- Email: [email protected]
Bolus electron conformal therapy for the treatment of recurrent inflammatory breast cancer: a case report
Medical Dosimetry 37 (2012) 208-213
Medical Dosimetry journal homepage: www.meddos.org
Bolus electron conformal therapy for the treatment of recurrent inflammatory breast cancer: a case report Michelle M. Kim, M.D., Rajat J. Kudchadker, Ph.D., James E. Kanke, C.M.D., Sean Zhang, Ph.D., and George H. Perkins, M.D. Department of Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX
A R T I C L E
I N F O
Article history: Received 22 February 2011 Accepted 21 July 2011 Keywords: Electron Conformal Bolus Breast
A B S T R A C T The treatment of locoregionally recurrent breast cancer in patients who have previously undergone radiation therapy is challenging. Special techniques are often required that both eradicate the disease and minimize the risks of retreatment. We report the case of a patient with an early-stage left breast cancer who developed inflammatory-type recurrence requiring re-irradiation of the chest wall using bolus electron conformal therapy with image-guided treatment delivery. The patient was a 51-year-old woman who had undergone lumpectomy, axillary lymph node dissection, and adjuvant whole-breast radiation therapy for a stage I left breast cancer in June 1998. In March 2009, she presented at our institution with biopsy-proven recurrent inflammatory carcinoma and was aggressively treated with multi-agent chemotherapy followed by mastectomy that left a positive surgical margin. Given the patient’s prior irradiation and irregular chest wall anatomy, bolus electron conformal therapy was used to treat her chest wall and draining lymphatics while sparing the underlying soft tissue. The patient still had no evidence of disease 21 months after treatment. Our results indicate that bolus electron conformal therapy is an accessible, effective radiation treatment approach for recurrent breast cancer in patients with irregular chest wall anatomy as a result of surgery. This approach may complement standard techniques used to reduce locoregional recurrence in the postmastectomy setting. 䉷 2012 American Association of Medical Dosimetrists.
Introduction The treatment of locoregionally recurrent breast cancer in patients who have undergone previous radiation therapy is challenging. In breast cancer patients with resectable disease recurrence, adjuvant radiation therapy may confer greater locoregional control than surgery or chemotherapy alone.1, 2 However, the added toxicity of adjuvant radiation therapy in the retreatment setting mandates the use of a radiation delivery approach that accurately targets areas at risk for harboring residual disease and spares surrounding normal issue. One such approach is electron conformal radiation therapy. Several techniques, including abutting electron fields, electron arc therapy, and custom bolus electron conformal therapy, have variable properties. The highly conformal dose distribution of the custom bolus technique has been described previously in the postmastectomy setting for primary disease, with satisfactory short-term clinical outcomes.3 Herein, we report the case of a patient with recurrent, inflammatory breast
Reprint requests to: Michelle M. Kim, M.D., 1515 Holcombe Boulevard Unit 97, Houston, TX, 77030. E-mail: [email protected]
cancer treated with surgery and re-irradiation using 3D custom bolus electron conformal therapy. Case Report In March 2009, a 51-year-old premenopausal woman presented to our institution with rapid-onset skin thickening, heaviness, and nipple inversion of the left breast. Eleven years earlier, she had been diagnosed with stage T1N0M0 invasive ductal carcinoma of the left breast, for which she underwent a lumpectomy and levels I and II axillary lymph node dissection followed by adjuvant radiation therapy of the whole breast. At that time, a standard tangential technique had been used to deliver 50.4 Gy in 1.8-Gy daily fractions using 6-MV photon beams, followed by a field size reduction for a 10-Gy tumor bed boost using 9-MeV electrons. After 5 years of tamoxifen therapy for estrogen receptor (ER)-positive disease, the patient remained disease-free for 4 years until she presented at our institution, where a punch biopsy of the skin of the left breast confirmed an inflammatory-type recurrence. The staging workup revealed no evidence of regional or distant metastases. The patient received 4 cycles of doxorubicin-based chemotherapy, which resulted in a partial response. Following this, a modified radical mastectomy of the left breast revealed extensive, invasive carcinoma with dermal and lymphovascular invasion involving all 4 quadrants of the breast. No identifiable lymph nodes were recovered from the axilla. Despite resection down to and including the pectoralis fascia, the carcinoma invaded within 1 mm of the deep and superior lateral margins. After determining that additional resection was not feasible, the decision was made to proceed with adjuvant re-irradiation. Given the 10-year interval since the patient’s last course of radiation therapy and the near-total removal of her previously irradiated breast tissue, the patient was consid-
0958-3947/$ – see front matter Copyright 䉷 2012 American Association of Medical Dosimetrists doi:10.1016/j.meddos.2011.07.004
M.M. Kim et al. / Medical Dosimetry 37 (2012) 208-213
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Fig. 1. Axial planning CT images show the marked irregularity of the patient’s chest wall anatomy from superior to inferior (A–D). Red indicates the radiation therapy target volume.
