Tumor volume and uterine body invasion assessed by MRI for prediction of outcome in cervical carcinoma treated with concurrent chemotherapy and radiotherapy.

OBJECTIVE: The aim of this study was to evaluate the prognostic significance of primary tumor volume and uterine body invasion assessed by pre-treatment MRI for uterine cervical cancer patient treated with concurrent chemotherapy and radiotherapy. METHODS: A retrospective analysis of 106 patients with IB-IIIB cervical carcinoma was performed. Potential prognostic factors were stage, clinical tumor diameter, histology, age, pelvic lymph node, vaginal extension, parametrial invasion, tumor volume and uterine body invasion status. Multivariate analyses were performed to identify the prognostic factor for overall survival (OS) and disease-free survival (DFS). RESULTS: The 5-year OS, DFS rate were 59.7 and 56.6%. Using multivariate analyses, a large tumor volume (>/=30 ml; P = 0.012) and uterine body invasion (P = 0.020) and positive pelvic lymph node (LN) enlargement (P = 0.040) showed a significantly unfavorable influence on OS. Using these three factors, patients were divided into four subgroups: the OS rates of patients with risk 0 (volume <30 ml, no uterine body invasion, and negative LN), risk 1 (one of these three factors), risk 2 (two of these three factors) and risk 3 (volume >/=30 ml, uterine body invasion, and positive LN) were 96.3, 77.5, 53.0 and 14.8%, respectively (P < 0.0001). CONCLUSIONS: Tumor volume and uterine body invasion determined by MRI were significant prognostic factors for patients with cervical carcinoma. Pelvic lymph node enlargement diagnosed by CT also proved to be a significant prognostic factor in OS. Using these three parameters, we devised a practical and effective model to predict OS.

Rectum dose analysis employing a multi-purpose brachytherapy phantom.

PURPOSE: It is difficult to reproduce a brachytherapy measurement because of changes in the rectal shape during inter-fraction. We constructed a multi-purpose brachytherapy phantom (MPBP) and reproduced the same conditions found in actual therapy. We further attempted to apply the measured optimal dose to reduce rectal complications. METHODS: A measured dose was administered at rectal reference point R1 using a diode detector in four patients who used a tandem and ovoid in brachytherapy for carcinoma of the cervix. A total number of 20 rectal dose measurements were performed five times per patient. In addition, discrepancies in the set-up of the diode detector were analyzed with each repetitive measurement. After reproducing the same conditions as found in actual therapy using a multi-function applicator (MFA) in the multi-purpose brachytherapy phantom constructed for this study, the dose was measured at reference points in the rectum using a thermoluminescence dosimeter (TLD). RESULTS: According to the discrepancies measured in the set-up using a diode detector, Patient 1 showed a maximum value of 11.25 +/- 0.95 mm in the Y direction, Patients 2 and 3 exhibited 9.90 +/- 2.40 mm and 20.85 +/- 4.50 mm in the Z direction, respectively. Patient 4 showed 19.15 +/- 3.33 mm in the Z direction. In addition, values of the mean dose according to the position of the diode detector were recorded as 122.82 +/- 7.96-323.78 +/- 11.16 cGy. In the measured results for TLD in an MPBP, relative error for Patients 1 and 4 at the rectal reference point R2 were a maximum of 8.6 and 7.7%, respectively. For Patients 2 and 3 they were 1.7 and 1.2%, respectively. Furthermore, the dose measured at point R1 and R2 exhibited values approximately 1.7-8.6% higher than the dose calculated in advance, excluding point R1 in Patient 2. The discrepancies in the set-up owing to repetitive measurements and alterations in dosage according to these changes were not analyzed. It was evident that the relative error between the calculated and measured value was within 15%, which was allowable according to the recommendations by the American Association of Physicists in Medicine (AAPM). CONCLUSIONS: The multi-purpose brachytherapy phantom constructed for this study successfully reproduced an optimal dose measured under the same conditions found in actual therapy in which the dose was precisely analyzed at a rectal reference point. In addition, these results were considered reliable and applicable for dose optimization before applying therapy using the measured data from the phantom in order to reduce rectal complications.

Determination of N(pp)(gas) and N(pp)(D) for a plane-parallel chamber.

The purpose of this work is to investigate the consistency of determining N(pp)(gas) and N(pp)(D) by using three independent calibration methods from the AAPM TG 39 and IAEA TRS 381 protocols: 1) calibration with a high-energy electron beam in a phantom; 2) in-phantom calibration in a (60)Co beam; and 3) in-air calibration in a (60)Co beam. The plane-parallel chamber considered was the PTW-Markus and the comparisons were made against a calibrated PTW cylindrical Farmer-type chamber 30001. The phantom material used for the electron beam and (60)Co in-phantom methods was a solid water phantom (RW3). For the electron beam method, the nominal energies were 18 and 21 MeV. An acrylic buildup of 0.5 g/cm(2) thickness was used for the (60)Co in-air method. For each method, N(pp)(gas) and N(pp)(D) were obtained for the plane-parallel chamber as proposed by the AAPM TG 39 and IAEA TRS 381 protocols. The absorbed doses were measured along the central axis at a distance of 100 cm (SSD=100 cm) with 10 x 10 cm(2) field size at the depth of the maximum for each electron beam. The values of N(pp)(gas) by the three independent calibration methods agreed to within +/-0.6%. This meant that any of the methods would give a fairly good value. Similar results were obtained for N(pp)(D). In comparing the results for the electron beam method at energies of 18 and 21 MeV, the latter gave better agreement. The ratios of N(pp)(gas) and N(pp)(D) for the three methods were in agreement within 0.7%. The results for the absorbed dose intercomparison in the AAPM TG 39 and IAEA TRS 381 protocols showed that they agreed to within +/-0.7% which meant that any of the calibration methods and two different protocols would give an accurate result.