Correlation of breast dose heterogeneity with breast size using 3D CT planning and dose-volume histograms

Comparison of dose distributions and organs at risk (OAR) doses in conventional tangential technique (CTT) and IMRT plans with different numbers of beam in left-sided breast cancer

AIM

Our aim was to improve dose distribution to the left breast and to determine the dose received by the ipsilateral lung, heart, contralateral lung and contralateral breast during primary left-sided breast irradiation by using intensity modulated radiotherapy (IMRT) techniques compared to conventional tangential techniques (CTT). At the same time, different beams of IMRT plans were compared to each other in respect to CI, HI and organs at risk (OAR) dose.

BACKGROUND

Conventional early breast cancer treatment consists of lumpectomy followed by whole breast radiation therapy. CTT is a traditional method used for whole breast radiotherapy and includes standard wedged tangents (two opposed wedged tangential photon beams). The IMRT technique has been widely used for many treatment sites, allowing both improved sparing of normal tissues and more conformal dose distributions. IMRT is a new technique for whole breast radiotherapy. IMRT is used to improve conformity and homogeneity and used to reduce OAR doses.

MATERIALS AND METHODS

Thirty patients with left-sided breast carcinoma were treated between 2005 and 2008 using 6, 18 or mixed 6/18 MV photons for primary breast irradiation following breast conserving surgery (BCS). The clinical target volume [CTV] was contoured as a target volume and the contralateral breast, ipsilateral lung, contralateral lung and heart tissues as organs at risk (OAR). IMRT with seven beams (IMRT7), nine beams (IMRT9) and 11 beams (IMRT11) plans were developed and compared with CTT and among each other. The conformity index (CI), homogeneity index (HI), and doses to OAR were compared to each other.

RESULTS

ALL OF IMRT PLANS SIGNIFICANTLY IMPROVED CI (CTT: 0.76; IMRT7: 0.84; IMRT9: 0.84; IMRT11: 0.85), HI (CTT: 1.16; IMRT7: 1.12; IMRT9: 1.11; IMRT11: 1.11), volume of the ipsilateral lung receiving more than 20 Gy (>V20 Gy) (CTT: 14.6; IMRT7: 9.08; IMRT9: 8.10; IMRT11: 8.60), and volume of the heart receiving more than 30 Gy (>V30 Gy) (CTT: 6.7; IMRT7: 4.04; IMRT9: 2.80; IMRT11: 2.98) compared to CTT. All IMRT plans were found to significantly decrease >V20 Gy and >V30 Gy volumes compared to conformal plans. But IMRT plans increased the volume of OAR receiving low dose radiotherapy: volume of contralateral lung receiving 5 and 10 Gy (CTT: 0.0-0.0; IMRT7: 19.0-0.7; IMRT9: 17.2-0.66; IMRT11: 18.7-0.58, respectively) and volume of contralateral breast receiving 10 Gy (CTT: 0.03; IMRT7: 0.38; IMRT9: 0.60; IMRT11: 0.68). The differences among IMRT plans with increased number of beams were not statistically significant.

CONCLUSION

IMRT significantly improved conformity and homogeneity index for plans. Heart and lung volumes receiving high doses were decreased, but OAR receiving low doses was increased.

Randomized controlled trial of forward-planned intensity modulated radiotherapy for early breast cancer: interim results at 2 years

PURPOSE

This single-center randomized trial was designed to investigate whether intensity-modulated radiotherapy (IMRT) reduces late toxicity in patients with early-stage breast cancer.

METHODS AND MATERIALS

The standard tangential plans of 1,145 nonselected patients were analyzed. The patients with inhomogeneous plans were randomized to a simple method of forward-planned IMRT or standard radiotherapy (RT). The primary endpoint was serial photographic assessment of breast shrinkage.

RESULTS

At 2 years, no significant difference was found in the development of any photographically assessed breast shrinkage between the patients randomized to the interventional or control group (odds ratio, 1.51; 95% confidence interval, 0.83-1.58; p = .41). The patients in the control group were more likely to develop telangiectasia than those in the IMRT group (odds ratio, 1.68; 95% confidence interval 1.13-2.40; p = .009). Poor baseline surgical cosmesis resulted in poor overall cosmesis at 2 years after RT. In patients who had good surgical cosmesis, those randomized to IMRT were less likely to deteriorate to a moderate or poor overall cosmesis than those in the control group (odds ratio, 0.63; 95% confidence interval, 0.39-1.03, p = .061).

CONCLUSIONS

IMRT can lead to a significant reduction in telangiectasia at comparatively early follow-up of only 2 years after RT completion. An important component of breast induration and shrinkage will actually result from the surgery and not from the RT. Surgical cosmesis is an important determinant of overall cosmesis and could partially mask the longer term benefits of IMRT at this early stage.

Forward planned intensity modulated radiotherapy (IMRT) for whole breast postoperative radiotherapy. Is it useful? When?

The purpose was to compare the dosimetric results observed in 201 breast cancer patients submitted to tangential forward intensity-modulated radiation therapy (IMRT) with those observed in 131 patients treated with a standard wedged 3D technique for postoperative treatment of whole breast, according to breast size and supraclavicular node irradiation. Following dosimetric parameters were used for the comparison: D(max), D(min), D(mean), V(95%) and V(107%) for the irradiated volume; D(max), D(mean), V(80%) and V(95%) for the ipsilateral lung; D(max), D(mean), V(80%) and V(95%) for the heart. Stratification was made according to breast size and supraclavicular (SCV) nodal irradiation. As respect to irradiated volume, a significant reduction of V(107%) (mean values: 7.0 ± 6.6 versus 2.4 ± 3.7, p < 0.001) and D(max) (mean % values: 111.2 ± 2.7 versus 107.7 ± 6.3, p < 0.001), and an increase of D(min) (mean % values: 65.0 ± 17.4 versus 74.9 ± 12.9, p < 0.001) were observed with forward IMRT. The homogeneity of dose distribution to target volume significantly improved with forward IMRT in all patient groups, irrespective of breast size or supraclavicular nodal irradiation. When patients treated with supraclavicular nodal irradiation were excluded from the analysis, forward IMRT slightly reduced V(80%) (mean values: 3.7 ± 2.6 versus 3.0 ± 2.4, p = 0.03) and V(95%) (mean values 1.9 ± 1.8 versus 1.2%± 1.5; p = 0.001) of the ipsilateral lung. The dose to the heart tended to be lower with IMRT but this difference was not statistically significant. Tangential forward IMRT in postoperative treatment of whole breast improved dosimetric parameters in terms of homogeneity of dose distribution to the target in a large sample of patients, independent of breast size or supraclavicular nodal irradiation. Lung irradiation was slightly reduced in patients not undergoing to supraclavicular irradiation.

Partial-volume segmentation for dose optimization in whole-breast radiotherapy: a comparative dosimetric and clinical analysis

PURPOSE

: To analyze the dosimetric and clinical benefit of a forward planned technique to optimize dose distribution in whole-breast irradation (WBI) using additional partial-volume segments (PVSeg).

