S. Packianathan

The Impact of Body Mass Index on Heterotopic Ossification

PURPOSE To analyze the impact of different body mass index (BMI) as a surrogate marker for heterotopic ossification (HO) in patients who underwent surgical repair (SR) for displaced acetabular fractures (DAF) followed by radiation therapy (RT). METHODS AND MATERIALS This is a single-institution retrospective study of 395 patients. All patients underwent SR for DAF followed by RT ± indomethacin. All patients received postoperative RT, 7 Gy, within 72 h. The patients were separated into four groups based on their BMI: <18.5, 18.5-24.9, 25-29.9, and >30. The end point of this study was to evaluate the efficacy of RT ± indomethacin in preventing HO in patients with different BMI. RESULTS Analysis of BMI showed an increasing incidence of HO with increasing BMI: <18.5, (0%) 0/6 patients; 18.5-24.9 (6%), 6 of 105 patients developed HO; 25-29.9 (19%), 22 of 117; >30 (31%), 51 of 167. Chi-square and multivariate logistic regression analysis showed that the correlation between odds of HO and BMI is significant, p < 0.0001. As the BMI increased, the risk of HO and Brooker Classes 3, 4 HO increased. The risk of developing HO is 1.0× (10%) more likely among those with higher BMI compared with those with lower BMI. For a one-unit increase in BMI the log odds of HO increases by 1.0, 95% CI (1.06-1.14). Chi-square test shows no significant difference among all other factors and HO (e.g., indomethacin, race, gender). CONCLUSIONS Despite similar surgical treatment and prophylactic measures (RT ± indomethacin), the risk of HO appears to significantly increase in patients with higher BMI after DAF. Higher single-fraction doses or multiple fractions and/or combination therapy with nonsteroidal inflammatory drugs may be of greater benefit to these patients.

Abstract C85: Do African-American veterans need distinct “Prostate Cancer Screening Guidelines” to overcome outcome disparities?

Background: The United States Preventive Task Force recommended against the prostate-specific antigen (PSA)-based screening for prostate cancer in 2012, a recommendation that applies to all American men. African-American men, however, have the highest incidence of prostate cancer and are more likely to be diagnosed with an advanced stage and poor prognostic-form of prostate cancer. The incidence of prostate cancer is almost 60% higher, and the mortality rate is two- to three-times greater among African Americans than that of Caucasian men1. The Veteran9s Health Administration is an unbiased, race-color blind, equal and open access, single-payor, government run health care system2. Yet, due to complex interactions of ethnicity, biology, comorbidities, environmental interactions, as well as social causes, African-American veterans are present with more aggressive disease and carry a worse outcome. Therefore African-American veterans need specific interventions to improve prostate cancer outcomes; i.e., improve survivals and quality of life. We hypothesize that by developing specific and structured prostate cancer screening recommendations, we can improve the overall prostate cancer outcomes among African-American veterans. Methods: We performed a PubMed search using the keywords: African American, African American veterans, Prostate cancer, Outcomes, Molecular markers, Prostate-specific Antigen velocity, and PSA density to derive data relevant to our hypothesis. Results: 1. Men over the age of 65 are most susceptible to prostate cancer, and the average age of veterans is 582. So, they are at a nearly optimal age for preventative prostate cancer screening. 2. The USPSTF guidelines were based on two studies, and one of these studies reported that only 4% of its participants were African American. So, it is inappropriate to use the same guidelines for African American veterans. 3. Several aspects of prostate cancer are different between African Americans and Caucasians. These differences include prostate cancer incidence and outcome, genetic differences, comorbidity, PSA levels, social barriers, and course of the disease. 4. Prior to the new USPSTF guidelines, African American veterans were just as likely as white veterans to undergo PSA testing3. 5. Among the diseases linked to comorbidity with prostate cancer, cardiovascular disease is the most frequent. Hence, the leading cause of death in both the African-American population and the African-American veteran population is cardiovascular disease.2 Conclusion: 1. Because there is no cure for metastatic prostate cancer, early diagnosis and intervention for African-American veterans will lead to saving lives; specific guidelines for prostate cancer will be very beneficial. 2. This will also decrease the costs of treating recurrent and metastatic disease and conserve the resources of the VA Health System. 3. Because the Veterans Health System is equal access, it is an optimal environment to test different prostate cancer screening guidelines for African Americans. 4. Specific draft guidelines will be presented. References: 1. Shenoy D, Packianathan S, Chen AM, Vijayakumar S. Do African-American men need separate prostate cancer screening guidelines? BMC Urology. 2016;16:19. doi:10.1186/s12894-016-0137-7. 2. Veterans Health Administration. Veterans Health Administration. http://www.va.gov/health/. Published June 21, 2016. Accessed June 23, 2016. 3. Hudson MA, Luo S, Chrusciel T, et al. Do Racial Disparities Exist in the Use of Prostate Cancer Screening and Detection Tools in Veterans? Urologic oncology. 2014;32(1):34.e9-34.18. doi:10.1016/j.urolonc.2013.01.003. Citation Format: Arthi Gadum Reddy, Divya Shenoy, Satya Packianathan, Shankar Giri, Srinivasan Vijayakumar. Do African-American veterans need distinct “Prostate Cancer Screening Guidelines” to overcome outcome disparities? [abstract]. In: Proceedings of the Ninth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2016 Sep 25-28; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2017;26(2 Suppl):Abstract nr C85.

