Katsumasa Nakamura

Variation of Clinical Target Volume Definition among Japanese Radiation Oncologists in External Beam Radiotherapy for Prostate Cancer

BACKGROUND We investigated the interobserver variation in the prostate target volume and the trend toward the use of diagnostic computed tomography (CT) or magnetic resonance (MR) images for treatment planning. METHODS Twenty-five radiation oncologists were asked to draw the external contour of the prostate on CT images (0.3 cm spacing) of a patient with localized prostate cancer. They also answered a questionnaire regarding the use of diagnostic CT or MR images for the contouring. RESULTS Of the 25 physicians, 28% rarely or never referred to the diagnostic CT images. In contrast, the physicians tended to refer to the MR images more frequently. Approximately 50% of the physicians believed in the usefulness of contrast-enhanced images for the delineation of the prostate. As for the variation of the prostate contouring, the median craniocaudal prostate length was 36 mm (range, 21-54 mm), and the median prostate volume was 43.5 cm(3) (range, 23.8-98.3 cm(3)). The interobserver variability was not significant in the duration as a radiation oncologist, the board certification status as radiation oncologists, and the number of treatment plans developed for prostate cancer during the last 1 year. CONCLUSION A wide variety of the definitions of the prostate was found among Japanese radiation oncologists.

External Beam Radiotherapy for Clinically Localized Hormone-Refractory Prostate Cancer: Clinical Significance of Nadir Prostate-Specific Antigen Value Within 12 Months

PURPOSE To analyze retrospectively the results of external beam radiotherapy for clinically localized hormone-refractory prostate cancer and investigate the clinical significance of nadir prostate-specific antigen (PSA) value within 12 months (nPSA12) as an early estimate of clinical outcomes after radiotherapy. METHODS AND MATERIALS Eighty-four patients with localized hormone-refractory prostate cancer treated with external beam radiotherapy were retrospectively reviewed. The total radiation doses ranged from 30 to 76 Gy (median, 66 Gy), and the median follow-up period for all 84 patients was 26.9 months (range, 2.7-77.3 months). RESULTS The 3-year actuarial overall survival, progression-free survival (PFS), and local control rates in all 84 patients after radiotherapy were 67%, 61%, and 93%, respectively. Although distant metastases and/or regional lymph node metastases developed in 34 patients (40%) after radiotherapy, local progression was observed in only 5 patients (6%). Of all 84 patients, the median nPSA12 in patients with clinical failure and in patients without clinical failure was 3.1 ng/mL and 0.5 ng/mL, respectively. When dividing patients according to low (<0.5 ng/mL) and high (>or=0.5 ng/mL) nPSA12 levels, the 3-year PFS rate in patients with low nPSA12 and in those with high nPSA12 was 96% and 44%, respectively (p < 0.0001). In univariate analysis, nPSA12 and pretreatment PSA value had a significant impact on PFS, and in multivariate analysis nPSA12 alone was an independent prognostic factor for PFS after radiotherapy. CONCLUSIONS External beam radiotherapy had an excellent local control rate for clinically localized hormone-refractory prostate cancer, and nPSA12 was predictive of clinical outcomes after radiotherapy.

Radical external beam radiotherapy for prostate cancer in Japan: differences in the patterns of care among Japan, Germany, and the United States

Optimal management of radiotherapy for prostate cancer patients has become a major concern for physicians in Japan. We reviewed published reports identifying the differences in the patterns of care for prostate cancer patients treated with radical external beam radiotherapy in Japan, Germany, and the United States. The reports indicate that Japanese patients have more advanced primary disease than patients in Germany or the United States. These patient characteristics for Japan and the United States have been almost unchanged for several years. Regarding radiotherapy, conformal radiotherapy was less frequently administered to patients in Japan than patients in Germany or the United States, and the total radiation dose was higher in Germany and the United States than in Japan. Concerning changes in trends in the patterns of radiotherapy, the percentage of patients treated with higher dose levels in the United States has rapidly increased, whereas the percentage of patients receiving these dose levels in Japan has remained extremely low. On the other hand, hormonal therapy has been used more frequently in Japan than in Germany or the United States. These findings indicate that patient characteristics and patterns of care for prostate cancer in Japan are considerably different from those in Germany or the United States.

Radiotherapy for patients with localized hormone‐refractory prostate cancer: results of the Patterns of Care Study in Japan

To evaluate the clinical results of radiotherapy (RT) for patients with regionally localized hormone‐refractory prostate carcinoma (HRPC).

