and comparable in image quality.

Site-Specific Education Using Digital Media to Improve Patient Understanding of the Radiotherapy Trajectory: An Interventional Study.

PURPOSE: The study assessed the effectiveness of a site-specific video educational material in improving patient understanding and confidence regarding radiation therapy trajectory. METHODS AND MATERIALS: A quasi experimental longitudinal pretest posttest study was conducted at a referral radiation therapy center from May 2020 to September 2020. It included 52 adult patients admitted for a first course radical radiation therapy. One generic and 6 site-specific (breast, pelvis, head and neck, brain, chest and abdomen, and bladder) animated cartoon videos were developed in house to provide concise overview of the overall patient's trajectory in radiation therapy, with full visual description of the procedures and specific preparation measures. A 14-item questionnaire was designed to assess pre- and postintervention levels of understanding and confidence of patients, with calculation of and an understanding and confidence score (UCS), range 0-14. RESULTS: The mean (standard deviation) UCS in pre- and postintervention was 9.36 (2.48) and 11.92 (1.34) out of 14, respectively, indicating a mean increase of 2.57 subsequent to the intervention (P < .001). The effect size was large with a Cohen's d = 1.01. Of the 14 dimensions explored, 8 were observed to have remarkable improvement, notably understanding the purpose of the tattoo mark, reason of daily or weekly imaging, and what to expect with radiation therapy. Participants with poor reading ability had greater increase in UCS (ΔUCS = 4.25 vs ≤2.33) and in 5 out of 8 dimensions with remarkable improvement. CONCLUSIONS: The use of digital educational material in radiation oncology meets the urgent need for providing patients with concise and site-specific information, while sparing extra hospital visits to meet education coordinators during the COVID-19 crisis. Additional studies are warranted to assess both the clinical and long-term effectiveness of the educational material, using a longitudinal controlled design.

Comparing Accuracy of Thermoplastic Mask versus Commercial Bra for the Immobilization of Pendulous Breast During Radiation Therapy Treatment: A Retrospective Cohort Study.

PURPOSE: This study aimed to compare thermoplastic mask with bra in terms of setup reproducibility and immobilization of pendulous breasts during radiation therapy (RT). METHODS AND MATERIALS: Forty-two female patients with breast cancer treated with either intensity modulated RT or 3-dimensional conformal RT were retrospectively reviewed. Of these, 21 benefited from thermoplastic mask immobilization and 21 used a bra. Setup accuracy was evaluated using consecutive cone beam computed tomography/electronic portal imaging device sessions over the first 3 days before treatment (systematic setting), followed by weekly cone beam computed tomography/electronic portal imaging device (random settings), and compared with the reference image to calculate the corresponding translational shift (setup error) in the 3 planes. Average absolute shift values in both systematic and random settings were compared between the 2 groups. Accuracy was analyzed by comparing the percentage of pooled settings within ±0.05 and ±0.1 cm of the reference image. RESULTS: Compared with a bra, use of the mask was associated with a smaller longitudinal shift in systematic settings (difference in mean: 0.27 cm; P = .027; Mann-Whitney U test) and a lesser lateral shift in random setting (difference in mean: 0.19 cm; P = .005; Mann-Whitney U test). In the pooled systematic settings, the mask performed relatively better than the bra in the lateral and longitudinal planes, with no statistical significance. In pooled random settings, mask showed greater accuracy than bra in the lateral plane with 86.0% versus 58.9% accuracy at ±0.5 cm (P < .001) and 48.8% versus 21.7% accuracy at ±0.1 cm (P < .001), respectively. There was no significant difference in the incidence of radiodermatitis between the 2 groups. However, a hypofractionation regimen was associated with a lower incidence of radiodermatitis, and the severity of skin reactions was positively correlated with treatment dose (unstandardized regression coefficient: B = .001; correlation coefficient: r = .571; P < .001). CONCLUSIONS: Masks provide superior reproducibility compared with commercially available bras.