Intensity modulation for breast treatment using static multi-leaf collimators

A Comparison of Field-in-Field and Intensity Modulated Radiation Therapy in Delivering Hypofractionated Radiation Therapy for Prostate Cancer

Purpose

This study compares the dosimetric performance of the field-in-field (FIF) technique with intensity modulated radiation therapy (IMRT) for delivering hypofractionated radiation therapy to prostate patients with cancer. The FIF technique uses 6 beams, whereas IMRT uses 9 beams.

Methods and Materials

This study was conducted on 15 patients with prostate cancer treated with step-and-shoot IMRT. The prescribed dose was 60 Gy in 20 fractions. The FIF plans contained 6 photon beams, and IMRT plans were designed using a 9-field step-and-shoot technique. Dose-volume histograms and dose distributions were evaluated to compare FIF and IMRT.

Results

The results of the planning target volume indices analysis showed a significant difference in the maximum dose, dose to 2% of volume, and homogeneity index in favor of FIF and in the mean dose, dose to 98% of volume, and D95 in favor of IMRT. The results of the organs-at-risk analysis showed significant differences in the volume of the rectum and bladder receiving 60 Gy in favor of FIF and the volume of the rectum and femoral heads receiving 30 Gy, as well as the mean dose to the rectum, in favor of IMRT. IMRT had a higher median number of monitor units (MUs) and segments (886 MU, 64 segments) compared to FIF (434 MUs, 6 segments).

Conclusions

The FIF technique and IMRT had comparable results in delivering hypofractionated radiation therapy for prostate cancer. The findings of this study may aid in decision-making for patients undergoing treatment.

The use of Hybrid Techniques in Whole-Breast Radiotherapy: A Systematic Review

Objectives The development of new techniques in radiotherapy (RT) provides a better planned target volume (PTV) dose distribution while further improving the protection of organs at risk (OARs). The study aims to present the dosimetric results of studies using hybrid techniques in whole-breast radiotherapy (WBRT). Methods: This systematic literature review was conducted by scanning the relevant literature in PubMed, Scopus, and Web of Science following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. Among the parameters are dose values for PTV and OARs beam contribute ratios, the value of monitors, and treatment times for different RT techniques. Initially, 586 articles were identified; 196 duplicate articles were removed leaving 391 articles for screening. Three-hundred and thirty-seven irrelevant articles were excluded, leaving 54 studies assessed for eligibility. A total of 22 articles met the search criteria to evaluate dosimetric results of hybrid and other RT techniques in WBRT. Results: According to the dosimetric data of the studies, hybrid intensity-modulated RT (H-IMRT) and hybrid volumetric-modulated arc therapy (H-VMAT) techniques give dosimetrically advantageous results in WBRT compared to other RT techniques. Conclusion: Hybrid techniques using appropriate beams contribute value and show great promise in improving dosimetric results in WBRT. However, there is a need for new studies showing the long-term clinical results of hybrid RT.

Cardiac Toxicity From Adjuvant Targeting Treatment for Breast Cancer Post-Surgery

Breast cancer is one of the most prevalent types of cancers worldwide, especially for females. Surgery is the preferred treatment for breast cancer, and various postoperative adjuvant therapies can be reasonably used according to different pathological characteristics, especially traditional radiotherapy, chemotherapy, and endocrine therapy. In recent years, targeting agent therapy has also become one of the selective breast cancer treatment strategies, including anti-HER-2 drugs, CDK4/6 inhibitor, poly ADP-ribose polymerase inhibitor, PI3K/AKT/mTOR pathway inhibitor, ER targeting drugs, and aromatase inhibitor. Because of the different pathologic mechanisms of these adjuvant therapies, each of the strategies may cause cardiotoxicity in clinic. The cardiac adverse events of traditional endocrine therapy, radiotherapy, and chemotherapy for breast cancer have been widely detected in clinic; however, the targeting therapy agents have been paid more attention with the extension of application. This review will summarize the cardiac toxicity of various adjuvant therapies for breast cancer, especially for targeting drug therapy.

Cost-effectiveness analysis of radiotherapy techniques for whole breast irradiation

Background

The current standard of care (SOC) for whole breast radiotherapy (WBRT) in the US is conventional tangential photon fields. Advanced WBRT techniques may provide similar tumor control and better normal tissue sparing, but it is controversial whether the medical benefits of an advanced technology are significant enough to justify its higher cost.

Objective

To analyze the cost-effectiveness of six advanced WBRT techniques compared with SOC.

Methods

We developed a Markov model to simulate health states for one cohort of women (65-year-old) with early-stage breast cancer over 15 years after WBRT. The cost effectiveness analyses of field-in-field (FIF), hybrid intensity modulated radiotherapy (IMRT), full IMRT, standard volumetric modulated arc therapy (STD-VMAT), multiple arc VMAT (MA-VMAT), non-coplanar VMAT (NC-VMAT) compared with SOC were performed with both tumor control and radiogenic side effects considered. Transition probabilities and utilities for each health state were obtained from literature. Costs incurred by payers were adopted from literature and Medicare data. Quality-adjusted life years (QALYs) and incremental cost-effectiveness ratio (ICER) were calculated. One-way sensitivity analyses and probabilistic sensitivity analyses (PSA) were performed to evaluate the impact of uncertainties on the final results.

Results

FIF has the lowest ICER value of 1,511 $/QALY. The one-way analyses show that the cost-effectiveness of advanced WBRT techniques is most sensitive to the probability of developing contralateral breast cancer. PSAs show that SOC is more cost effective than almost all advanced WBRT techniques at a willingness-to-pay (WTP) threshold of 50,000 $/QALY, while FIF, hybrid IMRT and MA-VMAT are more cost-effective than SOC with a probability of 59.2%, 72.3% and 72.6% at a WTP threshold of 100,000 $/QALY, respectively.

Conclusions

FIF might be the most cost-effective option for WBRT patients at a WTP threshold of 50,000 $/QALY, while hybrid IMRT and MA-VMAT might be the most cost-effective options at a WTP threshold of 100,000 $/QALY.

Dosimetric Comparison of Intensity-Modulated Radiotherapy, Volumetric Modulated Arc Therapy and Hybrid Three-Dimensional Conformal Radiotherapy/Intensity-Modulated Radiotherapy Techniques for Right Breast Cancer

This study aimed to compare different types of right breast cancer radiotherapy planning techniques and to estimate the whole-body effective doses and the critical organ absorbed doses. The three planning techniques are intensity-modulated radiotherapy (IMRT), volumetric modulated arc therapy (VMAT; two methods) and hybrid 3D-CRT/IMRT (three-dimensional conformal radiotherapy/intensity-modulated radiotherapy). The VMAT technique includes two methods to deliver a dose: non-continuous partial arc and continuous partial arc. A thermoluminescent dosimeter (TLD) is placed in the RANDO phantom to estimate the organ absorbed dose. Each planning technique applies 50.4 Gy prescription dose and treats critical organs, including the lung and heart. Dose-volume histogram was used to show the planning target volume (V95%), homogeneity index (HI), conformity index (CI), and other optimized indices. The estimation of whole-body effective dose was based on the International Commission on Radiation Protection (ICRP) Publication 60 and 103. The results were as follows: Continuous partial arc and non-continuous partial arc showed the best CI and HI. The heart absorbed doses in the continuous partial arc and hybrid 3D-CRT/IMRT were 0.07 ± 0.01% and 0% (V5% and V10%, respectively). The mean dose of the heart was lowest in hybrid 3D-CRT/IMRT (1.47 Gy ± 0.02). The dose in the left contralateral lung (V5%) was lowest in continuous partial arc (0%). The right ipsilateral lung average dose and V20% are lowest in continuous partial arc. Hybrid 3D-CRT/IMRT has the lowest mean dose to contralateral breast (organs at risk). The whole-body effective doses for ICRP-60 and ICRP-103 were highest in continuous partial arc (2.01 Sv ± 0.23 and 2.89 Sv ± 0.15, respectively). In conclusion, the use of VMAT with continuous arc has a lower risk of radiation pneumonia, while hybrid 3D-CRT/IMRT attain lower secondary malignancy risk and cardiovascular complications.

