Dosimetric comparisons between high dose rate interstitial and MammoSite™ balloon brachytherapy for breast cancer

Four-fraction ultra-accelerated minimal breast irradiation in early breast cancer: The initial feasibility results of an institutional experience

PURPOSE

To evaluate the feasibility, early toxicity, and clinical outcomes of early-breast cancer patients in a single-arm, phase I/II study of an ultra-accelerated, four-fraction schedule of minimal breast irradiation (4f-AMBI) using a multicatheter, minimally-invasive, intraoperative tumor bed implant (MITBI) during breast-conserving surgery (BCS).

METHODS AND MATERIALS

Eligible women aged >40 years with clinically and radiologically confirmed, unifocal invasive or in situ ≤3 cm tumors were considered as potential candidates for MITBI during BCS. After the pathology report, patients who met APBI criteria received ultra-accelerated four-fractions irradiation (6.2 Gy BID x 4fx over 2 days) with perioperative HDR-brachytherapy (PHDRBT). Early complications, toxicity, clinical outcomes, and cosmetic results were analyzed.

RESULTS

Of 89 patients initially implanted, 60(67.4%) were definitively included in the 4f-AMBI-protocol. The median age was 64.4 years; the median CTV was 32.1 cc (6.9-75.4 cc), and the external-V₁₀₀ was 43.1 cc (12.87-107 cc), representing 5% of the breast tissue irradiated with a median CTV D₉₀ of 6.2 Gy (5.6-6.28 Gy). The entire local treatment (BCS&MITBI-4f-AMBI) was completed at a median of 8 days (4-10 days). The rate of early complications was 11%. There were no major complications. Acute skin-subcutaneous G1 toxicity was reported in 11.7%, and late G1 toxicity on 36.7%. After a median follow-up of 27 months (11-51 months), the local, elsewhere, locoregional and distant-control rates were 100%, 98.3%, 100%, and 100% respectively. The early-cosmetic evaluation was excellent-good in 94.5% of patients evaluated.

CONCLUSIONS

Ultra-accelerated, four-fraction, minimal breast irradiation (4f-AMBI) using a minimally-invasive tumor bed implant procedure is safe, dosimetrically feasible, and shows small irradiated volumes. This program provides low toxicity rates and excellent short-term clinical and cosmesis outcomes.

Multicatheter interstitial brachytherapy versus stereotactic radiotherapy with CyberKnife for accelerated partial breast irradiation: a comparative treatment planning study with respect to dosimetry of organs at risk

Background

The aim of the study was to dosimetrically compare multicatheter interstitial brachytherapy (MIBT) and stereotactic radiotherapy with CyberKnife (CK) for accelerated partial breast irradiation (APBI) especially concerning the dose of organs at risk (OAR-s).

Patients and methods

Treatment plans of thirty-two MIBT and CK patients were compared. The OAR-s included ipsilateral non-target and contralateral breast, ipsilateral and contralateral lung, skin, ribs, and heart for left-sided cases. The fractionation was identical (4 x 6.25 Gy) in both treatment groups. The relative volumes (e.g. V100, V90) receiving a given relative dose (100%, 90%), and the relative doses (e.g. D0.1cm³, D1cm³) delivered to the most exposed small volumes (0.1 cm³, 1 cm³) were calculated from dose-volume histograms. All dose values were related to the prescribed dose (25 Gy).

Results

Regarding non-target breast CK performed slightly better than MIBT (V100: 0.7% vs. 1.6%, V50: 10.5% vs. 12.9%). The mean dose of the ipsilateral lung was the same for both techniques (4.9%), but doses irradiated to volume of 1 cm³ were lower with MIBT (36.1% vs. 45.4%). Protection of skin and rib was better with MIBT. There were no significant differences between the dose-volume parameters of the heart, but with MIBT, slightly larger volumes were irradiated by 5% dose (V5: 29.9% vs. 21.2%). Contralateral breast and lung received a somewhat higher dose with MIBT (D1cm³: 2.6% vs. 1.8% and 3.6% vs. 2.5%).

