Mitsuru Okubo

Static and moving phantom studies for radiation treatment planning in a positron emission tomography and computed tomography (PET/CT) system

ObjectiveTo determine an appropriate threshold value for delineation of the target in positron emission tomography (PET) and to investigate whether PET can delineate an internal target volume (ITV), a series of phantom studies were performed.MethodsAn ellipse phantom (background) was filled with 1028 Bq/ml of [18F] fluoro-2-deoxyglucose (18FDG), and six spheres of 10 mm, 13 mm, 17 mm, 22 mm, 28 mm, and 37 mm in diameter inside it were filled with 18FDG activity to achieve source-to-background (S/B) ratios of 10, 15, and 20. In static phantom experiments, an appropriate threshold value was determined so that the size of PET delineation fits to an actual sphere. In moving phantom experiments with total translations of 10 mm, 20 mm, and 30 mm and a period of oscillation of 4 s, the maximum size of PET delineation with the appropriate threshold value was measured in both the axial and sagittal planes.ResultsIn the static phantom experiments, the measured maximum 18FDG activities of spheres of less than 22 mm were lower than 80% of the injected 18FDG activity, and those for the larger spheres ranged from 90% to 110%. Appropriate threshold values determined for the spheres of 22 mm or more ranged from 30% to 40% of the maximum 18FDG activity, independent of the S/B ratio. Therefore, we adopted an appropriate threshold value as 35% of the measured maximum 18FDG activity. In moving phantom experiments, the maximum 18FDG activity of spheres decreased significantly, dependent on the movement distance. Although the sizes of PET delineation with 35% threshold value tended to be slightly smaller (<3 mm) than the actual spheres in the axial plane, the longest sizes in the sagittal plane were larger than the actual spheres.ConclusionsWhen a threshold value of 35% of the measured maximum 18FDG activity was adopted, the sizes of PET delineation were almost the same for static and moving phantom spheres of 22 mm or more in the axial plane. In addition, PET images have the potential to provide an individualized ITV.

Radiation Treatment Planning Using Positron Emission and Computed Tomography for Lung and Pharyngeal Cancers: A Multiple-Threshold Method for [18F]Fluoro-2-Deoxyglucose Activity

PURPOSE Clinical applicability of a multiple-threshold method for [(18)F]fluoro-2-deoxyglucose (FDG) activity in radiation treatment planning was evaluated. METHODS AND MATERIALS A total of 32 patients who underwent positron emission and computed tomography (PET/CT) simulation were included; 18 patients had lung cancer, and 14 patients had pharyngeal cancer. For tumors of <or=2 cm, 2 to 5 cm, and >5 cm, thresholds were defined as 2.5 standardized uptake value (SUV), 35%, and 20% of the maximum FDG activity, respectively. The cervical and mediastinal lymph nodes with the shortest axial diameter of >or=10 mm were considered to be metastatic on CT (LNCT). The retropharyngeal lymph nodes with the shortest axial diameter of >or=5 mm on CT and MRI were also defined as metastatic. Lymph nodes showing maximum FDG activity greater than the adopted thresholds for radiation therapy planning were designated LNPET-RTP, and lymph nodes with a maximum FDG activity of >or=2.5 SUV were regarded as malignant and were designated LNPET-2.5 SUV. RESULTS The sizes of gross tumor volumes on PET (GTVPET) with the adopted thresholds in the axial plane were visually well fitted to those of GTV on CT (GTVCT). However, the volumes of GTVPET were larger than those of GTVCT, with significant differences (p < 0.0001) for lung cancer, due to respiratory motion. For lung cancer, the numbers of LNCT, LNPET-RTP, and LNPET-2.5 SUV were 29, 28, and 34, respectively. For pharyngeal cancer, the numbers of LNCT, LNPET-RTP, and LNPET-2.5 SUV were 14, 9, and 15, respectively. CONCLUSIONS Our multiple thresholds were applicable for delineating the primary target on PET/CT simulation. However, these thresholds were inaccurate for depicting malignant lymph nodes.

A Two-step Intensity-modulated Radiation Therapy Method for Nasopharyngeal Cancer: The Kinki University Experience

OBJECTIVE The aim of this study was to analyze the clinical results of our adaptive radiation therapy scheme of a two-step intensity-modulated radiotherapy (IMRT) method for nasopharyngeal cancer (NPC) at Kinki University Hospital. METHODS Between 2000 and 2007, 35 patients with Stage I-IVB NPC treated by IMRT were included. For all patients, treatment-planning computed tomography was done twice before and during IMRT to a total dose of 60-70 Gy/28-35 fractions (median 68 Gy). Chemotherapy (cisplatin 80 mg/m(2)/3 weeks x 1-3 courses) was given concurrently with IMRT for 31 patients. RESULTS The 3- and 5-year overall survival rates for the 31 patients treated with concurrent chemotherapy were 88% and 83%, respectively. The 3- and 5-year loco-regional control rates for the 31 patients were 93% and 87%, respectively. Planning target volume delineation for the primary site or involved nodes was insufficient for three early cases, resulting in marginal recurrence in the three patients (9%). Except for one patient with early death, xerostomia scores at 1-2 years were: Grade 0, 11; Grade 1, 17; Grade 2, 5; Grade 3, 1. CONCLUSIONS Excellent overall survival and loco-regional control rates were obtained by a two-step IMRT method with concurrent chemotherapy for NPC, although marginal recurrence was noted in some early cases.

