A design of a DICOM-RT-based tool box for nonrigid 4D dose calculation.

The study was aimed to introduce a design of a DICOM-RT-based tool box to facilitate 4D dose calculation based on deformable voxel-dose registration. The computational structure and the calculation algorithm of the tool box were explicitly discussed in the study. The tool box was written in MATLAB in conjunction with CERR. It consists of five main functions which allow a) importation of DICOM-RT-based 3D dose plan, b) deformable image registration, c) tracking voxel doses along breathing cycle, d) presentation of temporal dose distribution at different time phase, and e) derivation of 4D dose. The efficacy of using the tool box for clinical application had been verified with nine clinical cases on retrospective-study basis. The logistic and the robustness of the tool box were tested with 27 applications and the results were shown successful with no computational errors encountered. In the study, the accumulated dose coverage as a function of planning CT taken at end-inhale, end-exhale, and mean tumor position were assessed. The results indicated that the majority of the cases (67%) achieved maximum target coverage, while the planning CT was taken at the temporal mean tumor position and 56% at the end-exhale position. The comparable results to the literature imply that the studied tool box can be reliable for 4D dose calculation. The authors suggest that, with proper application, 4D dose calculation using deformable registration can provide better dose evaluation for treatment with moving target.

Real-time monitoring and control on deep inspiration breath-hold for lung cancer radiotherapy--combination of ABC and external marker tracking.

PURPOSE: In this article, the breath-hold and gating concepts were combined for application of lung cancer radiation treatment. The tumor movement was immobilized based on deep inspiration breath hold (DIBH), in which the breath-hold consistency and stability were monitored by infrared (IR) tracking and controlled by gating with a predefined threshold. The authors' goal is to derive the benefits from both techniques, namely, the minimized treatment margin and the known advantages of deep inspiration. The efficacy of the technique in terms of tumor immobility and treatment setup accuracy was evaluated in the study. METHODS: Fourteen patients who were diagnosed with non small cell lung cancer were included in this study. The control of tumor immobility was investigated interfractionally and intrafractionally. The intrabreath-hold tumor motion was devised based on the external marker movement, in which the tumor-marker correlation was studied. The margin of the planning target volume (PTV) was evaluated based on two factors: (1) The treatment setup error accounts for the patient setup and interbreath-hold variations and (2) the intrabreath-hold tumor motion in which the residual tumor motion during irradiation was studied. RESULTS: As the result of the study, the group systematic error and group random error of treatment setup measured at the isocenter were 0.2(R) +/- 1.6, 1.0(A) +/- 2.0, and 0.3(S) +/- 1.5 mm in the left-right (LR), anterior-posterior (AP), and caudal-cranial (CC) directions, respectively. The Pearson correlation coefficient were 0.81 (LR), 0.76 (AP), and 0.85 (CC) mm and suggest tendency in linear correlation of tumor and marker movement. The intrabreath-hold tumor was small in all directions. The group PTV margins of 3.8 (LR), 4.6 (AP), and 4.8 (CC) mm were evaluated to account for both setup errors and residual tumor motion during irradiation. CONCLUSIONS: The study applies the DIBH technique in conjunction with IR positional tracking for tumor immobilization and treatment setup localization. The technique not only proved to be reliable in terms of good tumor immobility and accurate treatment positioning but also to be potentially useful for dose escalation treatment as regarding of the substantially reduced PTV margin and minimizing radiation toxicity from the fully expanded lung volume.

Stereotactic radiotherapy for locally recurrent nasopharyngeal carcinoma.

