Postmastectomy irradiation: rationale for treatment field selection

Incidental irradiation of internal mammary lymph nodes in breast cancer: conventional two-dimensional radiotherapy versus conformal three-dimensional radiotherapy

OBJECTIVE

To evaluate incidental irradiation of the internal mammary lymph nodes (IMLNs) through opposed tangential fields with conventional two-dimensional (2D) or three-dimensional (3D) radiotherapy techniques and to compare the results between the two techniques.

MATERIALS AND METHODS

This was a retrospective study of 80 breast cancer patients in whom radiotherapy of the IMLNs was not indicated: 40 underwent 2D radiotherapy with computed tomography for dosimetric control, and 40 underwent 3D radiotherapy. The total prescribed dose was 50.0 Gy or 50.4 Gy (2.0 or 1.8 Gy/day, respectively). We reviewed all plans and defined the IMLNs following the Radiation Therapy Oncology Group recommendations. For the IMLNs, we analyzed the proportion of the volume that received 45 Gy, the proportion of the volume that received 25 Gy, the dose to 95% of the volume, the dose to 50% of the volume, the mean dose, the minimum dose (Dmin), and the maximum dose (Dmax).

RESULTS

Left-sided treatments predominated in the 3D cohort. There were no differences between the 2D and 3D cohorts regarding tumor stage, type of surgery (mastectomy, breast-conserving surgery, or mastectomy with immediate reconstruction), or mean delineated IMLN volume (6.8 vs. 5.9 mL; p = 0.411). Except for the Dmin, all dosimetric parameters presented higher mean values in the 3D cohort (p < 0.05). The median Dmax in the 3D cohort was 50.34 Gy. However, the mean dose to the IMLNs was 7.93 Gy in the 2D cohort, compared with 20.64 Gy in the 3D cohort.

CONCLUSION

Neither technique delivered enough doses to the IMLNs to achieve subclinical disease control. However, all of the dosimetric parameters were significantly higher for the 3D technique.

Comparison of Chest Wall and Lymphatic Radiotherapy Techniques in Patients with Left Breast Carcinoma

OBJECTIVE

The aim of this study was to find the most appropriate technique for postmastectomy chest wall (CW) and lymphatic irradiation.

MATERIALS AND METHODS

Partially wide tangent, 30/70 photon/electron mix, 20/80 photon/electron mix and CW and internal mammary en face electron field, were studied on computerized tomography (CT) scans of 10 left breast carcinoma patients and dosimetric calculations have been studied. Dose volume histograms (DVH) obtained from treatment planning system (TPS) were used for minimal, maximal and mean doses received by the clinical target volumes and critical structures.

RESULTS

Partially wide tangent field resulted in the most homogeneous dose distribution for the CW and a significantly lower lung and heart doses compared with all other techniques. However, right breast dose was significantly higher for partially wide tangent technique than that each of the other techniques. Approximately 0.6-7.9% differences were found between thermoluminescent dosimeter (TLD) and treatment planning system (TPS). The daily surface doses calculating using Gafchromic® external beam therapy (EBT) dosimetry films were 161.8±2.7 cGy for the naked, 241.0±1.5 cGy when 0.5 cm bolus was used and 255.3±2.7 cGy when 1 cm bolus was used.

CONCLUSION

As a result of this study, partially wide tangent field was found to be the most appropriate technique in terms of the dose distribution, treatment planning and set-up procedure. The main disadvantage of this technique was the higher dose to the contralateral breast comparing the other techniques.

