CT planning of boost irradiation in radiotherapy of breast cancer after conservative surgery

Comparing Breast Conservation Surgery Seromas Contoured by Radiation Therapists versus those Contoured by a Radiation Oncologist in Radiation Therapy Planning for Early-Stage Breast Cancer

INTRODUCTION

In the management of early-stage breast cancer using radiation therapy, computed tomography (CT) simulation is used to identify the breast conservation surgery (BCS) seroma as a proxy for the tumour bed. The delineation or contouring of the seroma is generally a task performed by a radiation oncologist (RO). With increasing patient numbers and other demands placed on ROs, the scope of practice for radiation therapists (RTs) is continually expanding, and the need for skills transfer from one profession to another has been investigated in recent years. This study aims to compare the BCS seroma volumes contoured by RTs with those contoured by ROs to add evidence in support of expanding the RTs' role in the treatment planning process in the management of early-stage breast cancer.

METHODS

A study was undertaken using the CT-simulation (CT-sim) data sets of patients with early-stage breast cancer treated in 2013. The CT-sim data sets had BCS seromas contoured by 1 of 5 ROs as part of routine clinical management. This study involved 4 RTs who each used the patient information to identify and contour breast seromas on 50 deidentified CT-sim data sets. Metrics used to compare RT versus RO contours included volume size, overlap between volumes, and geographical distance from the centre of volumes.

RESULTS

There were 50 CT-sim data sets with 1 RO contour and 4 RT contours analysed. The contour volumes of the 4 RTs and the ROs were assessed. Although there were 50 CT-sim data sets presented to each RT, analysis was carried out on 45, 43, 46, and 45 CT-sim data sets. There were no comparisons made where contours were not delineated. The contour volumes of the 4 RTs and the ROs were assessed with an interclass correlation coefficient, with a result of excellent reliability (0.975, 95% [0.963, 0.985]). The DICE similarity coefficient was used to compare the overlap of each RT contour with the RO contour; the results were favourable with mean (95% CI) DSCs 0.685, 0.640, 0.678, and 0.681, respectively. Comparing the RT and RO geographical centre of the seroma volumes, good to excellent reliability between the RTs and ROs was demonstrated (95% CI mean RO vs RT distances (mm): 3.75, 4.99, 7.71, and 3.39). There was no statistically significant difference between the distances (P = 0.65).

CONCLUSION

BCS seromas contoured by RTs compared well with those contoured by an RO. This research has provided further evidence to support RTs in assuming additional contouring responsibilities in radiation therapy planning for patients with early-stage breast cancer.

Computed tomography-based virtual simulation versus ultrasound-based clinical setup in electron breast boost radiotherapy: Methodology for CT-based electron virtual simulation

PURPOSE

To compare clinical setup using ultrasound (U/S)-delineated target versus computed tomography (CT) virtual simulation using CT-outlined target in breast electron boost. To describe a methodology for electron virtual simulation and collision testing with the treatment planning system (TPS).

METHODS

The two techniques were compared in a prospective study on 12 patients, who were treated using a clinical setup. Target definition was performed by both U/S and CT imaging. The U/S-based target was made visible on CT images by placing a radio-opaque wire on U/S skin markings. The dose distribution of the clinical setup was reproduced in the TPS using the actual electron patient treatment parameters. A CT-based TPS virtual simulation/dose optimization was compared to the clinical setup technique.

RESULTS

Mean beam aperture was larger by 16.3 cm² (p = 0.011) for U/S compared to CT-outlined target. Target mean depth difference (CT minus U/S) was 0.03 cm (p = 0.875). Target coverage at depth was adequate in all cases with CT-based simulation while under/overcovering the target at depth by more than 5 mm in 2 out of 12 cases with clinical setup. Mean target V_90% was 98.5% (CT-based simulation) and 84.4% (clinical setup). Ipsilateral lung/breast were better spared with CT-based simulation. To date, the methodology for CT virtual simulation was applied on 152 patients and collision was avoided in all cases.

CONCLUSIONS

CT-based simulation and target delineation allows for improved definition of the en-face electron field with less amount of normal tissue irradiated while including the entire target with an adequate margin and optimal electron energy.

Comparison of two radiation techniques for the breast boost in patients undergoing neoadjuvant treatment for breast cancer

OBJECTIVE

After breast conservative surgery (BCS) and whole-breast radiotherapy (WBRT), the use of boost irradiation is recommended especially in patients at high risk. However, the standard technique and the definition of the boost volume have not been well defined.

