[en] Purpose: To evaluate the relative frequency and magnitude of intratreatment and intertreatment displacements in the patient positioning for pelvic radiotherapy using electronic portal imaging. Methods and Materials: Five hundred ninety-four electronic portal images of seven patients treated with a four-field pelvic technique were evaluated. All patients were treated prone without an immobilization device. Two fields were treated per day, from which an average of two electronic portal images were obtained for each field. No treatment was interrupted or adjusted on the basis of these images. Each image was aligned to the corresponding simulation film to measure the displacements in the mediolateral, craniocaudal, and anteroposterior directions relative to the simulated center. The intertreatment displacement was the displacement measured from the initial image for each daily treated field. For each daily treated field the intratreatment displacement was calculated by subtracting the displacement measured on the initial image from the displacement measured on the final image. Results: The frequency of intertreatment displacements exceeding 10 mm was 3%, 16%, and 23% for the mediolateral, craniocaudal, and anteroposterior translations, respectively. There were no intratreatment displacements exceeding 10 mm (p < 0.001). The frequency of intertreatment displacements exceeding 5 mm was 40, 52, and 51% for the mediolateral, craniocaudal, and anteroposterior translations, respectively; whereas, the frequency of intratreatment displacements exceeding 5 mm was 1, 5, and 7% for the same translations, respectively (p < 0.001). The standard deviation of the intertreatment displacements was at least three times as great as the standard deviation of the intratreatment displacements for all translations. These deviations were greater than the precision limit of the measurement technique, which is approximately 1 mm. Each patient had one direction where systematic error predominated in intertreatment positioning. Random error predominated for intratreatment positioning and for the other two directions in intertreatment positioning. Conclusions: During a course of pelvic radiotherapy, the frequency of intertreatment displacements exceeding 5 and 10 mm is significantly greater than the frequency of intratreatment displacements of these magnitudes. Errors in intertreatment positioning are predominantly systematic in one direction for each patient, whereas intratreatment error is predominantly random. Because patients do not move considerably during the daily treatment of a pelvic field, a single electronic portal image per daily field may be considered representative of the treated position

[en] Purpose: There is an increased incidence of breast cancer following mantle field radiation therapy for Hodgkin's disease (HD). We reviewed the experience at the Mallinckrodt Institute of Radiology (MIR) for radiation factors related to the development of breast cancer after mantle field radiation therapy for HD. Methods: The radiation therapy records of 152 women treated with mantle field irradiation for HD at MIR between 1966-1985 were reviewed for the development of breast cancer and treatment-related factors. All patients had a minimum of 5 years of follow-up. The treatment era (1966-1974 vs. 1975-1985), stage of HD, mediastinal dose, axillary dose, maximum dose from the anterior field (anterior d_max dose), the anterior-posterior:posterior-anterior (AP:PA) ratio, age at the time of treatment, length of follow-up, and history of splenectomy were analyzed as possible contributing factors for the development of breast cancer. The observed number of breast cancers was compared to the expected number based on age-adjusted incidences from the Connecticut Tumor Registry. Results: Ten breast cancers occurred in the population. Eight involved an upper outer quadrant. In a multivariate analysis, the development of breast cancer was significantly associated with axillary dose. Patients in the early treatment era were at an increased risk for the development of breast cancer due to high anterior d_max and breast doses from weighting the fields anteriorly on a low energy linear accelerator. The use of current radiation therapy techniques was not related to an increased risk of breast cancer with a median follow-up of 13 years. Conclusions: A high dose to the axilla and the anterior d_max point is significantly associated with the development of breast cancer after mantle field irradiation for HD. Efforts to protect the breast from high doses will likely lessen the increased risk of breast cancer in women treated with radiation therapy for HD

