Development of a phantom to evaluate the positioning accuracy of patient immobilization systems using thermoplastic mask and polyurethane cradle.

PURPOSE: The purpose of this study was to develop a new phantom to evaluate the positioning accuracy of patient immobilization systems. METHODS: The phantom was made of papers formed into a human shape, paper clay, and filling rigid polyester. Acrylonitrile butadiene styrene (ABS) pipes were inserted at anterior-posterior (A-P) and right-left (R-L) directions in the phantom to give static load by pulling ropes through the pipes. First, the positioning precision of the phantom utilizing a target locating system (TLS) was evaluated by moving the phantom on a couch along inferior-superior (I-S), A-P, and R-L directions in a range from -5 mm to +5 mm. The phantom's positions detected with the TLS were compared with values measured by a vernier caliper. Second, the phantom movements in a tensile test were chosen from patient movements determined from 15 patients treated for intracranial lesions and immobilized with a thermoplastic mask and polyurethane cradle. The phantom movement was given by minimum or maximum values of patient movements in each direction. Finally, the relationship between phantom movements and the static load in the tensile test was characterized from measurements using the new phantom and the TLS. RESULTS: The differences in all positions between the vernier caliper measurement and the TLS detected values were within 0.2 mm with frequencies of 100%, 95%, and 90% in I-S, A-P, and R-L directions, respectively. The phantom movements according to patient movements in clinical application in I-S, A-P, and R-L directions were within 0.58 mm, 0.94 mm, and 0.93 mm from the mean value plus standard deviation, respectively. The regression lines between the phantom movements and static load were given by y = 0.359x, y = 0.241x, and y = 0.451x in I-S, A-P, and R-L directions, respectively, where x is the phantom movement (mm) and y is the static load (kgf). The relationship between the phantom movements and static load may represent the performance of inhibiting patient movements, so the accuracy of the immobilization system in the intracranial lesion will be estimated in advance by basic tensile test on the new phantom. CONCLUSIONS: The newly developed phantom was useful to evaluate the accuracy of immobilization systems for a Cyberknife system for intracranial lesions.

Local control of metastatic lung tumors treated with SBRT of 48 Gy in four fractions: in comparison with primary lung cancer.

OBJECTIVE: The optimal dose of stereotactic body radiotherapy (SBRT) for metastatic lung tumors has not been clarified. Local control rates of metastatic lung tumors treated with SBRT of 48 Gy in four fractions, which is one of the common dose schedules for Stage I primary lung cancer in Japan, were examined. METHODS: Between 2006 and 2008, 12 metastatic lung tumors (colorectal cancer, 7; others, 5) in 10 patients and 56 lesions of Stage I primary lung cancer (T1, 43; T2, 13) in 52 patients were treated with SBRT of 48 Gy in four fractions at the isocenter. RESULTS: Two-year overall survival rates were 86% for patients with metastatic lung tumors and 96% for patients with Stage I primary lung cancer (P = 0.4773). One- and 2-year local control rates were 48% and 25% for metastatic lung tumors, and 91% and 88% for Stage I primary lung cancer, respectively (P < 0.0001). CONCLUSIONS: The local control rates after SBRT of 48 Gy in four fractions were significantly worse in metastatic lung tumors compared with Stage I primary lung cancer. In SBRT, metastatic lung tumors should be clearly differentiated from primary lung cancer and should be given higher doses.

Supraclavicular failure after breast-conserving therapy in patients with four or more positive axillary lymph nodes when prophylactic supraclavicular irradiation is omitted.

PURPOSE: The incidence of supraclavicular metastasis as the initial failure and the failure patterns in patients with four or more positive axillary lymph nodes (PALNs) after breast-conserving therapy (BCT) without prophylactic supraclavicular irradiation were investigated. MATERIALS AND METHODS: Between 1991 and 2002, a total of 48 women with four or more PALNs underwent BCT without prophylactic supraclavicular irradiation (33 patients with 4-9 PALNs; 15 patients with > or =10 PALNs). RESULTS: The median follow-up time was 50 months. Among the patients with 4-9 PALNs, 3% had isolated supraclavicular metastasis as the initial failure, and 30% had distant metastasis as the initial failure. Among patients with > or =10 PALNs, 7% had isolated supraclavicular metastasis as the initial failure, and 40% had distant metastasis as the initial failure. The 4-year isolated supraclavicular failure rates were 5% for all patients, 3% for patients with 4-9 PALNs, and 8% for patients with >/=10 PALNs. CONCLUSION: In patients who had undergone BCT and had had four or more PALNs, the major failure pattern was distant failure with or without locoregional failure; isolated supraclavicular failure as the initial failure comprised a less common failure pattern. Omission of prophylactic supraclavicular irradiation may be acceptable for this subset of patients.