METHODS

We retrospectively compared an anticipated pre-operative photon boost on the tumour, administered with low-dose fractionated radiotherapy, and neoadjuvant chemotherapy with two different sequential boost techniques, administered after BCS and standard adjuvant WBRT: (1) a standard photon beam (2) and an electron beam technique on the tumour bed of the same patients. The plans were analyzed for the dosimetric coverage of the CT-delineated irradiated volume. The minimal dose received by 95% of the target volume (D95), the minimal dose received by 90% of the target volume (D90) and geographic misses were evaluated.

RESULTS

15 patients were evaluated. The sequential photon and electron boost techniques resulted in inferior target volume coverage compared with the anticipated boost technique, with a median D95 of 96.3% (range 94.7-99.6%) and 0.8% (range 0-30%) and a median D90 of 99.1% (range 90.2-100%) and 54.7% (range 0-84.8%), respectively. We observed a geographic miss in 26.6% of sequential electron plans. The results of the anticipated boost technique were better: 99.4% (range 96.5-100%) and 97.1% (range 86.2-99%) for median D90 and median D95, respectively, and no geographic miss was observed. We observed a dose reduction to the heart, with left-sided breast irradiation, using the anticipated pre-operative boost technique, when analyzed for all dose-volume parameters. When compared with the sequential electron plans, the pre-operative photon technique showed a higher median ipsilateral lung Dmax.

CONCLUSION

Our data show that an anticipated pre-operative photon boost results in a better coverage with respect to the standard sequential boost while also saving the organs at risk and consequently fewer side effects.

ADVANCES IN KNOWLEDGE

This is the first dosimetric study that evaluated the association between an anticipated boost and neoadjuvant chemotherapy treatment.

Target localisation for tumour bed radiotherapy in early breast cancer

INTRODUCTION

To compare clinical and CT techniques in localisation of the tumour bed in patients undergoing adjuvant breast radiotherapy for breast cancer.

METHODS

Patients were CT scanned in the treatment position following clinical delineation of the whole breast, surgical scar and boost volume. Computed tomography boost volumes were contoured in three dimensions. A definitive treatment plan was generated to encompass the CT-localised planning target volume (PTV) with ≥90% isodose using electrons. A hypothetical plan was also generated to cover the clinically determined boost field for comparison. The primary end point was the difference in PTV coverage by the 90% isodose between the plans based on clinically and CT localised boost volumes.

RESULTS

The plans for 50 patients were evaluated. The median percentage of PTV encompassed by the 90% isodose using the clinical and CT techniques was 29% (range 5-90%) and 83% (range 25-100%), respectively. PTV coverage by the 90% isodose using the clinical technique was at least 10% less than that using CT technique in 88% of patients (95% confidence interval 77-95%; P < 0.0001).

CONCLUSION

Tumour bed boost PTV coverage was insufficient using clinical determination as compared with CT localisation. This study supports CT planning for target volume localisation of the tumour bed boost in patients treated with breast-conserving therapy for breast cancer.

Reducing interobserver variation of boost-CTV delineation in breast conserving radiation therapy using a pre-operative CT and delineation guidelines

AIMS

To investigate whether using a pre-operative CT scan (Preop-CT) (1) decreases interobserver variation of boost-CTV delineation in breast conserving therapy (BCT), and (2) influences the size of the delineated volumes.

PATIENTS AND METHODS

Thirty cT1-2N0-1 breast cancer patients underwent a CT-scan in radiation treatment position, prior to and after lumpectomy. Five observers delineated a boost-CTV, both with and without access to the Preop-CT. For each patient and for each observer pair, the conformity index (CI) and the distance between the centres of mass (COMd) for both boost volumes were calculated. In addition, all delineated volumes including the standard deviation (SD) with respect to the median delineation were calculated.

RESULTS

Using a Preop-CT reduced the mean COMd of the boost-CTV from 1.1cm to 1.0 cm (p<0.001). No effect was seen on the CI, but the boost-CTV volume reduced from 42 cc to 36 cc (p=0.005), implying a reduction of interobserver variation. We saw no significant change in the SD.

CONCLUSION

Use of a Preop-CT in BCT results in a modest but statistically significant reduction in interobserver variation of the boost-CTV delineations and in a significant reduction in the boost-CTV volume.