Stereotactic Body Radiation Therapy for Stage I Non-Small Cell Lung Cancer: A Retrospective, Single-Center Study of 55 Patients.

Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) is an effective treatment for patients with early-stage non-small cell lung cancer (NSCLC) who are not surgical candidates or who refuse surgical management. In this study, we report on our clinical outcomes and toxicity in the treatment of early-stage NSCLC with SBRT. Methods and Materials: Fifty-five patients with 59 T1-2N0M0 NSCLC lesions were treated at our institution between December 2009 and August 2014. The majority of the patients [38 (69%)] were treated with 50 Gy in 5 fractions, 7 patients (13%) with 48 Gy in 4 fractions, 8 patients (14%) with 60 Gy in 3 fractions, 1 patient (2%) with 62.5 Gy in 10 fractions, and 1 patient (2%) with 54 Gy in 3 fractions. Tumor response was evaluated using RECIST 1.1, and toxicity was graded using the CTCAE (Common Terminology Criteria for Adverse Events) version 3.0. The primary endpoints of this retrospective review included rates of overall survival, disease-free and progression-free survival, local failure, regional failure, and distant failure. A secondary endpoint included radiation-related toxicities. Results: The median follow-up was 23.8 months (range 1.1-57.6). The 3-year local control, progression-free survival, and overall survival rates were 91, 55, and 71%, respectively. The median age at diagnosis was 67.9 years (range 51.4-87.1). There were a total of 54 T1N0 tumors (92%) and 5 T2N0 lesions (8%). Adenocarcinoma was the most common pathology, comprising 54% of the lesions. A total of 16 of the patients (29%) failed. Among these, 5 local (9%), 14 regional (25%), and 4 distant failures (7%) were observed. On follow-up, one patient had grade 2 and another had grade 5 pneumonitis. Three patients experienced grade 2 chest wall tenderness. Two patients had grade 1 rib fractures, one of which could not be discerned from radiation-induced toxicity versus a traumatic fall. Conclusion: The University of Mississippi Medical Center SBRT experience has shown that SBRT provides satisfactory local control and overall survival rates with minimal toxicity in early-stage NSCLC patients.

SU‐E‐T‐414: TG‐129 Implementation On BrachyvisionTM

PURPOSE To outline the steps taken to clinically implement TG-129 on Brachyvision™ Treatment Planning System and to show the dosimetric differences that can be expected from the original COMS Eye Plaque model. METHODS The original COMS-Eye Plaque protocol was based on the following simplification: point source model in infinite water medium, 1D geometric function, 1D radial dose function and no anisotropy. Recently, AAPM Task Group 129 had made two specific recommendations: 1> Upgrade to TG-43U1 line source model; and 2> Report the heterogeneity corrected dose. Upgrading to line TG-43U1 line source model was done by a creating a seed collection in Brachyvision (version 11) for each plaque size. For each seed in the collection, both end coordinates had to be entered into the software. Full line source model was followed to compute the homogeneous dose at the prescription point. This homogeneous dose was converted to heterogeneous dose using a conversion table. Dose to prescription points for five different plaque sizes, including one customized notched plaque, was calculated using the implemented TG-129 model and compared against actual COMS derived doses from previously treated patient plans. Conversion to heterogeneous doses was done based on table 2 of TG-129 report. RESULTS As expected, dose difference between COMS and TG-129 was relatively minor, ranging from -0.15% to 1.91% at the prescription point. On the other hand, heterogeneous dose, which should be used for reporting purpose only, can be up to ∼17% lower than the corresponding homogeneous dose. CONCLUSION Conversion to TG-129 can be rapidly accomplished in 1-2 weeks. The initial time investment can be quickly recouped since the TPS plans created can be modified for different patient cases. Dosimetric difference between TG-129 and the original COMS model is small, generally less than 2%.

