Long-term Outcomes of Early-stage Non-stomach Gastrointestinal Mucosa-associated Lymphoid Tissue Lymphoma Treated With Radiation Therapy.

BACKGROUND/AIM: Non-stomach gastrointestinal mucosa-associated lymphoid tissue (MALT) lymphoma is rare, and there are only a few reports regarding radiation therapy (RT) for non-stomach gastrointestinal MALT lymphoma. There has been no established cure and no reports on RT use with long-term follow-up. Herein, we report a retrospective long-term investigation of early-stage non-stomach gastrointestinal MALT lymphoma. Our aim was to evaluate whether RT is a valid treatment option for this disease. PATIENTS AND METHODS: We retrospectively analyzed 6 patients who were diagnosed with early-stage non-stomach gastrointestinal MALT lymphoma and received RT. The median age was 66 years (range=38-89 years). The primary tumor originated from the duodenum in 2 patients and from the rectum in 4 patients. The RT dose was 30-34 Gy in 15-20 fractions to the involved site or field, depending on the case. RESULTS: The median follow-up time was 89.5 months (range=6-170). All patients had complete remission within 3 months after RT. The 5-year overall survival and progression-free survival rates were 83.3% and 100%, respectively. During the observation period, no patient had a confirmed recurrence. One patient died of causes unrelated to cancer or treatment. There were no late toxicities by RT. CONCLUSION: Our results show good long-term local control and no late toxicities requiring treatment. Moderate-dose RT was appropriate and well tolerated for early-stage non-stomach gastrointestinal MALT lymphoma.

Prognostic markers including immune and inflammatory factors predict outcomes in patients receiving postoperative radiation therapy for cholangiocarcinoma.

PURPOSE: This study aimed to analyze treatment outcomes and prognostic markers, including immune and inflammatory factors, of postoperative radiation therapy (RT) administered to patients with cholangiocarcinoma (CCA). METHODS: We retrospectively included 59 patients with CCA who underwent surgery and postoperative RT with curative intent from 2004 to 2019. Patients received external irradiation (50 Gy in 25 fractions) using three-dimensional RT. We analyzed prognostic factors of inflammation, such as pre-RT platelet count, hemoglobin, lymphocyte count ratio (LCR) of the leukocyte count, platelet-to-lymphocyte ratio (PLR), and neutrophil-to-lymphocyte ratio (NLR). RESULTS: Tumor stages were distributed as follows: I (n = 8), II (n = 25), III (n = 15), and IVA (n = 11). The median follow-up was 24 months. Two-year overall survival (OS), cause-specific survival (CSS), progression-free survival (PFS), and locoregional control (LRC) rates were 59.5%, 62.0%, 40.1%, and 66.7%, respectively. Univariate analysis revealed that lower LCR was significantly associated with shorter PFS (p = 0.0446). There was no significant difference between the median baseline values of PLR and NLR; and age ≥75, positive regional lymph node metastases (N+), and chemotherapy after RT were significantly associated with poor OS. Multivariate analysis revealed a significant association of N+ with worse OS, PFS, and CSS and that lower LCR was significantly associated with better PFS (p = 0.0234). Among late toxicity events, two patients (3.38%) were suspected with therapy-related liver toxicity. CONCLUSIONS: Lower LCR before RT was a better prognostic factor for postoperative RT of patients with CCA.

Safety and efficacy of peptide receptor radionuclide therapy with 177Lu-DOTA0-Tyr3-octreotate in combination with amino acid solution infusion in Japanese patients with somatostatin receptor-positive, progressive neuroendocrine tumors.