PATIENTS AND METHODS

: In two separate treatment periods, 265 breast cancer patients received tangential-field WBI and were retrospectively analyzed. Between 02/2004 and 03/2006, 96 patients were treated with one to two additional low-weighted PVSeg to reduce dose peaks within the target volume. 169 patients treated between 01/2000 and 12/2001 before implementation of this PVSeg technique served as comparison group. Total dose was 50-50.4 Gy (single dose, 1.8-2 Gy). The planning target volume (PTV) receiving at least 95%, 105% and 110% of the reference dose (V(95-110%)) and frequency of moist skin desquamation during radiotherapy were compared uni- and multivariately with patient- and treatment-related variables.

RESULTS

: The mean PTV was 1,144 ml (range, 235-2,365 ml). Moist skin desquamations developed in 16 patients (17%) with PVSeg compared to 30 patients (18%) without PVSeg (p = 0.482). In breast volumes > 1,100 ml, the corresponding figures were 19% versus 29% (p = 0.133). V(105%) was significantly reduced by the use of PVSeg (82 +/- 51 ml vs. 143 +/- 129 ml; p < 0.0001). In univariate analysis, the following variables had significant influence on the development of moist skin desquamation: V(95%) (p < 0.0001), V(105%) (p < 0.001), V(110%) (p = 0.012) adjuvant chemotherapy (p = 0.02), and single dose (p = 0.009). In multivariate analysis, only V(95%) (p = 0.002) remained significant.

CONCLUSION

: The use of PVSeg in WBI reduced dose peaks within the PTV while breast volumes > 1,100 ml benefited most. V(95%) was strongly correlated to the risk of developing moist skin desquamations.

Breast intensity-modulated radiation therapy reduces time spent with acute dermatitis for women of all breast sizes during radiation

PURPOSE

To study the time spent with radiation-induced dermatitis during a course of radiation therapy for breast cancer in women treated with conventional or intensity-modulated radiation therapy (IMRT).

METHODS AND MATERIALS

The study population consisted of 804 consecutive women with early-stage breast cancer treated with breast-conserving surgery and radiation from 2001 to 2006. All patients were treated with whole-breast radiation followed by a boost to the tumor bed. Whole-breast radiation consisted of conventional wedged photon tangents (n = 405) earlier in the study period and mostly of photon IMRT (n = 399) in later years. All patients had acute dermatitis graded each week of treatment.

RESULTS

The breakdown of the cases of maximum acute dermatitis by grade was as follows: 3%, Grade 0; 34%, Grade 1; 61%, Grade 2; and 2%, Grade 3. The breakdown of cases of maximum toxicity by technique was as follows: 48%, Grade 0/1, and 52%, Grade 2/3, for IMRT; and 25%, Grade 0/1, and 75%, Grade 2/3, for conventional radiation therapy (p < 0.0001). The IMRT patients spent 82% of weeks during treatment with Grade 0/1 dermatitis and 18% with Grade 2/3 dermatitis, compared with 29% and 71% of patients, respectively, treated with conventional radiation (p < 0.0001). Furthermore, the time spent with Grade 2/3 toxicity was decreased in IMRT patients with small (p = 0.0015), medium (p < 0.0001), and large (p < 0.0001) breasts.

CONCLUSIONS

Breast IMRT is associated with a significant decrease both in the time spent during treatment with Grade 2/3 dermatitis and in the maximum severity of dermatitis compared with that associated with conventional radiation, regardless of breast size.

Magnetic resonance images and linear measurements in the surgical treatment of breast asymmetry

BACKGROUND

Objective evaluation of breast asymmetry surgical treatment should consider not only breast shape but also breast volume.

METHODS

For this study, 22 patients with primary breast asymmetry were evaluated by magnetic resonance imaging (MRI) as well as linear measurements preoperatively and 6 months postoperatively. The mean difference between the pre- and postoperative linear measurements was graduated from excellent to poor. Breast volume was estimated by MRI from axial reconstruction for three-dimensional application using the Cavalieri formula and specific software.

RESULTS

A strong correlation (r = 0.817) was found between the pre- and postoperative breast volumes, as increased or decreased by the surgical procedure. Patients with less postoperative volume differences tended to have the best ratings with linear measurements. When the same surgical procedure was performed bilaterally or when only one breast was treated by surgery, greater volume symmetry was observed.

CONCLUSIONS

Linear measurements and MRI are objective methods for evaluating postoperative symmetry, and when used in association, can help plastic surgeons to achieve favorable results in mammary asymmetry treatment.

The prone technique for breast irradiation - is it ready for clinical trials?

PURPOSE

Our aim was to determine whether a radiotherapy technique for treating breast cancer patients in a prone position could be developed as a means of reducing toxicity. We also aimed to consider its suitability for testing in a large randomized study.

METHODS AND MATERIALS

Based on the sparse literature and techniques currently used at other centres, we designed a simple technique for simulation and treatment in the prone position. A specialised patient positioning device was designed to allow the breast to hang vertically downwards away from the chest wall and away from the contralateral breast. Planning and treatment were performed, and clinical data on the first 40 patients treated were reviewed.

RESULTS

The reasons given by clinicians for choosing the prone technique included a large, pendulous breast shape (36 patients), an elevated risk of pneumonitis (three patients) and inability to adopt a supine position due to arthritis (one patient). The treatment was well tolerated, although 50% of the patients still developed moist desquamation. All but one patient completed their full course of radiotherapy. Dosimetric analysis revealed high levels of dose homogeneity and low doses to surrounding normal structures. With a median follow-up of 11 months, only one patient has developed metastatic disease, and one has locally recurred.

CONCLUSIONS

This study shows that prone breast irradiation for patients with large or pendulous breasts can be readily developed in radiotherapy treatment centers and could be tested for efficacy in a large, multi-centre randomized trial.

A comprehensive clinical 3-dimensional dosimetric analysis of forward planned IMRT and conventional wedge planned techniques for intact breast radiotherapy

A forward planned intensity modulated technique was initiated for intact breasts radiotherapy (FPIMRT). Forty-three patients were selected to compare dose distributions achieved by FPIMRT to dose distributions produced by conventional wedge techniques (CW). For the simulation process, the treatment field margins were clinically defined by a physician, and a set of fiducial reference markers was placed on the patient. A computed tomography (CT) scan was then performed and the images were transferred to a 3-dimensional (3D) treatment planning system (TPS). The breast tissue was then contoured to allow for a quantitative dose volume analysis. The treatment plan was initially generated with conventional tangential beam arrangements and open fields. Multiple multileaf collimator (MLC) shaped segments were created for each tangential beam in an effort to produce dose homogeneity throughout the breast. 6-MV photon beams were used for treatment unless acceptable dose homogeneity could not be achieved due to large breast size. In this case, the beam energies of selected segments were modified to 15-MV. Once the FPIMRT plan was created, additional plans were generated using the same beam geometry and 2 tangential open fields with CW techniques and 15 degrees wedges (15DW), 30 degrees wedges (30DW), 45 degrees wedges (45 DW), and 60 degrees wedges (60DW). The dose distributions generated by the CW plans were then compared to the FPIMRT plan. This process was repeated for each patient, and the patient group was divided into 3 categories based on breast volume (small, medium, and large). Both point dose relationships, which compared global hot spot (GHS) magnitude and location and dose volume relationships, which compared breast volume coverage of the 105% and 110% isodose lines (IDL) relative to the prescribed dose (PD), were explored. For the patient group in our study, FPIMRT produced the smallest average GHS and the most evenly distributed location of GHS for all breast size categories when compared to all CW techniques. FPIMRT also produced the smallest average breast volume receiving greater than 105% of the PD (V(a105)) for the small- and medium-size breast patients and the smallest average breast volume receiving greater than 110% of the PD (V(a110)) for all breast size categories when compared to all CW techniques.

