In Japan, quality assurance (QA) for external beam teletherapy equipment is carried out according to QA protocols issued by the Japanese Society for Therapeutic Radiology and Oncology (JASTRO), which are modified from the IEC recommendations. The QA program in Japan is introduced in this paper.
It is advisable to do several tests daily, including the accuracy of the optical distance indicator, alignment of the sidelight, check of 10×10cm light field, and constancy of the dose monitor. Pencil marks on the wall and floor can be used to check light alignment.
Dose monitor calibration and flatness/symmetry and should be checked weekly. Monthly tests should include 8 items: depth dose characteristics of electron beam, radiation-light field congruence, indication of x-ray beam axis (patient entry and exit), indication of isocenter, distance indicator, and vertical movement of table. Film is used to test the flatness/symmetry, and congruence of the radiation and light field. The alignment of the intersection of the cross hair is useful to check the x-ray beam axis indication and vertical movement of table.
Checks of stability of each dose monitor system and mechanical alignment should be performed every 6 months or annually. Mechanical alignment is fundamentally important for the performance of a teletherapy unit. As a constancy check of the overall system, a split-field test is recommended due to its rapid and simple execution.

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Between January 1982 and December 1987, 119 patients with esophageal cancer were treated by radiotherapy at the Hyogo Medical Center for Adults. In 28 of these patients, high-dose-rate intraluminal irradiation following radical external irradiation was performed as boost therapy. In 19 of the 28 patients, a balloon applicator designed by the Center was used for high-dose-rate intraluminal irradiation. In the other 9, polyethylene tube alone was used. The three-year and five-year survival rates were 21.4% and 16.1%, respectively, amongall 28 patients. The three-year survival rates were 21.1% with our balloon applicator and 22.2% with the tube only. There was no significant difference in the CR rate by intraluminal irradiation (57.9% compared to 55.6%). However, among the patients with stage III the CR rate with the balloon applicator was significantly better than that with the tube only. The balloon applicator was easily fixed in place, provided adequate distance from the esohageal mucosa to the source, and could clarify the tumor site by filling it with 20% gastrografin. Severe complications and local recurrence were less frequent with our balloon applicator than with the tube only. In conclusion, high-dose-rate intraluminal irradiation with our balloon applicator appears to be an effective form of boost therapy.

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Radiotherapy for 67 cases with prostate cancer at the Cancer Institute Hospital during the period of January 1980 to December 1989 is reported. Mean age was 70 years (43-85), and clinical stages were classified as Stage A, 10; B, 24; C, 19; D, 11; not specified (NS), 3. Pathological classification showed well differentiated, 19; moderately differentiated, 20; poorly differentiated, 19; NS, 9. Treatment was performed as follows: radiotherapy (RT) only, 18; RT plus hormonal therapy, 34; RT plus transurethral resection of prostate (TURP), 13; RT plus chemotherapy, 2. Local irradiation to the prostate was conducted mainly by bilateral 120 degree arc rotation with 10 MV photons and a mean dose of 69±2 Gy (TDF = 118±10). Pelvic lymphnodes were treated by lymphadenectomy in 18 patients, or by whole pelvic radiotherapy in 6 cases. Overall survival (OS) and disease specific survival (DSS) at 5 year were 70% and 87%, and at 10 year 51% and 87%, respectively. According to the clinical staging, OS and DSS at 5 year were, respectively: Stage A, 100%, 100%; Stage B, 89%, 100%; Stage C, 63%, 81; Stage D, 37%, 65%. Pollakisuria (27%), urinary retention (19%), and bloody stool (8%) were temporally observed as acute radiation complications. Late radiation hazards manifested as rectal bleeding or tarry stool in 2 cases; one with overlapping field resulted in disseminated intravascular coagulation, and the other with mispositioning of the posterior margin of the radiation field, was finally salvaged by artificial anal replacement. Local radiotherapy by bilateral arc rotation method for prostate cancer would be warranted instead of radical prostatectomy.