Comparison of conventional and advanced radiotherapy techniques for left-sided breast cancer after breast conserving surgery

Whole breast radiotherapy (WBRT) after breast conserving surgery is the standard treatment to prevent recurrence and metastasis of early stage breast cancer. This study aims to compare seven WBRT techniques including conventional tangential, field-in-field (FIF), hybrid intensity-modulated radiotherapy (IMRT), IMRT, standard volumetric modulated arc therapy (STD-VMAT), noncoplanar VMAT (NC-VMAT), and multiple arc VMAT (MA-VMAT). Fifteen patients who were previously diagnosed with left-sided early stage breast cancer and treated in our clinic were selected for this study. WBRT plans were created for these patients and were evaluated based on target coverage and normal tissue toxicities. All techniques produced clinically acceptable WBRT plans. STD-VMAT delivered the lowest mean dose (1.1 ± 0.3 Gy) and the lowest maximum dose (7.3 ± 4.9 Gy) to contralateral breast, and the second lowest lifetime attributable risk (LAR) (4.1 ± 1.4%) of secondary contralateral breast cancer. MA-VMAT delivered the lowest mean dose to lungs (4.9 ± 0.9 Gy) and heart (5.5 ± 1.2 Gy), exhibited the lowest LAR (1.7 ± 0.3%) of secondary lung cancer, normal tissue complication probability (NTCP) (1.2 ± 0.2%) of pneumonitis, risk of coronary events (RCE) (10.3 ± 2.7%), and LAR (3.9 ± 1.3%) of secondary contralateral breast cancer. NC-VMAT plans provided the most conformal target coverage, the lowest maximum lung dose (46.2 ± 4.1 Gy) and heart dose (41.1 ± 5.4 Gy), and the second lowest LAR (1.8 ± 0.4%) of secondary lung cancer and RCE (10.5 ± 2.8%). MA-VMAT and NC-VMAT could be the preferred techniques for early stage breast cancer patients after breast conserving surgery.

Dosimetric comparison of three-dimensional conformal radiotherapy and intensity-modulated radiotherapy for left-sided chest wall and lymphatic irradiation

Introduction

The aim of this study was to compare five different techniques for chest wall (CW) and lymphatic irradiation in patients with left‐sided breast carcinoma.

Methods

Three‐dimensional conformal radiotherapy (3DCRT), forward‐planned intensity‐modulated radiotherapy (FP‐IMRT), inverse‐planned IMRT (IP‐IMRT; 7‐ or 9‐field), and hybrid IP‐/FP‐IMRT were compared in 10 patients. Clinical target volume (CTV) included CW and internal mammary (IM), supraclavicular (SC), and axillary nodes. Planning target volumes (PTVs), CTVs, and organs at risks (OARs) doses were analyzed with dose–volume histograms (DVHs).

Results

No differences could be observed among the techniques for doses received by 95% of the volume (D95%) of lymphatics. However, the FP‐IMRT resulted in a significantly lower D95% dose to the CW‐PTV compared to other techniques (P = 0.002). The 9‐field IP‐IMRT achieved the lowest volumes receiving higher doses (hotspots). Both IP‐IMRT techniques provided similar mean doses (Dmean) for the left lung which were smaller than the other techniques. There was no difference between the techniques for maximum dose (Dmax) of right breast. However, FP‐IMRT resulted in lower Dmean and volume of right breast receiving at least 5 Gy doses compared to other techniques.

Conclusion

The dose homogeneity in CW‐CTV was better using IMRT techniques compared to 3DCRT. Especially 9‐field IP‐IMRT provided a more homogeneous dose distribution in IM and axillary CTVs. Moreover, the OARs volumes receiving low radiation doses were larger with IP‐IMRT technique, while volumes receiving high radiation doses were larger with FP‐IMRT technique. Hybrid IMRT plans were found to have the advantages of both FP‐ and IP‐IMRT techniques.

Field-in-field breast planning for a jawless, double-stack MLC LINAC using flattening-filter-free beams

BACKGROUND

This study intends to develop an efficient field-in-field (FiF) planning technique with the Eclipse treatment planning system (TPS) to determine the feasibility of using the Halcyon treatment delivery system for 3D treatment of breast cancer.

METHODS

Ten treatment plans were prepared on the Halcyon treatment planning system and compared to the same patients' clinically delivered TrueBeam plans which used flattened 6 MV and 10 MV beams. Patients selected for this study were treated via simple, tangential breast irradiation and did not receive radiotherapy of the supraclavicular or internal mammary lymph nodes. Planning target volumes (PTV) volumes ranged from 519 cc to 1211 cc with a mean target volume of 877 cc. Several planning techniques involving collimator, gantry rotation, and number of FiF segments were investigated as well as the use of the dynamically flattened beam (DFB) - a predefined MLC pattern that is designed to provide a flattened beam profile at 10 cm depth on a standard water phantom. For comparison, the clinically delivered TrueBeam plans remained unaltered except for normalization of the target coverage to more readily compare the two treatment delivery techniques.

RESULTS

Using the physician defined PTV, normalized such that 98% of the volume was covered by 95% of the prescribed dose, the Halcyon plans were deemed clinically acceptable and comparable to the TrueBeam plans by the radiation oncologist. Resulting average global maximum doses in the test patients were identical between the TrueBeam and Halcyon plans (108% of Rx) and a mean PTV dose of 102.5% vs 101.6%, respectively.

CONCLUSIONS

From this study a practical and efficient planning method for delivering 3D conformal breast radiotherapy using the Halcyon linear accelerator has been developed. When normalized to the clinically desired coverage, hot spots were maintained to acceptable levels and overall plan quality was comparable to plans delivered on conventional C-arm LINACs.

Reproducible Deep-inspiration Breath-hold Irradiation with Forward Intensity-modulated Radiotherapy for Left-sided Breast Cancer Significantly Reduces Cardiac Radiation Exposure Compared to Inverse Intensity-modulated Radiotherapy

Aims and Background

To investigate the objective utility of our clinical routine of reproducible deep-inspiration breath-hold irradiation for left-sided breast cancer patients on reducing cardiac exposure.

Methods and Study Design

Free-breathing and reproducible deep-inspiration breath-hold scans were evaluated for our 10 consecutive left-sided breast cancer patients treated with reproducible deep-inspiration breath-hold. The study was based on the adjuvant dose of 50 Gy in 25 fractions of 2 Gy/fraction. Both inverse and forward intensity-modulated radiotherapy plans were generated for each computed tomography dataset.

