Intraoperative Electron Beam Radiotherapy Research Articles

Intraoperative radiotherapy electron boost in advanced and recurrent epithelial ovarian carcinoma: a retrospective study.

BackgroundRelapses of epithelial ovarian carcinoma (EOC) have a poor prognosis and are almost always fatal. The aim of this study was to evaluate the clinical outcome and toxicity of intraoperative electron beam radiation therapy (IOERT) in advanced and recurrent EOC.MethodsForty-five women with EOC were treated with IOERT. Twenty-five patients had primary disease (PD) without distant metastasis at IOERT, and 20 patients had an isolated local recurrence (ILR) after surgery. All 45 patients in this series underwent optimal cytoreductive (≤ 1 cm) surgery. The whole pelvic (WP) radiotherapy was intraoperatively delivered using 12 Mev electron beam; 43 patients received 18-20 Gy and two patients received 10 Gy. Thirty-three patients received postoperateive intraperitoneal (IP) chemotherapy, while seven patients received intravenous (IV) chemotherapy. Five patients refused concurrent chemotherapy. Overall survival (OS) rates were analyzed using the Kaplan-Meier method.ResultsTumor recurrence and metastasis were observed in 16 patients (35.6%). Of those, 14 patients (31.1%) relapsed and two patients (4.4%) had distant metastasis alone. Eight of 25 (32%) local failures were observed in the PD group, as compared to 6/20 (30%) in the ILR group (P = 0.885). Actuarial local control at five year follow-up was 31/45 (68.9%). Seventeen of the total 45 (37.8%) patients died. Nine of 25 (36%) in the PD group died, as compared to 8 of 20 (40%) in the ILR group. The 5-year OS and disease-free survival (DFS) rates were 28/45 (62.2%) and 25/45 (55.6%), respectively. In the PD group, the 5-year OS and DFS rates were 16/25 (64%) and 14/25 (56%) (P > 0.05, vs. the ILR group at 12/20 and 11/20, respectively). The OS and DFS in the IOERT plus IP group were 25/33 (75.8%) and 23/33 (69.7%), respectively, which were superior to the rates achieved with IOERT plus IV chemotherapy (P < 0.05, 2/7 and 1/7, respectively). The major complication of IOERT was neuropathy. Five (11.1%) patients developed peripheral neurotoxicity.ConclusionsIOERT may be feasible and effective as a boosting technique for advanced and recurrent ovarian cancer. IOERT plus IP chemotherapy may achieve high locoregional disease control and survival benefit with a low risk of toxicity. Peripheral nerves in the IOERT field are dose-limiting structures requiring nerve protection policies or a dose compromise to ensure against severe neurological damage.

Intraoperative Electron Beam Radiotherapy (IOERT) in the Management of Recurrent Ovarian Malignancies

To investigate disease control, survival outcomes, and tolerance of intraoperative electron beam radiation therapy (IOERT) as a component of treatment for women with recurrent ovarian malignancies. From November 1987 to January 2009, 20 patients with recurrent ovarian malignancies received IOERT after maximal surgical cytoreduction. Areas treated included the pelvis (14), para-aortic nodes (6), or inguinal nodes (1). The median IOERT dose was 12.5 Gy (range, 10-22.5 Gy). Sixteen patients also received perioperative external beam radiotherapy as a component of treatment (median, 50 Gy; range, 20-54.3 Gy). All patients were followed prospectively for outcome and toxicity evaluation. Median follow-up for surviving patients was 76.2 months (range, 1.5-175.8 months). The 5-year Kaplan-Meier estimate of local control was 59%, and central control (within the IOERT field) was 76%. All local relapses occurred in patients who had microscopic margin-positive resections. The 5-year freedom from distant relapse was 37%. The median disease-free interval after IOERT was 14 months. The median survival was 30 months, and the 5-year Kaplan-Meier estimate of survival was 49%. Six patients (29%) experienced grade 3 or higher toxicities, 2 of which (10%) were at least partly attributable to IOERT. Three patients experienced grade 1 or 2 peripheral neuropathy related to IOERT. Combined modality therapy with external beam radiotherapy, surgery, and IOERT is an option for the treatment of localized recurrent ovarian cancer, with acceptable rates of in-field failure and toxicity. Durable disease control is possible in select women treated with this regimen.