Acute toxicity and 2-year adverse effects of 30 Gy in five fractions over 15 days to whole breast after local excision of early breast cancer

AIMS

A pilot study was undertaken with the aim of documenting acute skin reactions and 2-year late adverse effects of a five-fraction course of adjuvant whole breast radiotherapy delivered over 15 days after local tumour excision of early breast cancer.

MATERIALS AND METHODS

Thirty women with early invasive breast cancer aged>or=50 years with a pathological tumour size<3 cm, complete microscopic resection, negative axillary node status and no requirement for cytotoxic therapy were prescribed 30 Gy in five fractions over 15 days to the whole breast using tangential 6-10 MV X-ray beams and three-dimensional dose compensation with written informed consent. Post-surgical baseline photographs of the breasts were taken, and acute skin erythema and moist desquamation were each scored weekly for 7 weeks using four-point graded scales (grade 0=none, 1=mild, 2=moderate, 3=severe). This was followed by an annual clinical assessment, including repeat photographs at 2 years.

RESULTS

Nine patients (30%, 95% confidence interval 14.7-49.4%) developed grade 2 erythema, with the remaining 21 patients developing milder degrees of reaction. Four (13.3%, 95% confidence interval 3.7-30.7) patients developed moist desquamation, grade 1 in three women and grade 2 in the fourth. At 2 years after treatment, 23/30 (77%) patients scored no change in photographic breast appearance compared with the pre-treatment baseline; seven (23%, 95% confidence interval 9.9-42.3) scored a mild change in breast appearance, and none developed a marked change. After a mean follow-up of 3.1 years (standard deviation 0.37, range 2.1-3.9 years) there have been no ipsilateral local tumour relapses.

CONCLUSIONS

Further evaluation of a five-fraction regimen of adjuvant whole breast radiotherapy in a phase III randomised trial is justified, including a regimen delivered in a total of 5 days.

Breast dose heterogeneity in CT-based radiotherapy treatment planning

The aim of this study was to evaluate the breast dose heterogeneity in CT-based radiotherapy treatment planning and to correlate with breast parameters. Also, the number of slices required for treatment planning in breast cancer by tangential field technique has been assessed by comparing the treatment plans according to International Commission on Radiation Units and Measurement (ICRU) 50 guidelines (1993) for single-slice, three-slice, and multi-slice (3D) planning . Sixty women who underwent isocentric tangential field breast radiotherapy were included in this study. The plans were optimized and analyzed with dose volume histograms. Sixty-three percent of the single-slice plans and 26.7% of the three-slice plans showed poor dose homogeneity as compared to the 3D plans. Dose inhomogeneity correlated better with breast volume (r² = 0.43) than the chest wall separation (r² = 0.37) and breast area product (r² = 0.36). Similarly, breast volume correlated better with breast area product (r² = 0.80) than with chest wall separation (r² = 0.56). Breast volume can be approximated to breast area product from the relation, breast volume = [(breast area product × 8.85) − 120.05]. The results of this study showed that most of the cases require 3D planning for breast cancer. It also showed that patients with large breast are prone to have more dose inhomogeneity with standard tangential field radiotherapy. In centers where 3D planning is not possible due to lack of facilities or workload, three slices–based planning can be performed to approximate the dosimetric advantage of 3D planning.

Characterisation of 6MV and 10MV superficial build up dosimetry in tangential beam radiography

Introduction: Although tangential radiotherapy is one of the major treatments for breast cancer, little has been done to address the skin toxicity and general dose inhomogeneity experienced in patients with larger breasts that are treated with 6MV photons. From our understanding of radiation in tissue at depth, it is proposed that 10MV photons could have a clear role in such patients through improved dose distribution. However, a greater build up depth with 10MV could mean that this energy is unacceptable.

Aims: To quantify and characterise superficial build up dosimetry in tangential breast irradiation for 6MV and 10MV photons.

Methods: Using Thermoluminescent Dosimeters (TLD’S), a comparative study was carried out investigating dose at a range of superficial depths in a phantom irradiated by tangential fields. Each delivering 2Gy for 6MV and 10MV photons.

Results: There was a 0.10Gy difference in maximum dose over a depth of 10.8 mm between 6MV and 10MV photons, along with an average difference of dose at depth of 0.09Gy.

Conclusion: Evidence has been obtained that eliminates comprise to superficial tissue if 10MV photons are used. Furthermore, reinforcement towards a more homogenous dose distribution with 10MV photons has been established.

Intra- and interfractional variations for prone breast irradiation: an indication for image-guided radiotherapy

PURPOSE

Intra- and interfractional errors for breast cancer patients undergoing breast irradiation in the prone position were analyzed.

METHODS AND MATERIALS

To assess intrafractional error resulting from respiratory motion, four-dimensional computed tomography scans were acquired for 3 prone and 3 supine patients, and the respiratory motion was compared for the two positions. To assess the interfractional error caused by daily set-up variations, daily electronic portal images of one of the treatment beams were taken for 15 prone-positioned patients. Portal images were then overlaid with images from the planning system that included the breast contour and the isocenter, treatment beam portal, and isocenter. The shift between the planned and actual isocenter was recorded for each portal image, and descriptive statistics were collected for each patient. The margins were calculated using the 2Sigma + 0.7sigma recipe, as well as 95% confidence interval based on the pooled standard deviation of the datasets.

RESULTS

Respiratory motion of the chest wall is drastically reduced from 2.3 +/- 0.9 mm in supine position to -0.1 +/- 0.4 mm in prone position. The daily set-up errors vary in magnitude from 0.0 cm to 1.65 cm and are patient dependent. The margins were defined by considering only the standard deviation to be 1.1 cm, and 2.0 cm when the systematic errors were considered using the 2Sigma + 0.7sigma recipe.

CONCLUSIONS

Prone positioning of patients for breast irradiation significantly reduces the uncertainty introduced by intrafractional respiratory motion. The presence of large systematic error in the interfractional variations necessitates a large clinical target volume-to-planning target volume margin and indicates the importance of image guidance for partial breast irradiation in the prone position, particularly using imaging modality capable of identifying the lumpectomy cavity.