Results

Reproducible deep-inspiration breath-hold plans with forward intensity-modulated radiotherapy significantly spared the heart and left anterior descending artery compared to generated free-breathing plans based on mean doses – free-breathing vs reproducible deep-inspiration breath-hold, left ventricle (296.1 vs 94.5 cGy, P = 0.005), right ventricle (158.3 vs 59.2 cGy, P = 0.005), left anterior descending artery (171.1 vs 78.1 cGy, P = 0.005), and whole heart (173.9 vs 66 cGy, P = 0.005), heart V20 (2.2% vs 0%, P = 0.007) and heart V10 (4.2% vs 0.3%, P = 0.007) – whereas they revealed no additional burden on the ipsilateral lung. Reproducible deep-inspiration breath-hold and free-breathing plans with inverse intensity-modulated radiotherapy provided similar organ at risk sparing by reducing the mean doses to the left ventricle, left anterior descending artery, heart, V10-V20 of the heart and right ventricle. However, forward intensity-modulated radiotherapy showed significant reduction in doses to the left ventricle, left anterior descending artery, heart, right ventricle, and contralateral breast (mean dose, 248.9 to 12.3 cGy, P = 0.005). The mean doses for free-breathing vs reproducible deep-inspiration breath-hold of the proximal left anterior descending artery were 1.78 vs 1.08 Gy and of the distal left anterior descending artery were 8.11 vs 3.89 Gy, whereas mean distances to the 50 Gy isodose line of the proximal left anterior descending artery were 6.6 vs 3.3 cm and of the distal left anterior descending artery were 7.4 vs 4.1 cm, with forward intensity-modulated radiotherapy. Overall reduction in mean doses to proximal and distal left anterior descending artery with deep-inspiration breath-hold irradiation was 39% (P = 0.02) and 52% (P = 0.002), respectively.

Conclusions

We found a significant reduction of radiation exposure to the contralateral breast, left and right ventricles, as well as of proximal and especially distal left anterior descending artery with the deep-inspiration breath-hold technique with forward intensity-modulated radiotherapy planning.

High Tangent Radiation Therapy With Field-in-Field Technique for Breast Cancer

Purpose:

We evaluated whether the field-in-field (FIF) technique improves the homogeneity of the target in high tangent radiation therapy (HTRT).

Materials and Methods:

This study included 30 patients. In total, 3 HTRT plans were created: 1 with conventional opposed fields (Conv-p), 1 with the FIF technique (FIF-p), and 1 with FIF technique using lung-blocked subfields (FIF-LB-p).

Results:

The maximum dose of the breast and planning target volume (PTV) was significantly lower for FIF-p and FIF-LB-p than Conv-p. Homogeneity index of PTV was also significantly lower for FIF-p and FIF-LB-p than Conv-p. Homogeneity index of the breast or PTV was significantly better for FIF-p than FIF-LB-p. The volumes of the breast or the PTV receiving 95% and 90% of the prescribed dose were also significantly better for FIF-p, indicating the advantages of FIF-p.

Conclusions:

The FIF technique was useful in HTRT and improved homogeneity in the target.

Inversely Planned Intensity Modulated Radiotherapy of the Breast Including the Internal Mammary Chain: A Plan Comparison Study

The aim of this paper is to evaluate the benefit of inversely planned intensity modulated radiotherapy (IMRT) in the adjuvant irradiation of breast cancer when internal mammary lymph nodes are included in the treatment volume. 20 patients treated with 3D-planned conventional radiotherapy (CRT) following breast conserving surgery were included in the study. We chose 10 patients with left-sided and 10 patients with right-sided tumors. All treatment volumes included the internal mammary chain. For plan comparison to the applied CRT plan an inverse IMRT-plan in ‘step-and-shoot’-technique was calculated.

For all patients IMRT resulted in an improved conformity of dose distribution to the target volume compared to CRT (mean COIN95: 0.798 vs. 0.514 with COIN95 = C1* C2 (C1= fraction of CTV that is covered by > 95% of the prescribed dose and C2 = volume of CTV that is covered by > 95% of the prescribed dose/total volume that is covered by > 95% of the prescribed dose). In all cases with matching adjacent beams, the homogeneity in the target volume was improved. The volume of the ipsilateral lung irradiated with a dose higher than 20 Gy was reduced with IMRT from 24.6% to 13.1% compared to CRT. For left-sided target volume the heart volume with a dose higher than 30 Gy was reduced from 6.2% to 0.2%.

The presented plan comparison study for irradiation of the breast and the parasternal lymph nodes showed a substantial improvement of the dose distribution by inversely planned IMRT compared to CRT. This is visible for the target volume, the ipsilateral lung and, in case of left-sided target volume, the heart. Despite an increase in integral dose to the entire normal tissue, the application of IMRT might be clinically advantageous in cases where no satisfying dose distribution can be obtained by CRT.

Helical Tomotherapy as a Means of Delivering Accelerated Partial Breast Irradiation

A novel treatment approach utilizing helical tomotherapy for partial breast irradiation for patients with early-stage breast cancer is described. This technique may serve as an alternative to high dose-rate (HDR) interstitial brachytherapy and standard linac-based approaches. Through helical tomotherapy, highly conformal irradiation of target volumes and avoidance of normal sensitive structures can be achieved. Unlike HDR brachytherapy, it is noninvasive. Unlike other linac-based techniques, it provides image-guided adaptive radiotherapy along with intensity modulation. A treatment planning CT scan was obtained as usual on a post-lumpectomy patient undergoing HDR interstitial breast brachytherapy. The patient underwent catheter placement for HDR treatment and was positioned prone on a specially designed position-supporting mattress during C T. The planning target volume (PTV) was defined as the lumpectomy bed plus a 20 mm margin. The prescription dose was 34 Gy (10 fx of 3.4 Gy) in both the CT based HDR and on the tomotherapy plan. Cumulative dose-volume histograms (DVHs) were generated and analyzed for the target, lung, heart, skin, pectoralis muscle, and chest wall for both HDR brachytherapy and helical tomotherapy. Dosimetric coverage of the target with helical tomotherapy was conformal and homogeneous. “Hot spots” (≥150% isodose line) were present around implanted dwell positions in brachytherapy plan whereas no isodose lines higher than 109% were present in the helical tomotherapy plan. Similar dose coverage was achieved for lung, pectoralis muscle, heart, chest wall and breast skin with the two methods. We also compared our results to that obtained using conventional linac-based three dimensional (3D) conformal accelerated partial breast irradiation. Dose homogeneity is excellent with 3D conformal irradiation, and lung, heart and chest wall dose is less than for either HDR brachytherapy or helical tomotherapy but skin and pectoral muscle doses were higher than with the other techniques. Our results suggest that helical tomotherapy can serve as an effective means of delivering accelerated partial breast irradiation and may offer superior dose homogeneity compared to HDR brachytherapy.