Application of Failure Mode and Effects Analysis to Intraoperative Radiation Therapy Using Mobile Electron Linear Accelerators

Failure mode and effects analysis (FMEA) represents a prospective approach for risk assessment. A multidisciplinary working group of the Italian Association for Medical Physics applied FMEA to electron beam intraoperative radiation therapy (IORT) delivered using mobile linear accelerators, aiming at preventing accidental exposures to the patient. FMEA was applied to the IORT process, for the stages of the treatment delivery and verification, and consisted of three steps: 1) identification of the involved subprocesses; 2) identification and ranking of the potential failure modes, together with their causes and effects, using the risk probability number (RPN) scoring system, based on the product of three parameters (severity, frequency of occurrence and detectability, each ranging from 1 to 10); 3) identification of additional safety measures to be proposed for process quality and safety improvement. RPN upper threshold for little concern of risk was set at 125. Twenty-four subprocesses were identified. Ten potential failure modes were found and scored, in terms of RPN, in the range of 42-216. The most critical failure modes consisted of internal shield misalignment, wrong Monitor Unit calculation and incorrect data entry at treatment console. Potential causes of failure included shield displacement, human errors, such as underestimation of CTV extension, mainly because of lack of adequate training and time pressures, failure in the communication between operators, and machine malfunctioning. The main effects of failure were represented by CTV underdose, wrong dose distribution and/or delivery, unintended normal tissue irradiation. As additional safety measures, the utilization of a dedicated staff for IORT, double-checking of MU calculation and data entry and finally implementation of in vivo dosimetry were suggested. FMEA appeared as a useful tool for prospective evaluation of patient safety in radiotherapy. The application of this method to IORT lead to identify three safety measures for risk mitigation.

An experimental attenuation plate to improve the dose distribution in intraoperative electron beam radiotherapy for breast cancer

Intraoperative electron beam radiotherapy (IOERT) is a technique in which a single-fraction high dose is intraoperatively delivered to subclinical tumour cells using an electron beam after breast-conserving surgery. In IOERT, an attenuation plate consisting of a pair of metal disks is commonly used to protect the normal tissues posterior to the breast. However, the dose in front of the plate is affected by backscatter, resulting in an unpredictable delivered dose to the tumour cells. In this study, an experimental attenuation plate, termed a shielding plate, was designed using Monte Carlo simulation, which significantly diminished the electron beam without introducing any backscatter radiation. The plate's performance was verified by measurements. It was made of two layers, a first layer (source side) of polymethyl methacrylate (PMMA) and a second layer of copper, which was selected from among other metals (aluminium, copper and lead) after testing for shielding capability and the range and magnitude of backscatter. The optimal thicknesses of the PMMA (0.71 cm) and copper (0.3 cm) layers were determined by changing their thicknesses during simulations. On the basis of these results, a shielding plate was prototyped and depth doses with and without the plate were measured by radiophotoluminescence glass dosimeters using a conventional stationary linear accelerator and a mobile linear accelerator dedicated for IOERT. The trial shielding plate functioned as intended, indicating its applicability in clinical practice.

Partial breast irradiation with electron beam for patients with breast cancer submitted to conservative surgery.