Patients with severe emphysema have a low risk of radiation pneumonitis following stereotactic body radiotherapy.

OBJECTIVE To evaluate the risk of radiation pneumonitis (RP) after stereotactic radiotherapy (SBRT) for patients presenting with severe pulmonary emphysema. METHODS This study included 40 patients with Stage I non-small-cell lung cancer who underwent SBRT, 75 Gy given in 30 fractions, at the Tokyo Medical University, Tokyo, Japan, between February 2010 and February 2013. The median age of the patients was 79 years (range, 49-90 years), and the male:female ratio was 24:16. There were 20 T1 and 20 T2 tumours. 17 patients had emphysema, 6 had slight interstitial changes on CT images and the remaining 17 had no underlying lung disease. The level of emphysema was classified into three groups according to the modified Goddards criteria (severe: three patients, moderate: eight patients and mild: six patients). Changes in the irradiated lung following SBRT were evaluated by CT. RESULTS On CT images, RP was detected in 34 (85%) patients, and not in 6 (15%) patients, during a median observation period of 313 days. Of the six patients, three had severe emphysema and three had no underlying lung disease. Patients with severe emphysema had lower risk of RP than those with moderate emphysema (p = 0.01), mild emphysema (p = 0.04) and no underlying lung disease (p = 0.01). CONCLUSION Patients with severe emphysema had a low risk of RP following SBRT. ADVANCES IN KNOWLEDGE Little is known about the association between RP and pulmonary emphysema. Patients with severe emphysema had lower risk of RP than those with no underlying lung disease.

Preliminary Results of Fractionated Stereotactic Radiotherapy After Cyst Drainage for Craniopharyngioma in Adults

PURPOSE To retrospectively evaluate the effectiveness of fractionated stereotactic radiotherapy (FSRT) for craniopharyngioma. METHODS AND MATERIALS Between 1999 and 2005, 16 patients with craniopharyngioma were referred to Tokyo Medical University Hospital. They received FSRT alone after histologic confirmation by needle biopsy and underwent cyst drainage via endoscopy. The median prescription dose fraction was 30 Gy in six fractions. All patients except 1 were followed up until December 2009 or death. RESULTS The median follow-up period was 52 months (range, 4-117 months). Of the 17 patients, 3 experienced recurrence 4 to 71 months after FSRT. The 3-year local control rate was 82.4%. One patient died of thyroid cancer, and the 3-year survival rate was 94.1%. Eight patients had improved visual fields at a median of 2.5 months after FSRT, but hormonal functions did not improve in any patient. CONCLUSIONS FSRT after cyst drainage seems to be safe and effective for patients with craniopharyngiomas, and it may be a safe alternative to surgery.

Dosimetric evaluation of compensator intensity modulation-based stereotactic body radiotherapy for Stage I non-small-cell lung cancer

OBJECTIVE To evaluate the dosimetry of compensator intensity modulation-based stereotactic body radiotherapy (SBRT) [non-coplanar intensity-modulated radiotherapy (ncIMRT)], its use was compared with that of three-dimensional conformation-based SBRT, for patients with Stage I non-small-cell lung cancer (NSCLC). METHODS 21 consecutive patients with Stage I NSCLC were treated with ncIMRT or SBRT at Tokyo Medical University. To compare the two techniques, ncIMRT and SBRT plans for each patient were generated, where the planning target volume (PTV) coverages were adjusted to be equivalent to each other. The prescribed dose was set as 75 Gy in 30 fractions. PTV coverage, conformity index, conformation number (CN) and homogeneity index (HI) were used to compare the two strategies. RESULTS There was no statistically significant difference between PTV coverage for the 100%, 95% and 90% dose levels in the SBRT plan and those in the ncIMRT plan. The CN values were 0.53 ± 0.13 in the SBRT plan and 0.72 ± 0.10 in the ncIMRT plan. These values were significantly better than those of the SBRT plan (p < 0.001). The HI in the ncIMRT plan was 1.04 ± 0.03%, which was also significantly better than that of SBRT. CONCLUSION The ncIMRT plan provided superior conformity and reduced the doses to the lung for patients with Stage I NSCLC. ADVANCES IN KNOWLEDGE The delivery technique with compensator intensity modulation-based SBRT was evaluated. Concerning target motion, this is thought to be more robust and safer than SBRT for early-stage NSCLC.