Comparison of plan optimization for single and dual volumetric-modulated arc therapy versus intensity-modulated radiation therapy during post-mastectomy regional irradiation

The aim of the present study was to investigate volumetric-modulated arc therapy (VMAT) with single arc (1ARC) and dual arc (2ARC), and intensity-modulated radiation therapy (IMRT), and to evaluate the quality and delivery efficiency of post-mastectomy regional irradiation. A total of 24 female patients who required post-mastectomy regional irradiation were enrolled into the current study, and 1ARC, 2ARC and IMRT plans were designed for each individual patient. The quality of these plans was evaluated by calculating the homogeneity index (HI), conformity index (CI) and specific volume dose to the ipsilateral lung, double lungs, contralateral breast, heart and spinal cord. For the delivery efficiency of these plans, the total treatment time (TTT) and the number of monitor units (MUs) were evaluated. The 1ARC and 2ARC VMAT plans exhibited significantly better HIs and CIs than IMRT. For dose-volume histogram analysis, 1ARC and 2ARC VMAT spared a more specific volume dose to the ipsilateral lung, double lungs, contralateral breast, heart and spinal cord than IMRT (P<0.05). A lower MU per 2.0-Gy fraction was required for 1ARC (539 MU) and 2ARC (608 MU) than for IMRT (1,051 MU). Thus, TTT was correspondingly reduced in 1ARC and 2ARC compared to IMRT (P<0.05). There was no significant dose-volume difference in all the organs at risk (OARs) between the 1ARC and 2ARC plans (P>0.05), and 2ARC VMAT displayed a better HI and CI than 1ARC VMAT (P<0.05). By contrast, 1ARC VMAT was superior to 2ARC VAMT with regard to MU and TTT (P<0.05). The 1ARC and 2ARC VMAT plans demonstrated significantly better dose distribution in a shorter treatment time than IMRT for post-mastectomy regional irradiation, and spared the majority of OARs without compromising target coverage. The results of the present study suggest that 2ARC VMAT may be an alternative to 1ARC in order to obtain a more optimal HI and CI.

Assessment of Intrafraction Breathing Motion on Left Anterior Descending Artery Dose During Left-Sided Breast Radiation Therapy

PURPOSE

To use 4-dimensional computed tomography (4D-CT) imaging to predict the level of uncertainty in cardiac dose estimates of the left anterior descending artery that arises due to breathing motion during radiation therapy for left-sided breast cancer.

METHODS AND MATERIALS

The fast helical CT (FH-CT) and 4D-CT of 30 left-sided breast cancer patients were retrospectively analyzed. Treatment plans were created on the FH-CT. The original treatment plan was then superimposed onto all 10 phases of the 4D-CT to quantify the dosimetric impact of respiratory motion through 4D dose accumulation (4D-dose). Dose-volume histograms for the heart, left ventricle (LV), and left anterior descending (LAD) artery obtained from the FH-CT were compared with those obtained from the 4D-dose.

RESULTS

The 95% confidence interval of 4D-dose and FH-CT differences in mean dose estimates for the heart, LV, and LAD were ±0.5 Gy, ±1.0 Gy, and ±8.7 Gy, respectively.

CONCLUSION

Fast helical CT is a good approximation for doses to the heart and LV; however, dose estimates for the LAD are susceptible to uncertainties that arise due to intrafraction breathing motion that cannot be ascertained without the additional information obtained from 4D-CT and dose accumulation. For future clinical studies, we suggest the use of 4D-CT-derived dose-volume histograms for estimating the dose to the LAD.

Usefulness of the dual energy field-in-field technique in breast tangential radiotherapy

PURPOSE

In the field-in-field (FIF) technique in breast tangential radiotherapy, the energy of the subfield is usually the same as the energy of the main field. However, some studies have applied 10-18 MV to subfields in patients with large breasts. We compared two FIF plans in 66 breast cancer patients: in one, the energy of the subfield was the same as that of the main field (the mono energy plan); in the other, it was higher (the dual energy plan).

MATERIALS AND METHODS

The photon energy of the subfield was 6 MV in the mono energy plan and 10 MV in the dual energy plan. The percentage of the planning target volume (PTV) receiving at least 105, 100, and 95% of the prescribed dose (V105, V100, and V95, respectively) was calculated, as were the maximum and mean doses delivered to the PTV (Dmax and Dmean, respectively). Clinical target volumes (CTVs) and the thickness of the breast between the chest wall and skin surface at the level of the nipple were measured.

RESULTS

V95% was significantly higher in the dual energy plan than in the mono energy plan in patients with CTVs or breast thickness in the highest quartile. There were no significant differences in the other parameters of the two plans in these patients.

CONCLUSION

These findings demonstrate the usefulness of the dual energy FIF technique in patients with large breasts receiving breast tangential radiotherapy.

Reducing the Human Burden of Breast Cancer: Advanced Radiation Therapy Yields Improved Treatment Outcomes

Radiation therapy is an important modality in the treatment of patients with breast cancer. While its efficacy in the treatment of breast cancer was known shortly after the discovery of x-rays, significant advances in radiation delivery over the past 20 years have resulted in improved patient outcomes. With the development of improved systemic therapy, optimizing local control has become increasingly important and has been shown to improve survival. Better understanding of the magnitude of treatment benefit, as well as patient and biological factors that confer an increased recurrence risk, have allowed radiation oncologists to better tailor treatment decisions to individual patients. Furthermore, significant technological advances have occurred that have reduced the acute and long-term toxicity of radiation treatment. These advances continue to reduce the human burden of breast cancer. It is important for radiation oncologists and nonradiation oncologists to understand these advances, so that patients are appropriately educated about the risks and benefits of this important treatment modality.

Determination of the optimal method for the field-in-field technique in breast tangential radiotherapy

Several studies have reported the usefulness of the field-in-field (FIF) technique in breast radiotherapy. However, the methods for the FIF technique used in these studies vary. These methods were classified into three categories. We simulated a radiotherapy plan with each method and analyzed the outcomes. In the first method, a pair of subfields was added to each main field: the single pair of subfields method (SSM). In the second method, three pairs of subfields were added to each main field: the multiple pairs of subfields method (MSM). In the third method, subfields were alternately added: the alternate subfields method (ASM). A total of 51 patients were enrolled in this study. The maximum dose to the planning target volume (PTV) (Dmax) and the volumes of the PTV receiving 100% of the prescription dose (V100%) were calculated. The thickness of the breast between the chest wall and skin surface was measured, and patients were divided into two groups according to the median. In the overall series, the average V100% with ASM (60.3%) was significantly higher than with SSM (52.6%) and MSM (48.7%). In the thin breast group as well, the average V100% with ASM (57.3%) and SSM (54.2%) was significantly higher than that with MSM (43.3%). In the thick breast group, the average V100% with ASM (63.4%) was significantly higher than that with SSM (51.0%) and MSM (54.4%). ASM resulted in better dose distribution, regardless of the breast size. Moreover, planning for ASM required a relatively short time. ASM was considered the most preferred method.

Progress and controversies: radiation therapy for invasive breast cancer

Radiation therapy is a critical component of the multidisciplinary management of invasive breast cancer. In appropriately selected patients, radiation not only improves local control, sparing patients the morbidity and distress of local recurrence, but it also improves survival by preventing seeding and reseeding of distant metastases from persistent reservoirs of locoregional disease. In recent years, considerable progress has been made toward improving our ability to select patients most likely to benefit from radiotherapy and to administer treatment in ways that maximize clinical benefit while minimizing toxicity and burden. This article reviews the role of radiation therapy in invasive breast cancer management, both after breast-conserving surgery and after mastectomy. It focuses particularly on emerging evidence that helps to define the clinical situations in which radiotherapy is indicated, the appropriate targets of treatment, and optimal approaches for minimizing both the toxicity and the burden of treatment, all in the context of the evolving surgical and systemic management of this common disease. It includes a discussion of new approaches in breast cancer radiotherapy, including hypofractionation and intensity modulation, as well as a discussion of promising avenues for future research.