Abstract Abstract #5146 Introduction: conservative surgery is the standard procedure for initial breast cancer, followed by radiation therapy. Follow up after this approach has shown that about 90% of local recurrence occurs at the same quadrant or close to the tumor bed as well as studies of pathology. Based on the experience of Milan we have started a study protocol of intraoperative electron beam radiation (IORT), in september,2005.Purpose: to evaluate the feasibility, acute complications and cosmetic results of partial breast radiation therapy with electron beam, in patients submitted to conservative surgery and sentinel node dissection.Elegibity criteria: T&amp;lt; or = 3 cm, clinically N0,no EIC,free surgical margins,unilateral tumo.Method: from sep/2005 to may/2008 we have evaluated 75 patients. All patients were submitted to conservative surgery at the Department of Radiation Therapy, in a surgical room near the Linear Accelerator. After removal of the tumor and histopathological analysis ( tumor size, surgical margins and sentinel nodal status), the surgeon places the plaque (made of lead and aluminium) to protect the chest wall and closes the tumor bed; the radiation oncologist measures the depth of the tumor bed to choose the electron beam energy, and puts the cone in place. The patient then is taken to the Linac room and we proceed to the irradiation. The dose is 21 Gy, isodose of 90%. After that we return to the surgical room and the surgical procedure is finished.Demographic caracteristics of the patients:mean age 58 years,breast side right 32(42%) left breast 43(58%),race white 66(88%) not white 9(12%) Results Staging – tumor size varied from 0.3 to 2.5 cm at histopatologic analisys, nodal status was N0 -63(84%), Nmic – 8 (10%) and N1–4(6%), histologic grade was GI–26(33%), GII -27(35%) and G III -22(32%)All patients were treated at a Linac, using an electron beam cone of 57 mm of intern diameter; 3 different cone angles were used according to the position of the tumor in the breast – degree 0 – 18 (24%), degree 15 – 34(45%), degree 30 – 23(31%); beam energy varied according to the depth of the breast tissue: 6 MeV – 35(47%), MeV – 35(47%),12 MeV – 4(5%),15 Mev – 1(1%).Systemic therapy 39(52%) patients had chemotherapy, 50(67%) hormonytherapy, 18(24%), none and 7(9%) are to decide ( still in chemo).We observed acute complications in 6(9%) patients such as seroma and local infection, clinically solved.Cosmetic results were bad in 2(2%) patient, fair in 10(12%), good in 32(43%) and excellent in 3 (43%). As for now two patients developed axillary metastasis 13 and 28 months after IORT, and were treated with axillary dissection.Conclusion: this is a quite feasible method for partial breast irradiation, with satisfactory results in terms of acute complications and cosmetic results. For local control and late complications we still have to wait more time and the reports of open trials. Meanwhile, it should be emphasized that these patients should only be treated in a study protocol. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5146.

Is Electron Beam Intraoperative Radiotherapy (ELIOT) Safe in Pregnant Women with Early Breast Cancer? In Vivo Dosimetry to Assess Fetal Dose

Electron beam intraoperative radiotherapy (ELIOT) is a new technique permitting breast radiotherapy to be completed in a single session. Since ELIOT is associated with much reduced irradiation to nontarget tissues, we carried out a study on nonpregnant breast cancer patients to estimate doses to the uterus during ELIOT to better evaluate the possible use of ELIOT in pregnant breast cancer patients. We performed in vivo dosimetry with thermoluminescence radiation detectors (TLDs) in 15 premenopausal patients receiving ELIOT to the breast (prescribed dose 21 Gy) using two mobile linear accelerators. The TLDs were positioned subdiaphragmatically on the irradiated side, at the medial pubic position, and within the uterus. A shielding apron (2 mm lead equivalent) was placed over the viscera from the subcostal to the subpubic region. TLDs showed mean doses of 3.7 mGy (range 1-8.5 mGy) at subdiaphragm, 0.9 mGy (range 0.3-2 mGy) pubic, and 1.7 mGy (range 0.6-3.2 mGy) in utero, for beam energies in the range 5-9 MeV. These findings indicate that ELIOT with a mobile linear accelerator and shielding apron would be safe for the fetus, as doses of a few mGy are not associated with measurable increased risk of fetal damage, and the threshold dose for deterministic effects is estimated at 100-200 mGy. We conclude that studies on the use of ELIOT in pregnant women treated with conservative breast surgery are justified.

Adjuvant intraoperative electron radiotherapy and external beam radiotherapy for locally advanced transitional cell carcinoma of the ureter

