論文

Esophageal squamous cell carcinoma (ESCC) is more sensitive to radiation and chemotherapy than other cancers of the digestive system, and combined modality therapy may represent a promising treatment method. The radiation-sensitizing effect of docetaxel on ESCC cell lines was investigated. A colony formation assay was performed in which ESCC cell lines (TE2, TE3) and A431 were exposed to docetaxel (from 1.0x10 11 to 107 M) for 3 h to determine the concentration of docetaxel that was not able to kill individual cells (i.e., the non-cytocidal concentration). Individual cell lines were then exposed to the non-cytocidal concentration of docetaxel prior to, during, and after irradiation to determine whether the timing of docetaxel administration affected cell survival. In addition, flow-cytometry was performed, and the cell cycle was examined prior to and after docetaxel exposure to assess the mechanism of docetaxel as a radiation sensitizer. Docetaxel exhibited a concentration-dependent cytocidal effect, with a different IC50 for each cell type. Almost no cytocidal effect was observed at the following docetaxel concentrations: A431, ≤1.0x1010 M; TE-2 and TE-3, ≤1.0x109 M. Concurrent treatment with docetaxel and radiation tended to decrease cell survival in all the cell lines compared with docetaxel or radiation alone. Cell survival was lowest when the cells were treated using X-ray irradiation after docetaxel exposure (p<0.05). Flow cytometry revealed that in all three cell lines, docetaxel exposure increased the G2/M cell fraction with a higher increase in the cell line that exhibited the highest radiosensitivity This study demonstrated that the administration of docetaxel at a non-cytocidal concentration prior to radiotherapy produced a synergistic cell-killing effect in SCC cell lines.

In the present study, the prostate medium determined from the CT images of 149 patients was developed. The dosimetric parameters such as Λ, GL(r) and F(r, θ) used in TG-43U1-based calculation for an iodine-125 (125I) brachytherapy-source were examined using Monte Carlo code Geant4. Clinical dosimetry parameters such as the D90 were evaluated among a subgroup of 50 randomly selected patients who had been treated with permanent brachytherapy between January 2008 and December 2008 at the Tokyo Medical Center. The results show a slight difference in the dose rate constant Λ (within 1.0%). The radial dose function GL(r) exhibits a prominent difference in the region over 3 cm, and this difference is maintained within 2.9% in the region close to the source. The calculated values of F(r, θ) for the prostate medium were similar to values for water (within 1%), except in the longitudinal axis. A comparison of D90 values shows a systematic dose overestimation of 2.8 ± 0.7 GY in water, where the distribution of the differences can be seen with a spread of 1.8 ± 0.3% compared to that in prostate medium. It was concluded that the introduction of any kind of tissue correction for the TG-43U1-based calculation was not necessary to allow for the differences in elemental compositions and densities between water and prostate medium. PACS number: 87.00.00; 87.55.dk; 87.55.K-; 87.56.B-.

Purpose: To investigate factors associated with Grade ≥3 radiation pneumonitis (RP) in patients with lung tumors treated with stereotactic body radiotherapy (SBRT). Methods and Materials: We retrospectively analyzed 128 patients with 133 lung tumors treated with SBRT. RP was graded according to the Common Terminology Criteria for Adverse Events version 3.0. Univariate analyses were used to identify predictive factors for RP. Results: The median follow-up period after SBRT was 12 months (range, 5-45 months). Incidences of Grades 0, 1, 2, and 3 RP were 27%, 52%, 16%, and 5%, respectively. No patients suffered Grade 4 or 5 RP. For all patients with Grade 2 or 3, symptoms occurred either simultaneously with or subsequent to graphical appearances. The latent period was the only significant factor associated with Grade ≥3 RP (p < 0.01). A latent period of 1 or 2 months indicated a 40% (6/15) risk for Grade 3. However, the risk for Grade 3 was 1.2% (1/82) 3 months after SBRT. No pretreatment clinical or dosimetric factors were significantly associated with Grade ≥3 RP. However, 4 of 7 patients with Grade 3 RP had severe pulmonary comorbidities. Conclusion: Only the latency period was a significant factor in the development of RP. No pretreatment clinical or dosimetric factors were significantly associated with Grade ≥3 RP. Patients, especially those with severe pulmonary comorbidities, should be carefully observed for the graphical appearance of RP within a few months during the follow-up period after SBRT.