PURPOSE: Peptide receptor radionuclide therapy (PRRT) with 177Lu-DOTA0-Tyr3-octreotate (177Lu-DOTATATE) is one of the most reliable treatments for unresectable, progressive neuroendocrine tumors (NETs) with somatostatin receptor expression. We have, for the first time, reported the results of the tolerability, safety, pharmacokinetics, dosimetry, and efficacy of this treatment for Japanese patients with NET. METHODS: Patients with unresectable, somatostatin receptor scintigraphy (SRS)-positive NETs were enrolled in this phase I clinical trial. They were treated with 29.6 GBq of 177Lu-DOTATATE (four doses of 7.4 GBq) combined with amino acid solution infusion plus octreotide long-acting release (LAR) 30 mg. The primary objective of this study was to evaluate the tolerability, safety, pharmacokinetics, and dosimetry of a single administration of this treatment in patients with SRS-positive NETs. RESULTS: Six Japanese patients (three men and three women; mean age 61.5 years; range 50-70 years) with SRS-positive unresectable NETs were recruited. 177Lu-DOTATATE was eliminated from the blood in a two-phase manner. Cumulative urinary excretion of radioactivity was 60.1% (range 49.0%-69.8%) within the initial 6 h. The cumulative renal absorbed dose for 29.6 GBq of 177Lu-DOTATATE was 16.8 Gy (range 12.0-21.2 Gy), and the biological effective dose was 17.0 Gy (range 12.2-21.5 Gy). Administration of 177Lu-DOTATATE was well tolerated, with no dose-limiting toxicities. Grade 3 lymphopenia occurred in two (33.3%) cases, but there were no other severe toxicities. Four patients achieved partial response (objective response rate, 66.7%), one patient had stable disease, and one patient had progressive disease. CONCLUSION: PRRT with 177Lu-DOTATATE was well-tolerated and showed good outcomes in Japanese patients with unresectable NETs. Peptide receptor radionuclide therapy, 177Lu-DOTA0-Tyr3-octreotate .

Outcome of Radiation Therapy for Stage IVB Uterine Cervical Cancer With Distant Lymph Nodes Metastases; Sequential Irradiation for Distant Lymph Nodes Metastases.

BACKGROUND/AIM: This study aimed to evaluate the outcome of radiation therapy for patients with distant lymph node (LN) metastases, without organ metastases from uterine cervical cancer (UCC). PATIENTS AND METHODS: Twenty-six patients with UCC with distant LN metastases received radiotherapy and were retrospectively analyzed. The sites of distant LN metastasis were as follows; Supraclavicular in 19, inguinal in nine, axillary in four, and others in three. The mean dose prescribed for these was 50 (range=40-60) Gy. RESULTS: The 2-year overall, cause-specific, and progression-free survival, and local control of primary tumor rates were 51.3%, 51.3%, 46.9%, and 67.9%. In multivariate analysis, performance status ≥1 (p=0.007), para-aortic LN metastases (p=0.001), and lack of high-dose-rate intracavitary brachytherapy (p=0.033) were significantly associated with poor overall survival. Performance status ≥1 (p=0.004), and para-aortic LN metastases (p=0.014) were significantly associated with poor cause-specific survival. CONCLUSION: This study demonstrated favorable local control in patients with UCC with distant LN metastases.

Impact of superselective intra-arterial and systemic chemoradiotherapy for gingival carcinoma; analysis of treatment outcomes and prognostic factors.