Feasibility of using nonflat photon beams for whole-breast irradiation with breath hold

Removing a flattening filter or replacing it with a thinner filter alters the characteristics of a photon beam, creating a forward peaked intensity profile to make the photon beam nonflat. This study is to investigate the feasibility of applying nonflat photon beams to the whole-breast irradiation with breath holds for a potential of delivery time reduction during the gated treatment. Photon beams of 6 MV with flat and nonflat intensity profiles were commissioned. Fifteen patients with early-stage breast cancer, who received whole-breast radiation without breathing control, were retrospectively selected for this study. For each patient, three plans were created using a commercial treatment planning system: (a) the clinically approved plan using forward planning method (FP); (b) a hybrid intensity-modulated radiation therapy (IMRT) plan where the flat beam open fields were combined with the nonflat beam IMRT fields using direct aperture optimization method (mixed DAO); (c) a hybrid IMRT plan where both open and IMRT fields were from nonflat beams using direct aperture optimization (nonflat DAO). All plans were prescribed for ≥ 95% of the breast volume receiving the prescription dose of 50 Gy (2.0 Gy per fraction). In comparison, all plans achieved a similar dosimetric coverage to the targeted volume. The average homogeneity index of the FP, mixed DAO, and nonflat DAO plans were 0.882 ± 0.024, 0.879 ± 0.023, and 0.867 ± 0.027, respectively. The average percentage volume of V105 was 57.66% ± 5.21%, 34.67% ± 4.91%, 41.64% ± 5.32% for the FP, mixed, and nonflat DAO plans, respectively. There was no significant difference (p &gt; 0.05) observed for the defined endpoint doses in organs at risk (OARs). In conclusion, both mixed DAO and nonflat DAO plans can achieve similar plan quality as the clinically approved FP plan, measured by plan homogeneity and endpoint doses to the ORAs. Nonflat beam plans may reduce treatment time in breath-hold treatment, especially for hypofractionated treatment.

Comparison of different breast planning techniques and algorithms for radiation therapy treatment

This work aims at investigating the impact of treating breast cancer using different radiation therapy (RT) techniques--forwardly-planned intensity-modulated, f-IMRT, inversely-planned IMRT and dynamic conformal arc (DCART) RT--and their effects on the whole-breast irradiation and in the undesirable irradiation of the surrounding healthy tissues. Two algorithms of iPlan BrainLAB treatment planning system were compared: Pencil Beam Convolution (PBC) and commercial Monte Carlo (iMC). Seven left-sided breast patients submitted to breast-conserving surgery were enrolled in the study. For each patient, four RT techniques--f-IMRT, IMRT using 2-fields and 5-fields (IMRT2 and IMRT5, respectively) and DCART - were applied. The dose distributions in the planned target volume (PTV) and the dose to the organs at risk (OAR) were compared analyzing dose-volume histograms; further statistical analysis was performed using IBM SPSS v20 software. For PBC, all techniques provided adequate coverage of the PTV. However, statistically significant dose differences were observed between the techniques, in the PTV, OAR and also in the pattern of dose distribution spreading into normal tissues. IMRT5 and DCART spread low doses into greater volumes of normal tissue, right breast, right lung and heart than tangential techniques. However, IMRT5 plans improved distributions for the PTV, exhibiting better conformity and homogeneity in target and reduced high dose percentages in ipsilateral OAR. DCART did not present advantages over any of the techniques investigated. Differences were also found comparing the calculation algorithms: PBC estimated higher doses for the PTV, ipsilateral lung and heart than the iMC algorithm predicted.

Research on different techniques in breast cancer radiotherapy

In breast cancer radiotherapy, the internal mammary lymphatic chain is treated in the target volume in a group of patients with high risk criteria. There are a number of different techniques in breast radiotherapy because of the variability of the anatomic region, structures and risk criteria in the irradiation field. When irradiating the target volume we also consider homogeneity of dose distribution and minimizing the dose to critical structures such as the heart and lung. In this study, we have evaluated the dose distribution of different radiotherapy techniques in twelve patients with left breast cancer who had breast conserving surgery or mastectomy. A two-dimensional computerized planning system (2-DCPS) was used for each patient to compare wide-field, oblique photon-electron, perpendicular photon-electron and oblique-electron techniques in terms of dose homogeneities in the target volume, the doses received by the heart and lung, and the coverage of the internal mammary chain. Critical structures were irradiated with acceptable dose percentages besides the internal mammary chain with both wide-field, photon-electron and oblique-electron techniques. The wide-field technique was easy to perform and exposed the heart to a smaller radiation dose than photon-electron techniques. The oblique electron techniques provide a minimal radiation dose to critical structures. In oblique electron techniques, if the internal mammary chain was not covered in the target volume, the heart dose was minimized. In conclusion, we suggest using oblique-electron techniques in breast irradiation where the internal mammary is in the target volume.

Second cancer incidence risk estimates using BEIR VII models for standard and complex external beam radiotherapy for early breast cancer

PURPOSE

To compare organ specific cancer incidence risks for standard and complex external beam radiotherapy (including cone beam CT verification) following breast conservation surgery for early breast cancer.

METHOD

Doses from breast radiotherapy and kilovoltage cone beam CT (CBCT) exposures were obtained from thermoluminescent dosimeter measurements in an anthropomorphic phantom in which the positions of radiosensitive organs were delineated. Five treatment deliveries were investigated: (i) conventional tangential field whole breast radiotherapy (WBRT), (ii) noncoplanar conformal delivery applicable to accelerated partial beast irradiation (APBI), (iii) two-volume simultaneous integrated boost (SIB) treatment, (iv) forward planned three-volume SIB, and (v) inverse-planned three volume SIB. Conformal and intensity modulated radiotherapy methods were used to plan the complex treatments. Techniques spanned the range from simple methods appropriate for patient cohorts with a low cancer recurrence risk to complex plans relevant to cohorts with high recurrence risk. Delineated organs at risk included brain, salivary glands, thyroid, contralateral breast, left and right lung, esophagus, stomach, liver, colon, and bladder. Biological Effects of Ionizing Radiation (BEIR) VII cancer incidence models were applied to the measured mean organ doses to determine lifetime attributable risk (LAR) for ages at exposure from 35 to 80 yr according to radiotherapy techniques, and included dose from the CBCT imaging.

RESULTS

All LAR decreased with age at exposure and were lowest for brain, thyroid, liver, and bladder (<0.1%). There was little dependence of LAR on radiotherapy technique for these organs and for colon and stomach. LAR values for the lungs for the three SIB techniques were two to three times those from WBRT and APBI. Uncertainties in the LAR models outweigh any differences in lung LAR between the SIB methods. Constraints in the planning of the SIB methods ensured that contralateral breast doses and LAR were comparable to WBRT, despite their added complexity. The smaller irradiated volume of the ABPI plan contributed to a halving of LAR for contralateral breast compared with the other plan types. Daily image guided radiotherapy (IGRT) for a left breast protocol using kilovoltage CBCT contributed <10% to LAR for the majority of organs, and did not exceed 22% of total organ dose.

CONCLUSIONS

Phantom measurements and calculations of LAR from the BEIR VII models predict that complex breast radiotherapy techniques do not increase the theoretical risk of second cancer incidence for organs distant from the treated breast, or the contralateral breast where appropriate plan constraints are applied. Complex SIB treatments are predicted to increase the risk of second cancer incidence in the lungs compared to standard whole breast radiotherapy; this is outweighed by the threefold reduction in 5 yr local recurrence risk for patients of high risk of recurrence, and young age, from the use of radiotherapy. APBI may have a favorable impact on risk of second cancer in the contralateral breast and lung for older patients at low risk of recurrence. Intensive use of IGRT increased the estimated values of LAR but these are dominated by the effect of the dose from the radiotherapy, and any increase in LAR from IGRT is much lower than the models' uncertainties.