Objective Surgery is the mainstay treatment for transitional cell carcinoma (TCC) of the ureter; however, local recurrence remains a common cause of treatment failure for locally advanced disease after surgery, and the benefit of adjuvant radiotherapy has not been completely determined. The objective of this analysis was to evaluate the outcome of postsurgical high dose radiotherapy consisting of intraoperative electron beam radiotherapy (IOERT) and external beam radiotherapy (EBRT) in locally advanced transitional cell carcinoma of the ureter. Methods Seventeen patients with pathologically diagnosed TCC of ureter were treated with nephroureterectomy and adjuvant radiation consisted of IOERT and EBRT according to an institutional research protocol. The dose of IOERT ranged between 10 to 20 Gy (median 14 Gy). Conventional EBRT given with the total dose ranged between 36 and 45 Gy (median 42 Gy). Chemotherapy was utilized in 10 of the 17 patients at the discretion of their primary oncologist. Results The median follow-up for all patients was 48 months (range, 10–91 months). The overall survivals of the entire group of patients at 1, 3, and 5 years were 82%, 65%, and 46%, respectively. The estimated locoregional control rates at 1, 3, and 5 year were 82%, 64%, and 51%, respectively. Depth of invasion (pT), histological grade, and presence of residual disease were significant prognostic factors in univariate analysis. Multivariate analysis revealed that independent prognostic factors for survival included histological grade (grade 1 + 2 vs. grade 3 + 4; P = 0.03) and presence of residual disease after surgery (R0 vs. R1 or R2 resection; P = 0.053). Acute and long-term adverse effects rated grade 3 or higher were seen in 4 and 2 patients, respectively. No grade 5 toxicity occurred. Conclusion IOERT and EBRT following surgery produced a 51% local control and 46% overall survival rate for locally advanced TCC of ureter at 5 years of follow-up, with acceptable rates of acute and late toxicity. Adjuvant IOERT appears to permit dose escalation safely in patients who received conventional adjuvant EBRT and chemotherapy. This strategy deserves to be optimized and then tested in a prospective trial to learn if it can further improve outcome.

Setup verification and in vivo dosimetry during intraoperative radiation therapy (IORT) for prostate cancer

The purpose of this study was to check the setup and dose delivered to the patients during intraoperative electron beam radiation therapy (IORT) for prostate cancer. Twenty eight patients underwent IORT after radical prostatectomy for prostate cancer by means of a dedicated mobile accelerator, Novac7 (by Hitesys, SpA, Italy). A 9 MeV electron beam at high dose per pulse was used. Eighteen patients received IORT at escalating doses of 16, 18, and 20 Gy at 85% isodose, six patients for each dose level. Further, ten patients received 20 Gy at 85% isodose. The electron applicator position was checked in all cases by means of two orthogonal images obtained with brilliance intensifier. Target and organ at risk doses were measured in vivo by a MOSFETs dosimetry system. MOSFETs and microMOSFET dosimeters were inserted into sterile catheters and directly positioned into the rectal lumen, for ten patients, and into the bladder to urethra anastomosis, in the last 14 cases. Verification at 0 degree led to very few adjustments of setup while verifications at 90 degrees often suggested to bring the applicator closer to the target. In vivo dosimetry showed an absorbed dose into the rectum wall < or =1% of the total dose. The average dose value inside the anastomosis, for the 12 patients analyzed, was 23.7 Gy with a standard deviation of +/-7.6%, when the prescription was 20 Gy at 85% isodose. Using a C-arm mobile image intensifier, it is possible to assess if the positioning is correct and safe. Radio-opaque clips and liquid were necessary to obtain good visible images. In vivo MOSFETs dosimetry is feasible and reliable. A satisfactory agreement between measured and expected doses was found.

Results from a 6-Year Experience with Intraoperative Electron Beam Irradiation as Additional Therapy in Advanced Tumors of the Anterior Skull Base

Results from a 6-Year Experience with Intraoperative Electron Beam Irradiation as Additional Therapy in Advanced Tumors of the Anterior Skull Base

Real-time In Vivo Dosimetry Using Micro-MOSFET Detectors During Intraoperative Electron Beam Radiation Therapy in Early-stage Breast Cancer

Real-time In Vivo Dosimetry Using Micro-MOSFET Detectors During Intraoperative Electron Beam Radiation Therapy in Early-stage Breast Cancer

Patterns of Failure and Local Control After Intraoperative Electron Boost Radiotherapy to the Presacral Space in Combination with Total Mesorectal Excision in Patients with Locally Advanced Rectal Cancer