PURPOSE: To study the treatment outcome in patients with locally recurrent nasopharyngeal carcinoma (NPC) who were treated with stereotactic radiotherapy (SRT). METHODS AND MATERIALS: Thirty patients with non-metastatic, locally recurrent NPC who were treated with curative intent between 1998 and 2002 were retrospectively analyzed. The International Union Against Cancer T-stage distribution at recurrence (rT) was as follows: rT1-14, rT2-7, rT3-3, and rT4-6. All patients were treated with SRT with a daily fractional dose of 2.5-4.5 Gy (median, 3 Gy) in 8-22 fractions (median, 18 fractions). Total equivalent dose (TED) was calculated by the linear-quadratic formula without a time factor correction. RESULTS: The 5-year actuarial overall survival rate, disease-specific survival rate, and local failure-free survival (LFFS) rate for the whole group were 40%, 41.4%, and 56.8%, respectively. The 3-year LFFS rates of rT1-2 and rT3-4 diseases were 65% and 66.7%, respectively. Seven of nine patients who received a TED <55 Gy recurred locally compared with 4 of 21 patients who received > or =55 Gy. Their corresponding 5-year LFFS rates were 22.2% and 75.8% (p = 0.005). The TED was the only factor significant in affecting the local control on univariate analyses. CONCLUSION: SRT is an effective treatment for locally recurrent NPC. TED > or =55 Gy should be given to secure a higher local control rate. The late complication rates were acceptable for patients with rT1-2 disease. For patients with rT3-4 disease, more works need to be done to further decrease the late complications.

Hypofractionated stereotactic radiotherapy for medically inoperable stage I non-small cell lung cancer--report on clinical outcome and dose to critical organs.

We report 20 cases using hypofractionation stereotactic radiotherapy in medically inoperable stage I non-small cell lung cancer with dose escalation of 45-54 Gy prescribed at 85 or 90% isodose level in 3-4 fractions. Two-year local control and cancer-specific survival were 94.7 and 77.6%, respectively, with minimal toxicity. Though, large fraction size can be safely given to peripheral lung tumors, normal tissue tolerance to hypofractionated radiotherapy to esophagus, trachea, main bronchi, aorta and heart remains unknown. Therefore we also reported the maximum point doses to these critical organs to contribute information to extend this technique to more centrally located lung tumors in future.

High-dose-rate intracavitary brachytherapy boost for early T stage nasopharyngeal carcinoma{private}.

PURPOSE: To investigate any possible therapeutic gain from dose escalation with brachytherapy for early T stage nasopharyngeal carcinoma (NPC). METHODS AND MATERIALS: One hundred forty-five patients with T1-2b N0-3 NPC were boosted with high-dose-rate intracavitary brachytherapy after completion of two-dimensional external radiotherapy (ERT) during the period from 1999 to 2003. To compare the efficacy of brachytherapy boost, another 142 patients with T1-2b N0-3 disease who were treated with ERT alone during 1994 to 1999 were evaluated. All patients were treated with ERT to a total dose of 66 Gy in 6.5 weeks. The brachytherapy boost group was given 10-12 Gy in 2 weekly fractions. RESULTS: Dose escalation beyond 66 Gy with brachytherapy boost was shown to improve local control and survival. The 5-year actuarial local failure-free survival, regional failure-free survival, distant metastasis-free survival, progression-free survival, cancer-specific survival, and overall survival rates for the brachytherapy group and the control group were 95.8% and 88.3% (p = 0.020), 96% and 94.6% (p = 0.40), 95% and 83.2% (p = 0.0045), 89.2% and 74.8% (p = 0.0021), 94.5% and 83.4% (p = 0.0058), and 91.1% and 79.6% (p = 0.0062), respectively. The 5-year major-complication-free survival rate was 89.5% for the brachytherapy group and 85.6% for the control group (p = 0.23). CONCLUSIONS: For patients who are treated with two-dimensional treatment techniques, dose escalation with brachytherapy boost improves local control and overall survival of patients with T1-T2a and possibly non-bulky T2b disease.

Nasopharyngeal intracavitary brachytherapy: the controversy of T2b disease.