Postmastectomy radiation therapy: an overview for the practicing surgeon

Locoregional control of breast cancer is the shared domain and responsibility of surgeons and radiation oncologists. Because surgeons are often the first providers to discuss locoregional control and recurrence risks with patients and because they serve in a key gatekeeping role as referring providers for radiation therapy, a sophisticated understanding of the evidence regarding radiotherapy in breast cancer management is essential for the practicing surgeon. This paper synthesizes the complex and evolving evidence regarding the role of radiation therapy after mastectomy. Although substantial evidence indicates that radiation therapy can reduce the risk of locoregional failure after mastectomy (with a relative reduction of risk of approximately two-thirds), debate persists regarding the specific subgroups who have sufficient risks of residual microscopic locoregional disease after mastectomy to warrant treatment with radiation. This paper reviews the evidence available to guide appropriate referral and patient decision making, with special attention to areas of controversy, including patients with limited nodal disease, those with large tumors but negative nodes, node-negative patients with high risk features, patients who have received systemic chemotherapy in the neoadjuvant setting, and patients who may wish to integrate radiation therapy with breast reconstruction surgery.

Skin dose effects of postmastectomy chest wall radiation therapy using brass mesh as an alternative to tissue equivalent bolus

PURPOSE

The use of brass mesh as a bolus is relatively uncommon in postmastectomy chest wall radiation therapy (PMRT). This study aimed to characterize the skin dose effects of using 2-mm fine brass mesh as an alternative to the traditional tissue-equivalent bolus during chest wall PMRT.

METHODS AND MATERIALS

Data were collected from patients who received PMRT using brass mesh at the University of California Davis Department of Radiation Oncology between January 2008 and June 2011. Several patient characteristics including age, body habitus, and ethnicity were analyzed along with several disease and treatment characteristics to determine whether or not they had an impact on the skin reaction observed during radiation treatment. Additionally, in vivo surface dose measurements were obtained for 16 of the 48 patients (33%).

RESULTS

Forty-eight female patients aged 28-83 received PMRT using brass mesh. As expected, the severity of skin toxicity increased with subsequent doses of radiation with all patients beginning treatment with no skin reaction (National Cancer Institute scores [NCIS] = 0) and the majority of patients completing treatment with either faint to moderate erythema (n = 19, 40%, NCIS = 1) or moderate to brisk erythema (n = 23, 48%, NCIS = 2). In vivo dosimetry analysis revealed surface doses between 81% and 122% of the prescribed dose, with an average of 99% of the prescribed radiation dose and standard deviation of 10% being delivered.

CONCLUSIONS

For postmastectomy chest wall radiation therapy, brass mesh is an effective alternative to tissue-equivalent bolus. The brass mesh achieved moderate erythema in the majority of patients at the end of treatment and the surface dose was validated using in vivo dosimetry.

Controversies in loco-regional treatment: post-mastectomy radiation for pT2-pT3N0 breast cancer arguments in favour

Post-mastectomy RT decreases the rate of locoregional recurrences of about 70% in all patients irrespective of age, tumor characteristics or systemic therapy. Post-mastectomy RT has to be proposed, moreover when locoregional lymph nodes are part of the PTV, if an optimal coverage of the PTV and a satisfactory sparing of the OAR could be obtained. Due to the results of meta-analysis, consensus conferences and randomized trials the long-term efficacy of RT in decreasing the risk of LRF is well established and the vast majority of women, treated with mastectomy, will benefit from it.

Radiation therapy and breast reconstruction: a critical review of the literature

BACKGROUND

The optimal timing and technique of breast reconstruction in patients who may require postmastectomy radiation therapy are controversial. To help surgeons make the best decisions, the authors reviewed the recent literature on this topic.

METHODS

The authors searched the MEDLINE database for studies of radiation therapy and breast reconstruction with most patients treated after 1985 and mean follow-up of more than 1 year. Forty-nine articles were reviewed.

RESULTS

Even with the latest prosthetic materials and modern radiation delivery techniques, the complication rate for implant-based breast reconstruction in patients undergoing postmastectomy radiation therapy is greater than 40 percent, and the extrusion rate is 15 percent. Modified sequencing of two-stage implant reconstruction, such that the expander is exchanged for the permanent implant before postmastectomy radiation therapy, results in higher rates of capsular contracture and is not generally feasible after neoadjuvant chemotherapy. Current evidence suggests that postmastectomy radiation therapy also adversely affects autologous tissue reconstruction. Even with modern radiation delivery techniques, immediate implant-based or autologous tissue breast reconstruction can distort the chest wall and limit the ability to treat the targeted tissues without excessive exposure of the heart and lungs. In patients for whom postmastectomy radiation therapy appears likely but may not be required, "delayed-immediate reconstruction," in which tissue expanders are placed at mastectomy, avoids the difficulties associated with radiation delivery after immediate reconstruction and preserves the opportunity for the aesthetic benefits of skin-sparing mastectomy.

