Faculty Bibliography

Importance/UNASSIGNED:Stereotactic body radiation therapy (SBRT) has become a standard treatment for patients with medically inoperable early-stage lung cancer. However, its effectiveness in patients medically suitable for surgery is unclear. Objective/UNASSIGNED:To evaluate whether noninvasive SBRT delivered on an outpatient basis can safely eradicate lung cancer and cure selected patients with operable lung cancer, obviating the need for surgical resection. Design, Setting, and Participants/UNASSIGNED:Single-arm phase 2 NRG Oncology Radiation Therapy Oncology Group 0618 study enrolled patients from December 2007 to May 2010 with median follow-up of 48.1 months (range, 15.4-73.7 months). The setting was a multicenter North American academic and community practice cancer center consortium. Patients had operable biopsy-proven peripheral T1 to T2, N0, M0 non-small cell tumors no more than 5 cm in diameter, forced expiratory volume in 1 second (FEV1) and diffusing capacity greater than 35% predicted, arterial oxygen tension greater than 60 mm Hg, arterial carbon dioxide tension less than 50 mm Hg, and no severe medical problems. The data analysis was performed in October 2014. Interventions/UNASSIGNED:The SBRT prescription dose was 54 Gy delivered in 3 18-Gy fractions over 1.5 to 2.0 weeks. Main Outcomes and Measures/UNASSIGNED:Primary end point was primary tumor control, with survival, adverse events, and the incidence and outcome of surgical salvage as secondary end points. Results/UNASSIGNED:Of 33 patients accrued, 26 were evaluable (23 T1 and 3 T2 tumors; 15 [58%] male; median age, 72.5 [range, 54-88] years). Median FEV1 and diffusing capacity of the lung for carbon monoxide at enrollment were 72.5% (range, 38%-136%) and 68% (range, 22%-96%) of predicted, respectively. Only 1 patient had a primary tumor recurrence. Involved lobe failure, the other component defining local failure, did not occur in any patient, so the estimated 4-year primary tumor control and local control rate were both 96% (95% CI, 83%-100%). As per protocol guidelines, the single patient with local recurrence underwent salvage lobectomy 1.2 years after SBRT, complicated by a grade 4 cardiac arrhythmia. The 4-year estimates of disease-free and overall survival were 57% (95% CI, 36%-74%) and 56% (95% CI, 35%-73%), respectively. Median overall survival was 55.2 months (95% CI, 37.7 months to not reached). Protocol-specified treatment-related grade 3, 4, and 5 adverse events were reported in 2 (8%; 95% CI, 0.1%-25%), 0, and 0 patients, respectively. Conclusions and Relevance/UNASSIGNED:As given, SBRT appears to be associated with a high rate of primary tumor control, low treatment-related morbidity, and infrequent need for surgical salvage in patients with operable early-stage lung cancer. Trial Registration/UNASSIGNED:ClinicalTrials.gov Identifier: NCT00551369.

Purpose: While Ir-192 remains the American mainstay isotope for gynecologic high dose rate (HDR) brachytherapy, Co-60 is an isotope that has been used abroad but has yet to impact the U.S. market. Co-60 has an advantage of a longer half-life than Ir-192 which may lead to long-term cost-savings; however, its higher energy requires greater shielding than does Ir-192. To assess clinicians' acceptability for this one-time shielding cost, a survey of U.S. radiation oncologists was conducted, and we previously reported their willingness-to-pay (WTP). The purpose of this study is to analyze what percentage of physicians would accept the onetime expense of additional shielding based on cost estimates from an internal shielding report and vendor price quotes for a single sample institution. Materials and Methods: A nationwide survey was undertaken to assess physician knowledge of Co-60 and their WTP a one-time expense for additional shielding, assuming a source more cost-effective than Ir-192 were available. With 440 respondents, 280 clinicians were decisionmakers who provided WTP answers, and the results were previously reported. Subsequently, we conducted shielding analysis of an HDR suite in a single sample institution to obtain the tenth-value layers (TVLs) necessary to maintain adequate shielding. Partnering with an external vendor of both lead and ultra-high density modular shielding, we calculated the costs necessary for design, shielding, shipping, and installation for both union and non-union settings, and compared these costs to decision makers' WTP. Results: For the single institution sample suite to appropriately shield for Co-60, 1.11 TVLs, 2.46 TVLs, and 1.15 TVLs would have to be added, respectively, to the walls, door, ceiling & floor to achieve the same current level of shielding. Cost estimates of adding shielding using proprietary ultra-high density modular shielding were $173.5K and $211K for non-union and union setting, respectively. Costs for lead shielding instead were $376.5K and $418K, respectively. The percentage of all 280 respondents who would accept these cost estimates for ultrahigh density modular shielding (union and non-union) or lead shielding (union and non-union) were 17.5%, 11.4%, 3.9%, and 3.2%, respectively. Of the 122 self-described decision-makers who were ABS members, the percentage of these who would accept these cost estimates for ultra-high density modular shielding (union and non-union) or lead shielding (union and non-union) were 18%, 9%, 2.4%, and 1.6%, respectively. of the 227 self-described decision-makers who were more than 5 years postresidency completion, the percentage of these who would accept these cost estimates for ultra-high density modular shielding (union and nonunion) or lead shielding (union and non-union) were 18.5%, 12.8%, 4.4%, and 3.5%, respectively. Conclusions: By comparing the cost of additional shielding for a sample institution's HDR suite with radiation oncologists' WTP, this multiinstitutional collaboration noted that less than 20% of clinicians would accept the most favorable financial situation of ultra-high density modular shielding with non-union labor. Percentage of cost-acceptability did not vary in subgroup analysis by ABS membership or years of experience. This analysis is limited by looking at the TVL requirements of only a single sample institution and cost estimates from a single vendor. However, knowing that the sole vendor of Co-60 afterloaders for gynecological cancer brachytherapy treatment has left the American market, we gain information by looking at the cost of shielding with reference to clinician WTP

