Functional liver image guided hepatic therapy (FLIGHT) with hepatobiliary iminodiacetic acid (HIDA) scans.

PURPOSE: Hepatobiliary iminodiacetic acid (HIDA) scans provide global and regional assessments of liver function that can serve as a road map for functional avoidance in stereotactic body radiation therapy (SBRT) planning. Functional liver image guided hepatic therapy (FLIGHT), an innovative planning technique, is described and compared with standard planning using functional dose-volume histograms. Thresholds predicting for decompensation during follow up are evaluated. METHODS AND MATERIALS: We studied 17 patients who underwent HIDA scans before SBRT. All SBRT cases were replanned using FLIGHT. The following dosimetric endpoints were compared for FLIGHT versus standard SBRT planning: functional residual capacity <15 Gy (FRC15HIDA), mean liver dose (MLD), equivalent uniform dose (EUD), and functional EUD (FEUD). Receiver operating characteristics curves were used to evaluate whether baseline HIDA values, standard cirrhosis scoring, and/or dosimetric data predicted clinical decompensation. RESULTS: Compared with standard planning, FLIGHT significantly improved FRC15HIDA (mean improvement: 5.3%) as well as MLD, EUD, and FEUD (P < .05). Considerable interindividual variations in the extent of benefit were noted. Decompensation during follow-up was associated with baseline global HIDA <2.915%/min/m2, FRC15HIDA <2.11%/min/m2, and MELD ≥11 (P < .05). CONCLUSIONS: FLIGHT with HIDA-based parameters may complement blood chemistry-based assessments of liver function and facilitate individualized, adaptive liver SBRT planning.

Effects of Proton Center Closure on Pediatric Case Volume and Resident Education at an Academic Cancer Center.

PURPOSE: To analyze effects of closure of an academic proton treatment center (PTC) on pediatric case volume, distribution, and resident education. METHODS AND MATERIALS: This was a review of 412 consecutive pediatric (age ≤18 years) cases treated at a single institution from 2012 to 2016. Residents' Accreditation Council for Graduate Medical Education case logs for the same years were also analyzed. Characteristics of the patient population and resident case volumes before and after closure of the PTC are reported. RESULTS: Overall pediatric new starts declined by approximately 50%, from 35 to 70 per 6 months in 2012 to 2014 to 22 to 30 per 6 months in 2015 to 2016. Central nervous system (CNS) case volume declined sharply, from 121 patients treated in 2012 to 2015 to 18 patients in 2015 to 2016. In 2012 to 2014 our institution treated 36, 24, and 17 patients for medulloblastoma/intracranial primitive neuroectodermal tumor, ependymoma, and low-grade glioma, respectively, compared with 0, 1, and 1 patient(s) in 2015 to 2016. Forty-nine patients were treated with craniospinal radiation (CSI) from 2012 to 2014, whereas only 2 patients underwent CSI between 2015 and 2016. Hematologic malignancy patient volume and use of total body irradiation remained relatively stable. Patients treated when the PTC was open were significantly younger (9.1 vs 10.7 years, P=.010) and their radiation courses were longer (35.4 vs 20.9 days, P<.0001) than those treated after its closure. Resident case logs showed only a small decline in total pediatric cases, because the percentage of pediatric cases covered by residents increased after PTC closure; however, residents logged fewer CNS cases after PTC closure versus before. CONCLUSIONS: Overall pediatric case volume decreased after PTC closure, as did the number of patients treated for potentially curable CNS tumors. Our findings raise important questions regarding resident training in pediatric radiation oncology as these cases become increasingly concentrated at specialized centers.

Tolerance of Superficial Dose to Setup Error With Tomotherapy: Is a Skin Flash Tool Required?

BACKGROUND: In cancers of the head and neck, gross tumor or areas at risk of microscopic disease often lie close to the skin, while the skin itself may not be at risk. With intensity-modulated radiotherapy, setup errors can lead to underdosage of superficial structures because the collimator will not by default open beyond the skin surface to apply coverage in the air overlying the skin. Thus, small setup errors can move superficial structures out of field for some beams. Some planning systems allow for manually extrapolating fluence for beams tangential to superficial targets. It is unclear whether this problem is significant with tomotherapy. METHODS: A head and neck phantom was utilized. A 3-mm bolus was used to represent the skin and allow placement of dosimeters at 3 mm depth. Thermoluminescent dosimeters were placed at reproducible points on the skin surface and at 3 mm depth. The phantom was irradiated, with the target volume deep to the thermoluminescent dosimeters receiving a dose of 5 Gy. This process was repeated with the phantom displaced 2.5 mm and again with a displacement of 5 mm. These displacements simulated setup errors that in clinical practice would correspond to bending or twisting of the neck that could not be corrected with rotations or translations. RESULTS: When the phantom was displaced 2.5 mm, the dose measured at 3 mm depth was 99.2% (95.9%-102.5%) of the control. With a 5-mm displacement, the dose at 3 mm only dropped to 91.1% (88.8%-93.4%) of the control. Dose measured at skin surface decreased to a greater degree with such setup error. CONCLUSIONS: Dose at superficial depths degraded only slightly with 2.5-mm and even 5-mm displacements. With the tomotherapy system, superficial dose appears to be robust to clinically relevant setup errors. However, if the skin is at risk, bolus should be used to ensure adequate coverage.