Volumetric changes in the lumpectomy cavity during whole breast irradiation after breast conserving surgery

Purpose

This study was performed to evaluate the change in the lumpectomy cavity volumes before and after whole breast radiation therapy (WBRT) and to identify factors associated with the change of volume.

Materials and Methods

From September 2009 to April 2010, the computed tomography (CT) simulation data from 70 patients obtained before and after WBRT was evaluated. The lumpectomy cavity volumes were contoured based on surgical clips, seroma, and postoperative changes. Significant differences in the data from pre-WBRT CT and post-WBRT CT were assessed. Multiple variables were examined for correlation with volume reduction in the lumpectomy cavity.

Results

The mean and median volume reduction in the lumpectomy cavity after WBRT were 17.6 cm³ and 16.1 cm³, respectively with the statistical significance (p < 0.001). The volume reduction in the lumpectomy cavity was inversely correlated with time from surgery to radiation therapy (R = 0.390). The presence of seroma was significantly associated with a volumetric change in the lumpectomy cavity after WBRT (p = 0.011).

Conclusion

The volume of lumpectomy cavity reduced significantly after WBRT. As the time from surgery to the start of WBRT increased, the volume reduction in the lumpectomy cavity during WBRT decreased. A strong correlation was observed between the presence of seroma and the reduced volume. To ensure appropriate coverage and to limit normal tissue exposure during boost irradiation in patients who has seroma at the time of starting WBRT, repeating CT simulation at boost planning is suggested.

Recommendations for clinical electron beam dosimetry: supplement to the recommendations of Task Group 25

The goal of Task Group 25 (TG-25) of the Radiation Therapy Committee of the American Association of.Physicists in Medicine (AAPM) was to provide a methodology and set of procedures for a medical physicist performing clinical electron beam dosimetry in the nominal energy range of 5-25 MeV. Specifically, the task group recommended procedures for acquiring basic information required for acceptance testing and treatment planning of new accelerators with therapeutic electron beams. Since the publication of the TG-25 report, significant advances have taken place in the field of electron beam dosimetry, the most significant being that primary standards laboratories around the world have shifted from calibration standards based on exposure or air kerma to standards based on absorbed dose to water. The AAPM has published a new calibration protocol, TG-51, for the calibration of high-energy photon and electron beams. The formalism and dosimetry procedures recommended in this protocol are based on the absorbed dose to water calibration coefficient of an ionization chamber at 60Co energy, N60Co(D,w), together with the theoretical beam quality conversion coefficient k(Q) for the determination of absorbed dose to water in high-energy photon and electron beams. Task Group 70 was charged to reassess and update the recommendations in TG-25 to bring them into alignment with report TG-51 and to recommend new methodologies and procedures that would allow the practicing medical physicist to initiate and continue a high quality program in clinical electron beam dosimetry. This TG-70 report is a supplement to the TG-25 report and enhances the TG-25 report by including new topics and topics that were not covered in depth in the TG-25 report. These topics include procedures for obtaining data to commission a treatment planning computer, determining dose in irregularly shaped electron fields, and commissioning of sophisticated special procedures using high-energy electron beams. The use of radiochromic film for electrons is addressed, and radiographic film that is no longer available has been replaced by film that is available. Realistic stopping-power data are incorporated when appropriate along with enhanced tables of electron fluence data. A larger list of clinical applications of electron beams is included in the full TG-70 report available at http://www.aapm.org/pubs/reports. Descriptions of the techniques in the clinical sections are not exhaustive but do describe key elements of the procedures and how to initiate these programs in the clinic. There have been no major changes since the TG-25 report relating to flatness and symmetry, surface dose, use of thermoluminescent dosimeters or diodes, virtual source position designation, air gap corrections, oblique incidence, or corrections for inhomogeneities. Thus these topics are not addressed in the TG-70 report.

Change in seroma volume during whole-breast radiation therapy

PURPOSE

After breast-conserving surgery, a seroma often forms in the surgical cavity. If not drained, it may affect the volume of tumor bed requiring a boost after whole-breast radiation therapy (WBRT). Our objective was to evaluate the change in seroma volume that occurs during WBRT, before boost planning.

METHODS AND MATERIALS

A retrospective review was performed of women receiving breast-conserving therapy with evidence of seroma at the time of WBRT planning. Computed tomography (CT) simulation was performed before WBRT and before the tumor bed boost. All patients received either a hypofractionated (42.4 Gy/16 fraction + 9.6 Gy/4 fraction boost) or standard fractionated (50.4 Gy/28 fraction + 10 Gy/5 fraction boost) regimen. Seroma volumes were contoured and compared on CT at the time of WBRT simulation and tumor bed boost planning.

