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The purpose of the present study was to determine the risk factors for developing thyroid disorders based on a dose–volume histograms (DVHs) analysis. Data from a total of 116 consecutive patients undergoing 3D conformal radiation therapy for head and neck cancers was retrospectively evaluated. Radiation therapy was performed between April 2007 and December 2010. There were 108 males and 8 females included in the study. The median follow-up term was 24 months (range, 1–62 months). The thyroid function was evaluated by measuring thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels. The mean thyroid dose, and the volume of thyroid gland spared from doses ≥10, 20, 30 and 40 Gy (VS10, VS20, VS30 and VS40) were calculated for all patients. The thyroid dose and volume were calculated by the radiotherapy planning system (RTPS). The cumulative incidences of hypothyroidism were 21.1% and 36.4% at one year and two years, respectively, after the end of radiation therapy. In the DVH analyses, the patients who received a mean thyroid dose <30 Gy had a significantly lower incidence of hypothyroidism. The univariate analyses showed that the VS10, VS20, VS30 and VS40 were associated with the risk of hypothyroidism. Hypothyroidism was a relatively common type of late radiation-induced toxicity. A mean thyroid dose of 30 Gy may be a useful threshold for predicting the development of hypothyroidism after radiation therapy for head and neck cancers.

The ongoing structure of radiation oncology in Japan in terms of equipment, personnel, patient load and geographic distribution was evaluated in order to radiation identify and improve any deficiencies. A questionnaire-based national structure survey was conducted from March 2010 to January 2011 by the Japanese Society for Therapeutic Radiology and Oncology (JASTRO). These data were analyzed in terms of the institutional stratification of the Patterns of Care Study (PCS). The total numbers of new cancer patients and total of cancer patients (new and repeat) treated with radiation in 2009 were estimated at 201,000 and 240,000, respectively. The type and numbers of systems in actual use consisted of Linac (816), telecobalt (9), Gamma Knife (46), 60 Co remote afterloading system (RALS) (29) and 192 Ir RALS systems (130). The Linac systems used dual energy function for 586 (71.8%), 3DCRT for 663 (81.3%) and IMRT for 337 units (41.3%). There were 529 JASTRO-certified radiation oncologists (ROs), 939.4 full-time equivalent (FTE) ROs, 113.1 FTE medical physicists and 1836 FTE radiation therapists. The frequency of interstitial radiation therapy use for prostate and of intensity-modulated radiotherapy increased significantly. PCS stratification can clearly identify the maturity of structures based on their academic nature and caseload. Geographically, the more JASTRO-certified physicians there were in a given area, the more radiation therapy tended to be used for cancer patients. In conclusion, the Japanese structure has clearly improved during the past 19 years in terms of equipment and its use, although a shortage of manpower and variations in maturity disclosed by PCS stratification remained problematic in 2009.

PurposeWe conducted a prospective multi-institutional study to determine the feasibility of trimodality therapy (TMT) comprising induction chemotherapy followed by extrapleural pneumonectomy (EPP) and radiation therapy in Japanese patients with malignant pleural mesothelioma (MPM). MethodsMajor eligibility criteria were histologically confirmed diagnosis of MPM, including clinical subtypes T0–3, N0–2, M0 disease; no prior treatment for the disease; age 20–75 years; Eastern Cooperative Oncology Group performance status 0 or 1; predicted postoperative forced expiratory volume >1000 ml in 1 s; written informed consent. Treatment methods comprised induction chemotherapy using pemetrexed (500 mg/m2) plus cisplatin (60 mg/m2) for three cycles, followed by EPP and postoperative hemithoracic radiation therapy (54 Gy). Primary endpoints were macroscopic complete resection (MCR) rate for EPP and treatment-related mortality for TMT.ResultsForty-two eligible patients were enrolled: median age 64.5 (range 43–74) years; M:F = 39:3, clinical stage I:II:III = 14:13:15; histological type epithelioid were sarcomatoid; biphasic; others = 28:1:9:4. Of 42 patients, 30 completed EPP with MCR and 17 completed TMT. The trial met the primary endpoints, with an MCR rate of 71 % (30/42) and treatment-related mortality of 9.5 % (4/42). Overall median survival time and 2-year survival rate for 42 registered patients were 19.9 months and 42.9 %, respectively. Two-year relapse-free survival rate of 30 patients who completed EPP with MCR was 37.0 %.ConclusionThis phase II study met the predefined primary endpoints, but its risk/benefit ratio was not satisfactory.Electronic supplementary materialThe online version of this article (doi:10.1007/s10147-015-0925-1) contains supplementary material, which is available to authorized users.

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