[en] Purpose: The goal was to determine an adequate planning target volume (PTV) margin for three-dimensional conformal radiotherapy (3D CRT) of prostate cancer. The uncertainty in the internal positions of the prostate and seminal vesicles and the uncertainty in the treatment set-ups for a single group of patients was measured. Methods: Weekly computed tomography (CT) scans of the pelvis (n=38) and daily electronic portal images (n=1225) were reviewed for six patients who received seven-field 3D CRT for prostate cancer. The weekly CT scans were registered in three dimensions to the original treatment planning CT scan using commercially available software. This registration permitted measurement of the motion in the center-of-volume (COV) of the prostate and seminal vesicles throughout the course of therapy. The daily portal images (PI) were registered to the corresponding simulation films to measure the set-up displacement for each of the seven fields. The field displacements were then entered into a matrix program which calculated the isocenter displacement by a least squares method. The uncertainty in the internal positions of the prostate and seminal vesicles (standard deviation of the motions) was added to the uncertainty in the set-up (standard deviation of the isocenter displacements) in quadrature to arrive at a total uncertainty. Positive directions were defined in the left, anterior, and superior directions. A discussion of an adequate PTV was based on these results. Results: The mean magnitude of motion for the COV of the prostate ± the standard deviation was 0 ± 1 mm in the left-right (LR) direction, 0.5 ± 2.8 mm in the anterior-posterior (AP) direction, and 0.5 ± 3.5 mm in the superior-inferior (SI) direction. The mean magnitude of motion for the COV of the seminal vesicles ± the standard deviation was -0.3 ± 1.5 mm in the LR, 0.6 ± 4.1 mm in the AP, and 0.7 ± 2.3 mm in the SI directions, respectively. For all patients the mean isocenter displacement ± the standard deviation was 0.5 ± 3.4 mm in the LR, 1.7 ± 3.3 mm in the AP, and -0.4 ± 2.4 mm in the SI directions, respectively. The total uncertainty, which includes organ position and set-up uncertainty, for the prostate was 3.5 mm, 4.3 mm, and 4.2 mm in the LR, AP, and SI directions, respectively. For the seminal vesicles, the total uncertainty was 3.7 mm, 5.3 mm, and 3.3 mm in the LR, AP, and SI directions, respectively. The percent change in rectal volume correlated with motion of the prostate in the AP direction and with motion of the seminal vesicles in the SI direction. To account for the uncertainties with a 95% or 99% probability, PTV margins equal to two times or three times the total uncertainties are required (10 - 16 mm), respectively. Conclusions: PTV margins of 10 - 16 mm are required to encompass all (99%) possible positions of the prostate or seminal vesicles during 3D CRT. PTV margins of 7 - 11 mm will encompass the measured uncertainties with a 95% probability. PTV margins as small as 5 mm may not adequately cover the target volume. Clinicians and investigators are using 5 - 10 mm as a range for PTV margins in a current 3D CRT dose escalation protocol for prostate cancer (RTOG 94-06). Results from this trial will determine whether toxicity and local tumor control are acceptable

[en] Purpose: To determine whether the clinical implementation of an electronic portal imaging device can improve the precision of daily external beam radiotherapy. Methods and Materials: In 1991, an electronic portal imaging device was installed on a dual energy linear accelerator in our clinic. After training the radiotherapy technologists in the acquisition and evaluation of portal images, we performed a randomized study to determine whether online observation, interruption, and intervention would result in more precise daily setup. The patients were randomized to one of two groups: those whose treatments were actively monitored by the radiotherapy technologists and those that were imaged but not monitored. The treating technologists were instructed to correct the following treatment errors: (a) field placement error (FPE) > 1 cm; (b) incorrect block; (c) incorrect collimator setting; (d) absent customized block. Time of treatment delivery was recorded by our patient tracking and billing computers and compared to a matched set of patients not participating in the study. After the patients radiation therapy course was completed, an offline analysis of the patient setup error was planned. Results: Thirty-two patients were treated to 34 anatomical sites in this study. In 893 treatment sessions, 1,873 fields were treated (1,089 fields monitored and 794 fields unmonitored). Ninety percent of the treated fields had at least one image stored for offline analysis. Eighty-seven percent of these images were analyzed offline. Of the 1,011 fields imaged in the monitored arm, only 14 (1.4%) had an intervention recorded by the technologist. Despite infrequent online intervention, offline analysis demonstrated that the incidence of FPE > 10 mm in the monitored and unmonitored groups was 56 out of 881 (6.1%) and 95 out of 595 (11.2%), respectively; p < 0.01. A significant reduction in the incidence of FPE > 10 mm was confined to the pelvic fields. The time to treat patients in this study was 10.78 min (monitored) and 10.10 min (unmonitored). Features that were identified that prevented the technologists from recognizing more errors online include poor image quality inherent to the portal imaging device used in this study, artifacts on the portal images related to table supports, and small field size lacking sufficient anatomical detail to detect FPEs. Furthermore, tools to objectively evaluate a portal image for the presence of field placement error were lacking. These include magnification factor corrections between the simulation of portal image, online measurement tools, image enhancement tools, and image registration algorithms. Conclusion: The use of an electronic portal imaging device in our clinic has been implemented without a significant increase in patient treatment time. Online intervention and correction of patient positioning occurred rarely, despite FPEs of > 10 mm being present in more than 10% of the treated fields. A significant reduction in FPEs exceeding 10 mm was made in the group of patients receiving pelvic radiotherapy. It is likely that this improvement was made secondarily to a decrease in systematic error and not because of online interventions. More significant improvements in portal image quality and the availability of online image registration tools are required before substantial improvements can be made in patient positioning with online portal imaging