The effect of respiratory cycle and radiation beam-on timing on the dose distribution of free-breathing breast treatment using dynamic IMRT

In breast cancer treatment, intensity-modulated radiation therapy (IMRT) can be utilized to deliver more homogeneous dose to target tissues to minimize the cosmetic impact. We have investigated the effect of the respiratory cycle and radiation beam-on timing on the dose distribution in free-breathing dynamic breast IMRT treatment. Six patients with early stage cancer of the left breast were included in this study. A helical computed tomography (CT) scan was acquired for treatment planning. A four-dimensional computed tomography (4D CT) scan was obtained right after the helical CT scan with little or no setup uncertainty to simulate patient respiratory motion. After optimizing based on the helical CT scan, the sliding-window dynamic multileaf collimator (DMLC) leaf sequence was segmented into multiple sections that corresponded to various respiratory phases per respiratory cycle and radiation beam-on timing. The segmented DMLC leaf sections were grouped according to respiratory phases and superimposed over the radiation fields of corresponding 4D CT image set. Dose calculation was then performed for each phase of the 4D CT scan. The total dose distribution was computed by accumulating the contribution of dose from each phase to every voxel in the region of interest. This was tracked by a deformable registration program throughout all of the respiratory phases of the 4D CT scan. A dose heterogeneity index, defined as the ratio between (D20-D80) and the prescription dose, was introduced to numerically illustrate the impact of respiratory motion on the dose distribution of treatment volume. A respiratory cycle range of 4-8 s and randomly distributed beam-on timing were assigned to simulate the patient respiratory motion during the free-breathing treatment. The results showed that the respiratory cycle period and radiation beam-on timing presented limited impact on the target dose coverage and slightly increased the target dose heterogeneity. This motion impact tended to increase the variation of target dose coverage and heterogeneity between treatment fractions with different radiation beam-on timing. The target dose coverage and heterogeneity were more susceptible to the radiation beam-on timing for patients with long respiratory cycle (longer than 6 s) and large breast motion amplitudes (larger than 0.7 cm). The same results could be found for respiratory cycle up to 8 s and respiratory motion amplitude up to 1 cm. The heart dose distribution did not change significantly regardless of respiratory cycle and radiation beam-on timing.

Effective beam directions using radiobiologically optimized IMRT of node positive breast cancer

The purpose of this study was to investigate the optimal coplanar beam directions when treating an early breast cancer with locoregional lymphatic spread with a few radiobiologically optimized intensity modulated beams. Also to determine the increase in the probability of complication-free cure with the number of beam portals and the smallest number required to perform a close to optimal treatment for this tumour site. Four test patients with stage II left-sided breast cancer were studied with heart, lung and contralateral breast as principal organs at risk. The clinical target volume consisted of the breast tissue remaining after surgery, the axillary, the internal mammary as well as the supraclavicular lymph nodes. Through an exhaustive search of all possible beam directions the most effective coplanar beams with one to four intensity modulated photon beam portals were investigated. Comparisons with uniform beam treatment techniques and up to 12 intensity modulated beams were also made. The different plans were optimized using the probability of complication-free tumour cure, P(+), as biological objective function. When using two intensity modulated beam directions three major sets of suitable directions were identified denoted by A, P and T. A corresponds to an anterior oblique pair of beams around 25 degrees and 325 degrees , P is a perpendicular lateral pair at around 50 degrees and 130 degrees whereas T is a more conventional tangential pair at around 155 degrees and 300 degrees . Interestingly, these configurations identify simply three major effective beam directions namely at 30 degrees +/-20 degrees , 145 degrees +/-20 degrees and 310 degrees +/-15 degrees . For the three intensity modulated beam technique a combination of these three effective beam directions generally covered the global maximum of the probability of complication-free tumour control. The improvement in complication-free cure probability with two optimally selected intensity modulated beams is around 10% when compared to a uniform beam technique with three to four beam portals. This increase is mainly due to a reduction by almost 1% in the probability of injury to the heart and an increase of 6% in the probability of local tumour control. When three or four biologically optimized beam portals are used a further increase in the probability of complication-free cure of about 6% can often be obtained. This improvement is caused by a small decrease in the probability of injury to the heart, left lung and other surrounding normal tissue, as well as a slight further increase in the probability of tumour control. The increase in the treatment outcome is minimal when more than four intensity modulated beams are employed. A small increase in dose homogeneity in the target volume and a slight decrease in the normal tissue volume receiving high dose may be seen, but without appreciably improving the complication-free cure probability. For a stage II breast cancer, three and in more complex cases four optimally oriented beams are sufficient to reach close to the maximum probability of complication-free tumour control when biologically optimized intensity modulated dose delivery is used. Angle of incidence optimization may then be advantageous starting from the given most effective three beam directions.

Oncoplastic surgery of the breast: Rationale and experience of 30 cases

A definition of oncoplastic surgery of the breast is presented, and its objectives and advantages over the usual conservative procedures are discussed. The oncological safety of these procedures are demonstrated, especially in surgery of larger tumors. Technical possibilities are discussed and a classification of the procedures presented. Data from 30 cases operated in our institution are depicted. The need for better training of the breast surgeon is discussed and the advantages of the same surgeon to perform the whole procedure presented.

Intensity-modulated radiotherapy results in significant decrease in clinical toxicities compared with conventional wedge-based breast radiotherapy

PURPOSE

We have previously demonstrated that intensity-modulated radiotherapy (IMRT) with a static multileaf collimator process results in a more homogenous dose distribution compared with conventional wedge-based whole breast irradiation (WBI). In the present analysis, we reviewed the acute and chronic toxicity of this IMRT approach compared with conventional wedge-based treatment.

METHODS AND MATERIALS

A total of 172 patients with Stage 0-IIB breast cancer were treated with lumpectomy followed by WBI. All patients underwent treatment planning computed tomography and received WBI (median dose, 45 Gy) followed by a boost to 61 Gy. Of the 172 patients, 93 (54%) were treated with IMRT, and the 79 patients (46%) treated with wedge-based RT in a consecutive fashion immediately before this cohort served as the control group. The median follow-up was 4.7 years.

RESULTS

A significant reduction in acute Grade 2 or worse dermatitis, edema, and hyperpigmentation was seen with IMRT compared with wedges. A trend was found toward reduced acute Grade 3 or greater dermatitis (6% vs. 1%, p = 0.09) in favor of IMRT. Chronic Grade 2 or worse breast edema was significantly reduced with IMRT compared with conventional wedges. No difference was found in cosmesis scores between the two groups. In patients with larger breasts (> or =1,600 cm(3), n = 64), IMRT resulted in reduced acute (Grade 2 or greater) breast edema (0% vs. 36%, p <0.001) and hyperpigmentation (3% vs. 41%, p = 0.001) and chronic (Grade 2 or greater) long-term edema (3% vs. 30%, p = 0.007).

CONCLUSION

The use of IMRT in the treatment of the whole breast results in a significant decrease in acute dermatitis, edema, and hyperpigmentation and a reduction in the development of chronic breast edema compared with conventional wedge-based RT.

Four-Week Course of Radiation for Breast Cancer Using Hypofractionated Intensity Modulated Radiation Therapy With an Incorporated Boost

PURPOSE

Standard radiation for early breast cancer requires daily treatment for 6 to 7 weeks. This is an inconvenience to many women, and for some a barrier for breast conservation. We present the acute toxicity of a 4-week course of hypofractionated radiation.

METHODS AND MATERIALS

A total of 75 patients completed radiation on a Phase II trial approved by the hospital institutional review board. Eligibility criteria were broad to include any patient normally eligible for standard radiation: age >or=18 years, invasive or in situ cancer, American Joint Committee on Cancer Stage 0 to II, breast-conserving surgery, and any systemic therapy not given concurrently. The median age was 52 years (range, 31-81 years). Of the patients, 15% had ductal carcinoma in situ, 67% T1, and 19% T2; 71% were N0, 17% N1, and 12% NX. Chemotherapy was given before radiation in 44%. Using photon intensity-modulated radiation therapy and incorporated electron beam boost, the whole breast received 45 Gy and the lumpectomy bed 56 Gy in 20 treatments over 4 weeks.