CONCLUSIONS

In patients who will receive or have already received postmastectomy radiation therapy, the optimal approach is delayed autologous tissue reconstruction after postmastectomy radiation therapy. If postmastectomy radiation therapy appears likely but may not be required, delayed-immediate reconstruction may be considered.

Postmastectomy Electron Beam Chest Wall Irradiation in Women With Breast Cancer: A Clinical Step Toward Conformal Electron Therapy

PURPOSE

Electron beam radiotherapy of the chest wall with or without lymph node irradiation has been used at the Institut Curie for >20 years. The purpose of this report was to show the latest improvements of our technique developed to avoid hot spots and improve the homogeneity.

METHODS AND MATERIALS

The study was split into two parts. A new electron irradiation technique was designed and compared with the standard one (dosimetric study). The dose distributions were calculated using our treatment planning software ISIS (Technologie Diffusion). The dose calculation was performed using the same calculation parameters for the new and standard techniques. Next, the early skin toxicity of our new technique was evaluated prospectively in the first 25 patients using Radiation Therapy Oncology Group criteria (clinical study).

RESULTS

The maximal dose found on the five slices was 53.4 +/- 1.1 Gy for the new technique and 59.1 +/- 2.3 Gy for the standard technique. The hot spots of the standard technique plans were situated at the overlap between the internal mammary chain and chest wall fields. The use of one unique field that included both chest wall and internal mammary chain volumes solved the problem of junction. To date, 25 patients have been treated with the new technique. Of these patients, 12% developed Grade 0, 48% Grade 1, 32% Grade 2, and 8% Grade 3 toxicity.

CONCLUSIONS

This report describes an improvement in the standard postmastectomy electron beam technique of the chest wall. This new technique provides improved target homogeneity and conformality compared with the standard technique. This treatment was well tolerated, with a low rate of early toxicity events.

Immediate Breast Reconstruction can Impact Postmastectomy Irradiation

OBJECTIVE

Immediate breast reconstruction is an attractive option for patients who undergo mastectomy. The purpose of this study was to qualitatively assess the effect of immediate reconstruction on the design of postmastectomy radiotherapy fields at our institution.

METHODS

We retrospectively reviewed the records of 152 patients treated at our institution with postmastectomy radiotherapy over a 1-year period. We identified 18 postmastectomy radiotherapy plans in the setting of prior reconstruction. By consensus, 2 board-certified radiation oncologists scored the 18 plans in terms of 4 outcomes: coverage of the chest wall breadth, coverage of the ipsilateral internal mammary chain (IMC) region, minimization of lung exposure, and avoidance of the heart.

RESULTS

Only 4 of the 18 plans resulted in optimal treatment of the chest wall breadth and IMC region while well avoiding the heart and lung. Of the remaining 14 plans, 12 compromised coverage of the chest wall breadth medially and/or laterally, and 9 provided no IMC coverage.

CONCLUSION

Immediate breast reconstruction may impose limitations on the treatment planning of postmastectomy radiotherapy, particularly in regard to providing broad coverage of the chest wall and IMC region while avoiding excess exposure of the heart and lung.

Evaluation of set-up deviations during the irradiation of patients suffering from breast cancer treated with two different techniques

PURPOSE

To compare reproducibility of set-up for two different treatment techniques for external irradiation of the breast.