Conclusions

The target volume can be properly irradiated by both techniques with similar dose distributions and high dose conformity. Regarding the dose to the non-target breast, heart, and contralateral organs the CK was superior, but the nearby organs (skin, ribs, ipsilateral lung) received less dose with MIBT. The observed dosimetric differences were small but significant in a few parameters at the examined patient number. More studies are needed to explore whether these dosimetric findings have clinical significance.

Is it important to define skin sub-volumes in breast brachytherapy?

Aim:

To evaluate clinically pertinent skin dose and volume parameters for the development of toxicities following accelerated partial breast irradiation (APBI).

Methods:

Three skin structures of various thicknesses inside the body (2 mm, 3 mm, 4 mm) were contoured over the treated breast retrospectively in a cohort of 62 women who underwent APBI using multi-catheter interstitial brachytherapy. The correlation statistics between the various skin structures and acute and late skin sequelae were evaluated using the Mann–Whitney U test and receiver-operating characteristic analysis. A p-value of <0·05 was considered significant.

Results:

At a median follow-up period of 54 months (range: 28–86), a significant correlation was seen between dose received by 0·2 (D0·2) cc of skin 4 mm inside the body as well as volume receiving 100% dose (V100) of skin 3 mm inside the body with cosmesis at 2 years and at last follow-up. The threshold for the two parameters for prediction of excellent or good cosmesis was 90% of the prescribed dose and 0·05 cc, respectively. No significant dosimetric or volumetric correlation was seen with other sequelae like wound dehiscence, fat necrosis, telangiectasia and atrophy.

Conclusion:

The results of this study support the use of dose and volumetric indices of the sub-volumes of the skin for correlation with clinical endpoints. However, the same should be validated prospectively in a larger cohort of women undergoing breast brachytherapy.

Measurement of mean cardiac dose for various breast irradiation techniques and corresponding risk of major cardiovascular event

After breast conserving surgery, early stage breast cancer patients are currently treated with a wide range of radiation techniques including whole breast irradiation (WBI), accelerated partial breast irradiation (APBI) using high-dose rate (HDR) brachytherapy, or 3D-conformal radiotherapy (3D-CRT). This study compares the mean heart’s doses for a left breast irradiated with different breast techniques. An anthropomorphic Rando phantom was modified with gelatin-based breast of different sizes and tumors located medially or laterally. The breasts were treated with WBI, 3D-CRT, or HDR APBI. The heart’s mean doses were measured with Gafchromic films and controlled with optically stimulated luminescent dosimeters. Following the model reported by Darby (1), major cardiac were estimated assuming a linear risk increase with the mean dose to the heart of 7.4% per gray. WBI lead to the highest mean heart dose (2.99 Gy) compared to 3D-CRT APBI (0.51 Gy), multicatheter (1.58 Gy), and balloon HDR (2.17 Gy) for a medially located tumor. This translated into long-term coronary event increases of 22, 3.8, 11.7, and 16% respectively. The sensitivity analysis showed that the tumor location had almost no effect on the mean heart dose for 3D-CRT APBI and a minimal impact for HDR APBI. In case of WBI large breast size and set-up errors lead to sharp increases of the mean heart dose. Its value reached 10.79 Gy for women with large breast and a set-up error of 1.5 cm. Such a high value could increase the risk of having long-term coronary events by 80%. Comparison among different irradiation techniques demonstrates that 3D-CRT APBI appears to be the safest one with less probability of having cardiovascular events in the future. A sensitivity analysis showed that WBI is the most challenging technique for patients with large breasts or when significant set-up errors are anticipated. In those cases, additional heart shielding techniques are required.