A meta-analysis showed that chemoradiotherapy (CCRT) improved survival in patients with advanced head and neck squamous cell carcinoma (HNSCC). CCRT has become widely used in treating such patients. The purpose of CCRT in the treatment of resectable HNSCC is to improve survival while preserving organs and functions, and so CCRT is a potential alternative to surgery. However, problems regarding CCRT were revealed such as severe dysphasia and difficulty of salvage surgery. Recently, induction chemotherapy has attracted attention again, the purpose of which is to predict the response of subsequent CCRT or to improve outcomes. Moreover, chemotherapy is concurrently used with postoperative radiotherapy or definitively used for recurrent or metastatic HNSCC. In this article, we review the current state of chemotherapy for HNSCC and consider the problems in Japan.

Background: The prognostic significance of sentinel lymph node (SLN) micrometastases and the need for axillary lymph node dissection (ALND) on patients with micrometastases in SLNs remain controversial. Methods: A prospective database of 657 breast cancer patients who underwent SLN biopsy (SLNB) was analyzed. SLNs were detected using a combined method of isosulfan blue dye and small-sized technetium-99m-labeled tin colloid. Results: Micrometastases in SLNs were found in 50 (7.6%) of 657 patients. Twenty-nine (58.0%) of 50 patients with micrometastatic SLNs underwent ALND and no further metastases were found in non-sentinel lymph nodes. Among 21 patients (42.0%) with micrometastatic SLNs who decided to forego ALND, no axillary lymph node recurrence has been observed during a median follow-up time of 47 months. There is no significant difference in recurrence-free survival between the patients with micrometastatic and negative SLNs (p = 0.90). Conclusions: These data suggest that it may not be necessary to perform ALND on patients with micrometastases in SLNs and that the presence of micrometastases in SLNs may not be associated with prognosis.

This study aimed to assess the imaging appearances of focal liver reactions following stereotactic body radiotherapy (SBRT) for small hepatocellular carcinoma (HCC) and to examine relationships between imaging appearance and baseline liver function. We retrospectively studied 50 lesions in 47 patients treated with SBRT (30-40 Gy in 5 fractions) for HCC, who were followed up for more than 6 months. After SBRT, all patients underwent regular follow-ups with blood tests and dynamic CT scans. At a median follow-up of 18.1 months (range 6.2-43.7 months), all lesions but one were controlled. 3 density patterns describing focal normal liver reactions around HCC tumours were identified in pre-contrast, arterial and portal-venous phase scans: iso/iso/iso in 4 patients (Type A), low/iso/iso in 8 patients (Type B) and low/iso (or high)/high in 38 patients (Type C). Imaging changes in the normal liver surrounding the treated HCC began at a median of 3 months after SBRT, peaked at a median of 6 months and disappeared 9 months later. Liver function, as assessed by the Child-Pugh classification, was the only factor that differed significantly between reactions to treatment showing "non-enhanced" (Type A and B) and "enhanced" (Type C) appearances in CT. Hence, liver tissue with preserved function is more likely to be well enhanced in the delayed phase of a dynamic contrast-enhanced CT scan. The CT appearances of normal liver seen in reaction to the treatment of an HCC by SBRT were therefore related to background liver function and should not be misread as recurrence of HCC.

Potentially lethal damage (PLD) and its repair were studied in confluent human fibroblasts by analyzing the kinetics of chromosome break rejoining and misrejoining in irradiated cells that were either held in noncycling G0 phase or allowed to enter G1 phase of the cell cycle immediately after 6 Gy irradiation. Virally mediated premature chromosome condensation (PCC) methods were combined with fluorescence in situ hybridization (FISH) to study chromosomal aberrations in interphase. Flow cytometry revealed that the vast majority of cells had not yet entered S phase 15 h after release from G0. By this time some 95 of initially produced prematurely condensed chromosome breaks had rejoined, indicating that most repair processes occurred during G1. The rejoining kinetics of prematurely condensed chromosome breaks was similar for each culture condition. However, under noncycling conditions misrepair peaked at 0.55 exchanges per cell, while under cycling conditions (G1) it peaked at 1.1 exchanges per cell. At 12 h postirradiation, complex-type exchanges were sevenfold more abundant for cycling cells (G1) than for noncycling cells (G0). Since most repair in G0/G1 occurs via the non-homologous end-joining (NHEJ) process, increased PLD repair may result from improved cell cycle-specific rejoining fidelity of the NHEJ pathway.