RESULTS

Twenty-four patients with evidence of seroma were identified and all patients received WBRT without drainage of the seroma. Mean seroma volume before WBRT and at boost planning were significantly different at 65.7 cm(3) (SD, 50.5 cm(3)) and 35.6 cm(3) (SD, 24.8 cm(3)), respectively (p < 0.001). Mean and median reduction in seroma volume during radiation were 39.6% (SD, 23.8%) and 46.2% (range, 10.7-76.7%), respectively. Fractionation schedule was not correlated with change in seroma volume. Length of time from surgery to start of radiation therapy showed an inverse correlation with change in seroma volume (Pearson correlation r = -0.53, p < 0.01).

CONCLUSIONS

The volume of seroma changes significantly during WBRT. Consequently, the accuracy of breast boost planning is likely affected, as is the volume of normal breast tissue irradiated. CT-based boost planning before boost irradiation is suggested to ensure appropriate coverage.

Local relapse rates are falling after breast conserving surgery and systemic therapy for early breast cancer: can radiotherapy ever be safely withheld?

Rates of local tumour relapse after breast conservation treatment in women with early breast cancer are falling. Explanations for this decline are considered in this review including advances in breast cancer management and aging of the breast cancer population. Breast surgery has become more standardised following publication of practice guidelines and is mostly carried out by specialist surgeons. Systemic therapies (hormonal therapy and chemotherapy) are now more effective and are recommended to a higher proportion of patients than ever before. Radiotherapy techniques have also improved. The contributions of each factor are difficult to quantify precisely, but all are likely to be relevant. In order to identify a subgroup of women that might safely be spared radiotherapy, several factors are analysed, including the prognostic significance for local relapse of tumour characteristics (pathologic data, gene-expression profiles), patient characteristics and life expectancy (age and comorbidities).

High definition three-dimensional ultrasound to localise the tumour bed: a breast radiotherapy planning study

BACKGROUND AND PURPOSE

Complex radiation techniques, such as conformal radiotherapy for partial breast irradiation, require accurate localisation of the tumour bed. This study investigated high definition 3D ultrasound for breast tumour bed localisation. Study aims were: firstly, to determine how easily a tumour cavity could be visualised with 3D ultrasound; secondly, to determine the accuracy of computed tomography (CT) and 3D ultrasound co-registration; thirdly, to compare 3D ultrasound with other methods of localisation.

MATERIALS AND METHODS

3D ultrasound examinations were carried out in 40 women attending for breast radiotherapy. 3D position data were co-registered with the radiotherapy planning CT. 2D ultrasound and CT, surgical clips and CT, and CT alone were also used to localise the tumour bed in 32/40, 14/40 and 5/40 patients, respectively. Tumour bed volume and centre of gravity measurements for all methods of localisation were compared.

RESULTS

Mean surgery to imaging interval was 44 days (range 23-86 days). The post-operative cavity was seen in all cases using the 3D ultrasound, and was graded as highly visible, visible and subtle in 21/40 (53%), 12/40 (30%) and 7/40 (17%) cases, respectively. There was a statistically significant improvement in the ability of 3D ultrasound to localise the tumour bed compared with 2D ultrasound. CT-ultrasound registration was achieved in all cases. Two-dimensional and 3D ultrasound showed smaller tumour bed volumes than clips.

CONCLUSIONS

Three-dimensional ultrasound localisation of the tumour bed appears superior to 2D ultrasound. It can also be co-registered with a planning CT, thus allowing additional information on the size and location of the tumour bed to be integrated into complex radiotherapy planning.

CT planning for breast cancer

Radiotherapy to the affected breast or chest wall is well established as an integral part of postoperative management of breast cancer. However, it is known to be associated with increased cardiac and pulmonary morbidities and mortalities. Modern technologies, such as CT planning, have shown to improve treatment planning by accurately delivering optimal doses to the target volumes, while minimizing doses to sensitive structures, thus reducing potential treatment-related adverse effects. The purpose of this study is to report on our experiences with CT planning of adjuvant radiotherapy for breast cancer.