The importance of the implant quality in APBI - Gliwice experience. Dosimetric evaluation

This study includes four years of our clinical trials to improve implant quality in multicatheter accelerated partial breast irradiation (APBI). The progress in dosimetric and volumetric parameters of the treatment plans was evaluated. One hundred and ninety-one women, for whom treatment plans were made based on three dimensional imaging, were selected for the study. To evaluate progress made in our APBI procedure, following parameters and indices were taken into account: percentage of the target volume receiving the reference dose (PTV_ref), minimum dose in the target volume expressed as a percentage of reference dose (PTV_min), dose homogeneity index (DHI), and conformity index (COIN). Additionally, the plan quality index was calculated for every group as the sum of mean values of four evaluated parameters. PTV_ref have increased from the mean value of 83.4% at the beginning to recent 94.8%. The maximum value equals to 95.4%. The same trend can be observed with PTV_min value, which has been improved from 51.7% to 70.1%, maximally. DHI and COIN mean values present similar progress. DHI value increased from 0.53 level to 0.68, and COIN from 0.58 in 2009 to 0.74. Plan quality index has increased from 2.46 in 2009 to 3.06, recently. The implant quality is crucial for the accurate dose distribution. This paper shows the progress that was made in APBI procedure to improve implant quality. Nowadays, our implant technique is based on three-dimensional CT imaging results in acceptable dose distributions.

Comparison study of the partial-breast irradiation techniques: dosimetric analysis of three-dimensional conformal radiation therapy, electron beam therapy, and helical tomotherapy depending on various tumor locations

The partial-breast irradiation (PBI) technique, an alternative to whole-breast irradiation, is a beam delivery method that uses a limited range of treatment volume. The present study was designed to determine the optimal PBI treatment modalities for 8 different tumor locations. Treatment planning was performed on computed tomography (CT) data sets of 6 patients who had received lumpectomy treatments. Tumor locations were classified into 8 subsections according to breast quadrant and depth. Three-dimensional conformal radiation therapy (3D-CRT), electron beam therapy (ET), and helical tomotherapy (H-TOMO) were utilized to evaluate the dosimetric effect for each tumor location. Conformation number (CN), radical dose homogeneity index (rDHI), and dose delivered to healthy tissue were estimated. The Kruskal-Wallis, Mann-Whitney U, and Bonferroni tests were used for statistical analysis. The ET approach showed good sparing effects and acceptable target coverage for the lower inner quadrant-superficial (LIQ-S) and lower inner quadrant-deep (LIQ-D) locations. The H-TOMO method was the least effective technique as no evaluation index achieved superiority for all tumor locations except CN. The ET method is advisable for treating LIQ-S and LIQ-D tumors, as opposed to 3D-CRT or H-TOMO, because of acceptable target coverage and much lower dose applied to surrounding tissue.

A comprehensive analysis of cardiac dose in balloon-based high-dose-rate brachytherapy for left-sided breast cancer

PURPOSE

To investigate radiation dose to the heart in 60 patients with left-sided breast cancer who were treated with balloon-based high-dose-rate brachytherapy using MammoSite or Contura applicators.

METHODS AND MATERIALS

We studied 60 consecutive women with breast cancer who were treated with 34 Gy in 10 twice-daily fractions using MammoSite (n = 37) or Contura (n = 23) applicators. The whole heart and the left and right ventricles were retrospectively delineated, and dose-volume histograms were analyzed. Multiple dosimetrics were reported, such as mean dose (D(mean)); relative volume receiving 1.7, 5, 10, and 20 Gy (V1.7, V5, V10, and V20, respectively); dose to 1 cc (D(1cc)); and maximum point dose (D(max)). Biologic metrics, biologically effective dose and generalized equivalent uniform dose were computed. The impact of lumpectomy cavity location on cardiac dose was investigated.