Does participation in clinical trials influence the implementation of new techniques? A look at changing techniques in breast radiotherapy in the UK

AIMS

To examine the effect of UK breast radiotherapy trials on the adoption of new radiotherapy techniques over the last 15 years.

MATERIALS AND METHODS

The data were taken from questionnaires returned to the national radiotherapy quality assurance team for each of the major trials (START, Supremo, FAST, IMPORT) with additional information sought from heads of radiotherapy physics departments where needed.

RESULTS

The peak years for the introduction of three-dimensional radiotherapy corresponded to the opening of new trials requiring these techniques. Some non-trial centres had still not implemented three-dimensional techniques for breast cancer patients at the time the most recent questionnaire was completed (2009).

CONCLUSION

Clinical trials provide the framework and impetus for introducing more accurate radiotherapy for UK women with early breast cancer.

Dosimetric evaluation of conventional radiotherapy, 3-D conformal radiotherapy and direct machine parameter optimisation intensity-modulated radiotherapy for breast cancer after conservative surgery

INTRODUCTION

The use of conservative surgery combined with whole-breast irradiation (WBI) has been established as a valid alternative to mastectomy for the management of early-stage breast cancer. The aim of this study was to compare dosimetric parameters of the planning target volume(PTV) and organs at risk (OARs) between conventional radiation therapy (CR), 3-D conformal radiation therapy (3DCRT), and direct machine parameter optimisation intensity-modulated radiation therapy (DMPO-IMRT) after breast-conserving surgery.

METHODS AND MATERIALS

Computed tomography (CT) scans from 20 patients (13 left-sided and 7 right-sided) previously treated with T1N0 or ductal carcinoma were selected for this dosimetric planning study. We designed CR, 3DCRT and DMPO-IMRT plans for each patient. The prescribed dose was 50 Gy/2 Gy/25 f, 95% of PTV received the prescription dose. Doses were computed with a commercially available treatment planning system using convolution/superimposition (CS) algorithm. Plans were compared according to dose-volume histogram (DVH) analysis in terms of PTV homogeneity and conformity indices (HI and CI) as well as OARs dose and volume parameters.

RESULTS

Both the HI and CI of the PTV showed statistically significant difference between CR, 3DCRT and DMPO-IMRT with those of DMPO-IMRT were best (P < 0.05). Compared with CR, 3DCRT showed smaller exposed volumes of ipsilateral lung, contralateral breast and heart while DMPO-IMRT indicated larger exposed volumes of ipsilateral lung (except for V20 and V30), contralateral breast and heart. In addition, DMPO-IMRT demonstrated an increase of exposed volume of ipsilateral lung (except for V30), contralateral breast and heart compared with 3DCRT.

CONCLUSIONS

In WBI of breast cancer after conservative surgery, 3DCRT and DMPO-IMRT improved the homogeneity and conformity of the PTV compared with CR. Meanwhile, 3DCRT reduced the irradiated volumes of OARs at all dose levels listed in our study while DMPO-IMRT reduced the irradiated volumes of OARs in high-dose areas but increased the irradiated volumes of OARs in low-dose areas.

Quality assurance analysis of participating centres' protocol compliance to a UK multicentre hypofractionated breast (FAST) trial

OBJECTIVES

The FAST (FASTer radiotherapy for breast radiotherapy) trial is a UK Phase 2 multicentre randomised clinical trial evaluating a five-fraction schedule of whole-breast radiotherapy following local excision of early breast cancer. The purpose of this quality assurance study was to analyse the radiotherapy planning data in order to confirm compliance with the trial protocol.

METHODS

915 patients were recruited between 2004 and 2007 from 18 centres. The protocol required that all centres should use three-dimensional dose compensations to optimise radiotherapy plans. Planning techniques, maximum dose (D(max)) and dose-volume histograms from treatment plans were evaluated and compared between centres. The homogeneity of plans was tested by creating a cut-off value of 5% for the percentage of breast volume receiving >105% of the prescribed dose.

RESULTS

672 data sets from 15 centres were available. 93% (624/672) of plans were treated using forward-planned multileaf collimator (MLC) segments, 6% with breast compensators and 1% with inverse-planned MLC segments. 94% (635/672) of patients had a D(max)≤107% of the prescribed dose. 11% (74/672) of plans delivered >105% of the prescribed dose to >5% of the breast volume.

CONCLUSION

Reviewing the data in this study, 95% of plans submitted by centres complied with the protocol. With the improved breast radiotherapy standards shown in FAST centres, the following recommendations were suggested for future UK breast radiotherapy trials: (i) the minimum, mean and maximum dose to the whole-breast planning target volume (PTV) should be recorded and assessed; (ii) apart from having a D(max)≤107% of the prescribed dose, ≤5% of PTV should a receive dose >105% of the prescription dose.

Quantification of cold spots caused by geometrical uncertainty in field-in-field techniques for whole breast radiotherapy

OBJECTIVE

To quantify the cold spot under geometrical uncertainties in field-in-field techniques for whole breast radiotherapy.

METHODS

Ten consecutive patients from both the left- and right-sided treatment site groups who received whole breast radiotherapy with the field-in-field technique were included. Virtual plans were made with moving isocenters to the posterior direction having two amplitudes (5 and 10 mm) and prescribing the same monitor unit as the original plan (FIF_5 and FIF_10). The planning target volume for evaluation was defined by subtracting the areas within 5 mm from the skin and within 5 mm from the lung from the whole breast. The differences in V90, V95 and D98 of planning target volume for evaluation were measured between the original and virtual plans. As a reference, the same measurements were taken for the wedge techniques (Wedge_5 and Wedge_10).

RESULTS

The differences in V95 were -0.2% on FIF_5, -1.7% on FIF_10, -0.5% on Wedge_5 and -1.5% on Wedge_10. The differences in V90 were -0.02% on FIF_5, -0.3% on FIF_10, -0.05% on Wedge_5 and -0.1% on Wedge_10. The differences in D98 were 0 Gy on FIF_5, -0.1 Gy on FIF_10, -0.2 Gy on Wedge_5 and -0.4 Gy on Wedge_10. The differences in D98 between the original plans and virtual scenarios for field-in-field techniques were significantly smaller than those for wedge techniques, but there were no statically significant differences in V90 and V95.

CONCLUSIONS

The quantity of the cold spots caused by the geometrical uncertainties in field-in-field techniques was similar to that for the wedge techniques and was acceptable.