BACKGROUND: We compared outcomes and toxicities between concurrent retrograde super-selective intra-arterial chemoradiotherapy (IACRT) and concurrent systemic chemoradiotherapy (SCRT) for gingival carcinoma (GC). METHODS: We included 84 consecutive patients who were treated for non-metastatic GC ≥ stage III, from 2006 to 2018, in this retrospective analysis (IACRT group: n = 66; SCRT group: n = 18). RESULTS: The median follow-up time was 24 (range: 1-124) months. The median prescribed dose was 60 (6-70.2) Gy (IACRT: 60 Gy; SCRT: 69 Gy). There were significant differences between the two groups in terms of 3-year overall survival (OS; IACRT: 78.8, 95% confidence interval [CI]: 66.0-87.6; SCRT: 50.4, 95% CI: 27.6-73.0; P = 0.039), progression-free survival (PFS; IACRT: 75.6, 95% CI: 62.7-85.2; SCRT: 42.0, 95% CI: 17.7-70.9; P = 0.028) and local control rates (LC; IACRT: 77.2, 95% CI: 64.2-86.4; SCRT: 42.0, 95% CI: 17.7-70.9; P = 0.015). In univariate analysis, age ≥ 65 years, decreased performance status (PS) and SCRT were significantly associated with worse outcomes (P < 0.05). In multivariate analysis, age ≥ 65 years, clinical stage IV, and SCRT were significantly correlated with a poor OS rate (P < 0.05). Patients with poorer PS had a significantly worse PFS rate. Regarding acute toxicity, 22 IACRT patients had grade 4 lymphopenia, and osteoradionecrosis was the most common late toxicity in both groups. CONCLUSIONS: This is the first report to compare outcomes from IACRT and SCRT among patients with GC. ALL therapy related toxicities were manageable. IACRT is an effective and safe treatment for GC.

Outcomes of treatment for localized prostate cancer in a single institution: comparison of radical prostatectomy and radiation therapy by propensity score matching analysis.

OBJECTIVES: To compare the outcomes of radical prostatectomy (RP), intensity-modulated radiation therapy (IMRT), and low-dose-rate brachytherapy (BT) using propensity score matching analysis in patients with clinically localized prostate cancer. METHODS: A group of 2273 patients with clinically localized prostate cancer between January 2004 and December 2015 at the Yokohama City University hospital were identified. The records of 1817 of these patients, who were followed up for a minimum of 2 years, were reviewed; 462 were treated with RP, 319 with IMRT, and 1036 with BT. The patients were categorized according to the National Comprehensive Cancer Network risk classification criteria, and biochemical outcomes and overall survival rates were examined. Biochemical failure for RP was defined as prostate-specific antigen (PSA) levels > 0.2 ng/ml, and for IMRT and BT as nadir PSA level + 2 ng/ml. Propensity scores were calculated using multivariable logistic regression based on covariates, including the patient's age, preoperative PSA, Gleason score, number of positive cores, and clinical T stage. RESULTS: Median follow-up was 77 months for the RP, 54 months for IMRT, and 66 months for BT patients. After the propensity scores were adjusted, a total of 372 (186 each) and 598 (299 each) patients were categorized into RP vs IMRT and RP vs BT groups, respectively. Kaplan-Meier analysis did not show any statistically significant differences in terms of overall survival rate between these groups (RP vs IMRT: p = 0.220; RP vs BT: p = 0.429). IMRT was associated with improved biochemical failure-free survival compared to RP in all risk groups (high-risk: p < 0.001; intermediate-risk: p = 0.009; low-risk: p = 0.001), whereas significant differences were observed only in the intermediate-risk group (p = 0.003) within the RP vs BT group. CONCLUSION: The results of our propensity score analysis of mid-term localized prostate cancer treatment outcomes demonstrated no significant differences in the overall survival rate. Despite the difference in biochemical failure definition between surgery and radiotherapeutic approaches, the results of this study demonstrate improved biochemical control favoring IMRT and BT as compared to RP.

Outcome of Radiation Therapy for Locally Advanced Vulvar Carcinoma: Analysis of Inguinal Lymph Node.

BACKGROUND/AIM: The aim of this study was to define the outcome of radiation therapy for vulvar carcinoma, and to investigate the effectiveness of therapeutic and prophylactic inguinal lymph node (ILN) irradiation. Because reports about the treatment of ILN were limited. PATIENTS AND METHODS: Thirty consecutive vulvar carcinoma patients were treated using external beam radiation therapy (EBRT) for definitive disease (n=25) or postoperatively (n=5). Twenty-four (80%) had squamous cell carcinoma (SCC). Tumor stages (2002 UICC) ranged from 0 to IVB, with no distant metastases. RESULTS: The median total prescribed dose for primary tumor was 64.8 Gy. The 2-year overall survival rate was 25.3%. The outcome was significantly better in patients with ILNs<30 mm (p=0.005) and patients receiving prescribed doses >60 Gy (p=0.002). CONCLUSIONS: ILN diameters ≤30 mm and prescribed doses over 60 Gy were associated with ILN control in patients with vulvar carcinoma.