Background: The aim was to identify preimplant factors affecting postimplant prostate volume and the increase in prostate volume after transperineal interstitial prostate brachytherapy with 125I free seeds.Methods: We reviewed the records of 180 patients who underwent prostate brachytherapy with 125I free seeds for clinical T1/T2 prostate cancer. Eighty-one (45%) of the 180 patients underwent neoadjuvant hormonal therapy. No patient received supplemental external beam radiotherapy. Postimplant computed tomography was undertaken, and postimplant dosimetric analysis was performed. Univariate and multivariate analyses were performed to identify preimplant factors affecting postimplant prostate volume by computed tomography and the increase in prostate volume after implantation.Results: Preimplant prostate volume by transrectal ultrasound, serum prostate-specific antigen, number of needles, and number of seeds implanted were significantly correlated with postimplant prostate volume by computed tomography. The increase in prostate volume after implantation was significantly higher in patients with neoadjuvant hormonal therapy than in those without. Preimplant prostate volume by transrectal ultrasound, number of needles, and number of seeds implanted were significantly correlated with the increase in prostate volume after implantation. Stepwise multiple linear regression analysis showed that preimplant prostate volume by transrectal ultrasound and neoadjuvant hormonal therapy were significant independent factors affecting both postimplant prostate volume by computed tomography and the increase in prostate volume after implantation.Conclusions: The results of the present study show that preimplant prostate volume by transrectal ultrasound and neoadjuvant hormonal therapy are significant preimplant factors affecting both postimplant prostate volume by computed tomography and the increase in prostate volume after implantation.

Sebaceous carcinoma is a rare malignant tumor typically originating in the skin of the eyelid. We report an unusual case of sebaceous carcinoma originating in the parotid gland of a 23-year-old woman. The patient underwent F-18 2-fluoro-2-deoxy-glucose positron emission tomography/computed tomography (FDG PET/CT) to determine the initial clinical stage. FDG PET/CT revealed strong uptake in the primary lesion but neither regional lymphatic nor distant metastasis were seen. These findings allowed for an accurate prediction of the nodal status, which contributed to precise determination of the initial stage. FDG PET/CT scans may be useful for the initial staging of cutaneous sebaceous carcinomas as well.

Background: Sentinel lymph node biopsy (SLNB) is commonly performed using radioisotopes and/or blue dye. However, it is still undefined which reagent is more suitable for identifying sentinel lymph nodes (SLN). Patients and Methods: A consecutive series of 640 breast cancer patients who had undergone SLNB at the Keio University Hospital from 2001 to 2006 was analyzed. The SLN was identified by a combination of technetium-99m tin colloid and isosulfan blue dye. The correlation between clinicopathological factors and the distribution of radioisotopes and blue dye was analyzed. The single metastatic lymph node revealed by axillary lymph node dissection (ALND) is the 'true SLN', and the distribution of radioisotopes and blue dye to the 'true SLN' was also analyzed. Results: Blue-dye- and radioisotope-positive SLN were identified in 79.6 and 94.7% of the patients, respectively. Taken together, SLN were identified in 625 patients (97.7%) by radioisotope and/or blue dye. No significant correlation was observed between clinicopathological features and the distribution of the reagents. ALND found 73 patients with single lymph node metastasis, and 73 'true SLN' were identified by blue dye in 65.7% (48/73), and by radioisotope in 95.9% (70/73) of the cases. Conclusion: These data suggest that radioisotopes are superior to blue dye in detecting SLN in breast cancer.

Background: Salvage esophagectomy is potentially the only treatment available that can offer a chance of long-term survival when definitive chemoradiotherapy (CRT) fails to achieve local control for patients with esophageal squamous cell carcinoma (ESCC). However, salvage esophagectomy is a highly invasive procedure with various postoperative complications compared to planned esophagectomy after neoadjuvant chemoradiotherapy (CRT). We hypothesize that severe postoperative complications may affect not only surgical mortality but also tumor recurrence and long-term survival for patients with salvage esophagectomy after definitive CRT. Methods: For the present study we reviewed the surgical procedures, postoperative complications, and the prognosis of 65 consecutive patients with thoracic ESCC who underwent the esophagectomy after neoadjuvant (neoadjuvant group: n = 40) or definitive (salvage group: n = 25) CRT. Results: Most patients underwent right-transthoracic extended esophagectomy and reconstruction using gastric conduit by way of subcutaneous route with left cervical anastomosis. The incidence of postoperative pneumonia was found to be higher in the salvage group than in the neoadjuvant group. In both groups, the survival of patients with R0 resection was significantly better than those with R1/R2 resection. Moreover, in the salvage group, the postoperative survival rate of patients with pneumonia or bacteremia/sepsis was significantly lower than that for patients who did not suffer the same complications. In the neoadjuvant group, R0 resection was selected to be the only independent prognostic factor in univariate and multivariate analysis. In contrast, in the salvage group, R0 resection and bacteremia/sepsis remained significant and were independent of the other factors in multivariate analysis. Conclusions: This study reveals that postoperative morbidity affects not only the perioperative mortality but also the long-term survival of patients with ESCC who undergo salvage esophagectomy after definitive CRT.