Fig. 2. Representative axial (A) and sagittal (B) CT images of radiation dose lines in the chest wall and underlying lung tissue from a comparison tangential field plan using 30⬚ wedges and 6-MV photons.
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M.M. Kim et al. / Medical Dosimetry 37 (2012) 208-213
Fig. 3. Two-beam (A) and 3-beam (B) segmented electron fields plan. Using low-energy 4-MeV appositional electrons, significant dosing to underlying lung is seen.
Fig. 4. Two-beam (A) and 3-beam (B) segmented electron fields plan in a region of irregular chest wall anatomy. Significant underdosing of the target volume (light green) is seen using low-energy, 4-MeV electrons.
Fig. 5. Axial (A) and sagittal (B) CT images of isodose lines from the custom bolus plan using a single appositional 12-MeV electron field.
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Fig. 6. Dose distribution from the custom bolus plan in regions of dynamic and irregular chest wall anatomy. Purple indicates 90% of the prescribed radiation dose.
ered a candidate for adjuvant re-irradiation. However, her recent surgery had resulted in a highly irregular chest wall anatomy, with areas of the midchest wall that were thin enough to pose a substantial risk of overtreating previously irradiated structures (including the ribs, intercostal musculature, pleural surface, and lung), which were not at risk for harboring disease. Representative computed axial tomography (CT) images of the irregular radiation therapy target volume (shown in red) are depicted in Fig. 1 from superior to inferior (Fig. 1A–D). Several radiation therapy techniques were considered, including a standard medial and lateral tangential technique using 6-MV photon beams and 30⬚ wedges matched to a medial electron field to cover the internal mammary chain. Figure 2 shows representative axial (Fig. 2A) and sagittal (Fig. 2B) CT images of this plan. In Fig. 3, comparison 2-field (Fig. 3A) and 3-field (Fig. 3B) segmented electron field plans are shown using appositional 4-MeV electrons. A significant overdosing of the underlying lung is seen in the thinner areas of the chest wall. In contrast, a significant underdosing of the target volume (shown in light green) is apparent in areas of irregular chest wall anatomy for both the 2-field (Fig. 4A) and 3-field (Fig. 4B) plans. Figure 5 depicts axial (Fig. 5A) and sagittal (Fig. 5B) images from the 3D custom bolus plan. Using a single, appositional 12-MeV electron field, the 3D custom bolus technique permitted conformal coverage of the areas of surgical change while sparing the deepest part of the rib cage and intrathoracic organs from high-dose radiation (Fig. 6). In Figs. 2–6, the 90% isodose line is depicted in purple.