METHODS AND MATERIALS

In total, the analysis comprised 56 pairs of portal and simulator films for 14 consecutive patients treated following breast conserving therapy and 98 pairs of portal and simulator films for 20 consecutive patients treated after mastectomy. For the first group the tangential field technique (TF technique) was used, for the second the inverse hockey stick technique (IHS technique). Evaluation of the treatment reproducibility was performed in terms of systematic and random error calculated for the whole groups, comparison of set-up accuracy by means of comparison of cumulative distribution of the length of the displacement vector.

RESULTS

In the IHS and TF techniques for medial and lateral fields, displacement larger than 5 mm occurred in 28.3, 15.8 and 25.4%, respectively. For the IHS technique, the systematic errors for lateral and cranial-caudal direction were 1.9 and 1.7 mm, respectively (1 SD), the random errors for lateral and cranial-caudal direction were 2.0 and 2.5 mm. For the TF technique, the systematic errors for ventral-dorsal and cranial-caudal direction were 2.6 and 1.3 mm for medial field and 3.7 and 0.7 mm for lateral fields, respectively, the random errors for lateral and cranial-caudal direction were 2.2 and 1.0 mm for medial field and 2.9 and 1.1 for lateral field, respectively. Rotations were negligible in the IHS technique. For the TF technique the systematic and random components amounted to about 2.0 degrees (1 SD).

CONCLUSIONS

Both the inverse hockey stick and standard tangential techniques showed good reproducibility of patients' set-up with respect to cranial-caudal direction. For the TF technique, the accuracy should be improved for the medial field with respect to the ventral-dorsal direction.

Lymphedema Secondary to Postmastectomy Radiation: Incidence and Risk Factors

BACKGROUND

Postmastectomy radiotherapy (PMRT) has proven benefits for certain patients with breast cancer; however, one of its complications is lymphedema. This study examines the incidence of and risk factors associated with lymphedema secondary to PMRT.

METHODS

The charts of patients treated with mastectomy at Roswell Park Cancer Institute between January 1, 1995, and April 20, 2001, who received PMRT were reviewed. Univariate analysis of patient, disease, and treatment variables was conducted. Multivariate analysis was performed on variables found to be significant in univariate analysis.

RESULTS

One hundred five patients received PMRT. The incidence of lymphedema was 27%. Patient age, body mass index, disease stage, positive lymph nodes, nodes resected, postoperative infection, duration of drainage, chemotherapy, and hormonal therapy were not associated with lymphedema. Total dose (P =.032), posterior axillary boost (P =.047), overlap technique (P =.037), radiotherapy before 1999 (P =.028), and radiotherapy at Roswell Park Cancer Institute (P =.028) were significantly associated with lymphedema. Increased lymphedema was noted with supraclavicular, internal mammary, mastectomy scar boost, and chest wall tangential photon beam radiation, but the associations were not statistically significant.

CONCLUSIONS

The high incidence and debilitating effects of lymphedema must be weighed against the benefits of PMRT. Efforts to prevent lymphedema should be emphasized.

Normal and Abnormal US Findings at the Mastectomy Site

Evaluation of a mastectomy site is more effective with ultrasonography (US) than with either mammography or chest computed tomography because abnormalities are usually small and close to the skin surface. US does not involve the use of ionizing radiation and has a multiplanar scanning capability. The technique is readily available and inexpensive, and it allows real-time monitoring of needle tip placement during biopsy of a lesion. Normal US anatomy of the chest wall after mastectomy usually consists of four layers: skin, subcutaneous fat, pectoral muscles, and rib and intercostal muscle. The axilla is changed in appearance after lymph node dissection, but it remains the same in patients who have undergone simple mastectomy. US can accurately depict benign and malignant conditions in the mastectomy site, including fluid collection, fibrosis, local recurrent tumor, and metastatic lymphadenopathy, and can enable accurate diagnosis based on findings at fine needle aspiration biopsy.

Impact of locoregional radiotherapy in node-positive patients treated by breast-conservative treatment

PURPOSE

The aim of this study is to evaluate the impact of locoregional radiation in node-positive patients treated by tumorectomy and radiation therapy.