RESULTS

The average ± standard deviation of D(mean) was 2.45 ± 0.94 Gy (range, 0.56-4.68) and 3.29 ± 1.28 Gy (range, 0.77-6.35) for the heart and the ventricles, respectively. The average whole heart V5 and V10 values were 10.2% and 1.3%, respectively, and the heart D(max) was >20 Gy in 7 of 60 (11.7%) patients and >25 Gy in 3 of 60 (5%) patients. No cardiac tissue received ≥30 Gy. The V1.7, V5, V10, V20, and D(mean) values were all higher for the ventricles than for the whole heart. For balloons located in the upper inner quadrant of the breast, the average whole heart D(mean) was highest. The D(mean), biologically effective dose, and generalized equivalent uniform dose values for heart and ventricles decreased with increasing minimal distance from the surface of the balloon.

CONCLUSIONS

On the basis of these comprehensive cardiac dosimetric data, we recommend that cardiac dose be routinely reported and kept as low as possible in balloon-based high-dose-rate brachytherapy treatment planning for patients with left-sided breast cancer so the correlation with future cardiac toxicity data can be investigated.

Image guided, adaptive, accelerated, high dose brachytherapy as model for advanced small volume radiotherapy

Brachytherapy has consistently provided a very conformal radiation therapy modality. Over the last two decades this has been associated with significant improvements in imaging for brachytherapy applications (prostate, gynecology), resulting in many positive advances in treatment planning, application techniques and clinical outcome. This is emphasized by the increased use of brachytherapy in Europe with gynecology as continuous basis and prostate and breast as more recently growing fields. Image guidance enables exact knowledge of the applicator together with improved visualization of tumor and target volumes as well as of organs at risk providing the basis for very individualized 3D and 4D treatment planning. In this commentary the most important recent developments in prostate, gynecological and breast brachytherapy are reviewed, with a focus on European recent and current research aiming at the definition of areas for important future research. Moreover the positive impact of GEC-ESTRO recommendations and the highlights of brachytherapy physics are discussed what altogether presents a full overview of modern image guided brachytherapy. An overview is finally provided on past and current international brachytherapy publications focusing on "Radiotherapy and Oncology". These data show tremendous increase in almost all research areas over the last three decades strongly influenced recently by translational research in regard to imaging and technology. In order to provide high level clinical evidence for future brachytherapy practice the strong need for comprehensive prospective clinical research addressing brachytherapy issues is high-lighted.

Accelerated partial breast irradiation with IMRT: new technical approach and interim analysis of acute toxicity in a phase III randomized clinical trial

PURPOSE

To evaluate with a randomized clinical trial the possibility of treating the index quadrant with external intensity-modulated radiotherapy (IMRT) in a selected group of patients with early-stage breast cancer and to analyze the acute toxicity.

METHODS AND MATERIALS

From September 2005, a randomized Phase III clinical trial has been conducted to compare conventional (tangential field) fractionated whole breast treatment (Arm A) with accelerated partial breast irradiation plus intensity-modulated radiotherapy (Arm B). For intensity-modulated radiotherapy, the clinical target volume was drawn with a uniform 1-cm margin around the surgical clips in three dimensions. The ipsilateral and contralateral breast, ipsilateral and contralateral lung, heart, and spinal cord were contoured as organs at risk. All the regions of interest were contoured according to the International Commission on Radiation Units and Measurements reports 50 and 62 recommendations.

RESULTS

In September 2008, 259 patients were randomized and treated. The mean clinical target volume in Arm B was 44 cm(3) and the mean planning target volume was 123 cm(3). The mean value of the ratio between the planning target volume and the ipsilateral breast volume was 21%. The rate of Grade 1 and Grade 2 acute skin toxicity was 22% and 19% in Arm A (Radiation Therapy Oncology Group scale), respectively. The tolerance in Arm B was excellent with only 5% Grade 1 and 0.8% Grade 2 acute skin toxicity. The planning constraints were fully satisfied in most patients. In a very few cases, this was not possible because of very unfavorable anatomy. Quality assurance procedures were performed according to our internal quality assurance protocol, with excellent results.