A Computed Tomography-based Protocol vs Conventional Clinical Mark-up for Breast Electron Boost

AIMS

Computed tomography planning of whole breast radiotherapy (WBRT) improves breast coverage and reduces the normal tissue dose. Computed tomography planning may increase tumour bed boost treatment accuracy. The aims of this investigation were (1) to compare the breast boost volume treated with clinical mark-up with the volume delineated with computed tomography planning and (2) to study tumour bed volume changes between the initial planning computed tomography scan and a second computed tomography scan at the time of breast boost mark-up.

MATERIALS AND METHODS

Women receiving adjuvant WBRT and an electron boost after breast-conserving surgery were eligible. As per standard practice, WBRT was computed tomography planned while the boost electron portal was clinically defined. Electron field borders were then traced with wire and a second computed tomography scan was carried out in the boost treatment position. Post-surgical radiological abnormalities were contoured to create a tumour bed clinical target volume (CTV) on both scans (CTV1 and CTV2). A 1cm margin to CTV2 defined the planning target volume (PTV). The proportions of the CTV2 and PTV receiving 90% (V90) and 80% (V80) of the dose were calculated. Changes in volume between CTV1 and CTV2 were analysed.

RESULTS

Data from 47 eligible patients were analysed. The mean V90 for the PTV was 61%. Lower electron energy (P<0.001) and small field sizes (P=0.004) were associated with a low V90. The mean CTV decreased by 4.3 cm3 (P=0.014) and was smaller in those with a long surgery to computed tomography interval (P=0.008). On average, the 90% isodose covered 61 cm3 of normal tissue.

CONCLUSIONS

Conventional clinical breast boost planning is inaccurate. Electron boost computed tomography planning together with appropriate surgical clip placement and the use of mammograms and pathological information should provide optimal coverage of the tumour site. The boost could usually be planned from the initial computed tomography scan.

Planning the breast tumor bed boost: changes in the excision cavity volume and surgical scar location after breast-conserving surgery and whole-breast irradiation

PURPOSE

The aims of this study were to determine the changes in breast and excision cavity volumes after whole-breast irradiation and the adequacy of using the surgical scar to guide boost planning.

METHODS AND MATERIALS

A total of 30 women consecutively treated for 31 breast cancers were included in this study. Simulation CT scans were performed before and after whole-breast irradiation. CT breast volumes were delineated using clinically defined borders. Excision cavity volumes were contoured based on surgical clips, the presence of a hematoma, and/or other surgical changes. Hypothetical electron boost plans were generated using the surgical scar with a 3-cm margin and analyzed for coverage.

RESULTS

The mean CT breast volumes were 774 and 761 cc (p = 0.22), and the excision cavity volumes were 32.1 and 25.1 cc (p < 0.0001), before and after 40 Gy (39-42 Gy) of whole-breast irradiation, respectively. The volume reduction in the excision cavity was inversely correlated with time elapsed since surgery (R = 0.46, p < 0.01) and body weight (R = 0.50, p < 0.01). The scar-guided hypothetical plans failed to cover the excision cavity adequately in 62% and 53.8% of cases using the pretreatment and postradiation CTs, respectively. Per the hypothetical plans, the minimum dose to the excision cavity was significantly lower for tumors located in the inner vs. outer quadrants (p = 0.02) and for cavities >20 cc vs. <20 cc (p = 0.01).

CONCLUSIONS

This study demonstrates a significant reduction in the volume of the excision cavity during whole-breast irradiation. Scar-guided boost plans provide inadequate coverage of the excision cavity in the majority of cases.

Intraoperative radiotherapy given as a boost for early breast cancer: long-term clinical and cosmetic results

PURPOSE

The standard radiotherapy (RT) of breast cancer consists of 50 Gy external beam RT (EBRT) to the whole breast followed by an electron boost of 10-16 Gy to the tumor bed, but this has several cosmetic disadvantages. Intraoperative radiotherapy (IORT) could be an alternative to overcome these.

METHODS AND MATERIALS

We evaluated 50 women with early breast cancer operated on in a dedicated IORT facility. Median dose of 10 Gy was delivered using 9-MeV electron beams. All patients received postoperative EBRT (50 Gy in 2 Gy fractions). Late toxicity and cosmetic results were assessed independently by two physicians according to the Common Terminology Criteria for Adverse Event v3.0 grading system and the European Organization for Research and Treatment of Cancer questionnaires.

RESULTS

After a median follow-up of 9.1 years (range, 5-15 years), two local recurrences were observed within the primary tumor bed. At the time of analysis, 45 patients are alive with (n = 1) or without disease. Among the 42 disease-free remaining patients, 6 experienced Grade 2 late subcutaneous fibrosis within the boost area. Overall, the scores indicated a very good quality of life and cosmesis was good to excellent in the evaluated patients.