External-Beam Radiotherapy for Localized or Locally Advanced Prostate Cancer in Japan: A Multi-Institutional Outcome Analysis

BACKGROUND The outcomes of patients with localized or locally advanced prostate cancer treated with external-beam radiotherapy are not well known in Japan. METHODS Thirty-four institutions combined data on 679 patients with localized or locally advanced prostate cancer treated with a total dose >/=60 Gy between 1995 and 2002. RESULTS With a median follow-up of 46 months, the 5-year overall, clinical progression-free, and biochemical relapse-free survival rate were 93.0, 95.3 and 71.9% for all patients, respectively. The 5-year progression-free, and biochemical relapse-free survival rates according to the risk group were 100%, 90.8% in the low-risk group, 98.3%, 75.7% in the intermediate-risk group and 93.6%, 67.6% in the high-risk group, respectively. The multivariate analysis for biochemical relapse-free survival revealed that prostate-specific antigen (relative risk, 1.002; 95% CI, 1.001-1.003; P = 0.0041), Gleason score (relative risk, 1.166; 95% CI, 1.046-1.302; P = 0.0055), T classification (relative risk, 2.897; 95% CI, 1.999-4.230; P = 0.0000), pelvic irradiation (relative risk, 2.042; 95% CI, 1.328-3.273; P = 0.0008), and androgen abletion (relative risk, 0.321; 95% CI, 0.240-0.427; P = 0.0000) were significant prognostic factors. Only 1.1% of patients experienced late morbidity of Grade 3. CONCLUSION Radiotherapy for prostate cancer seemed to be effective, with little risk of normal tissue complications.

Effective palliative radiotherapy in primary malignant melanoma of the esophagus: a case report

IntroductionPrimary malignant melanoma of the esophagus is a rare but highly aggressive tumor with poor prognosis. Surgical resection is the treatment of choice. However, some cases may be diagnosed with advanced inoperable disease. Palliative radiotherapy may be used to relieve symptoms caused by the esophageal tumor.Case presentationWe report on a case of advanced inoperable primary malignant melanoma of the esophagus treated with palliative radiotherapy. The patients dysphagia resolved with radiotherapy.ConclusionMalignant melanoma of the esophagus is rare. Patients with advanced inoperable malignant melanomas of the esophagus benefit from radiation therapy. Radiation therapy is effective for palliation.

SU‐GG‐T‐257: Modeling of Beam Profiles Based On Three Gaussian Functions in Lung Stereotactic Body Radiotherapy for Acceptance Test of Radiotherapy Planning System

Purpose: The purpose of this study was to estimate beam profiles in lung stereotactic body radiotherapy for acceptance test of radiotherapy planning system (RTP) system. The beam profiles measured by an ionization chamber were approximated by using three Gaussian functions, and compared with profile data calculated by two RTP systems. Method and Materials: X‐ray linear accelerator with 4,6,10MV (Varian 21EX) was used to deliver symmetric beam profile for a field size of 5×5cm2. A lung phantom consisted of a lung equivalent material (thickness : 170 mm) sandwiched by two Solid Waters, whose thickness were 30 mm and 50 mm for anterior and posterior sides, respectively. Measured beam profiles were approximated by manually determining three amplitudes and standard deviations of three Gaussian functions corresponding to three point spread functions of an x‐ray focus, x‐ray or electron scatter, and a detector,and by integrating the composed function. Finally, we evaluated our method by comparing the approximated beam profiles with those calculated by two algorithms in two RTP systems, i.e., Convolution/superposition (CS) (Philips Pinnacle) and analytical anisotropic algorithm (AAA) (Varian Eclipse).Results: Difference between the measured and approximated beam profiles were 4% at 20–80% doses, and 1.5% difference at the other doses. The fringe values (distance between the 50 and 90% levels) of beam profiles approximated by Gaussian functions and calculated by CS and AAA algorithms were 4.7, 6.1, 6.4 mm for 4MV x‐ray, 5.7, 6.9, 7.1 mm for 6MV x‐ray, and 6.8, 7.7, 8.2 mm for 10MV x‐ray, respectively. Conclusion: It was suggested the beam profile model based on the three Gaussian functions may be useful for acceptance test of a RTP system.

SU‐GG‐J‐41: Automated Estimation of a Tumor Region and Its Displacement On EPID Cine Images Without Implanted Markers in Lung Stereotactic Body Radiotherapy

Purpose: The purpose of this study was to develop a method for automated estimation of a lungtumor region and its displacement on an electronic portal imaging device(EPID) during lung stereotactic body radiotherapy(SBRT) without implanted markers. Method and Materials: Our method for automated estimation of the tumor region and its displacement was based on a template matching technique with cross‐correlation coefficient between a target template image and each consecutive portal (CP) image, which was acquired in cine mode with the EPID in each treatment. Each target region was segmented in the first EPID cine image, which was referred to as the reference portal (RP) image, based on a multiple‐gray level thresholding technique and a region growing technique, and then a target template image was extracted as “a tumor template”. The displacement vector of a target was determined from the position in which the target template image took the maximum cross‐correlation value within the CP image.EPIDimages with 512×384 pixels (pixel size: 0.56 mm) were acquired in a cine mode at a sampling rate of 0.5 frame/sec by using x‐ray energies of 4, 6, or 10 MV on linear accelerators. We applied our proposed method to EPID cine images of 12 cases (ages: 51–83, mean: 73) with a non‐small cell lungcancer.Results: For 12 cases, the target displacements obtained by our method agreed with those determined by the manual method by a mean correlation value of 0.839. Each tumor region segmented by our proposed method was overlapped by 60% on average with that determined by the manual method. Conclusion: This preliminary result suggested that our proposed method may be useful for estimating of displacements of target positions without implanted markers in lungSBRT.