Radiation Therapy for Uterine Cervical Cancer With Lung Metastases Including Oligometastases.

BACKGROUND/AIM: To investigate the role and outcomes of radiation therapy (RT) for stage IVB uterine cervical cancer (UCC) patients with lung (oligo) metastases due to the lack of recent reports on the subject. PATIENTS AND METHODS: The cohort for this retrospective study comprised 23 consecutive patients with UCC (squamous cell carcinoma, n=13) and lung metastases who had received pelvic RT. Ten had lung metastases only, including 7 with oligometastases (≤4 lung metastases); the remaining 13 also had other distant metastases. RESULTS: Nine (39.1%) of the 22 patients (95.7%) completed RT without interruption. The 1-year primary progression-free rate was 95.2%. The 1-year overall survival rate was 47.2 % (estimated median survival: 9 months). Significant prognostic factors for survival included: i) ≤4 lung metastases (p=0.035), ii) unilateral lung metastases (p=0.039), iii) primary tumor diameter <100 mm (p<0.001), and iv) ECOG performance status <1 (p=0.015). CONCLUSION: RT is safe and effective for stage IVB UCC patients with lung metastases.

Outcome of postoperative radiation therapy for cholangiocarcinoma and analysis of dose-volume histogram of remnant liver.

The aim of this study was to analyze dose-volume histogram (DVH) of the remnant liver for postoperative cholangiocarcinoma (CCA) patients, to find toxicity rates, and to confirm efficacy of postoperative radiation therapy (RT).Thirty-two postoperative CCA patients received partial liver resection and postoperative RT with curative intent. The "liver reduction rate" was calculated by contouring liver volume at computed tomography (CT) just before the surgery and at CT for planning the RT. To evaluate late toxicity, the radiation-induced hepatic toxicity (RIHT) was determined by the common terminology criteria for adverse events toxicity grade of bilirubin, aspartate transaminase, alanine transaminase, alkaline phosphatase, and albumin, and was defined from 3 months after RT until liver metastasis was revealed. The radiation-induced liver disease (RILD) was also evaluated.Tumor stages were distributed as follows: I: 1, II: 8, IIIA: 1, IIIB: 6, IIIC: 14, IVA: 2. Median prescribed total dose was 50 Gy. Median follow-up time was 27 months. Two-year overall survival (OS): 72.4%, disease-free survival: 47.7%, local control: 65.3%, and the median survival time was 40 months. The median "liver reduction rate" was 21%. The OS had statistically significant difference in nodal status (P = .032) and "liver reduction rate" >30% (P = .016). In the association between the ≥grade 2 RIHT and DVH, there were significantly differences in V30 and V40 (P = .041, P = .034), respectively. The grade ≥2 RIHT rates differ also significantly by sex (P = .008). Two patients (6.2%) were suspected of RILD.We suggest that RT for remnant liver should be considered the liver V30, V40 to prevent radiation-induced liver dysfunction.

Acute and late toxicities in localized prostate cancer patients treated with low-dose 125I brachytherapy (110 Gy) in combination with external beam radiation therapy versus brachytherapy alone (160 Gy).