CONCLUSION

Our results confirm that IORT given as a boost after breast-conserving surgery is a reliable alternative to conventional postoperative fractionated boost radiation.

Interobserver variability of clinical target volume delineation of glandular breast tissue and of boost volume in tangential breast irradiation

BACKGROUND AND PURPOSE

To determine the interobserver variability of clinical target volume delineation of glandular breast tissue and of boost volume in tangential breast irradiation.

PATIENTS AND METHODS

Eighteen consecutive patients with left sided breast cancer treated by breast conserving surgery agreed to participate in our study. Volumes of the glandular breast tissue (CTV breast) and of the boost (CTV boost) were delineated by five observers. We determined 'conformity indices' (CI) and the ratio between the volume of each CTV and the mean volume of all CTVs (CTV ratio). Subsequently we determined the most medial, lateral, anterior, posterior, cranial and caudal extensions both of CTV breast and CTV boost for all observers separately.

RESULTS

The mean CI breast was 0.87. For one observer we noted the highest CTV ratio in 17 out of 18 cases. No association was noted between CI breast and menopausal status. The mean CI boost was 0.56. We did not find a relation between the presence or absence of clips and the CI boost. For another observer we noted the lowest CTV boost ratio in 10 out of 17 cases.

CONCLUSIONS

We recommend that each institute should determine its interobserver variability with respect to CTV breast and CTV boost before implementing the delineation of target volumes by planning CT in daily practice.

Sonographic guidance for electron boost planning after breast-conserving surgery

PURPOSE

This study was conducted to determine the feasibility of using sonography for electron boost planning in breast cancer treatment and to define the factors that influence the accuracy and reproducibility of this technique.

PATIENTS AND METHODS

Seventy-seven patients underwent 102 sonographic examinations after breast-conserving surgery and before and after radiotherapy. The size of the electron boost field was defined by measuring the postoperative cavity. Reproducibility of the sonographic findings was investigated in 25 of the patients who were examined before and after radiotherapy (at a total dose of 46-50.4 Gy). Depth (distance from the skin surface to the posterior aspect of the postoperative cavity) was measured, and sonographic appearance of the postoperative cavity was evaluated. Type of surgical procedure, time elapsed since surgery, use of systemic therapy, menopausal status, breast size, and radiation dose were investigated for their influence on sonographic appearance and visualization of the postoperative cavity.

RESULTS

The postoperative cavity was well visualized in 78% of patients and visualized with some difficulty in 22%. In all but 5 patients, it was hypoechoic and inhomogeneous. The mean depth of the postoperative cavity after radiotherapy was 27 +/- 4 mm. Smaller breast (p < 0.001) and younger age (p < 0.05) were associated with decreased visibility of the postoperative cavity. Sonographic appearance was the same before and after radiotherapy, but the mean difference in postoperative cavity depth between the 2 measurements was 2 mm (range, 0-4 mm). In 43/77 (56%) of the patients, changes in electron energy or in field size were required after sonographic measurement.

CONCLUSION

Sonography is a useful and reproducible means of electron boost planning, helping to avoid underdosage of the postoperative cavity and overdosage of normal tissue.

Breast boost: are we missing the target?

BACKGROUND

Randomized trials have shown improved local control with the use of a breast boost for patients given breast-conserving treatment for breast carcinoma. Although the use of a breast boost is routine practice, no standard technique has been established. The authors compared the commonly used clinical technique with a technique based on computed tomography (CT) imaging of surgical clips in the tumor bed.

METHODS

Thirty patients underwent CT simulation for postoperative radiation treatment planning as part of breast conservation therapy. During simulation, a CT-compatible wire was placed on the patient's skin, outlining the intended electron boost field; an electron boost volume (EBV) was generated by contouring the tissue underlying the wire. Also contoured was a CT-based clinical target volume (CTV) using surgical clips and postsurgical changes in the tumor bed as a guide. A planning target volume (PTV) was generated using a 1 cm margin around the CTV. An electron beam treatment plan was generated for each technique using the FOCUS three-dimensional treatment planning system. Dose-volume histograms (DVH) were generated to determine the fraction of the PTV receiving 90% of the prescribed dose if treatment was delivered using the EBV. In addition, DVH analysis was done to determine the volume of normal tissue unnecessarily irradiated when using the EBV.