METHODS

A retrospective study including all our 1368 T1-2 node-positive patients was conducted. Conservative surgery was followed by breast irradiation. Axillary and supraclavicular irradiation was left to the discretion of the treating radiation oncologist.

RESULTS

In the group receiving locoregional radiation (472 patients), the 10-year regional control was 97% vs. 91% for the group receiving radiation to the breast only (896 patients) (p = 0.004). In a Cox model analysis, locoregional radiation is associated with a better regional control rate (hazard ratio: 0.27; 95% confidence interval: 0.13-0.54, p = 0.0001). Locoregional radiotherapy is associated with a better rate of locoregional control (hazard ratio: 0.56; 95% confidence interval: 0.38-0.8, p = 0.002). In particular, for the N>3 group, the substantial 10-year locoregional failure rate (26% with breast irradiation only) is cut by 50%. Locoregional radiotherapy, however, is not associated with a lower rate of distant metastases.

CONCLUSION

Locoregional radiation decreases the rate of locoregional failure by nearly 50%. Locoregional radiotherapy should be considered for node-positive patients, especially if they have more than 3 positive nodes.

Significant reductions in heart and lung doses using deep inspiration breath hold with active breathing control and intensity-modulated radiation therapy for patients treated with locoregional breast irradiation

PURPOSE

To evaluate the heart and lung sparing effects of moderate deep inspiration breath hold (mDIBH) achieved using an active breathing control (ABC) device, compared with free breathing (FB) during treatment with deep tangents fields (DT) for locoregional (LR) irradiation of breast cancer patients, including the internal mammary (IM) nodes (IMNs). To compare the DT-mDIBH technique to other standard techniques and to evaluate the dosimetric effect of intensity-modulated radiation therapy (IMRT).

METHODS AND MATERIALS

Fifteen patients (9 left-sided and 6 right-sided lesions) with Stages 0-III breast cancer underwent standard FB and ABC computed tomographic (CT) scans in the treatment position. A dosimetric planning study was performed. In FB, the 9 left-sided patients were planned with a 5-field technique where electron fields covering the IM region were matched to shallow tangents using wedges (South West Oncology Group [SWOG] protocol S9927 technique A). This method was compared with a 3-field DT technique covering the breast and the IMNs (SWOG S9927 technique B). Compensation with IMRT was then compared with wedges for each technique. For the 15 total patients, dosimetric planning using DT with IMRT was then reoptimized on the mDIBH CT data set for comparison. Dose-volume histograms for the clinical target volume (CTV) (including the IMNs), planning target volume (PTV), ipsilateral and contralateral breast, and organs at risk (OAR) were analyzed. In addition, normal tissue complication probabilities (NTCP) for lung and heart, mean lung doses, and the number of monitor units (MUs) for a 1.8 Gy fraction were compared.

RESULTS

For the 9 left-sided patients, the mean percentage of heart receiving more than 30 Gy (heart V30) was lower with the 5-field wedged technique than with the DT wedged technique (6.8% and 19.1%, respectively, p < 0.004). For the DT technique, the replacement of wedges with IMRT slightly diminished the mean heart V30 to 16.3% (p < 0.51). The introduction of mDIBH to the DT-IMRT technique reduced the heart V30 by 81% to a mean of 3.1% (p < 0.0004). Compared with 5-field IMRT, DT-IMRT with mDIBH reduced the heart V30 for 6 of the 9 patients, entirely avoiding heart irradiation in 2 of these 6 patients. For DT-IMRT, mDIBH reduced the mean lung dose and NTCP to levels obtained with the 5-field IMRT technique. For the 15 patients planned with DT-IMRT in FB, the use of mDIBH reduced the mean percentage of both lungs receiving more than 20 Gy from 20.4% to 15.2% (p < 0.00007). With DT-IMRT, more than 5% of the contralateral breast received more than 10 Gy for 6 of the 9 left-sided patients in FB, 3 of those 9 patients in mDIBH, and only 1 of those 9 patients planned with 5 fields. The mean % of the PTV receiving more than 55 Gy (110% of the prescribed dose) was 36.4% for 5-field wedges, 33.4% for 5-field IMRT, 28.7% for DT-wedges, 12.5% for DT-IMRT, and 18.4% for DT-IMRT mDIBH. The CTV remained covered by the 95% isodose in all the DT plans but one (99.1% of the volume covered). DT-wedges required more MUs than DT-IMRT (mean of 645 and 416, respectively, p < 0.00004).