RESULTS

The maximum acute skin toxicity by the end of treatment was Grade 0 in 9 patients (12%), Grade 1 in 49 (65%) and Grade 2 in 17 (23%). There was no Grade 3 or higher skin toxicity. After radiation, all Grade 2 toxicity had resolved by 6 weeks. Hematologic toxicity was Grade 0 in most patients except for Grade 1 neutropenia in 2 patients, and Grade 1 anemia in 11 patients. There were no significant differences in baseline vs. 6-week posttreatment patient-reported or physician-reported cosmetic scores.

CONCLUSIONS

This 4-week course of postoperative radiation using intensity-modulated radiation therapy is feasible and is associated with acceptable acute skin toxicity and quality of life. Long-term follow-up data are needed. This radiation schedule may represent an alternative both to longer 6-week to 7-week standard whole-breast radiation and more radically shortened 1-week, partial-breast treatment schedules.

Prone breast irradiation for pendulous breasts

The purpose of this study was to quantify the differences in doses in the organs at risk and to compare the PTV coverage and dose homogeneity of patients with pendulous breasts between prone and supine position. In 10 patients a CT-based treatment plan was made in prone and supine position. Data about dose homogeneity and doses to organs at risk were collected. Dose homogeneity turned out to be better in prone position and doses in organs at risk were lower, but with the current technique, this occurred at the cost of a reduced PTV coverage.

Determination of critical dosimetric parameters for breast radiation using forward-planned segmented fields for intensity modulation

The purpose of this study was to determine factors associated with acute skin toxicity from breast radiation for optimizing forward-planned intensity modulation. Treatment plans in 100 patients who received breast radiation using three-dimensional treatment planning were analyzed. Fifty-two patients were treated with tangent fields using wedges (nonsegmented), and 48 patients were treated with forward-planned fields segmented by a multileaf collimator to modulate intensity. Clinical and dosimetric variables were recorded. Acute skin toxicity was prospectively documented using a standard scale. Body weight, breast target volume, maximum body dose (encompassing 10 mL), and volume of body receiving >50 Gy and 55 Gy (V50Gy, and V55Gy) were associated with acute toxicity. Patients treated with segmented plans had significantly larger breast targets and were treated to lower prescription isodoses, confounding comparison with nonsegmented plans. Consequently, datasets from patients treated with segmented plans were used to design new nonsegmented plans for paired comparison. Segmented plans were superior with respect to dosimetric endpoints predictive of toxicity in this paired comparison. Limitations of 55 Gy for maximum body dose and 1100 mL for V50Gy appeared to be appropriate values to guide forward treatment planning of segmented fields.

Randomised trial of standard 2D radiotherapy (RT) versus intensity modulated radiotherapy (IMRT) in patients prescribed breast radiotherapy

BACKGROUND

Radiation dose distributions created by two dimensional (2D) treatment planning are responsible for partial volumes receiving >107% of the prescribed dose in a proportion of patients prescribed whole breast radiotherapy after tumour excision of early breast cancer. These may contribute to clinically significant late radiation adverse effects.

AIM

To test three dimensional (3D) intensity modulated radiotherapy (IMRT) against 2D dosimetry using standard wedge compensators in terms of late adverse effects after whole breast radiotherapy.

METHODS

Three hundred and six women prescribed whole breast radiotherapy after tumour excision for early stage cancer were randomised to 3D IMRT (test arm) or 2D radiotherapy delivered using standard wedge compensators (control arm). All patients were treated with 6 or 10MV photons to a dose of 50Gy in 25 fractions to 100% in 5 weeks followed by an electron boost to the tumour bed of 11.1Gy in 5 fractions to 100%. The primary endpoint was change in breast appearance scored from serial photographs taken before radiotherapy and at 1, 2 and 5 years follow up. Secondary endpoints included patient self-assessments of breast discomfort, breast hardness, quality of life and physician assessments of breast induration. Analysis was by intention to treat.

RESULTS

240 (79%) patients with 5-year photographs were available for analysis. Change in breast appearance was identified in 71/122 (58%) allocated standard 2D treatment compared to only 47/118 (40%) patients allocated 3D IMRT. The control arm patients were 1.7 times more likely to have a change in breast appearance than the IMRT arm patients after adjustment for year of photographic assessment (95% confidence interval 1.2-2.5, p=0.008). Significantly fewer patients in the 3D IMRT group developed palpable induration assessed clinically in the centre of the breast, pectoral fold, infra-mammary fold and at the boost site. No significant differences between treatment groups were found in patient reported breast discomfort, breast hardness or quality of life.

CONCLUSION

This analysis suggests that minimisation of unwanted radiation dose inhomogeneity in the breast reduces late adverse effects. Incidence of change in breast appearance was statistically significantly higher in patients in the standard 2D treatment arm compared with the IMRT arm. A beneficial effect on quality of life remains to be demonstrated.

Comparison between breast volume measurement using 3D surface imaging and classical techniques

Quantification of the complex breast region can be helpful in breast surgery, which is shaped by subjective influences. However, there is no generally recognized method for breast volume calculation. Three-dimensional (3D) body surface imaging represents a new alternative for breast volume computation. The aim of this work was to compare breast volume calculation with 3D scanning and three classic methods, focusing on relative advantages, disadvantages, and reproducibility. Repeated breast volume calculations of both breasts in six patients (n=12) were performed using a 3D laser scanner, nuclear magnetic resonance imaging (MRI), thermoplastic castings, and anthropomorphic measurements. Mean volumes (cc) and mean measurement deviations were calculated, and regression analyses were performed. MRI showed the highest measurement precision, with a mean deviation (expressed as a percentage of mean breast volume) of 1.56+/-0.52% compared with 2.27+/-0.99% for the 3D scanner, 7.97+/-3.53% for thermoplastic castings, and 6.26+/-1.56% for the anthropomorphic measurements. Breast volume calculations using MRI showed the best agreement with 3D scanning measurement (r=0.990), followed by anthropomorphic measurement (r=0.947), and thermoplastic castings (r=0.727). Compared with three classical methods of breast volume calculation, 3D scanning provides acceptable accuracy for breast volume measurements, better spatial interpretation of the anatomical area to be operated on (due to lack of chest deformation), non-invasiveness, and good patient tolerance. After this preliminary study and further development, we believe that 3D body surface scanning could provide better preoperative planning and postoperative control in everyday clinical practice.

Choice of beam energy and dosimetric implications for radiation treatment in a subpopulation of women with large breasts in the United States and Japan

Radiation complications are often related to the dose inhomogeneity (hot spot) in breast tissue treated with conservative therapy, especially for large patients. The effect of photon energy on radiation dose distribution is analyzed to provide guidelines for the selection of beam energy when tangential fields and limited slices are used to treat women with large breasts. Forty-eight patients with chest wall separation > 22 cm were selected for dosimetric analysis. We compared the maximum dose in the central axis (CAX) plane (2D) using 6-, 10-, and 18-MV photon beams in all patients and 3D data set for 16 patients. Correlation between hot spot dose (HSD), separation, breast cup size, breast volume, and body weight was derived with beam energy. Among the 48 patients in this study, HSD > 10% in the CAX plane was noted in 98%, 46%, and 4% of the population when 2D dosimetry was performed; however, with 3D study, it was in 50%, 19%, and 6% of the patients with 6-MV, 10-MV and 18-MV beams, respectively. The chest wall separation, body weight, and breast volume were correlated with the HSD in both the 2D and 3D plans. Patient's bra size was not correlated with the hot spot. The chest wall separation was found to be the most important parameter to correlate with hot spot in tangential breast treatment. Simple guidelines are provided for dose uniformity in breast with respect to chest wall separation, body weight, bra size, and breast volume with tangential field irradiations.