As per standard radiation treatment planning, a noncontrast, free-breathing CT scan was acquired using 1.25-mm thickness slices. The CT images were imported into a standard treatment planning system (Pinnacle, Philips Medical Systems, Andover, MA), and the at-risk soft tissue of the operative bed was carefully delineated with a margin and designated as the planning target volume (PTV). The images were then exported into the bolus-design planning software (p.d. version 4.0., decimal, Inc., Sanford, FL) to create a virtual custom bolus that conformed to the distal contours of the PTV and the external contours of the patient’s chest wall. The bolus parameters were then exported back into the treatment planning system for dose calculation. After the treatment plan was carefully reviewed to ensure coverage of the PTV, the bolus specifications were sent to a custom bolus manufacturer (.decimal, Inc.) that fabricated a custom wax bolus with radiation properties defined previously.4 The bolus was manufactured from machinable wax (Machinable Wax, Inc., Lake Ann, MI), which has a density of 0.93 g/cm3. After extensive quality assurance testing, the completed custom bolus was returned. The turnaround time for the entire process was 23 hours. After receiving the custom bolus from the manufacturer, a noncontrast CT scan was repeated with the custom bolus in place to verify its fit on the patient’s chest wall. The resultant CT images were used to calculate the final planned radiation dose. For daily treatment, routine imaging with either kilovoltage x-rays or cone-beam CT was acquired to ensure proper daily setup, positioning, and alignment of the custom
212
M.M. Kim et al. / Medical Dosimetry 37 (2012) 208-213
Fig. 7. Representative cone-beam CT image from actual treatment and reference image demonstrating optimal fit to the patient’s chest wall with minimal air gaps.
bolus. In Fig. 7, reference and representative daily cone-beam CT images from a treatment session demonstrate a good fit of the custom bolus with minimal air gaps. A single appositional field using 12-MeV electrons was used to deliver 50 Gy in 2-Gy daily fractions, with the distal 90% isodose line covering the chest wall and internal mammary nodal chain. A subsequent 10-Gy boost in 2-Gy daily fractions was delivered to the superolateral quadrant of the primary field in the area with close surgical margins using the same bolus technique. These techniques permitted coverage of the area of surgical change in the chest wall with the 90% isodose line, along with maximal sparing of the left lung from low and high dose (V20 approximately 23%, V40 approximately 4%). A 6-MV oblique photon field was matched to the primary electron field using a half-beam block technique to deliver 54 Gy in 2-Gy daily fractions to the supraclavicular nodal basin—slightly dose-escalated in keeping with previously established guidelines for recurrent disease.5 Figure 8 shows axial (Fig. 8A) and 3D skin rendering (Fig. 8B) images of the supraclavicular field with target coverage by the 90% isodose line. As expected, the patient developed grade 2 erythema and hyperpigmentation in areas of the treatment field that did not cause desquamation. Mild pruritus was effectively treated with 1% hydrocortisone cream, and the patient did not require any treatment breaks. Six months after completing radiation therapy, the patient was noted to have an erythematous, maculopapular rash conforming to the areas of high-dose radiation therapy. A punch biopsy revealed eosinophils and spongiosis consistent with the inflammatory effects of radiation treatment (Fig. 9). Twenty-one months after completing bolus electron conformal therapy, the patient had no evidence of disease.
Discussion The effective control of locally recurrent breast cancer must be balanced against the risks of retreatment. Several studies have sug-
gested that particle beam radiation therapy for local breast cancer recurrence after mastectomy may confer durable local control with acceptable toxicity, with reports of locoregional control ranging from 62–74% at 5 years.6 – 8 The median cumulative dose delivered in these studies ranged from 59.3–100 Gy with acceptable rates of morbidity and no instances of skin necrosis. However, significant dose heterogeneity may occur after surgery in patients with irregular chest wall anatomy who are treated with conventional radiation therapy. The variable densities of the target volume and underlying tissue also may result in incidental overtreatment. Electron conformal therapy capitalizes on the physical properties of electron beams, permitting the treatment of irregular target volumes at limited depths. Several such techniques have been described. In contrast to radiation delivery techniques that use abutting electron fields of different energies, bolus electron conformal therapy avoids the characteristic hot and cold spots created at the junctions of segmented fields.9 In addition, techniques such as electron arc therapy that are used for improved dose uniformity in areas at high risk for recurrence are not available at most institutions, whereas bolus electron conformal therapy is readily available through commercial software and bolus manufacturing companies. Finally, because it can achieve a higher skin surface dose than conventional techniques,
Fig. 8. Matched oblique supraclavicular field using 6-MV photons. Representative axial CT image (A); yellow indicates 90% of prescribed radiation dose. Three-dimensional skin rendering (B) of nondivergent, supraclavicular field.