CONCLUSION

mDIBH significantly reduces heart and lung doses when DT are used for LR breast irradiation including the IMNs. Compared with shallow tangents matched with electrons, DT with mDIBH reduces the heart dose (in most patients) and results in comparable lung toxicity parameters, but may increase the dose to the contralateral breast. IMRT improves dose homogeneity, slightly reduces the dose to the heart, and diminishes the number of MUs required.

A custom three-dimensional electron bolus technique for optimization of postmastectomy irradiation

PURPOSE

Postmastectomy irradiation (PMI) is a technically complex treatment requiring consideration of the primary tumor location, possible risk of internal mammary node involvement, varying chest wall thicknesses secondary to surgical defects or body habitus, and risk of damaging normal underlying structures. In this report, we describe the application of a customized three-dimensional (3D) electron bolus technique for delivering PMI.

METHODS AND MATERIALS

A customized electron bolus was designed using a 3D planning system. Computed tomography (CT) images of each patient were obtained in treatment position and the volume to be treated was identified. The distal surface of the wax bolus matched the skin surface, and the proximal surface was designed to conform to the 90% isodose surface to the distal surface of the planning target volume (PTV). Dose was calculated with a pencil-beam algorithm correcting for patient heterogeneity. The bolus was then fabricated from modeling wax using a computer-controlled milling device. To aid in quality assurance, CT images with the bolus in place were generated and the dose distribution was computed using these images.

RESULTS

This technique optimized the dose distribution while minimizing irradiation of normal tissues. The use of a single anterior field eliminated field junction sites. Two patients who benefited from this option are described: one with altered chest wall geometry (congenital pectus excavatum), and one with recurrent disease in the medial chest wall and internal mammary chain (IMC) area.

CONCLUSION

The use of custom 3D electron bolus for PMI is an effective method for optimizing dose delivery. The radiation dose distribution is highly conformal, dose heterogeneity is reduced compared to standard techniques in certain suboptimal settings, and excellent immediate outcome is obtained.

Deep inspiration breath hold to reduce irradiated heart volume in breast cancer patients

PURPOSE

To evaluate the use of deep inspiration breath hold (DIBH) during tangential breast radiation therapy as a means of reducing irradiated cardiac volume.

METHODS AND MATERIALS

The Active Breathing Control (ABC) device designed at William Beaumont Hospital, Michigan was used to quantify the potential benefit of radiation delivery during DIBH for five left-sided breast cancer patients. This device initiates a breath hold at a predefined, reproducible lung volume. For each patient, two CT scans were acquired with and without breath hold, and virtual simulation was performed for regular tangent and wide-tangent techniques. The resulting dose-volume histograms were calculated, and the volume of heart irradiated to 25 Gy or more was assessed.

RESULTS

The influence of ABC on irradiated heart volumes varied considerably among the five patients. Three patients with substantial cardiac volume in the treatment field during normal respiration showed a significant dose-volume histogram reduction when deep inspiration was applied, with decreases in the heart volume receiving 25 Gy of more than 40 cc observed. For one patient, deep inspiration reduced irradiated cardiac volumes only with the wide-tangent technique, while one patient showed no substantial irradiated volume decrease.

CONCLUSION

A DIBH technique during tangential breast irradiation has the potential to significantly decrease irradiated cardiac volume for suitably selected patients. The magnitude of the impact of the breath hold application depends on patient anatomy, lung capacity, and pulmonary function.