To evaluate local control and patterns of failure in patients treated with intraoperative electron beam radiotherapy (IOERT) after total mesorectal excision (TME), to appraise the effectiveness of intraoperative target definition. We analyzed the outcome of 243 patients with rectal cancer treated with IOERT (median dose, 10 Gy) after TME. Eighty-eight patients received neoadjuvant and 122 patients adjuvant external beam radiotherapy (EBRT) (median dose, 41.4 Gy), and in 88% simultaneous chemotherapy was applied. Median follow-up was 59 months. Local failure was observed in 17 patients (7%), resulting in a 5-year local control rate of 92%. Only complete resection and absence of nodal involvement correlated positively with local control. Considering IOERT fields, seven infield recurrences were seen in the presacral space, resulting in a 5-year local control rate of 97%. The remaining local relapses were located as follows: retrovesical/retroprostatic (5), anastomotic site (2), promontorium (1), ileocecal (1), and perineal (1). Intraoperative electron beam radiotherapy as part of a multimodal treatment approach including TME is a highly effective regimen to prevent local failure. The presacral space remains the site of highest risk for local failure, but IOERT can decrease the percentage of relapses in this area.

Results from a 6-Year Experience with Intraoperative Electron Beam Irradiation as Additional Therapy in Advanced Tumors of the Anterior Skull Base

Results from a 6-Year Experience with Intraoperative Electron Beam Irradiation as Additional Therapy in Advanced Tumors of the Anterior Skull Base

Surgery and Intraoperative Radiation Therapy in Treatment of Advanced Cancer of the External and Middle Ear

The purpose of this study was to evaluate the use of intraoperative electron beam radiotherapy (IORT) as an adjuvant modality in the treatment of advanced external auditory canal and temporal squamous cell carcinomas (SCC).

Preoperative Chemoradiation and Intra-Operative Radiotherapy for Pancreatic Carcinoma

In recent years, preoperative chemoradiation has received growing interest for the treatment of locally advanced pancreatic cancer. In an attempt to improve resectability and disease control, we used preoperative radiation therapy and concomitant 5-fluorouracil in a combined modality therapy protocol. The aim of the study was to evaluate definitive results in terms of toxicity, response and clinical outcome. Twenty-eight patients with unresectable (cT4, 19 patients) or resectable (cT3, 9 patients) nonmetastatic pancreatic tumors received radiotherapy (39.6 Gy) plus 5-fluorouracil (continuous infusion, days 1-4 at 1000 mg/m(2)/day). After 4 weeks, patients were evaluated for surgical resection. In 9 resected patients, electron-beam intra-operative radiotherapy (10 Gy) was given before reconstruction. Thereafter, in resected patients, adjuvant chemotherapy was prescribed. During chemoradiation, 1 patient (3.6%) developed grade 3 acute gastrointestinal toxicity and 2 patients (7.1%) developed grade 3 hematological toxicity. Three of 19 patients with unresectable tumors had tumor downstaging (15.8%). Two patients showed partial response (response rate, 7.1%; 95% CI, 0.2-25.3) and 4 patients (14.3%) had minimal tumor response. Four patients (14.3%) showed progressive disease after chemoradiation. One postoperative death was recorded. The median survival time was 11.3 months (20.5 and 9.0 months in resected and unresected patients, respectively). Only one local failure was recorded in 8 patients resected with negative margins. Although the response rate is still low, our preliminary results suggest that preoperative 5-fluorouracil chemoradiation is well tolerated and may result in tumor downstaging. Delivery of intra-operative radiotherapy seems to be associated with a low rate of local recurrences.

New trends in radiotherapy for breast cancer

New radiotherapy techniques are under development to improve tumor control and to decrease the long-term side effects of breast cancer. These include accelerated partial breast irradiation, intensity modulated and image guided radiotherapy. Follow-up data of multicatheter brachytherapy accelerated partial breast irradiation and intraoperative electron beam radiotherapy confirm excellent 5-year local control rates in well selected patients. Early side effects seem to be improved, but recent data show increasing skin toxicity in multicatheter and intracavitary balloon brachytherapy. Intraoperative radiotherapy, proton beam partial breast irradiation, intensity modulated and image guided radiotherapy improve dose homogeneity and decrease normal tissue complication probability. For breast-only treatment, two tangential fields with different segments provide an attractive and feasible alternative to the conventional technique. The proposed intensity modulated radiotherapy techniques for comprehensive locoregional radiotherapy, however, result in increased doses to the contralateral lung and breast. Input from long-term clinical data on new radiotherapy techniques is needed. Consensus on target volume contouring and dose volume constraints for nontarget tissue has not yet been reached. Further research on skin toxicity with multicatheter or intracavitary brachytherapy is needed to improve the results.