Purpose: Rapid dose fall off from planning target volume (PTV) is required to spare organs at risk (OAR) that is hallmark of advanced treatment techniques (IMRT, VMAT, and SBRT). Along with conformity index (CI) and homogeneity index (HI) recently, gradient index (GI) was introduced to provide a measurable quality index for dose fall off from PTV. However, it is not clear if GI can be used in IMRT and if there are consistent differences between the two techniques. Methods: Dose volume histogram data for 700 patients equally divided between SBRT and IMRT were retrospectively analyzed. GI was calculated for each patient which is ratio of the volume of at half the prescription (PIV50%) to prescription isodose volume (PIV100%) which was calculated treatment plan and from PTV and CI. Physical distance ratio between OAR and PTV coverage was determined based on the cube root of the GI as an additional tool along with gradient measure distance (rPIV50%-rPIV100%) for the evaluation of SBRT and IMRT plans. Results: The GI varied widely between IMRT and SBRT patients due to inherent differences in techniques. The GIs are nearly constant 4.3 +/-1.1 and 12.8 +/-4.4 for SBRT and IMRT, respectively. The size of PTV is inversely related to GI with data more consistent in SBRT compared to IMRT. The gradient measure increases with PTV size in a well-defined way (0.5-1.5 cm) compared to IMRT where data is widely spread. This can be used as a surrogate for distance between PTV and OAR in IMRT and SBRT. Conclusion: Gradient index and measure are effective parameters in evaluating dose gradient that show consistent differences between treatment techniques. These tools could provide an opportunity for plan evaluation especially the distance from the PTV to OAR to optimize the dose to reduce complications

PURPOSE/OBJECTIVE:Ir-192 is the predominant source for high-dose-rate (HDR) brachytherapy in United States markets. Co-60, with longer half-life and fewer source exchanges, has piloted abroad with comparable clinical dosimetry but increased shielding requirements. We sought to identify practitioner knowledge of Co-60 and establish acceptable willingness-to-pay (WTP) thresholds for additional shielding requirements for use in future cost-benefit analysis. METHODS AND MATERIALS/METHODS:A nationwide survey of U.S. radiation oncologists was conducted from June to July 2015, assessing knowledge of HDR sources, brachytherapy unit shielding, and factors that may influence source-selection decision-making. Self-identified decision makers in radiotherapy equipment purchase and acquisition were asked their WTP on shielding should a more cost-effective source become available. RESULTS:Four hundred forty surveys were completed and included. Forty-four percent were ABS members. Twenty percent of respondents identified Co-60 as an HDR source. Respondents who identified Co-60 were significantly more likely to be ABS members, have attended a national brachytherapy conference, and be involved in brachytherapy selection. Sixty-six percent of self-identified decision makers stated that their facility would switch to a more cost-effective source than Ir-192, if available. Cost and experience were the most common reasons provided for not switching. The most common WTP value selected by respondents was <$25,000. CONCLUSIONS:A majority of respondents were unaware of Co-60 as a commercially available HDR source. This investigation was novel in directly assessing decision makers to establish WTP for shielding costs that source change to Co-60 may require. These results will be used to establish WTP threshold for future cost-benefit analysis.