RESULTS

Although the electron cone size remained unchanged in most patients for both EBV and PTV, the isocenter differed more than 1 cm in the medial-lateral direction in 5 patients and in the cephalocaudal direction in 12 patients. The en face gantry angle differed for most patients. On average, only 51% (range, 27-79%) of the PTV received 90% or more of the prescribed dose when the electron plan was generated using the EBV (P < 0.0001). Ten patients received the prescription dose to less than 50% of the PTV. Mean volume of normal tissue receiving more than 50% of prescribed dose was 64.5 cm(3) (range, 24-119 cm(3)).

CONCLUSIONS

Clinical delineation of the tumor bed not only carries a significant risk of missing the target, but unnecessarily treats breast tissue that may otherwise be spared. Better delineation of the tumor bed, which optimizes coverage of the target volume and spares normal breast tissue, has the potential to improve both local control and cosmetic outcome. The authors recommend the use of surgical clips to delineate the target volume, followed by CT-based treatment planning, accounting for not only microscopic disease, but also organ motion and daily setup error.

Impact of boost irradiation with surgically placed radiopaque clips on local control in breast-conserving therapy

BACKGROUND

The purpose of this study was to determine whether boost irradiation relying on radiopaque clips placed surgically around the resected margin of breast cancer contributes to increasing the local control rate in patients with close or positive margins in breast-conserving therapy (BCT).

METHODS

Among 837 patients with breast cancer who underwent BCT between November 1987 and December 1998, 181 patients with close or positive surgical margins received boost irradiation following conventional tangential whole breast irradiation. Since 1994, four radiopaque clips were surgically placed around the resected margin of the breast cancer in 155 patients treated with wide excision. The four clips were clearly and accurately identified with a CT-simulator (CT-S). The boost irradiation field was automatically determined with a safety margin of 3 cm according to one-to-one correspondence of radiopaque clips to pathologically close or positive surgical margins. In the remaining 26 patients treated before 1994, the boost irradiation field was determined according to the skin tattoo of the primary tumor.

RESULTS

The median follow-up period of the 155 patients receiving the radiopaque clips was 42 months (range: 19 to 78), and that of the 26 patients without the clips was 87 months. Local recurrence was observed in two of the 155 patients who underwent boost irradiation using the radiopaque clips 39 and 54 months after the surgery, while 4 of the 26 patients developed local recurrence 14, 23, 51, and 76 months after BCT. In three of the four patients without the clips developing local recurrences, local recurrences were observed at the margin of the boost irradiation field. The 5-year local recurrence-free survival rate of patients who received boost irradiation with the radiopaque clips was 97%, and that of patients without the clips was 88%. The difference of local recurrence-free survival rates between the patients with and without the clips was significant (p<0.05).

CONCLUSION

Surgically placed radiopaque clips appear to be useful for determining adequate boost field in the BCT using the CT-S and help increase the local control rate.

[Breast-conserving surgery and irradiation for early breast cancer: value of surgical clips in the surgical cavity]

PURPOSE

To evaluate, qualitatively and quantitatively, the role of surgical clips in planning the tumor bed electron or brachytherapy boost in patients undergoing breast-conserving surgery and radiotherapy.

PATIENTS AND METHODS

In 60 patients with breast cancer stage I or II, the excision cavity boundaries were marked by clips at surgery. Patients received a boost with brachytherapy (n = 51) or electron beam (n = 9) after whole breast irradiation. The boost target volume was first planned using clinical, mammography and operative information and its accuracy evaluated by screening the surgical clips and, if necessary, adjusting the field to encompass all clips and to include the scar. Dosimetry was retrospectively performed for each brachytherapy patient and for each surgical clip.

RESULTS

It was necessary to modify the target volume field in 11 cases (18%). The average dose received by the surgical clips was 116.1% of the dose delivered to the reference isodose (median: 101.75%, range: 16-457%). However, dose heterogeneity was important in the same patient and between patients.

CONCLUSION

Delineation of the boost target volume with surgical clips is more accurate than with clinical landmarks alone but this technique does not allow measurements of the clip-chest wall and clip-skin distances. Virtual simulation with CT-scan cuts is recommended for optimising boost planning.

Breast electron boost planning: comparison of CT and US

PURPOSE

To compare computed tomography (CT) with ultrasonography (US) for depiction of the biopsy cavity.