PURPOSE: The aim of this analysis was to compare acute and late toxicities between low-dose-rate brachytherapy (LDR-BT) (110 Gy) in combination with 45 Gy in 25 fractions external beam radiation therapy (EBRT) and LDR-BT (160 Gy) alone for localized prostate cancer. MATERIAL AND METHODS: One hundred five consecutive patients with localized prostate cancer treated from May 2014 to May 2017 were included in this retrospective analysis. Sixty patients received combination therapy and 45 patients received BT monotherapy. The LDR-BT procedure was performed using 125I seeds. RESULTS: The median follow-up time was 28 months in both groups. Three-year effect rates were overall survival: 100% in both groups. The biochemical failure rate was 2.3% in the combination group and 0% in the monotherapy group (p = 0.373). No patients died during the study period. In both groups, almost all the patients experienced acute urethritis. There was a significant difference between the combination therapy group (8.3%) and BT monotherapy group (11.1%) in late genitourinary (GU) toxicities ≥ grade 2 (p = 0.035). Only 2 patients (3.3%) in the combination therapy group developed late ≥ grade 2 rectal hemorrhage. There were no significant differences between two groups in hematuria ≥ grade 2 (p = 0.068) or rectal hemorrhage ≥ grade 2 (p = 0.206). CONCLUSIONS: To our knowledge, this is the first report to compare the GU and gastrointestinal toxicities between the combination therapy and BT monotherapy (160 Gy) for localized prostate cancer. Unexpectedly, there were more late GU toxicities (except for hematuria) in the BT monotherapy group.

Radiation Therapy for Patients with Bone Metastasis from Uterine Cervical Cancer: Its Role and Optimal Radiation Regimen for Palliative Care.

AIM: To determine the role of radiation therapy for patients with bone metastasis from uterine cervical cancer and identify an optimal radiation regimen. PATIENTS AND METHODS: A total of 20 patients with bone metastases from uterine cervical cancer received radiation therapy to the pelvis. The median total dose of 60.2 Gy in the 2 Gy per fraction-equivalent dose (EQD2) was delivered to cervical tumors of all patients. Thirteen patients underwent chemotherapy during and/or following radiation therapy. RESULTS: In 18 of 20 patients, the primary tumors disappeared or were markedly reduced after radiation therapy. In all but one of 17 patients with pelvic pain and bleeding, these symptoms disappeared or were remarkably relieved. However, three patients had primary tumor progression at 7, 9, and 15 months after irradiation with total doses of 56.8, 58.4, and 68.3 Gy in EQD2, respectively. Two of these patients had relapses of bleeding and pain. The primary progression-free rate considering all patients was 69% at 1 year and 34% at 2 years. The corresponding overall survival rates were 34% at 1 year, and 8% at 2 years, with an estimated median survival time of 7 months. The number of metastatic bone sites (p=0.027) and administration of chemotherapy (p<0.001) were significant prognostic factors for survival. CONCLUSION: Radiation therapy is effective for relief of pelvic symptoms in patients with bone metastasis from uterine cervical cancer. For patients who are expected to survive for more than 1 year, almost curative-dose irradiation to primary tumors is recommended.

Impact of the early detection of esophageal neoplasms in hypopharyngeal cancer patients treated with concurrent chemoradiotherapy.

AIMS: We examined the risk factors and prognostic factors for synchronous esophageal neoplasia (SEN) by comparing the characteristics of hypopharyngeal cancer (HPC) patients with and without SEN. METHODS: We examined 183 patients who were treated with definitive radiotherapy for HPC. Lugol chromoendoscopy screening of the esophagus was performed in all patients before chemoradiotherapy. RESULTS: Thirty-six patients had SEN, 49 patients died of HPC and two died of esophageal cancer. The patients with SEN exhibited significantly higher alcohol consumption than those without SEN (P = 0.018). The 5-year overall survival (OS) rate of the 36 patients with SEN was lower than that of the other patients (36.2% vs 63.4%, P = 0.006). The SEN patients exhibited significantly shorter HPC cause-specific survival than the other patients (P = 0.039). Both the OS (P = 0.005) and the HPC cause-specific survival (P = 0.026) of the patients with SEN were significantly shorter than those of the patients without SEN in multivariate analysis. Category 4/T1 stage esophageal cancer was treated with concurrent chemoradiotherapy (CCRT), endoscopic treatment or chemotherapy. The 5-year survival rates for esophageal cancer recurrence for CCRT, endoscopic treatment and chemotherapy were 71.5, 43.7 and 0%, respectively. The median (range) survival time (months) of CCRT, endoscopic treatment and chemotherapy was 22.7 (7.5-90.6), 46.44 (17.3-136.7) and 7.98 (3.72-22.8), respectively. CONCLUSION: Advanced HPC patients with SEN might have a poorer prognosis than those without SEN even when the esophageal cancer is detected early and managed appropriately.