Radiation therapy after breast-conserving surgery

The authors critically reviewed previous articles concerning the significance of breast irradiation following breast-conserving surgery in terms of the following subject items: indications for breast-conserving therapy, the significance and complications of breast irradiation, the timing of the start of breast irradiation, the significance of boost irradiation, the potential improvement of survival with systemic therapy plus breast irradiation, the significance of axillary dissection, indications and the significance of regional nodal irradiation, accelerated hypofractionated radiotherapy, omission of breast irradiation in low-risk patients, and future directions. In addition, our previously reported results of breast irradiation following breast-conserving surgery at the Keio University Hospital are outlined. Our newly developed tangential irradiation technique directed to the axilla and a recently introduced three-dimensional simulation technique for radiotherapy treatment planning are also presented.

Cosmetic outcome of breast conservative treatment for early stage breast cancer

PURPOSE

To evaluate the cosmetic outcome of breast conservative therapy and to examine the degree of agreement between the patients' and oncologists' ratings. We also analyze the influence of several factors on cosmesis.

METHODS AND MATERIALS

We retrospectively evaluated 145 patients with primary breast cancer treated by local excision and radiotherapy between January 2000 and May 2001. Cosmetic outcome was evaluated by doctors and patients and was scored as excellent, good, fair or poor.

RESULTS

73% of patients rated cosmesis as excellent or good while the percentage was 71% when rated by radiation oncologists. The degree of cosmesis concordance evaluated by oncologists and patients was low (kappa = 0.3). In our study the variables which significantly influence on the cosmetic outcome were concomitant adjuvant chemotherapy (p = 0.04) and radiation therapy boost, either by electron beam or brachytherapy (p = 0.013).

CONCLUSION

The cosmetic outcome of breast conserving therapy was good. There was a similar rating by the patient and radiation oncologist, but the level of concordance between patients and doctors was low. Factors that significantly influence the cosmesis appear to be concomitant adjuvant chemotherapy and radiation therapy boost.

Intensity-modulated radiotherapy of breast cancer using direct aperture optimization

BACKGROUND AND PURPOSE

To design a clinically reliable and efficient step-and-shoot IMRT delivery technique for the treatment of breast cancer using direct aperture optimization (DAO). Using DAO, segments are created and optimized within the same optimization process.

PATIENTS AND METHODS

The DAO technique implemented in the Pinnacle treatment planning system, which is called direct machine parameter optimization (DMPO), was used to generate IMRT plans for twelve breast cancer patients. The prescribed dose was 50 Gy. Two DMPO plans were generated. The first approach uses DMPO only; the second technique combines DMPO with two predefined segments (DMPO(segm)), having shapes identical to the conventional tangential fields. The weight of these predefined segments is optimized simultaneously with DMPO. The DMPO plans were compared with normal two-step (TS) IMRT, creating segments after optimizing the intensity.

RESULTS

Dose homogeneity within the target volume was 4.8+/-0.6, 4.3+/-0.5 and 3.8+/-0.5 Gy for the TS, DMPO and DMPO(segm) plans, respectively. Comparing the IMRT plans with an idealized dose distribution obtained using only beamlet optimization, the degradation of the dose distribution was less for the DMPO plans compared with the two-step IMRT approach. Furthermore, this degradation was similar for all patients, while for the two-step IMRT approach it was patient specific.

CONCLUSIONS

An efficient step-and-shoot IMRT solution was developed for the treatment of breast cancer using DMPO combined with two predefined segments.

Moving to a High-tech Approach to the Irradiation of Early Breast Cancer: Is It Possible to Balance Efficacy, Morbidity and Resource Use?

There is substantial evidence documenting the potential morbidity associated with radiotherapy in early breast cancer. An appraisal of current standard radiation practice is therefore necessary, given that women are surviving longer, have an improved quality of life, and are overcoming subsequent side-effects caused by postoperative irradiation. New technology allows the application of more complex approaches. This discussion paper considers some of the benefits of the widespread use of new complex approaches, such as intensity-modulated radiotherapy (IMRT) in the light of staffing and equipment shortfalls, and possible consequences on waiting times for treatment. The discussion is considered under the following themes: (1) which women with breast cancer benefit from complex treatment approaches? (2) What is the role of treatment accuracy in limiting morbidity? And (3) what is the potential effect of complex breast irradiation approaches on service delivery? In the UK, and globally, many departments are struggling to meet waiting-time guidelines. The use of more complex approaches for breast irradiation may increase this difficulty. However, a number of simple technical changes can be used to enhance efficacy and reduce levels of normal tissue morbidity. A sub-set of women who are at greatest risk from normal tissue morbidity or reduced cosmesis should be accurately defined in order to allow departments to plan their treatment strategies with optimal use of resources.

Does breast size affect the scatter dose to the ipsilateral lung, heart, or contralateral breast in primary breast irradiation using intensity-modulated radiation therapy (IMRT)?

PURPOSE

To evaluate the relationship between the primary breast volume and dose received by the ipsilateral lung, heart (for left-breast cancers), and contralateral breast during primary breast irradiation using intensity-modulated radiation therapy (IMRT).

METHODS AND MATERIALS

Sixty-five patients with breast carcinoma were treated using 6-MV photons with IMRT technique using the Eclipse Planning System following breast conserving surgery. All patients had a treatment planning CT scan. The primary breast, ipsilateral lung, and heart were contoured on the axial CT slices. The primary breast volume was calculated using the Eclipse Planning System. The mean ipsilateral lung and heart doses were obtained from the dose-volume histogram. The contralateral breast dose was measured using paired thermoluminescent dosimeters (TLDs) placed on the patient's contralateral breast, 4 cm from the center of the medial border of the primary breast irradiation field.

RESULTS

The mean dose delivered with photons to the primary breast for all patients was 49.97 Gy. The mean volume of the primary irradiated breast was 1167.9 cc. As a percentage, the mean ipsilateral lung, heart, and contralateral breast doses were 11.2%, 6.1%, and 7.2%, respectively. The primary breast volume positively correlated with the contralateral breast dose (P < 0.0005). There was no significant correlation between the breast volume and the ipsilateral lung or heart dose (P = 0.463 and 0.943, respectively).

CONCLUSION

This study suggests that the primary breast size significantly affects the scatter dose to the contralateral breast but not the ipsilateral lung or heart dose when using IMRT for breast irradiation.

Intensity modulated radiation therapy (IMRT) decreases acute skin toxicity for women receiving radiation for breast cancer

OBJECTIVE

To determine the clinically observed incidence and severity of acute skin toxicity with breast intensity modulated radiation therapy (IMRT), and compare the results with a matched cohort of patients treated by conventional radiation therapy. Our hypothesis is that measures to decrease dose inhomogeneity within the breast and skin with IMRT will improve acute skin toxicity.