Purpose: To retrospectively assess the efficacy, toxicity, and prognostic factors of weekly low-dose docetaxel-based chemoradiotherapy for Stage III/IV oropharyngeal or hypopharyngeal carcinoma. Methods and Materials: Between 2001 and 2005, 72 consecutive patients with locally advanced oropharyngeal or hypopharyngeal carcinoma were treated with concurrent chemoradiotherapy (CCR; radiation at 60 Gy plus weekly docetaxel [10 mg/m2]). Thirty of these patients also received neoadjuvant chemotherapy (NAC; docetaxel, cisplatin, and 5-fluorouracil) before concurrent chemoradiotherapy. Survival was calculated according to the Kaplan-Meier method. The prognostic factors were evaluated by univariate and multivariate analyses. Results: The median follow-up was 33 months, with overall survival, disease-free survival, and locoregional control rates at 3 years of 59%, 45%, and 52%, respectively. Thirty-six patients (50%) experienced more than one Grade 3 to 4 acute toxicity. Grade 3 mucositis occurred in 32 patients (44%), Grade 4 laryngeal edema in 1 (1%). Grade ≥3 severe hematologic toxicity was observed in only 2 patients (3%). Grade 3 dysphagia occurred as a late complication in 2 patients (3%). Multivariate analyses identified age, T stage, hemoglobin level, and completion of weekly docetaxel, but not NAC, as significant factors determining disease-free survival. Conclusions: Docetaxel is an active agent used in both concurrent and sequential chemoradiotherapy regimens. Mucositis was the major acute toxicity, but this was well tolerated in most subjects. Anemia was the most significant prognostic factor determining survival. Further studies are warranted to investigate the optimal protocol for integrating docetaxel into first-line chemoradiotherapy regimens, as well as the potential additive impact of NAC.

We made a prototype gamma camera system with CdZnTe semiconductor detectors that work at room temperature. The effective field of view of this detector is 195 x 156 mm2 with a pixel size of 2.46 x 2.46 mm2. We evaluated the performance of the detector in terms of the energy resolution, intrinsic spatial resolution, system spatial resolution and system sensitivity. The performance of the detector was evaluated with methods based on the NEMA standard (NU1). The results showed that the mean energy resolution was 5.55 % FWHM for 99mTc, the intrinsic spatial resolution 2.46 mm FWHM, the system spatial resolutions 7.1 mm FWHM (without scatterer) and 7.4 mm FWHM (with scatterer), and the system sensitivity 46.3 cps/MBq. The performance of the system was also evaluated with some SPECT phantoms and the feasibility of the detector was confirmed with the SPECT images.

Background: We aimed to calculate the frequency and features of the development of a prostate-specific antigen (PSA) bounce after prostate brachytherapy alone, to correlate the bounce with clinical and dosimetric factors and to identify factors that predict PSA bounce. Methods: PSA bounce was evaluated in 86 patients with T1-T2 prostate cancer who underwent radioactive seed implantation using iodine-125 (I-125) without hormonal therapy or external-beam radiation therapy (EBRT) from September 2004 to December 2007. A PSA bounce was defined as a rise of at least 0.4 ng/ml greater than a previous PSA level with a subsequent decline equal to, or less than, the initial nadir. Results: Calculated by the Kaplan-Meier method, the incidence of PSA bounce at a 2-year follow-up was 26%. Median time to the PSA bounce was 15 months. Univariate analysis demonstrated that age, dose received by 90% of the prostate gland (D90), volume of gland receiving 100% of the prescribed dose (V100), and V150 were significantly associated with the PSA bounce, while pretreatment PSA level, Gleason score, pretreatment prostate volume, clinical T stage, and V200 were not. In multivariate analysis, age 67 years or less and D90 more than 180 Gy were identified as independent factors for predicting the PSA bounce (P < 0.05). Conclusion: PSA bounce is not a rare phenomenon after prostate brachytherapy. It is more common in younger patients and patients receiving higher doses of radiation.