MATERIALS AND METHODS

Thirty-two consecutive patients who underwent radiation therapy following lumpectomy with a planned electron boost were examined. At the time of simulation for whole-breast radiation therapy, all patients underwent planning CT (CT 1) at 3-mm section intervals. At the time of electron boost simulation, US was performed to define the biopsy cavity. In 17 cases, a second CT examination (CT 2) was performed at the time of electron boost simulation. CT and US studies were reviewed jointly and assigned a cavity visualization score (CVS) of 1 (cavity not visualized) to 5 (all cavity margins clearly defined).

RESULTS

The median CVS at CT 1 was 5; at CT 2, 4; and at US, 4. For patients who underwent all three studies, the median CVS at CT 1 was 5; at CT 2, 4; and at US, 4. Factors related to CVS at CT 1 were homogeneous versus heterogeneous appearance (score, 5 vs 4), surgery-to-CT interval (< or =30 days, 5; 31-60 days, 4; >60 days, 4), and cavity size (>15 cm(3), 5; <15 cm(3), 4). In all cases, cavity volume decreased somewhat during the CT 1-to-CT 2 interval.

CONCLUSION

CT performed at the time of whole-breast simulation can be used to plan electron boost fields, with cavity visualization similar to that at US.

A study testing the routine use of ultrasound measurements when selecting the electron energy for breast boost radiotherapy

The determination of the depth of the tumour bed within the breast requiring an electron therapy boost dose is generally judged clinically and can be inconsistent between individual radiotherapists. High frequency ultrasound provides a reproducible, safe and quick method of measuring this depth. In order to improve current working practice at the Royal Marsden NHS Trust the routine use of ultrasound when planning breast boost radiotherapy was established. Fifty-three early stage postoperative breast cancer patients had both clinical and ultrasound assessments of boost depth performed. These measurements were converted into electron energy and compared. Measurements ranged from 0.8 cm to 4.9 cm and electron energy from 4 MeV to 15 MeV. As a direct result of the ultrasound measurements taken, 60% of patients had their electron energy changed from that chosen by the clinically assessed measurement. Overall, the energy was as likely to be increased as decreased. Breast size did not influence the need for change but patients with small breasts never required an increase in the energy from that chosen clinically. It was concluded that the use of ultrasound, once integrated into the planning process, can improve accuracy when selecting electron energy for patients receiving breast boost irradiation.

Patterns of radiotherapy for early breast cancer in Northern Italy compared with European and national standards

PURPOSE

To assess the current practice of early breast cancer (EBC) post-operative irradiation in Northern Italy and to evaluate its conformance with European standards and recently defined national guidelines.

MATERIALS AND METHODS

Fifty Radiotherapy departments in Northern Italy received a questionnaire assessing parameters on pre-treatment evaluation of patients, on preparation, prescription and execution phases of irradiation (XRT), on surgery-XRT-chemotherapy integration and on follow-up. The analysis of collected information was compared with both the 1991 EORTC-EUSOMA guidelines and the 1997 AIRO (Italian Association for Radiation Oncology) minimal requirements on EBC post-operative irradiation.

RESULTS

Thirty-nine out of 50 (78%) departments answered the questionnaire. All treat T1-T2 tumours, after tumourectomy or, mostly, quadrantectomy. The mean interval between surgery and XRT is 45 +/- 14 days. Chemotherapy is delivered concurrently in 70% of departments, CTV is represented by residual mammary gland in 100% of cases, while 38% and 52% of departments occasionally treat internal mammary and axillary or supra-clavicular nodes, respectively. Total dose delivered to the whole breast is 46-50 Gy in 98% (1.8-2 Gy/fraction). The tumour bed is boosted in 79% of cases. An immobilization device is used in 28% of cases CTV is clinically localized in 62% of patients. Tangential fields are simulated in 85% of centres, with film storage in 78% of cases. Co-60 units are used in 58% and/or 4-6 MV X-rays in 70% of centres, mostly utilizing beam modifiers. Computerized treatment planning is performed in 95% of cases. Fifty-five percent of departments prescribe the dose at the ICRU point. Portal films are routinely taken in 50% of cases. Boost irradiation is mainly performed using external XRT. Lastly, acute and late side effects and cosmesis are respectively evaluated in 100%, 98% and 90% of centres.

CONCLUSIONS

Results on current practice in Northern Italy generally show a good conformance with European standards. However, some variables related to treatment prescription, simulation and treatment planning need to be standardized. This set of information was largely utilized by the AIRO to define national guidelines adapted to the Italian resources and situation.