MATERIALS AND METHODS

The study population consists of 73 women with early stage breast cancer treated with breast-conserving surgery and IMRT. The IMRT technique involves an iteration method for optimization to generate the IMRT plan, Monte Carlo dose calculation, and a step-and-shoot technique using multileaf collimation for beam delivery. Other aspects of the technique including the clinical definition of the clinical target volume by the physician, patient positioning, tangential beam orientation, dose and field sizes were unchanged compared conventional tangential radiation. These patients were matched one-to-one to a control group of 60 women treated with conventional photon radiation by using their bra size and chest wall separation. The study end point was acute skin toxicity.

RESULTS

There were no observed differences in the acute toxicity based upon common terminology criteria for adverse events (CTC) for acute radiation dermatitis. There was no desquamation in 42% of IMRT patients, dry desquamation in 37% and moist desquamation in 21%. The degree of desquamation was greater for conventional patients compared with IMRT patients -52% grade 0, 10% grade 1, and 38% grade 2 (P = 0.001). Subgroup analysis showed desquamation was significantly lower with IMRT for small (P = 0.038) and large breast sizes (P = 0.037), but not medium sizes (P = 0.454). For large breast sizes, the incidence of moist desquamation grade 2 was 48% with IMRT compared with 79% in controls. Significant predictors of moist desquamation on stepwise logistic regression were use of IMRT (P = 0.0011) and breast size (P < 0.0001).

CONCLUSIONS

IMRT is associated with a decrease in severity of acute desquamation compared with a matched control group treated with conventional radiation therapy. As with conventional radiation, breast size remains the most important prognostic factor for acute skin toxicity. The CTC grading system for acute radiation dermatitis is not sensitive when applied to modern breast cancer treatment because of its dependence of subjective rating of erythema and inability to gauge variations in desquamation. Further study of patient symptoms, quality of life, and cosmesis is needed to evaluate the benefit of IMRT for breast cancer.

Comparison of three concomitant boost techniques for early-stage breast cancer

PURPOSE

Whole breast radiotherapy (RT) followed by a tumor bed boost typically spans 5-6 weeks of treatment. Interest is growing in RT regimens, such as concomitant boost, that decrease overall treatment time, lessening the time/cost burden to patients and facilities.

METHODS AND MATERIALS

Computed tomography (CT) scans from 20 cases were selected for this retrospective, dosimetric study to compare three different techniques of concomitant boost delivery: (1) standard tangents plus an electron boost, (2) intensity-modulated RT (IMRT) tangents using custom compensators plus an electron boost, and (3) IMRT tangents plus a conformal photon boost. The equivalent uniform dose model was used to compare the plans.

RESULTS

The average breast equivalent uniform dose value for the three techniques (standard, IMRT plus electrons, and IMRT plus photons) was 48.6, 47.9, and 48.3, respectively. The plans using IMRT more closely approximated the prescribed dose of 46 Gy to the whole breast. The breast volume receiving >110% of the dose was less with the IMRT tangents than with standard RT (p = 0.037), but no significant difference in the maximal dose or other evaluated parameters was noted.

CONCLUSION

Although the IMRT techniques delivered the prescribed dose with better dose uniformity, the small improvement seen did not support a goal of improved resource use.

Comparaison simulation classique–simulation virtuelle au cours d'une irradiation mammaire : étude prospective sur 14 patientes

PURPOSE

To compare conventional 2D simulation and virtual simulation on 14 patients with breast cancer.

PATIENTS AND METHODS

Patients were simulated for treatment using standard procedure. They subsequently underwent CT scan in the treatment position. The CTV was defined as breast tissue. The PTV was obtained by adding a 3D margin of 1 cm around CTV. Organs at risk (lungs and heart) were outlined. Ballistics and dose distribution obtained with the two planning methods were compared.

RESULTS

With conventional simulation, 95% of CTV received 95% of the dose prescribed. Virtual simulation significantly improved dosimetric coverage of PTV without increasing irradiation volume of lung and heart. In 2D simulation, using three slices allowed optimisation by adjusting wedge angle. The five-slice plan was a much better predictor of the maximum dose regions when compared to the three-slice plan. Using entire CT data didn't give any benefit.

CONCLUSION

Variations in CTV delineation and PTV definition limit interest of virtual simulation. In classic simulation, a 5 CT slice-plan can be used to optimise dose distribution.

Complications of radiotherapy: improving the therapeutic index

For every course of radiotherapy treatment, the potential benefit has to be weighed against the risk of normal tissue damage. Radiation-induced proctitis during and after radical radiotherapy for prostate cancer can be decreased by reducing both the size of the target volume and the margins required around this volume. In the future, target volumes could be reduced by both CT/MRI co-registration and dose painting using MR spectroscopy of choline and citrate in the prostate. Improved immobilisation and image-guided radiotherapy should allow reduced margins without compromising the effectiveness of treatment. Similarly, in breast radiotherapy treatment, lung and cardiac complications can be reduced by better patient positioning and ensuring that doses to the heart and lung are minimised during radiotherapy treatment planning. Cosmesis can be improved by using 3D breast planning techniques rather than the conventional 2D approach. These ongoing improvements and developments in radiotherapy treatment planning are leading to treatments which offer both better tumour volume coverage, and are minimising the risk of treatment-related complications. In time, these changes should allow the escalation in dose delivered to the tumour volume with the potential for increased cure rates.

Reduction of radiotherapy-induced late complications in early breast cancer: the role of intensity-modulated radiation therapy and partial breast irradiation

Radiotherapy after conservation surgery has been proven to decrease local relapse and death from breast cancer, and is now firmly established in the management of early breast carcinoma. Currently, the challenge is to optimise the therapeutic ratio by minimising treatment-related morbidity, while maintaining or improving local control and survival. The second part of this review examines the role of two approaches: intensity-modulated radiation therapy (IMRT) and partial breast irradiation, as means of improving the therapeutic ratio. Discussion of IMRT includes both inverse- and forward-planned methods: the breast usually requires minimal modulation to improve dose homogeneity, and therefore lends itself to simpler forward-planned IMRT techniques; whereas inverse-planned IMRT may be useful in selected cases. There are many dosimetry studies reporting the superiority of IMRT over conventional breast radiotherapy, but there is still a paucity of clinical data regarding patient benefit from these techniques. A critical literature review of clinical partial breast radiotherapy studies focuses on the influence of irradiated breast volume, dose and fractionation, and patient selection on normal tissue side-effects and local control. Clinical reports of partial breast irradiation show several encouraging, but some concerning results about local recurrence rates. Therefore, mature results from randomised trials comparing partial breast irradiation with whole-breast radiotherapy are required. Accurate localisation of the tumour bed and application of appropriate clinical target volumes and planning target volumes are discussed in detail, as these concepts are fundamental for partial breast irradiation.

Reduction of radiotherapy-induced late complications in early breast cancer: the role of intensity-modulated radiation therapy and partial breast irradiation

Radiotherapy after conservation surgery has been proven to decrease local relapse and death from breast cancer, and is now firmly established in the management of early breast carcinoma. Currently, the challenge is to minimise the morbidity caused by this treatment without losing its efficacy. This review will be divided into two parts, with Part I focusing on the radiation factors contributing to late normal tissue complications after radiotherapy for early breast cancer. Three major normal tissue side-effects will be discussed: cosmetic outcome, cardiac complications and pulmonary side-effects.