High-dose cytarabine is one of the major components of the conditioning regimen for hematopoietic stem cell transplantation (HSCT), and frequently causes severe oral mucositis. We have recently demonstrated that cytarabine is excreted into the saliva in patients receiving high-dose cytarabine, and proposed that it might locally and directly contribute to the development of oral mucositis. Therefore, this study was performed to assess whether removing the excreted cytarabine in the saliva by intensive mouth rinse during high-dose cytarabine infusion could reduce the incidence of oral mucositis. Fifteen patients with hematologic malignancies undergoing allogeneic HSCT who received total body irradiation (12 Gy) and high-dose cytarabine at a dose of 3 g/m 2 every 12 h for 4 days as a conditioning were evaluated. Patients were instructed to rinse their mouths using ice-cold water every 10 min, starting simultaneously with the 2-h cytarabine infusion and continuing up to 1 h after completion of each infusion. Oral mucositis was graded on a daily basis according to the National Cancer Institute, Common Toxicity Criteria. Thirty-five patients who previously underwent the same conditioning without mouth rinse served as controls. The incidence of Grades 2-3 and Grade 3 oral mucositis was significantly reduced in patients who performed mouth rinse as compared with the controls (40 vs. 80%, P = 0.009; 0 vs. 25. 7%, P = 0.02). In conclusion, mouth rinse during and shortly after high-dose cytarabine infusion could be an effective and inexpensive measure in reducing the incidence of moderate to severe oral mucositis caused by high-dose cytarabine. This finding strongly suggests the role of cytarabine excretion in the saliva in the development of cytarabine-associated oral mucositis.

Purpose: To clarify the incidence, symptoms, and timing of extrapulmonary fibrosis developing after hypofractionated stereotactic body radiotherapy. Patients and Methods: We analyzed 379 consecutive patients who underwent stereotactic body radiotherapy for lung tumors at four institutions between February 2001 and March 2007. The median follow-up time was 29 months (range, 1-72). We investigated the subjective and objective characteristics of the extrapulmonary masses, redelineated the origin tissue of each on the treatment planning computed tomography scan, and generated dose-volume histograms. Results: In 9 patients (2.4%), extrapulmonary masses were found 3-36 months (median, 14) after irradiation. Coexisting swelling occurred in 3 patients, chest pain in 2, thumb numbness in 1, and arm edema in 1 patient. Extrapulmonary masses occurred in 5 (5.4%) of 92 and 4 (1.4%) of 287 patients irradiated with a 62.5-Gy and 48.0-Gy isocenter dose, respectively. The mean and maximal dose to the origin tissue was 25.8-53.9 Gy (median, 43.7) and 47.5-62.5 Gy (median, 50.2), respectively. In 5 of 9 patients, the standardized uptake values on 18F-fluorodeoxyglucose-positron emission tomography was 1.8-2.8 (median, 2.2). Percutaneous needle biopsy was performed in 3 patients, and all the specimens showed benign fibrotic changes without malignant cells. Conclusion: All patients should be carefully followed after stereotactic body radiotherapy. The findings of any new lesion should prompt an assessment for radiation-induced extrapulmonary fibrosis before an immediate diagnosis of recurrence is made. Careful beam-shape modification and dose prescription near the thoracic outlet are required to prevent forearm neuropathy and lymphedema.

Purpose: We have used dynamic conformal multiple arc therapy (DCMAT) for stereotactic body radiotherapy (SBRT) since 2001. We investigated the consistency of DCMAT for SBRT using dose-volume histogram analysis. Methods and Materials: A total of 50 patients with peripheral lung tumors underwent SBRT. The median tumor diameter was 2.4 cm (range, 0.9-5.9). Treatment planning was performed using a superposition algorithm. The prescribed 50 Gy dose was divided into five fractions. The prescribed dose was defined as 80% of the maximal dose in the planning target volume (PTV), and the leaf margins were modified to ensure the PTV was included in the 80% isodose surface. The dose-volume histogram analysis was used to assess the PTV and normal lung volume. Results: The median dose covering 95% of the PTV was 50.27 Gy (range, 46.14-52.67), essentially consistent with the prescribed dose. The median homogeneity and conformity index was 1.41 (range, 1.31-1.53) and 1.73 (range, 1.41-2.21), respectively. The median volume of lung receiving ≥20 Gy (V20) was 4.2% (range, 1.4-10.2%). A linear correlation was found between the tumor diameter and V20, and an even stronger correlation was found between the PTV/(normal lung volume) and V20. The estimated V20 was 7.1% (range, 3.9-10.4%) for a 5-cm-diameter tumor, assumed to be the maximal size limitation for SBRT. Conclusion: SBRT with DCMAT achieved high conformity and delivered adequate doses within the PTV. The median dose covering 95% of the PTV was consistent with the prescribed dose. V20 can be estimated using the tumor diameter and normal lung volume. DCMAT was thus both a feasible and a reproducible method of SBRT delivery.