Thallium-201 SPECT in prognostic assessment of malignant gliomas treated with postoperative radiotherapy.

OBJECTIVE: This study was designed to investigate the value of preoperative thallium-201 (201Tl) SPECT as a predictor of outcome in malignant glioma. METHODS: From January 1990 to September 2003, 109 patients with glioma were treated with postoperative radiotherapy. Of these, 36 patients with malignant gliomas who underwent preoperative 201Tl-SPECT were included in this study (grade 3: n=14, grade 4: n=22). On early (10 minutes) and delayed (2 hours) images after 111 MBq 201TlCl injection, we calculated radioactivity ratios of tumors to contralateral normal brain (T/N ratios) and retention indices (RIs). For early and delayed images, we compared outcome between a high T/N ratio group (T/N ratio equal or greater than the average) and a low T/N ratio group (T/N ratio less than the average). We also divided the patients into two groups on the basis of RI; a high RI group (RI equal or greater than the average) and a low RI group (RI less than the average), and similarly compared outcome between the two groups. RESULTS: Median survival time was 12 months for both grade 3 and grade 4 tumors; however, two-year survival was 53% for grade 3 and 15% for grade 4. In both early and delayed images, outcome was significantly better for patients with low T/N ratios (early < 4.71, delayed < 3.96) than those with high T/N ratios (early: p = 0.030, delayed: p = 0.049). However, no significant survival difference was apparent between the low- (< -12.25) and high RI groups. In grade 3 glioma, patients with high T/N ratios demonstrated a tendency toward poorer outcome, although this trend was not significant (early: p = 0.079, delayed: p = 0.099). Overall outcome was poor for grade 4 glioma, and the difference in survival between low and high T/N ratio groups was not significant (early: p = 0.51, delayed: p = 0.53). However, long survival was seen only in patients with lower T/N ratios. CONCLUSIONS: Differences of 201Tl uptake in malignant gliomas could predict outcome. 201Tl-SPECT is potentially useful in the management of patients with malignant gliomas.

Thallium-201 scintigraphy in bone and soft-tissue tumors: a comparison of dynamic, early and delayed scans.

OBJECTIVE: It has been reported that delayed scan of thallium-201 (201Tl) scintigraphy is useful for differentiating malignant tumors from benign lesions and for evaluating treatment response. However, physiological muscle uptake which usually increases in delayed scans, often makes it difficult to evaluate 201Tl uptake and its washout in bone and soft-tissue tumors. The purpose of this study was to evaluate whether the delayed scan is necessary and whether a dynamic scan is useful in the evaluation of bone and soft-tissue tumors. METHODS: We studied 175 cases of bone and soft-tissue tumors (malignant 45, benign 130). Dynamic scans were acquired every 5 seconds for 10 minutes after 201Tl injection, and time activity curves (TACs) were generated by adaptive smoothing methods. Early and delayed scans were acquired at 10-15 minutes and 2 hours after injection. 201Tl images were visually interpreted and the radioactivity count ratio (T/N) of tumors to normal tissues and washout rate [WR = (early T/N - delayed T/N)/early T/N] were defined. RESULTS: When there were no 201Tl uptake in dynamic (n = 67) and early scans (n = 68), no tumor uptake was also appreciated in delayed scans, and all but two cases of negative scans were benign. In 107 lesions, although there were significant differences in T/Ns between malignant and benign lesions both on early scans (2.84 +/- 1.45 vs. 2.05 +/- 1.13, p < 0.05) and delayed scans (2.17 +/- 1.03 vs. 1.58 +/- 0.64, p < 0.05), there was a substantial overlap. The T/Ns decreased in delayed scans (i.e., WR > 0) in 100 of 107 cases due to increase of surrounding muscle uptake, and there was no difference in WR between malignant tumors and benign lesions (0.21 +/- 0.14 vs. 0.19 +/- 0.14). CONCLUSIONS: For evaluating bone and soft-tissue tumors, delayed scan had little clinical usefulness and it may be time consuming. Dynamic scan would be useful for demonstrating the differences between tumor blood flow and 201Tl uptake in tumors.

Healing focal "flare" phenomenon after radiotherapy in a bone metastasis from bladder cancer.

"Flare" phenomenon has been primarily reported as a transient increase in the number or intensity of lesions on bone scans in patients receiving hormonal or chemotherapy. It has been well documented in patients with metastatic breast or prostate carcinoma, and recently reported in those with lung cancer. We present a case of bone metastasis from bladder carcinoma, in which healing flare phenomenon was observed after radiotherapy.