CONCLUSION

In the present preliminary analysis, we have demonstrated that accelerated partial breast irradiation is feasible, with very low acute toxicity.

Review of MammoSite brachytherapy: advantages, disadvantages and clinical outcomes

BACKGROUND

The MammoSite radiotherapy system is an alternative treatment option for patients with early-stage breast cancer to overcome the longer schedules associated with external beam radiation therapy. The device is placed inside the breast surgical cavity and inflated with a combination of saline and radiographic contrast to completely fill the cavity. The treatment schedule for the MammoSite monotherapy is 34 Gy delivered in 10 fractions at 1.0 cm from the balloon surface with a minimum of 6 hours between fractions on the same day.

MATERIAL AND METHODS

This review article presents the advantages, disadvantages, uncertainties and clinical outcomes associated with the MammoSite brachytherapy (MSB).

RESULTS

Potential advantages of MSB are: high localised dose with rapid falloff for normal tissue sparing, minimum delay between surgery and RT, catheter moves with breast, improved local control, no exposure to staff, likely side-effects reduction and potential cost/time saving (e.g. for country patients). The optimal cosmetic results depend on the balloon-to-skin distance. Good-to-excellent cosmetic results are achieved for patients with balloon-skin spacing of > or =7 mm. There have been very few published data regarding the long term tumour control and cosmesis associated with the MSB. The available data on the local control achieved with the MSB were comparable with other accelerated partial breast irradiation techniques. The contrast medium inside the balloon causes dose reduction at the prescription point. Current brachytherapy treatment planning systems (BTPS) do not take into account the increased photon attenuation due to high Z of contrast. Some BTPS predicted up to 10% higher dose near the balloon surface compared with Monte Carlo calculations using various contrast concentrations (5-25%).

CONCLUSION

Initial clinical results have shown that the MammoSite device could be used as a sole radiation treatment for selected patients with early stage breast cancer providing good local control, minimal complication rate and excellent cosmesis.

Dose volume histogram analysis of normal structures associated with accelerated partial breast irradiation delivered by high dose rate brachytherapy and comparison with whole breast external beam radiotherapy fields

PURPOSE

To assess the radiation dose delivered to the heart and ipsilateral lung during accelerated partial breast brachytherapy using a MammoSite applicator and compare to those produced by whole breast external beam radiotherapy (WBRT).

MATERIALS AND METHODS

Dosimetric analysis was conducted on patients receiving MammoSite breast brachytherapy following conservative surgery for invasive ductal carcinoma. Cardiac dose was evaluated for patients with left breast tumors with a CT scan encompassing the entire heart. Lung dose was evaluated for patients in whom the entire lung was scanned. The prescription dose of 3400 cGy was 1 cm from the balloon surface. MammoSite dosimetry was compared to simulated WBRT fields with and without radiobiological correction for the effects of dose and fractionation. Dose parameters such as the volume of the structure receiving 10 Gy or more (V10) and the dose received by 20 cc of the structure (D20), were calculated as well as the maximum and mean doses received.

RESULTS

Fifteen patients were studied, five had complete lung data and six had left-sided tumors with complete cardiac data. Ipsilateral lung volumes ranged from 925-1380 cc. Cardiac volumes ranged from 337-551 cc. MammoSite resulted in a significantly lower percentage lung V30 and lung and cardiac V20 than the WBRT fields, with and without radiobiological correction.

CONCLUSION

This study gives low values for incidental radiation received by the heart and ipsilateral lung using the MammoSite applicator. The volume of heart and lung irradiated to clinically significant levels was significantly lower with the MammoSite applicator than using simulated WBRT fields of the same CT data sets.