Clinical Dosimetric Study of Three Radiotherapy Techniques for Postoperative Breast Cancer: Helical Tomotherapy, IMRT, and 3D-CRT

This paper is to investigate the dosimetric characteristics of Helical Tomotherapy (HT), step-and-shoot intensity-modulated radiation therapy (SaS-IMRT) and three-dimensional conformal radiation therapy (3D-CRT) for the postoperative breast cancer as well as their dosimetric comparison of the normal tissues. CT images of 10 postoperative patients with early stage breast cancer were transferred into HT, SaS-IMRT and 3D-CRT planning systems respectively after the target region and normal tissues were outlined by the same physician to assure the contour consistency. Each prescribed dose for three different modalities of plans was given to a total of 50 Gy in 25 fractions. Doses and irradiated volumes in heart, lungs, as well as conformity index (CI) and homogeneity index (HI) were evaluated for detailed comparison. All three plans showed appropriate coverage for the prescribed target dose in the dosimetric comparison. The CI in HT and SaS-IMRT as well as 3D-CRT was 0.68 ± 0.12, 0.58 ± 0.08 and 0.40 ± 0.08, respectively. The HI were 1.10 ± 0.03, 1.14 ± 0.02 and 1.17 ± 0.04, which appeared intergroup significant differences (p < 0.05). V5, V10, as well as V20 of the heart were smallest in 3D-CRT than HT and SaS-IMRT. V5 of the ipsilateral lung was the smallest in 3D-CRT than HT and SaS-IMRT (p < 0.05); However, V20 and V30 were smaller in HT and SaS-IMRT than 3D-CRT (p < 0.05). V5 of the contralateral lung was the smallest in 3D-CRT than other groups, with V10~V30 were basically similar in numeric values with not obvious discrepancy. Comparing with SaS-IMRT and 3D-CRT, HT technique in treating breast cancer had the best conformity and homogeneity index as well as steepest dose gradient due to its highly modulated beamlets with rotational technique. The heart volume irradiated was the smallest in conventional 3D-CRT, with SaS-IMRT was the largest among the three techniques, as expected. The volume of the contralateral lung irradiated was the smallest in 3D-CRT than other groups. V5 of the ipsilateral lung was the smallest in 3D-CRT than other two groups. V10~V30 in HT and SaS-IMRT were similar and better than 3D-CRT dosimetrically. We conclude that HT technique had advantages over SaS-IMRT and 3D-CRT based on the dosimetric comparison in this study, especially in the high dose region of ipsilateral lung, target homogeneity and dose uniformity.

Simultaneous integrated boost in breast conserving treatment of breast cancer: a dosimetric comparison of helical tomotherapy and three-dimensional conformal radiotherapy

BACKGROUND AND PURPOSE

To evaluate the dosimetry of helical tomotherapy (HT) and three-dimensional conformal radiotherapy (3D-CRT) in breast cancer patients undergoing whole breast radiation with simultaneous integrated boost (SIB) of the tumor bed.

MATERIAL AND METHODS

Thirteen patients with breast cancer treated by lumpectomy and requiring whole breast radiotherapy with tumor bed boost were planned using both HT and 3D-CRT using the field-in-field technique. The whole breast and tumor bed were prescribed 50.68 Gy and 64.4 Gy, respectively, in 28 fractions. Dosimetries for both techniques were compared.

RESULTS

Coverage of the whole breast was adequate with both techniques (V(95%)=96.22% vs. 96.25%, with HT and 3D-CRT, respectively; p=0.64). Adequate tumor bed coverage was also achieved, although it was significantly lower with HT (V(95%)=97.18% vs. 99.72%; p<0.001). Overdose of the breast volume outside the tumor bed was significantly lower with HT (V(54.23 Gy)=12.47% vs. 30.83%; p<0.001). Ipsilateral lung V(20 Gy) (6.34% vs. 10.17%; p<0.001), V(5 Gy) (16.54% vs. 18.53%; p<0.05) and mean dose (4.05 Gy vs. 6.36 Gy; p<0.001) were significantly lower with HT. In patients with left-sided tumors, heart V(30 Gy) (0.03% vs. 1.14%; p<0.05) and mean dose (1.35 Gy vs. 2.22 Gy; p<0.01) were significantly lower with HT, but not V(5 Gy). Contralateral breast V(5 Gy) (0.27% vs. 0.00%; p<0.01) and maximum dose were significantly increased with HT.

CONCLUSIONS

In breast cancer treated with SIB, both HT and 3D-CRT provided adequate target volume coverage and low heart doses. Tumor bed coverage was slightly lower with HT, but HT avoided unnecessary breast overdosage while improving ipsilateral lung dosimetry.

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.

Irregular surface compensation for radiotherapy of the breast: correlating depth of the compensation surface with breast size and resultant dose distribution

Irregular surface compensation uses dynamic multileaf collimators to modify the fluence to an irregular surface along the cranio-caudal axis. The depth of the compensation surface can be varied by specifying a user-defined parameter called the transmission penetration depth (TPD). In our institution, a review has been carried out of 60 breast patients treated using irregular surface compensation of the tangent fields. The effect of changes in the TPD on the dose distribution was investigated, and the optimum TPD was correlated with the maximum field separation (S(max)) along the posterior border. Reducing the TPD below 50% pushes the dose towards the front of the breast. This reduces hot spots at the medial and lateral regions next to the posterior border of the tangential fields, particularly for patients with large separation. In 23/60 patients, with a mean S(max) of 23.9 +/- 1.6 cm, a TPD between 35% and 45% was used to reduce the proportion of the planning target volume receiving more than 107% of the prescribed dose by 3.4% +/- 2.8%. Our department protocol states that, subject to an acceptable dose distribution, a TPD of 40% is used if S(max) is greater than 24 cm; for smaller separations, a TPD of 50% is used.

Variability of target and normal structure delineation for breast cancer radiotherapy: an RTOG Multi-Institutional and Multiobserver Study

PURPOSE

To quantify the multi-institutional and multiobserver variability of target and organ-at-risk (OAR) delineation for breast-cancer radiotherapy (RT) and its dosimetric impact as the first step of a Radiation Therapy Oncology Group effort to establish a breast cancer atlas.

METHODS AND MATERIALS

Nine radiation oncologists specializing in breast RT from eight institutions independently delineated targets (e.g., lumpectomy cavity, boost planning target volume, breast, supraclavicular, axillary and internal mammary nodes, chest wall) and OARs (e.g., heart, lung) on the same CT images of three representative breast cancer patients. Interobserver differences in structure delineation were quantified regarding volume, distance between centers of mass, percent overlap, and average surface distance. Mean, median, and standard deviation for these quantities were calculated for all possible combinations. To assess the impact of these variations on treatment planning, representative dosimetric plans based on observer-specific contours were generated.

RESULTS

Variability in contouring the targets and OARs between the institutions and observers was substantial. Structure overlaps were as low as 10%, and volume variations had standard deviations up to 60%. The large variability was related both to differences in opinion regarding target and OAR boundaries and approach to incorporation of setup uncertainty and dosimetric limitations in target delineation. These interobserver differences result in substantial variations in dosimetric planning for breast RT.

CONCLUSIONS

Differences in target and OAR delineation for breast irradiation between institutions/observers appear to be clinically and dosimetrically significant. A systematic consensus is highly desirable, particularly in the era of intensity-modulated and image-guided RT.

Planning and delivery of intensity-modulated radiation therapy

Intensity modulated radiation therapy (IMRT) is an advanced form of external beam radiation therapy. IMRT offers an additional dimension of freedom as compared with field shaping in three-dimensional conformal radiation therapy because the radiation intensities within a radiation field can be varied according to the preferences of locations within a given beam direction from which the radiation is directed to the tumor. This added freedom allows the treatment planning system to better shape the radiation doses to conform to the target volume while sparing surrounding normal structures. The resulting dosimetric advantage has shown to translate into clinical advantages of improving local and regional tumor control. It also offers a valuable mechanism for dose escalation to tumors while simultaneously reducing radiation toxicities to the surrounding normal tissue and sensitive structures. In less than a decade, IMRT has become common practice in radiation oncology. Looking forward, the authors wonder if IMRT has matured to such a point that the room for further improvement has diminished and so it is pertinent to ask what the future will hold for IMRT. This article attempts to look from the perspective of the current state of the technology to predict the immediate trends and the future directions. This article will (1) review the clinical experience of IMRT; (2) review what we learned in IMRT planning; (3) review different treatment delivery techniques; and finally, (4) predict the areas of advancements in the years to come.