Comparison of a lung fitting algorithm with CT data for tangential fields in radiotherapy of the breast

A method of estimating the shape and position of the lung in tangential breast fields is presented for patients who have not been CT scanned. Using the Osiris system, the external contour is obtained optically, and an estimated lung structure superimposed on the transverse outlines based on the measured lung depth in the tangential fields and an analysis of the typical lung shapes obtained from CT images. The accuracy of this fit was determined by comparison with a set of 64 CT images imported into the Osiris system. Dose distributions were calculated by two treatment planning systems: ADAC Pinnacle and GE Target2. The computed dose distributions for 6 MV photons were compared against measured doses in a specialized breast phantom. For the worst case of lung fit compared with CT, the dosimetric error (based upon ADAC Pinnacle calculations) was 2.0% in the shadow of the lung. For the complete patient data set, the relative dose errors to these points were reduced from a mean value of 8.4% and standard deviation (SD)=1.8% (no lung correction) to a mean of 0.2% and SD=1.0% (lung correction using fitted lung). It was also found that for every 1 cm of lung path length the dose to the breast along that path length increased by approximately 1%. The results of these investigations indicated that the lung fit model was satisfactory for routine clinical use, so that good dosimetric results can be obtained using lung correction without the need for CT imaging.

Clinical use of intensity-modulated radiotherapy: part II

Intensity-modulated radiotherapy (IMRT) is a novel conformal radiotherapy technique which is gaining increasingly widespread use. This second clinical article aims to summarize the published data pertaining to prostate cancer, pelvic irradiation, gynaecological and breast cancer. Prostate cancer patients represent the largest group treated to date. The main indication has been radiation dose escalation within acceptable normal tissue late toxicity. Phase II data are promising, but no randomized clinical trial data are available to support its use. Pelvic IMRT aims to deliver radical radiation doses to pelvic lymph nodes while sparing the bowel and bladder. Indications for breast IMRT data are reviewed, and current data presented. Further data from randomized trials are required to confirm the anticipated benefits of IMRT in patients.

Evaluation of the dosimetric consequences of adding a single asymmetric or MLC shaped field to a tangential breast radiotherapy technique

Fifteen consecutive patients had standard treatment plans generated using our departmental protocol and two further plans produced using either an asymmetric, or MLC shaped additional field, from each tangential direction. The mean percentage of the PTV receiving over 107% of the isocentre dose was 19.8% for the standard planned patients (95% confidence interval 12.3-27.4%). This was reduced to 6.0% for the asymmetric field technique (95% confidence interval 4.1-8.0%) and 5.3% for the MLC technique (95% confidence interval 2.8-7.7%). These high dose volume reductions were therefore significant at the 95% confidence level. It was also concluded that both alternative planning techniques offer the greatest potential when the standard plan indicated that more than 20% of the PTV would receive greater than 107% of the prescribed dose. Under these circumstances the segmented field techniques led to a reduction of at least 15 percentage points in this figure. It is this group of patients who stand to benefit most from application of these simple additional field techniques.

Survey of tangential field planning and dose distribution in the UK: background to the introduction of the quality assurance programme for the START trial in early breast cancer

A background survey of UK breast radiotherapy techniques was performed prior to the introduction of the quality assurance programme for the Standardization of Radiotherapy (START) trial in breast cancer, a UK multicentre randomized trial of different dose fractionations for breast radiotherapy. Analysis of patient treatment plans was performed at this initial stage of the quality assurance programme to ensure eventual uniformity of treatment within the randomized trial and hence ensure reliable end results. As an integral part of this initial survey, three patient outlines of different size and shape were circulated between November 1997 and January 1998 to 56 UK radiotherapy centres. Dose distributions were produced according to the routine planning protocol of each department to provide information on treatment planning techniques. Criteria used for treatment plan production and the resultant dose distributions were analysed. The dose distributions varied between centres. Dose inhomogeneity of no more than 10% was achieved, on the central axis, for all chest wall and medium breast size plans. The number of larger breast size distributions exceeding a 10% dose gradient across the treatment volume was 54% (26). Most centres in the UK determine the breast dose distribution by planning on a two-dimensional contour taken along the central plane of the breast. Variation in the breast contour either side of this central plane is not taken into account. Care with plan optimization by selecting the most appropriate beam parameters can lead to an improvement in breast dosimetry.

Three-dimensional distribution of radiation within the breast: an intercomparison of departments participating in the START trial of breast radiotherapy fractionation

PURPOSE

To examine the ability of computer planning systems to calculate the dose to the breast correctly in three dimensions. Both the absolute dose at the center of the breast and the accuracy of the isodose distributions were investigated.

METHODS AND MATERIALS

Measurements were performed in a water-filled breast phantom using an ionization chamber. Thirty-six sets of data obtained during the Standardization of Breast Radiotherapy breast fractionation trial quality assurance program were included in the analysis. The planning systems were grouped according to the algorithms used on the basis of the definitions given in International Commission on Radiation Units and Measurements Report No. 24.

RESULTS

Thirty-two of the 36 planning systems overestimated the dose to the center of the breast, with a mean measured/calculated dose ratio of 0.979 (SD 0.013). The relative dose within 2 cm of the lung was also overestimated.

CONCLUSION

Only one algorithm (collapsed cone) investigated in this study was able to calculate the dose at the center of the breast correctly in tangential breast radiotherapy. With modern algorithms, it is important to include a correction for the lower density of the lung, because the dose close to the interface between breast and lung tissue will also be lower than anticipated.

Dose-position and dose-volume histogram analysis of standard wedged and intensity modulated treatments in breast radiotherapy

The aim of this work was to evaluate the positional distribution of dose in a concise manner and to analyse dose-histogram results in tangential breast radiotherapy in 300 patients, randomized to standard wedged or intensity modulated radiotherapy (IMRT), for future correlation with clinical outcome data. A simple method for analysing the dose-position relationship in the treatment volume was used to compare the spatial distribution of dose in patients. The breast was divided into equal thirds (upper, middle and lower) and dose was assessed using three dose bands; 95-105%, >105-110% and >110% of the prescription dose. The effect of using IMRT on the dosimetry was assessed from dose-volume histogram data using the following parameters: percentage of the target volume receiving a dose less than 95%, greater than 105%, either less than 95% or greater than 105% of that prescribed; the mean dose; and the maximum dose. Doses greater than 105% were predominantly in the upper and lower regions of the breast in the standard wedged treatment. 96% of these patients received doses greater than 105% in the upper region of the breast and 70% received doses greater than 105% in the lower breast. Only 4% of patients allocated IMRT received doses greater than 105% in either region. Analysis of dose-volume histogram data showed that IMRT reduced the volume receiving a dose greater than 105% by a mean of 10.7% (p= or <0.001); the mean change in the volume receiving a dose less than 95% was 0.2% (p=0.63). Average mean plan dose was 101.6% for standard treatment and 99.6% for IMRT (p<0.001 for each compared with 100.0% ideal). The mean value of maximum dose was reduced from 111% to 106% in the group of patients randomized to IMRT. A simple method for describing the relationship between dose and position in the breast, which is helpful for the effective correlation of dosimetry and clinical effects, is reported. Further, application of IMRT to the tangential field irradiation of the breast has been demonstrated to reduce high dose regions in both volume and dose level without compromising either minimum dose coverage or mean dose delivered to the breast.