Accelerated partial breast irradiation as part of breast conserving therapy of early breast carcinoma: a systematic review

New strategies for adjuvant radiotherapy of early breast cancer are being investigated in several phase III randomised trials at the present time. Accelerated partial breast irradiation (APBI) is a way to offer an early breast cancer patient, who has had breast conservative surgery, an adjuvant radiotherapy of short duration aimed at the tumour bed with a certain margin. The rationale of this strategy is that most local recurrences appear close to the tumorectomy cavity and a wish to spare the patient late radiation morbidity. This review discusses the background for APBI, the different techniques, and we highlight possible pitfalls using these techniques. A systematic overview of all phase I and II studies is provided. Patient selection for this therapy is pivotal and based on evidence from previous studies on patient/tumour characteristics and pattern of local recurrences we propose inclusion criteria for patients in APBI protocols.

New trends in radiotherapy for breast cancer

PURPOSE OF REVIEW

New radiotherapy techniques are under development to improve tumor control and to decrease the long-term side effects of breast cancer. These include accelerated partial breast irradiation, intensity modulated and image guided radiotherapy.

RECENT FINDINGS

Follow-up data of multicatheter brachytherapy accelerated partial breast irradiation and intraoperative electron beam radiotherapy confirm excellent 5-year local control rates in well selected patients. Early side effects seem to be improved, but recent data show increasing skin toxicity in multicatheter and intracavitary balloon brachytherapy. Intraoperative radiotherapy, proton beam partial breast irradiation, intensity modulated and image guided radiotherapy improve dose homogeneity and decrease normal tissue complication probability. For breast-only treatment, two tangential fields with different segments provide an attractive and feasible alternative to the conventional technique. The proposed intensity modulated radiotherapy techniques for comprehensive locoregional radiotherapy, however, result in increased doses to the contralateral lung and breast.

SUMMARY

Input from long-term clinical data on new radiotherapy techniques is needed. Consensus on target volume contouring and dose volume constraints for nontarget tissue has not yet been reached. Further research on skin toxicity with multicatheter or intracavitary brachytherapy is needed to improve the results.

Dose-volume characteristics of a 50-kV electronic brachytherapy source for intracavitary accelerated partial breast irradiation

PURPOSE

To describe dose-volume data from a 50-kV electronic brachytherapy source in intracavitary accelerated partial breast irradiation.

METHODS AND MATERIALS

Three spherical balloon applicators were imaged on a CT scanner in a water phantom and inflated throughout their suggested fill volume range. The planning target volume (PTV) was defined as a 1-cm margin around the balloon surface. Plans were created achieving 80%, 85%, and 90% coverage of the PTV, with a prescription dose of 34Gy in 10 fractions. The PTV, V(90), V(100), V(150), V(200), and V(300) were recorded for each plan.

RESULTS

For 80% target coverage, the V(200) varies from 11 to 14 cm(3) and the V(150) from 26 to 49 cm(3) over all the balloon applicators and fill volumes. For 85% coverage, the V(200) varies from 14 to 18 cm(3) and the V(150) from 27 to 53 cm(3). For 90% coverage, the V(200) varies from 16 to 22 cm(3) and the V(150)cm(3) from 30 to 61 cm(3).

CONCLUSIONS

Fifty-kilovolt electronic brachytherapy can provide PTV coverage similar to (192)Ir in the setting of intracavitary accelerated partial breast irradiation.

Evidence based radiation oncology: Breast cancer

PURPOSE

Radiotherapy is, similar to surgery, a local treatment. In the case of breast cancer, it is generally given after conservative or after more extensive, tumour and patient adapted, surgery. The target volumes can be the breast and/or the thoracic wall and/or the regional lymph node areas. The integration and the extent of radiotherapy as part of the comprehensive treatment of the breast cancer patient, including the amount of surgery and the sequencing with the systemic treatments, has to be well discussed with all medical specialists involved in treating breast cancer on a multidisciplinary basis. Guidelines for the appropriate prescription and execution of radiotherapy are of utmost importance. However, individualisation based on the individual patients' and tumours' characteristics should always be envisaged.