Long-term results of intraoperative presacral electron boost radiotherapy (IOERT) in combination with total mesorectal excision (TME) and chemoradiation in patients with locally advanced rectal cancer

We analyzed the long-term results of patients with locally advanced rectal cancer using a multimodal approach consisting of total mesorectal excision (TME), intraoperative electron-beam radiation therapy (IOERT), and pre- or postoperative chemoradiation (CRT). Between 1991 and 2003, 210 patients with locally advanced rectal cancer (65 International Union Against Cancer [UICC] Stage II, 116 UICC Stage III, and 29 UICC Stage IV cancers) were treated with TME, IOERT, and preoperative or postoperative CHT. A total of 122 patients were treated postoperatively; 88 patients preoperatively. Preoperative or postoperative fluoropyrimidine-based CRT was applied in 93% of these patients. Median age was 61 years (range, 26-81). Median follow-up was 61 months. The 5-year actuarial overall survival (OS), disease-free survival (DFS), local control rate (LC), and distant relapse free survival (DRS) of all patients was 69%, 66%, 93%, and 67%, respectively. Multivariate analysis revealed that UICC stage and resection status were the most important independent prognostic factors for OS, DFS, and DRS. The resection status was the only significant factor for local control. T-stage, tumor localization, type of resection, and type of chemotherapy had no significant impact on OS, DFS, DRS, and LC. Acute and late complications > or =Grade 3 were seen in 17% and 13% of patients, respectively. Multimodality treatment with TME and IOERT boost in combination with moderate dose pre- or postoperative CRT is feasible and results in excellent long-term local control rates in patients with intermediate to high-risk locally advanced rectal cancer.

Outcomes in a series of 103 retroperitoneal sarcomas

Aims To report the effect on outcome of selection in patients receiving intra-operative electron beam radiation (IOERT) and external beam radiation therapy (EBRT). Methods One hundred and three patients treated for primary RS were studied. Median follow-up was 27 months. Clinical presentation, tumor characteristics, and treatment methods were analyzed to determine impact on survival and recurrence and if selection was occurring. Results Mean age was 55 ± 17 years. Mean tumor size was 15 ± 6 cm and 88 were high-grade. Complete gross tumor resection (CR) occurred in 62 patients and improved survival vs. both debulking ( p = 0.0005) and biopsy ( p < 0.0001). The 5- and 10-year survival rates were 62% and 52% for those with CR vs. 29% and 20% after incomplete resection. Among the 62 CR patients, there was selection to receive additional EBRT ± IOERT in patients with high-grade tumors ( p = 0.005) and/or microscopically positive margins ( p = 0.011). In these high-risk patients there was a trend for IOERT to further augment survival vs. EBRT alone and to increase the time to both local and distant recurrences ( p = 0.036). Conclusions Complete gross resection is the primary form of curative treatment for retroperitoneal sarcomas. Selection led to patients with high-risk tumors receiving additional radiation therapy. There appears to be a beneficial effect of IOERT plus EBRT in these high-risk patients after complete tumor resection.

Neutron production from a mobile linear accelerator operating in electron mode for intraoperative radiation therapy