Extraosseous uptake often seen on Tc-99m methylene diphosphonate bone scintigraphy has clinical significance. In a routine follow-up study on a 54-year-old female patient with breast cancer, we encountered a rare finding of pericardial metastasis clearly demonstrated by Tc-99m methylene diphospho- nate bone scintigraphy. This incidental finding of increased uptake in the periphery of the cardiac contour on a bone scan reflects radionuclide accumulation in pericardium, myocardium, or pericardial effusion itself. In our case, an additional computed tomography examination of the chest was useful for making the definitive diagnosis of dystrophic calcification of the pericardium.

Objective: Immunoliposome (PEG, GAH, liposome; PGL), consisting of F(ab)2 fragment of monoclonal antibody, GAH and polyethyleneglycol- coated (PEGylated) liposome was provided. Immunoliposome, PGL was labeled with technetium-99m (Tc-99m) by two methods: labeling F(ab)2 fragment with Tc-99m; Tc-99m-PGL, and entrapping Tc-99m into liposome; PGL[Tc-99m]. The objective of this study was to compare the biodistribution of Tc-99m-PGL and PGL[Tc-99m] in human gastric cancer xenografted mice. Methods: Tc-99m-PGL, PGL[Tc-99m], and Tc-99m-entrapped liposome; Lipo[Tc-99m] were prepared. They were injected into human gastric cancer, MKN45, xenografted mice via the tail vein, and their biodistribution was studied. Results: No marked accumulation of either PGL[Tc-99m] or Lipo[Tc-99m] was observed in the stomach. The uptake of Tc-99m-PGL by the liver, spleen, and lung was higher than that by the tumor. On the other hand, the uptake of PGL[Tc-99m] by the lung and spleen was markedly lower as compared with that of Tc-99m-PGL; the accumulation of PGL[Tc-99m] was lower in the lung and higher in the spleen as compared with that of the tumor. Although the liver uptake of PGL[Tc-99m] was markedly decreased as compared with that of Tc-99m-PGL, it was higher than the uptake of the tumor. The Tc-99m-PGL was strongly taken up by the tumor, with a high level of incorporation also seen in the stomach. These findings suggest the need for further study of the labeling stability. Conclusions: PGL[Tc-99m] appears to show promise for high tumor uptake and retention. This is an important implication for the potential application of immunoliposomes entrapped with Re-186, instead of Tc-99m, in internal radiotherapy.

Purpose: To retrospectively analyze the clinical outcomes of stereotactic body radiotherapy (SBRT) for patients with Stages 1A and 1B non-small-cell lung cancer. Methods and Materials: We reviewed the records of patients with non-small-cell lung cancer treated with curative intent between Dec 2001 and May 2007. All patients had histopathologically or cytologically confirmed disease, increased levels of tumor markers, and/or positive findings on fluorodeoxyglucose positron emission tomography. Staging studies identified their disease as Stage 1A or 1B. Performance status was 2 or less according to World Health Organization guidelines in all cases. The prescribed dose of 50 Gy total in five fractions, calculated by using a superposition algorithm, was defined for the periphery of the planning target volume. Results: One hundred twenty-one patients underwent SBRT during the study period, and 63 were eligible for this analysis. Thirty-eight patients had Stage 1A (T1N0M0) and 25 had Stage 1B (T2N0M0). Forty-nine patients were not appropriate candidates for surgery because of chronic pulmonary disease. Median follow-up of these 49 patients was 31 months (range, 10-72 months). The 3-year local control, disease-free, and overall survival rates in patients with Stages 1A and 1B were 93% and 96% (p = 0.86), 76% and 77% (p = 0.83), and 90% and 63% (p = 0.09), respectively. No acute toxicity was observed. Grade 2 or higher radiation pneumonitis was experienced by 3 patients, and 1 of them had fatal bacterial pneumonia. Conclusions: The SBRT at 50 Gy total in five fractions to the periphery of the planning target volume calculated by using a superposition algorithm is feasible. High local control rates were achieved for both T2 and T1 tumors.