BACKGROUND: Locally persistent nasopharyngeal carcinoma (NPC) carries an increased risk of local failure if additional treatment is not given. It has been shown that intracavitary brachytherapy is effective in the treatment of patients with T1 and T2a NPC, although its role in the treatment of T2b disease had remained uncertain. The objectives of the current study were to evaluate the outcomes of patients with T2b, locally persistent NPC who were treated with high-dose-rate (HDR) intracavitary brachytherapy and to explore whether routine brachytherapy boost could improve the local control of patients who had T2b NPC at initial diagnosis. METHODS: Thirty-four patients with locally persistent NPC who were treated during 1992-2000 with HDR intracavitary brachytherapy were analyzed retrospectively. All patients had T2b disease at initial diagnosis. They were treated with HDR intracavitary brachytherapy at doses of 22.5-24.0 grays (Gy) in 3 weekly sessions. To compare the efficacy of brachytherapy, another 403 consecutive patients with nonmetastatic T2b NPC who were treated with curative intent by external radiotherapy (ERT) during the same period were evaluated. RESULTS: An improvement in the 5-year actuarial local failure-free survival rate (brachytherapy group vs. ERT group: 96.9% vs. 81.5%; P = 0.024), the disease-specific survival rate (84.5% vs. 68.1%; P = 0.021), and the overall survival rate (78.3% vs. 63.1%; P = 0.034) was demonstrated in the group that had locally persistent NPC who were salvaged with brachytherapy. In assessing local control, the addition of brachytherapy was just short of statistical significance on multivariate analysis (P = 0.054). The complication rates were comparable between the brachytherapy group and the ERT group. CONCLUSIONS: The results suggested that patients with T2b NPC who have locally persistent disease can be salvaged effectively with brachytherapy. Their local control was even better than that achieved by patients who had clinical remission of local disease at the completion of ERT. Furthermore, it is possible that routine brachytherapy boost, after the completion of ERT, may improve local control in patients who have T2b disease at initial diagnosis. However, its exact benefit can be elucidated only by prospective, randomized studies.

Treatment results of high-dose-rate remote afterloading brachytherapy for cervical cancer and retrospective comparison of two regimens.

PURPOSE: To review the treatment results and complications of high-dose-rate (HDR) intracavitary brachytherapy for patients with carcinoma of the cervix in a single institute and to compare them with those of low-dose-rate (LDR) brachytherapy reported in the literature. METHODS AND MATERIALS: Two hundred twenty patients with carcinoma of the cervix were treated by primary radiotherapy between 1991 and 1998. The median age was 63 (range 24-84). The distribution according to Federation of Gynecology and Obstetrics (FIGO) staging system was as follows: Stage IB, 11.4%; IIA, 9.1%; IIB, 50.9%; IIIA, 3.6%; IIIB, 23.2%; and IVA, 1.8%. They were treated with whole pelvic irradiation giving 40 Gy to the midplane in 20 fractions over 4 weeks. This was followed by parametrial irradiation, giving 16-20 Gy in 8-10 fractions. HDR intracavitary brachytherapy was given weekly, with a dose of 7 Gy to point A for three fractions and, starting from 1996, 6 Gy weekly for four fractions. The median overall treatment time was 50 days (range 42-73 days). The median follow-up time was 4.7 years (range 3 months to 11.1 years). Multivariate analysis was performed using the Cox regression proportional hazards model. RESULTS: The complete remission rate after radiotherapy was 93.4% (211/226). The 5-year actuarial failure-free survival (FFS) and cancer-specific survival (CSS) rates for stage IB, IIA, IIB, IIIA, IIIB, and IVA were 87.7% and 86.6%, 85% and 85%, 67.8% and 74%, 46.9% and 54.7%, 44.8% and 50.4%, 0% and 25%, respectively. On multivariate analysis, young age (< 50) (p = 0.0054), adenocarcinoma (p = 0.0384), and stage (p = 0.0005) were found to be independent poor prognostic factors. The 5-year actuarial major complication rates (Grade 3 or above) were as follows: proctitis, 1.0%; cystitis, 0.5%; enteritis, 1.3%; and overall, 2.8%. On multivariate analysis, history of pelvic surgery was a significant prognosticator. The two HDR fractionation schedules were not a significant prognosticator in predicting disease control and complications. CONCLUSION: Our experience in treating cervical cancer with HDR intracavitary brachytherapy is encouraging. Our treatment results and complication rates were compatible with those of the LDR series. Further studies are eagerly awaited to better define the optimal fractionation schedule for HDR brachytherapy and the schedule on how chemotherapy may be combined with it.