Intraoperative electron beam radiotherapy is increasingly performed using mobile linac delivering therapeutic radiation doses in unshielded operating rooms. While no special neutron-shielding problem should arise for operation at 10 MeV or less, it is not clear whether this holds true for operation at higher energies. This paper reports the measured neutron production from a Mobetron mobile electron linac, operated at 12 MeV, and compares the results with those from a conventional linac, also operated at 12 MeV in electron mode. Neutron leakage measurements were performed by means of passive bubble detectors in the scattering foil, patient and floor planes. Neutron dose equivalent rates per unit of electron dose delivered by the Mobetron at its normal treatment distance (50 cm SSD) were 0.33 µSv Gy−1 at the accelerator head, 0.18 µSv Gy−1 in the patient plane at 15 cm from the beam axis and 0.31 µSv Gy−1 at the floor plane, on the beam axis and under the beam stopper. For a weekly workload of 250 Gy, the weekly neutron dose equivalents at 12 MeV for the Mobetron at a distance of 300 cm from the scattering foil were 14.3 and 1.7 µSv/week for floor below and adjoining areas on the same floor, respectively. Neutron dose equivalent rates generated from Mobetron are at least one order of magnitude lower than ones produced by a conventional linac operated at the same energy in electron mode. Mobetron can be used at 12 MeV in an unshielded operating room for a weekly workload of up to 250 Gy if the bremsstrahlung x-rays are shielded to negligible levels.

Prognostic factors for disease-free survival in patients with T3–4 or N+ rectal cancer treated with preoperative chemoradiation therapy, surgery, and intraoperative irradiation

Fluoropyrimidine-radiosensitizing agents in conjunction with preoperative radiotherapy have proven to induce tumor and nodal downstaging effects, sphincter preservation promotion, and mid-term favorable survival rates. Intraoperative electron beam radiation therapy may improve pelvic control in patients with locally advanced rectal cancer stages. Potential predictive factors for response and disease-free survival, with intense local multidisciplinary approach, are analyzed. One hundred fifteen patients with rectal cancer were treated with oral 5-fluorouracil or Tegafur with preoperative radiotherapy, surgery, and intraoperative electron beam radiation therapy to identify potential pre- and on-treatment characteristics that might be of prognostic value for disease outcome. Univariate and multivariate analyses were performed. Older patients and those treated with Tegafur were more likely to achieve a major histologic response, categorized as persistence of minimal residual microscopic disease foci in the surgical specimen ("mic" response). Factors unfavorably associated with disease-free survival in the multivariate model were male gender and persistence of macroscopic disease in the rectal wall ("mac" response). Accordingly, 3-year disease-free survival rates in the groups of patients with 0, 1, or 2 of these risk factors were 100%, 81%, and 53%, respectively (p < 0.001). Females with an intense pathologic response (pT(mic) residue) to preoperative chemoradiotherapy have an excellent 3-year disease-free survival. This information might be of interest for stratification of patients in the development of adjuvant treatment trials.

Real-time in vivo dosimetry using micro-MOSFET detectors during intraoperative electron beam radiation therapy in early-stage breast cancer

Purpose In a previous paper we reported the results of off-line in vivo measurements using radiochromic films in IOERT. In the present study, a further step was made, aiming at the improvement of the effectiveness of in vivo dosimetry, based on a real-time check of the dose. Materials and methods Entrance dose was determined using micro-MOSFET detectors placed inside a thin, sterile, transparent catheter. The epoxy side of the detector was faced towards the beam to minimize the anisotropy. Each detector was plugged into a bias supply (standard sensitivity) and calibrated at 5 Gy using 6 MeV electrons produced by a conventional linac. Detectors were characterized in terms of linearity, precision and dose per pulse dependence. No energy and temperature dependence was found. The sensitivity change of detectors was about 1% per 20 Gy accumulated dose. Correction factors to convert surface to entrance dose were determined for each combination of energy and applicator. From November 2004 to May 2005, in vivo dosimetry was performed on 45 patients affected by early-stage breast cancer, who underwent IOERT to the tumour bed. IOERT was delivered using electrons (4–10 MeV) at high dose per pulse, produced by either a Novac7 or a Liac mobile linac. Results The mean ratio between measured and expected dose was 1.006±0.035 (1 SD), in the range 0.92–1.1. The procedure uncertainty was 3.6%. Micro-MOSFETs appeared suitable for in vivo dosimetry in IOERT, although some unfavourable aspects, like the limited lifetime and the anisotropy with no build-up, were found. Prospectively, a real-time action level (±6%) on dose discrepancy was defined. Conclusions Excellent agreement between measured and expected doses was found. Real-time in vivo dosimetry appeared feasible, reliable and more effective than the method previously published.