Radiation therapy for stage IVA uterine cervical cancer: treatment outcomes including prognostic factors and risk of vesicovaginal and rectovaginal fistulas.

PURPOSE: To evaluate the safety and efficacy of radiation therapy for stage IVA uterine cervical cancer and to identify an optimal radiation regimen. RESULTS: Seventeen of the 28 patients developed recurrence after radiation therapy (local recurrence in 10 and distant metastasis in 12). The local control and distant metastasis-free rates at 3 years in all patients were 61% and 49%, respectively. Fourteen patients died after radiation therapy, and all but 2 died of tumor progression. The disease-free, cause-specific, and overall survival rates at 3 years in all patients were 32%, 49%, and 45%, respectively, and the estimated median survival time was 32 months. Tumor size (P = 0.007) and involvement in the lower third of vagina (P = 0.006) were significant prognostic factors for local control. Older age (P = 0.018) and performance status (P = 0.020) were significant prognostic factors for distant metastasis. The presence of hydronephrosis was the sole significant prognostic factor for survival (P = 0.026). Only 2 patients developed grade 3 late toxicities (vesicovaginal fistula and radiation proctitis, respectively). MATERIALS AND METHODS: Twenty-eight patients with stage IVA uterine cervical cancer received radiation therapy. All patients initially received external pelvic irradiation at a median dose of 50.4 Gy in 28 fractions. Twenty patients also received high-dose-rate intracavitary brachytherapy at a median dose of 22 Gy in 4 fractions. These fraction sizes were lower than conventional sizes. The total median dose for all 28 patients was 68.7 Gy. CONCLUSIONS: Radiation therapy is safe and effective for treatment of stage IVA uterine cervical cancer. The reduced radiation dose per fraction may contribute to the prevention of vesicovaginal fistula formation.

Pharmacokinetics of single dose radium-223 dichloride (BAY 88-8223) in Japanese patients with castration-resistant prostate cancer and bone metastases.

OBJECTIVE: This open-label, non-randomized, phase I study examined the pharmacokinetics (PK) and radiation dosimetry of a single dose of radium-223 in Japanese patients with castration-resistant prostate cancer (CRPC) and bone metastases. METHODS: Six male Japanese patients (mean age 72.5 years, range 65-79 years) with histologically or cytologically confirmed stage IV adenocarcinoma of the prostate were recruited. A single IV dose of radium-223 was delivered intravenously (IV) via slow bolus over a 2-5 min period: Cohort 1 received 50 kBq/kg and Cohort 2 received 100 kBq/kg. RESULTS: Following IV injection, radium-223 was rapidly eliminated from the blood in a multi-phasic manner. The fraction of the injected activity of radium-223 retained in the whole body 24 h following injection was 85 %. Biodistribution results showed initial bone uptake was 52 % (range 41-57 %). The maximum activity of radium-223 in the bone was observed within 2 h of dosing. Activity of radium-223 passed through the small intestine within 24 h. No activity was detected in other organs. The major radiation dose from radium-223 was found in osteogenic cells; calculated absorbed doses in osteogenic cells and in the red marrow were 0.76 Gy/MBq and 0.09 Gy/MBq, respectively. CONCLUSIONS: In Japanese patients with CRPC and bone metastases, radium-223 (IV) achieved maximum activity in the bone rapidly and passed through the intestine within 24 h, without signs of activity in other organs. The PK profile and absorbed radiation dose in organs and tissues in Japanese patients were similar to data from non-Japanese patients. Trial registration identification: NCT01565746.