Radiotherapy in patients with extramammary Paget's disease--our own experience and review of the literature.

Background: There are few reports on radiotherapy methods for treating extramammary Pagets disease (EMPD). The aim of this study was to explore the outcome of radiotherapy for EMPD. Patients and Methods: Between June 1995 and October 2010, 14 patients with EMPD (7 male and 7 female; median age 77 years) underwent radiotherapy at the Tokyo Medical University Hospital. The median total irradiation dose was 50 Gy, delivered in 20-33 fractions. Case reports of patients with EMPD were obtained from the PubMed database for the period of 1991-2012. 66 patients (median age 73 years) were identified. Radiotherapy outcomes were analyzed. Results: All patients achieved complete response within the irradiated volume during a median observation period of 71.4 months. The 5-year locoregional progression-free survival and overall survival were 91.7% (95% confidence interval (CI) 53.9-98.8%) and 84.3% (95% CI 50.3-95.8%), respectively. From the PubMed database, the 5-year local progression-free survival and locoregional progression-free survival were 84.5% (95% CI 65.3-93.6%) and 77.5% (95% CI 57.3-89.0%), respectively. 12 (18%) patients had a recurrence in the inguinal lymph nodes. Conclusion: Radiotherapy yielded good local control and survival, which suggests that it was effective for patients with EMPD and in particular medically inoperable EMPD.

Predicting risk factors for radiation pneumonitis after stereotactic body radiation therapy for primary or metastatic lung tumours

OBJECTIVE To investigate risk factors for radiation-induced pneumonitis (RP) after hypofractionated stereotactic body radiotherapy (SBRT) in patients with lung tumours. METHODS From May 2004 to January 2016, 66 patients with 71 primary or metastatic lung tumours were treated with SBRT; these 71 cases were retrospectively analyzed for RP. To explore the risk factors for RP, the following factors were investigated: age, sex, performance status, operability, number of treatments, respiratory gating, pulmonary emphysema, tumour location and subclinical interstitial lung disease (ILD). Irradiated underlying lung volumes of more than 5 Gy, 10 Gy, 20 Gy and 30 Gy (Lung V5, V10, V20 and V30), mean lung dose and volumes of gross tumour volume (in cubic centimetre) and planning target volume were calculated for possible risk factors of RP. RESULTS The median follow-up period was 32 months. RP of Grade 2 or more, according to the Common Terminology Criteria for Adverse Events v. 4.0, was detected in 6 (8.4%) of the 71 cases. Grade 5 RP was identified in two cases. Of the risk factors of RP, subclinical ILD was the only factor significantly associated with the occurrence of RP of Grade 2 or more (p < 0.001). Both cases with Grade 5 RP had ILD with a honeycombing image. CONCLUSION Subclinical ILD was the only significant factor for Grade 2-5 RP. In addition, the cases with honeycombing had a high potential for fatality related to severe RP. Patients with subclinical ILD should be carefully monitored for the occurrence of severe RP after SBRT. Advances in knowledge: Hypofractionated SBRT for primary or metastatic lung tumours provides a high local control rate and safe treatment.

Preliminary results of radiotherapy for primary intraocular non-Hodgkin lymphoma

Abstract This study aimed to retrospectively evaluate the efficacy of radiotherapy for primary intraocular non-Hodgkin lymphoma (PIOL). Between May 1998 and October 2010, 22 immunocompetent patients (four men, 18 women; median age 70 years, range 53–79 years) were diagnosed with PIOL. Magnetic resonance imaging showed no intracranial involvement in any patient. Patients received radiotherapy at a median total dose of 30 Gy (range 30–40 Gy). Three-year overall survival, progression-free survival and local control rates were 89% (95% confidence interval [CI]: 75, 103), 49% (95% CI: 24, 73) and 95% (95% CI: 86, 105) over a median of 36 months of observation, respectively. Twelve patients (55%) had intracranial relapse at a median of 28 months after initiation of radiotherapy. Visual acuity improved or was stable in 81% of treated eyes. The only grade ≥ 3 toxicity was cataract formation (five patients). Radiotherapy without chemotherapy for PIOL achieved high local control rates with acceptable toxicities.

Cryptogenic organizing pneumonia associated with radiation: A report of two cases

Cryptogenic organizing pneumonia (COP) following radiotherapy is occasionally diagnosed as radiation pneumonitis or bacterial pneumonia. The current study presents two cases of COP following radiotherapy: A 48-year-old premenopausal female with breast cancer and an 84-year-old male with non-small cell lung cancer. In the cases of breast cancer and lung cancer, patients were first diagnosed with bacterial pneumonia and radiation pneumonitis, respectively. In the two cases, computed tomography disclosed the migration of ground glass shadows, which were finally resolved without any fibrotic changes. The two cases were finally diagnosed as COP associated with radiotherapy. When an infiltrating shadow is present outside of the irradiated field, COP must be included in the differential diagnosis.