The Effect of Respiratory Motion on Forward Intensity Modulated Radiotherapy for Breast Cancer

This study evaluated the effect of respiratory movement on field-in-field (FIF) forward intensity-modulated radiotherapy (IMRT) for the treatment of breast cancer. FIF forward IMRT was performed on ten patients receiving radiotherapy to the whole breast after conservation surgery. Assuming that breast motion follows a sophisticated cyclic function, the changes in hot and cold region, dose homogeneity index (DHI), and skin dose were examined at different respiration amplitudes of 1 cm, 2 cm, and 3 cm. FIF forward IMRT significantly improved the hot region, DHI, and skin dose, but slightly worsened the cold region, compared to the two wedged tangential technique (TWT). Interestingly, we found that the respiration amplitude affected the DHI and cold region but had no effect on the hot region and skin dose. The DHI was slightly improved at 1 cm of amplitude probably due to the blurring effect, remained unchanged at 2 cm of amplitude, and was worsened at 3 cm of amplitude. FIF forward IMRT significantly increased the cold region at 2 cm and 3 cm of respiration amplitude compared to the TWT. At 3 cm of respiration amplitude, an average cold region of 3.27 cm3 was observed. In summary, our data indicate that during FIF forward IMRT, respiration movement has an important effect on various endpoints depending on the respiration amplitude of the patient.

An investigation into methods of IMRT planning applied to breast radiotherapy

The purpose of this study was to investigate methods used to modulate dose distributions in radiotherapy planning, to determine the fundamental features of these and to establish the attainable dose uniformity. Published modulation methods were categorized, and a simple physical model devised to predict the weight of the wedged beam and the relative dose distribution for each category. Each technique was applied to patient data with planning target volume sizes ranging from below 500 cm(3) to 2200 cm(3). The spatial distribution of high-dose regions in the breast, and maximum dose for the heart and lung, were determined for each plan. The dose uniformity was analysed by evaluating the volume of the breast (V(I)) receiving <95% and <105% of the prescribed dose. The difference between V(105%) and V(95%) for each method for each patient data set was also calculated. The simple model predicted the trend in percentage weight of the wedge beam and the form of the dose distribution in the transverse plane with the modulation method. Improvements in the dose uniformity were seen for the majority of modulation methods. The magnitude of the change was between 5.6% and 11.1% (p<0.05) of the breast volume for breast sizes above 500 cm(3). Some modulation methods introduced high dose at the chest wall. In conclusion, the majority of the methods improved dose uniformity for breast sizes of 500 cm(3) or greater. No method showed a clear advantage over the others. The use of modulation methods should be governed by consideration of its effects relative to a simple wedge plan.

A multicenter randomized trial of breast intensity-modulated radiation therapy to reduce acute radiation dermatitis

PURPOSE

Dermatitis is a frequent adverse effect of adjuvant breast radiotherapy. It is more likely in full-breasted women and when the radiation is distributed nonhomogeneously in the breast. Breast intensity-modulated radiation therapy (IMRT) is a technique that ensures a more homogeneous dose distribution.

PATIENTS AND METHODS

A multicenter, double-blind, randomized clinical trial was performed to test if breast IMRT would reduce the rate of acute skin reaction (notably moist desquamation), decrease pain, and improve quality of life compared with standard radiotherapy using wedges. Patients were assessed each week during and up to 6 weeks after radiotherapy.

RESULTS

A total of 358 patients were randomly assigned between July 2003 and March 2005 in two Canadian centers, and 331 were included in the analysis. Breast IMRT significantly improved the dose distribution compared with standard radiation. This translated into a lower proportion of patients experiencing moist desquamation during or up to 6 weeks after their radiation treatment; 31.2% with IMRT compared with 47.8% with standard treatment (P = .002). A multivariate analysis found the use of breast IMRT (P = .003) and smaller breast size (P < .001) were significantly associated with a decreased risk of moist desquamation. The use of IMRT did not correlate with pain and quality of life, but the presence of moist desquamation did significantly correlate with pain (P = .002) and a reduced quality of life (P = .003).

CONCLUSION

Breast IMRT significantly reduced the occurrence of moist desquamation compared with a standard wedged technique. Moist desquamation was correlated with increased pain and reduction in the quality of life.

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.

Accelerated Intensity-Modulated Radiotherapy to Breast in Prone Position: Dosimetric Results

PURPOSE

To report the physics and dosimetry results of a trial of accelerated intensity-modulated radiotherapy to the whole breast with a concomitant boost to the tumor bed in patients treated in the prone position.

METHODS AND MATERIALS

Patients underwent computed tomography planning and treatment in the prone position on a dedicated treatment platform. The platform has an open aperture on the side to allow for the index breast to fall away from the chest wall. Noncontrast computed tomography images were acquired at 2.5- or 3.75-mm-thick intervals, from the level of the mandible to below the diaphragm. A dose of 40.5 Gy was delivered to the entire breast at 2.7-Gy fractions in 15 fractions. An additional dose of 0.5 Gy was delivered as a concomitant boost to the lumpectomy site, with a 1-cm margin, using inverse planning, for a total dose of 48 Gy in 15 fractions. No more than 10% of the heart and lung volume was allowed to receive >18 and >20 Gy, respectively.

RESULTS

Between September 2003 and August 2005, 91 patients were enrolled in the study. The median volume of heart that received > or =18 Gy was 0.5%, with a maximal value of 4.7%. The median volume of ipsilateral lung that received > or =20 Gy was 0.8%, with a maximum of 7.2%.

CONCLUSION

This technique for whole breast radiotherapy is feasible and enables an accelerated regimen in the prone position while sparing the lung and heart.

Simultaneous-integrated boost intensity-modulated radiation therapy (SIB-IMRT) in the treatment of early-stage left-sided breast carcinoma

We assessed the feasibility and impact of simultaneous-integrated boost intensity-modulated radiation therapy (SIB-IMRT) in the treatment of left breast carcinoma and compared target coverage and normal tissue doses with SIB-IMRT and 3-dimensional (3D) conformal RT using opposed tangential fields. For each of 10 patients with early-stage left-sided invasive breast carcinoma, 5 plans were generated; the first 4 were 3D conformal opposed tangential fields-2 with wedges, 2 with compensators and either photon or electron boost. A dose of 50.4 Gy in 28 fractions was prescribed to the left breast and an additional 16 Gy in 8 fractions to the lumpectomy bed. When compared to the tangential plans, SIB-IMRT maintained coverage (V(95%)) to the left breast and lumpectomy bed without significantly increasing the left breast maximum dose. SIB-IMRT was able to reduce the lung mean dose, maximum dose, and the V(20) by 55-104 cGy, 983-1298 cGy (p < 0.001), and 3.7-4.4%, respectively. In addition, SIB-IMRT reduced the maximum heart dose by 1032-1173 cGy and contralateral breast dose was increased (although p = NS). The mean and maximum dose to the unspecified tissues was also significantly reduced by 81-88 cGy and 516-942 cGy, respectively. SIB-IMRT resulted in a significant improvement in target dose conformality by up to 67%. Our findings that SIB-IMRT could improve dose conformality, reduce total treatment times, and reduce some of the normal structure doses presents it as an alternative technique for adjuvant breast radiotherapy; however this needs to be studied further in the clinic setting.