[en] Purpose: To determine an adequate planning target volume (PTV) margin for three-dimensional conformal radiotherapy (3D CRT) of prostate cancer, the uncertainties in the internal positions of the prostate and seminal vesicles (SV) and in the treatment setups were measured. Methods and Materials: Weekly computed tomography (CT) scans of the pelvis (n = 51) and daily electronic portal images (n = 1630) were reviewed for eight patients who received seven-field 3D CRT for prostate cancer. The CT scans were registered in three dimensions to the original planning CT scan using commercially available software to measure the center-of volume (COV) motion of the prostate and SV. The daily portal images were registered to the corresponding simulation films to measure the setup displacements. The standard deviation (SD) of the internal organ motions was added to the SD of the setups in quadrature to determine the total uncertainty. Positive directions were left, anterior, and superior. Rotations necessary to register the CT scans and portal images were minimal and not further analyzed. Results: The mean motion for the COV of the prostate ± the SD was 0 ± 0.9 mm in the left-right (LR), 0.5 ± 2.6 mm in the anterior-posterior (AP), and 1.5 ± 3.9 mm in the superior-inferior (SI) directions. The mean motion for the COV of the SV ± the SD was 0.3 ± 1.7 mm in the LR, 0.7 ± 3.8 mm in the AP, and 0.9 ± 3.5 mm in the SI directions. For all patients the mean isocenter displacement ± the SD was 0 ± 3.1 mm in the LR, 1.4 ± 3.0 mm in the AP, and -0.4 ± 2.1 mm in the SI directions. The total uncertainty for the prostate was 3.2 mm, 4.0 mm, and 4.4 mm in the LR, AP, and SI directions, respectively. For the SV, the total uncertainty was 3.5, 4.8, and 4.1 mm in the LR, AP, and SI directions, respectively. Conclusions: PTV margins of 10 to 16 mm are required to encompass all (99%) possible positions of the prostate or SV during 3D CRT. PTV margins of 7 to 11 mm will encompass the measured uncertainties with a 95% probability. PTV margins of 5 mm may not adequately cover the intended volume

[en] Purpose: To retrospectively review our experience using radiation therapy as a palliative treatment in ovarian carcinoma. Methods and Materials: Eighty patients who received radiation therapy for ovarian carcinoma between 1983 and 1998 were reviewed. The indications for radiation therapy, radiation therapy techniques, details, tolerance, and response were recorded. A complete response required complete resolution of the patient's symptoms, radiographic findings, palpable mass, or CA-125 level. A partial response required at least 50% resolution of these parameters. The actuarial survival rates from initial diagnosis and from the completion of radiation therapy were calculated. Results: The median age of the patients was 67 years (range 26 to 90 years). A median of one laparotomy was performed before irradiation. Zero to 20 cycles of a platinum-based chemotherapy regimen were delivered before irradiation (median = 6 cycles). The reasons for palliative treatment were: pain (n=22), mass (n=23), obstruction of ureter, rectum, esophagus, or stomach (n=12), a positive second-look laparotomy (n=9), ascites (n=8), vaginal bleeding (n=6), rectal bleeding (n=1), lymphedema (n=3), skin involvement (n=1), or brain metastases with symptoms (n=11). Some patients received treatment for more than one indication. Treatment was directed to the abdomen or pelvis in 64 patients, to the brain in 11, and to other sites in 5. The overall response rate was 73%. Twenty-eight percent of the patients experienced a complete response of their symptoms, palpable mass, and/or CA-125 level. Forty-five percent had a partial response. Only 11% suffered progressive disease during therapy that required discontinuation of the treatment. Sixteen percent had stable disease. The duration of the responses and stable disease lasted until death except in 10 patients who experienced recurrence of their symptoms between 1 and 21 months (median = 9 months). The 1-, 2-, 3-, and 5-year actuarial survival rates from diagnosis were 89%, 73%, 42%, and 33%, respectively. The survival rates calculated from the completion of radiotherapy were 39%, 27%, 13%, and 10%, respectively. Five percent of patients experienced Grade 3 diarrhea, vomiting, myelosuppression, or fatigue. Fourteen percent of patients experienced Grade 1 or 2 diarrhea, 19% experienced Grade 1 or 2 nausea and vomiting, and 11% had Grade 1 or 2 myelosuppression. Conclusions: In this series of radiation therapy for advanced ovarian carcinoma, the response, survival, and tolerance rates compare favorably to those reported for current second- and third-line chemotherapy regimens. Cooperative groups should consider evaluating prospectively the use of radiation therapy before nonplatinum and/or nonpaclitaxel chemotherapy in these patients