Severe COPD is correlated with mild radiation pneumonitis following stereotactic body radiotherapy.

BACKGROUND: The primary cause of COPD and lung cancer is smoking. Thus, patients with COPD frequently have lung cancer that often is inoperable. Stereotactic body radiation therapy (SBRT) is anticipated to be the standard of care for inoperable early stage non-small cell lung cancer. The most critical toxicity following SBRT is radiation pneumonitis (RP). We analyzed predictive factors for RP following SBRT and investigated the degree and occurrence of RP in patients with severe COPD. METHODS: We retrospectively evaluated 265 lung tumors treated with SBRT between 2005 and 2010 with a minimum follow-up of 6 months. Predictive factors for RP, including GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage and pack-years smoked, were evaluated by univariate and multivariate analyses. RP was graded according to the Common Terminology Criteria for Adverse Events version 3.0 scale. RESULTS: Median follow-up was 19.2 months (range, 6.0-72.0 months). RP grades of 0, 1, 2, 3, 4, and 5 occurred in 101, 102, 49, 12, 0, and one of these patients, respectively. Multivariate analysis revealed that high normal lung volume receiving ≥ 20 Gy, fewer pack-years smoked, and high total dose were significant predictive factors for RP ≥ grade 1, and high normal lung volume receiving 20 Gy, fewer pack-years smoked, and a history of lung resection were predictive for RP ≥ grade 2. RP in patients with more severe COPD was relatively milder than in patients with normal lung function and with mild COPD. Pack-year scales were significantly correlated with GOLD stage. CONCLUSIONS: RP following SBRT in patients with severe COPD was relatively mild. Heavy smoking was the strongest negative predictor for severe RP and was correlated with severe COPD. Further follow-up and quantitative analysis of lung function might be needed to ascertain longer tolerability to SBRT.

Analysis of suitable prescribed isodose line fitting to planning target volume in stereotactic body radiotherapy using dynamic conformal multiple arc therapy.

PURPOSE: To assess the most suitable value of a relative prescribed dose in clinical treatment plans of stereotactic body radiotherapy (SBRT) using dynamic conformal multiple arc therapy to treat lung tumors. METHODS AND MATERIALS: We retrospectively generated alternative SBRT plans for typical examples of 8 patients who had been treated with SBRT for a lung tumor with a prescribed dose of 50 Gy in 5 fractions. The prescribed dose had been defined as 80% of the maximal dose in the planning target volume (PTV) ("the 80% isodose plan"). Alternative 20%-90% isodose plans at 10% intervals were generated (64 plans; 8 plans for each of the 8 patients), and factors related to leaf margins, target volume, normal lung volume, and monitor units were compared using dose-volume histogram analysis. RESULTS: We could generate all the 64 plans. Compared with the 80% isodose plan, the V20 and mean lung dose (MLD) were both lower in the 60% plan; the V20 was approximately 19% lower (4.72% vs 3.84%) and the MLD was 13% lower (4.0 Gy vs 3.5 Gy). Mean PTV and ITV doses were higher in the lower percentage isodose plans. Compared with the 80% isodose plan, in the 60% isodose plan the mean PTV was 19% higher (56.1 Gy vs 66.8 Gy) and the mean ITV was 30% higher (59.6 Gy vs 77.4 Gy). The mean total monitor units increased more steeply than did the mean homogeneity index. The mean conformity index values in the 60% and 70% isodose plans were less than 1.15. CONCLUSIONS: The 60% isodose plan was considered the best plan in this analysis because of the lower comparative dosimetric factors in normal lung tissue (including V20 and MLD) and the higher comparative mean PTV and internal target volume doses achieved, along with good conformity index values. In clinical use, accurate estimation and commissioning should be performed for the dose distribution prior to selecting a plan. Further investigation is warranted to determine whether the calculated dosimetric advantages result in improved outcomes.