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A total of 48 patients with carcinoma of the oral tongue, who were treated with surgery after irradiation of the primary lesion and neck node were analyzed. Twenty-six of 33 patients with clinically negative nodes (N0 Group) and all 15 patients with clinically positive nodes (N1-2 Group) underwent neck dissection. Four patients (15%: 4/26) had occult node metastases. Three patients in the N0 Group (9%: 3/33) subsequently developed metastases to the neck after treatment. Incidence of cervical node metastases in the N0 Group was 21%(7/33). Of the six metastatic nodes in the N0 Group and the 36 metastatic nodes in the N1-2 Group, 14 with IIa, 15 with IIb, three with III and ten with IV ab & c histopathological change (Ohboshi-shimozato's Classification) were found. The combination of preoperative irradiation and neck dissection for regional lymph nodes of the oral tongue was effective against occult and subsequent metastases.

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Spatial coordinates of brachytherapy sources calculated by three methods, conventional geometrical formulas, the least squares method and approximation method with constant magnification, were compared with each other using a clinical case. The conventional geometrical formulas are theoretically correct, but sometimes induce greater errors than the ones produced by the approximation method. In particular, when a position is near the XZ plane consisting of two X-ray beam central axes and is not near the origin of spatial coordinates, the conventional geometrical formulas easily magnify the errors in the measured image coordinates on the radiographs. Because of small error propagation, the least squares method is very useful for clinical applications to calculate the position using all measured image coordinates.

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The present study was conducted on 132 patients at the Department of Radiotherapy of the National Cancer Center Hospital, during the 17 years from 1962 until the end of 1979. They underwent radiotherapy as inititial treatment for retaining eyes affected by retinoblastoma. The 5-years eye retention rate was 50% for the unilateral disease and 83% for the bilateral disease, a significantly more favorable rate for the bilateral type. The 5-year survival rate was 96% for the unilateral group and 85% for the bilateral group, a significantly higher survival rate for the unilateral disease. In patients followed up for more than 5 years after radiotherapy, 33 eyes were evaluated for development and severity of cataracts; 40% of the cataracts were of moderate or marked severity. Five patients (3.7%) had secondary cancer in and near the irradiated field.

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The number of institutions using casts for radiotherapy has increased in Japan in recent years. We conducted a national survey using a questionnaire to determine the way in which casts are being used in Japan as the first step towards introducing multi-institute exchange of information on their use. The survey investigated the proportion of institutions using casts, opinions on cast usefulness, and problems related to their use. As of January, 1992, 103 institutions were using casts, indicating that just under 20% of Japanese institutions have adopted casts, in radiotherapy. Most of the responding institutions believe that a cast is useful. However, many institutions pointed out that the casts are not covered by the national health insurance system, and expressed the hope that this problem would be rectified as soon as possible. In addition, various opinions were expressed on the use of casts, such as need for measures to alleviate radiotherapeutic dermatitis, and to solve the problems associated with discarding used casts. We believe that this type of interinstitutional exchange of information will continue to be necessary in the future.

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One hundred and sixty-nine cervical lymph node-metastases from head and neck squamous cell carcinomas treated with either even fractionation or uneven fractionation regimens were analyzed in the present investigation. Logistic multivariate regression analysis indicated that: type of fractionation (even vs uneven), size of metastases, T value of primary tumors, and total dose are independent variables out of 18 variables that significantly influenced the rate of tumor clearance. The data, with statistical bias corrected by the regression equation, indicated that the uneven fractionation scheme significantly improved the rate of tumor clearance for the same size of metastases, total dose, and overall time compared to the even fractionation scheme.
Futher analysis by a linear-quadratic cell survival model indicated that the clinical improvement by uneven fractionation might not be explained entirely by a larger dose per fraction. It is suggested that tumor cells irradiated with an uneven fractionation regimen might repopulate more slowly, or they might be either less hypoxic or redistributed in a more radiosensitive phase in the cell cycle than those irradiated with even fractionation. This conclusion is clearly not definite, but it is suitable, pending the results of further investigation.

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