Evaluation of superficial dosimetry between treatment planning system and measurement for several breast cancer treatment techniques.

PURPOSE: Dosimetric accuracy in radiation treatment of breast cancer is critical for the evaluation of cosmetic outcomes and survival. It is often considered that treatment planning systems (TPS) may not be able to provide accurate dosimetry in the buildup region. This was investigated in various treatment techniques such as tangential wedges, field-in-field (FF), electronic compensator (eComp), and intensity-modulated radiotherapy (IMRT). METHODS: Under Institutional Review Board (IRB) exemption, radiotherapy treatment plans of 111 cases were retrospectively analyzed. The distance between skin surface and 95% isodose line was measured. For measurements, Gafchromic EBT2 films were used on a humanoid unsliced phantom. Multiple layers of variable thickness of superflab bolus were placed on the breast phantom and CT scanned for planning. Treatment plans were generated using four techniques with two different grid sizes (1 × 1 and 2.5 × 2.5 mm(2)) to provide optimum dose distribution. Films were placed at different depths and exposed with the selected techniques. A calibration curve for dose versus pixel values was also generated on the same day as the phantom measurement was conducted. The DICOM RT image, dose, and plan data were imported to the in-house software. On axial plane of CT slices, curves were drawn at the position where EBT2 films were placed, and the dose profiles on the lines were acquired. The calculated and measured dose profiles were separated by check points which were marked on the films before irradiation. The segments of calculated profiles were stretched to match their resolutions to that of film dosimetry. RESULTS: On review of treatment plans, the distance between skin and 95% prescribed dose was up to 8 mm for plans of 27 patients. The film measurement revealed that the medial region of phantom surface received a mere 45%-50% of prescribed dose. For wedges, FF, and eComp techniques, region around the nipple received approximately 80% of prescribed dose, although only IMRT showed inhomogeneous dose profile. At deeper depths mainly (6-11 mm depths), film dosimetry showed good agreement with the TPS calculation. In contrast, the measured dose at a 3-mm depth was higher than TPS calculation by 15%-30% for all techniques. For the tangential and IMRT techniques, 1 × 1 mm(2) grid size showed a smaller difference than that with a 2.5 × 2.5 mm(2) grid size compared to the measurements. CONCLUSIONS: In general, TPS even with advanced algorithms do not provide accurate dosimetry in the buildup region, as verified by EBT2 film for all treatment techniques. For all cases, TPS and measured doses were in agreement from 6 mm in depth but differed at shallower depths. Grid size plays an important role in dose calculation. For accurate dosimetry small grid size should be used where differences are lower between TPS and measurements.

Primary radiation therapy for medically inoperable patients with clinical stage I and II endometrial carcinoma.

OBJECTIVE: To determine the outcomes associated with primary radiation therapy for medically inoperable, clinical stage I and II, endometrial adenocarcinoma (EAC). METHODS: A multi-institution, retrospective chart review from January 1997 to January 2009 was performed. Overall survival (OS), disease-specific survival (DSS), progression-free survival (PFS) and time to progression (TTP) were assessed using the Kaplan-Meier method. Disease-specific survival was analyzed using a competing risks approach. RESULTS: Seventy-four patients were evaluable. The median age and BMI were 65 years (range 36-92 years) and 46 kg/m(2) (range 23-111 kg/m(2)), respectively. 85.1% had severe systemic disease, most frequently cardiopulmonary risk and morbid obesity. With a mean follow-up of 31 months, 13 patients (17.6%) experienced a recurrence. The median PFS and OS were 43.5 months and 47.2 months, respectively. Overall, 35 women died, including 4 women who died of unknown cause. Of the remaining 31 women, 7 patients (9.5%) died of disease, while 24 died of other causes (32.4%). The hazard ratio comparing the risk of death due to other causes to the risk of death due to disease was 3.4 (95% CI 1.4-9.4, p=0.003). Among patients who are alive three years after diagnosis, 14% recurred and the conditional recurrence estimate did not exceed 16%. CONCLUSIONS: Primary radiation therapy for clinical stage I and II EAC is a feasible option for medically inoperable patients and provides disease control, with fewer than 16% of surviving patients experiencing recurrence.

Evaluation of response after stereotactic body radiotherapy for hepatocellular carcinoma.

BACKGROUND: Hepatocellular carcinoma (HCC) is increasing in incidence due to hepatitis C. Stereotactic body radiotherapy (SBRT) is a noninvasive, effective therapy in the management of liver malignancies. The authors evaluated radiological response in 26 patients with HCC treated with SBRT at Indiana University. METHODS: Between March 2005 and June 2008, 26 patients with HCC who were not surgical candidates were enrolled in a phase 1 to 2 trial. Eligibility criteria included solitary tumors ≤ 6 cm or up to 3 lesions with sum diameters ≤ 6 cm, and well-compensated cirrhosis. All patients had imaging before, at 1 to 3 months, and every 3 to 6 months after SBRT. RESULTS: Patients received 3 to 5 fractions of SBRT. Median SBRT dose was 42 Gray (Gy) (range: 24-48 Gy). Median follow-up was 13 months. Per Response Evaluation Criteria in Solid Tumors (RECIST), 4 patients had a complete response (CR), 15 had a partial response (PR), and 7 achieved stable disease (SD) at 12 months. One patient with SD experienced progression marginal to the treated area. The overall best response rate (CR + PR) was 73%. In comparison, by European Association for the Study of the Liver (EASL) criteria, 18 of 26 patients had ≥ 50% nonenhancement at 12 months. Thirteen of 18 demonstrated 100% nonenhancement, being > 50% in 5 patients. Kaplan-Meier 1- and 2-year survival estimates were 77% and 60%, respectively. CONCLUSIONS: SBRT is effective therapy for patients with HCC with an overall best response rate (CR + PR) of 73%. Nonenhancement on imaging, a surrogate for ablation, may be a more useful indicator than size reduction in evaluating HCC response to SBRT in the first 6 to 12 months, supporting EASL criteria.

Intra-articular chromic phosphate (³²P) in the treatment of diffuse pigmented villonodular synovitis.

PURPOSE: Pigmented villonodular synovitis (PVNS) is an uncommon proliferative lesion of synovial tissue. In diffuse PVNS, recurrence rates are high after resection alone. Adjuvant external beam radiation therapy contributes to improved local control. Limited data exist for intra-articular radioisotope therapy after surgical resection. We report institutional experience with intra-articular chromic phosphate ((32)P). METHODS AND MATERIALS: Records were reviewed from the Department of Radiation Oncology at Indiana University. Nine cases of PVNS treated with (32)P were identified (mean age=40). Seven patients were treated at time of recurrence and 2 patients were treated prophylactically. Intra-articular injections were performed by accessing the joint space, aspirating joint fluid, reinjecting 1-2 mCi of (32)P, and barbitaging to ensure good distribution in the joint space. No external beam radiation therapy was delivered. One patient was lost to followup. Mean followup of remaining patients was 20 months (range, 2-48). RESULTS: Eleven injections were performed in 9 patients. Eight had PVNS in the knee(s) and 1 patient had involvement of the hip. Two patients were treated more than once, one for a recurrence in the same joint at 13 months and another for PVNS of a contralateral joint. Three clinical recurrences (2, 13, and 28 months) were noted. Two of three recurrences were in patients who had bulky diffuse PVNS at the time of injection. Overall local control was 70%. In patients without bulky diffuse PVNS at the time of injection, local control was 88%. CONCLUSION: We report success using intra-articular injections of (32)P after synovectomy in patients with PVNS.