The influence of pregnancy on heterotopic ossification post-displaced acetabular fractures surgical repair

Pregnancy is associated with maternal bone mineral density loss and modulation of calcium metabolism. We hypothesized that pregnancy may decrease the risk of heterotopic ossification (HO) after trauma. This is a single‐institution, University of Mississippi Medical Center, retrospective study investigating the effect of pregnancy on the incidence HO after surgical repair (SR) of displaced acetabular fractures. Between January 1998 and 2010, 257 non‐pregnant women (Group A) and 16 pregnant women (Group B) were identified. All the non‐pregnant women received radiation therapy (RT) ± indomethacin. None of the pregnant women in group B received any prophylaxis. After a median follow‐up of 6.6 years the incidence of HO in all patients was 27% (75/273). In Group A, non‐pregnant, women who received RT ± indomethacin, 29% developed HO; HO risk was 0.4. In Group B, 16 pregnant patients, only one developed HO (6%); HO risk was 0.06. Thus, the risk of HO appears to be nearly six‐fold higher in non‐pregnant women despite prophylactic RT ± indomethacin. Our data suggest that pregnancy may be associated with a reduced risk of HO after SR of displaced acetabular fractures. Further analysis with a larger pregnant patient sample is necessary to confirm this finding.

Computerized tomography-based radiotherapy improves heterotopic ossification outcomes☆

PURPOSE To report the impact of computerized tomography (CT) based radiotherapy (RT) on heterotopic ossification (HO) outcomes. METHODS This is a single institution, retrospective study of 532 patients who were treated for traumatic acetabular fractures (TAF). All patients underwent open-reduction internal-fixation (ORIF) of the TAF followed by RT for HO prophylaxis. Postoperative RT was delivered within 72h, in a single fraction of 7Gy. The patients were divided into 2 groups based on RT planning: CT (A) vs. clinical setup (B). RESULTS At a median follow up of 8years the incidence of HO was 21.6%. Multivariate regression analysis revealed that group (A) vs. (B) had HO incidence of 6.6% vs. 24.6% (p<0.001), respectively. Furthermore, HO Brooker grade ≥3 was observed in 2.2% vs. 10.8% (p=0.007) in group (A) vs. (B), respectively. Thus, the odds of developing HO and Brooker grades ≥3 were 4.7 and 4.5 times higher, respectively, in patients who underwent clinical setup. CONCLUSION Our data suggest that using CT based RT allowed more accurate delineation of the tissues and better clinical outcomes. Although CT-based RT is associated with additional cost the efficacy of CT-based RT reduces the risk of HO, thereby decreasing the need for additional surgical interventions.

SU‐E‐T‐588: 3D Image‐Based Customized Radiation Treatment Planning for Syed Interstitial HDR Brachytherapy for Patients with Parametrial Spread of Cervix Carcinoma

Purpose: To investigate the clinical parameters involved in Syed interstitial HDR brachytherapy for patients with cervical carcinoma. Method and Materials:Our institution uses 3‐D image based treatment planning for all Syed Interstitial implants for advanced cervical carcinoma patients with known parametrical spread. Between 8/2009 and 10/2010, eight such patients were treated at our facility with Syed Interstitial HDR brachytherapy. The high risk CTV (HRCTV), intermediate risk CTV (IRCTV), and organs at risk (OAR: rectum, bladder, sigmoid, and small bowel) were contoured on the planning CT scan. All patients received 7 fractions of 4.2 Gy each in 4 days given bid prescribed to the HRCTV. Planning objectives included keeping doses to the OARs below 80% of prescription dose, to have D90 for the HRCTV greater than 90% of the prescription dose, and for V150 and V200 to be less than 50% and 20%, respectively. OARs were evaluated using doses to 2cc (D2cc). CT scan was performed each day. Results: Between 18 and 21 needles were implanted but only 14 needles were used. Because of needle movements, an average of 2.4 plans were required. The average dose to 2cc (D2cc) of bladder was 63±5% of the prescription dose (29.4 Gy). This value for the rectum was 64%±3.4% . The sigmoid and the small bowel D2cc values were generally all less than 40% of the prescription dose. The D90 for the HRCTV was on average 31.7 Gy, whereas the D90 for the IRCTV was on average 20 Gy. V150 and V200 were on average, 51% and 28%, respectively. Conclusion: It is recommended that CT/MRI images be used for Syed interstitial HDR planning to adequately define the HRCTV, IRCTV, and OAR. The implanted needles always move during patient transfers to and from the HDR suite; thus, CT scans should be repeated daily.