MATERIALS AND METHODS

Based on a review of the literature the level of evidence that is available for the indications for radiotherapy is summarised, as well as the main clinical questions that are unanswered today. An overview of the recent and ongoing clinical trails in breast cancer will highlight some of the current ongoing debates.

CONCLUSIONS

In the case of breast cancer, radiotherapy, given after as well conservative as extensive risk-adapted surgery, significantly reduces the risk of local and regional recurrences. Especially for patients with an intermediate to high absolute risk for local recurrences, a positive influence on overall survival has been shown, notably when appropriate radiotherapy techniques are used. Most important is that the best results that we can offer to our breast cancer patients for all clinical endpoints (local and regional control; quality of life; cosmetic results; survival) can be obtained by a multidisciplinary and patient-oriented approach, involving all those involved in the treatment of breast cancer patients.

Breast-conserving treatment with partial or whole breast irradiation for low-risk invasive breast carcinoma--5-year results of a randomized trial

PURPOSE

To report the 5-year results of a randomized study comparing the survival and cosmetic results of breast-conserving treatment with partial breast irradiation (PBI) or conventional whole breast irradiation (WBI).

METHODS AND MATERIALS

Between 1998 and 2004, 258 selected patients with T1 N0-1mi, Grade 1-2, nonlobular breast cancer without presence of extensive intraductal component and resected with negative margins were randomized after breast-conserving surgery to receive 50 Gy/25 fractions WBI (n = 130) or PBI (n = 128). The latter consisted of either 7 x 5.2 Gy high-dose-rate (HDR) multicatheter brachytherapy (BT; n = 88) or 50 Gy/25 fractions electron beam (EB) irradiation (n = 40).

RESULTS

At a median follow-up of 66 months, the 5-year actuarial rate of local recurrence was 4.7% and 3.4% in the PBI and WBI arms, respectively (p = 0.50). There was no significant difference in the 5-year probability of overall survival (94.6% vs. 91.8%), cancer-specific survival (98.3% vs. 96.0%), and disease-free survival (88.3% vs. 90.3%). The rate of excellent to good cosmetic result was 77.6% in the PBI group (81.2% after HDR BT; 70.0% after EB) and 62.9% in the control group (52.2% after telecobalt; 65.6% after 6-9-MV photons; p(WBI/PBI) = 0.009).

CONCLUSIONS

Partial breast irradiation using interstitial HDR implants or EB to deliver radiation to the tumor bed alone for a selected group of early-stage breast cancer patients produces 5-year results similar to those achieved with conventional WBI. Significantly better cosmetic outcome can be achieved with carefully designed HDR multicatheter implants compared with the outcome after WBI.

A treatment planning study comparing whole breast radiation therapy against conformal, IMRT and tomotherapy for accelerated partial breast irradiation

PURPOSE AND BACKGROUND

Conventional early breast cancer treatment consists of a lumpectomy followed by whole breast radiation therapy. Accelerated partial breast irradiation (APBI) is an investigational approach to post-lumpectomy radiation for early breast cancer. The purpose of this study is to compare four external beam APBI techniques, including tomotherapy, with conventional whole breast irradiation for their radiation conformity index, dose homogeneity index, and dose to organs at risk.

METHODS AND MATERIALS

Small-field tangents, three-dimensional conformal radiation therapy, intensity-modulated radiation therapy and helical tomotherapy were compared for each of 15 patients (7 right, 8 left). One radiation conformity and two dose homogeneity indices were used to evaluate the dose to the target. The mean dose to organs at risk was also evaluated.

RESULTS

All proposed APBI techniques improved the conformity index significantly over whole breast tangents while maintaining dose homogeneity and without a significant increase in dose to organs at risk.

CONCLUSION

The four-field IMRT plan produced the best dosimetric results; however this technique would require appropriate respiratory motion management. An alternative would be to use a four-field conformal technique that is less sensitive to the effects of respiratory motion.