M.M. Kim et al. / Medical Dosimetry 37 (2012) 208-213
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Conclusion Electron conformal therapy using 3D custom bolus enables the spatial modulation of an electron field that is appropriate for individual patient anatomy. It is an accessible, effective treatment technique for the irradiation of irregular chest wall anatomy in the setting of primary or recurrent disease. Bolus electron conformal therapy may complement standard radiation therapy techniques used in the postmastectomy setting. References
Fig. 9. Ten months after treatment, an erythematous, maculopapular rash conforming to the areas of high-dose radiation therapy was evident. A prior punch biopsy revealed eosinophils and spongiosis consistent with inflammation and the effects of radiation treatment, but no evidence of recurrent disease.
bolus electron conformal therapy enables the treatment of the dermal lymphatics, which were at risk in the case of our patient. The highly conformal properties of this technique make treatment well tolerated, with satisfactory immediate results in a range of clinical settings.3, 10
1. Deutsch, M.; Parsons, J.A.; Mittal, B.B. Radiation therapy for local-regional recurrent breast carcinoma. Int. J. Radiat. Oncol. Biol. Phys. 12:2061–5; 1986. 2. Schwaibold, F.; Fowble, B.L.; Solin, L.J.; et al. The results of radiation therapy for isolated local regional recurrence after mastectomy. Int. J. Radiat. Oncol. Biol. Phys. 21:299 –310; 1991. 3. Perkins, G.H.; McNeese, M.D.; Antolak, J.A.; et al.A custom three-dimensional electron bolus technique for optimization of postmastectomy irradiation. Int. J. Radiat. Oncol. Biol. Phys. 51:1142–51; 2001. 4. Low, D.A.; Starkschall, G.; Bujnowski, S.W.; et al. Electron bolus design for radiotherapy treatment planning: Bolus design algorithms. Med. Phys. 19:115–24; 1992. 5. Liao, Z.; Strom, E.A.; Buzdar, A.U.; et al. Locoregional irradiation for inflammatory breast cancer: Effectiveness of dose escalation in decreasing recurrence. Int. J. Radiat. Oncol. Biol. Phys. 47:1191–200; 2000. 6. Gaffney, D.K.; Lee, C.M.; Leavitt, D.D.; et al. Electron arc irradiation of the postmastectomy chest wall in locally recurrent and metastatic breast cancer. Am. J. Clin. Oncol. 26:241– 6; 2003. 7. Janjan, N.A.; McNeese, M.D.; Buzdar, A.U.; et al. Management of locoregional recurrent breast cancer. Cancer 58:1552– 6; 1986. 8. Laramore, G.E.; Griffin, T.W.; Parker, R.G.; et al. The use of electron beams in treating local recurrence of breast cancer in previously irradiated fields. Cancer 41:991–5; 1978. 9. Tapley, N.D.; Montague, E.D. Elective irradiation with the electron beam after mastectomy for breast cancer. AJR Am. J. Roentgenol. 126:127–34; 1976. 10. Low, D.A.; Starkschall, G.; Sherman, N.E.; et al. Computer-aided design and fabrication of an electron bolus for treatment of the paraspinal muscles. Int. J. Radiat. Oncol. Biol. Phys. 33:1127–38; 1995.
Medical Dosimetry journal homepage: www.meddos.org
Bolus electron conformal therapy for the treatment of recurrent inflammatory breast cancer: a case report Michelle M. Kim, M.D., Rajat J. Kudchadker, Ph.D., James E. Kanke, C.M.D., Sean Zhang, Ph.D., and George H. Perkins, M.D. Department of Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, Houston, TX
A R T I C L E
I N F O
Article history: Received 22 February 2011 Accepted 21 July 2011 Keywords: Electron Conformal Bolus Breast
A B S T R A C T The treatment of locoregionally recurrent breast cancer in patients who have previously undergone radiation therapy is challenging. Special techniques are often required that both eradicate the disease and minimize the risks of retreatment. We report the case of a patient with an early-stage left breast cancer who developed inflammatory-type recurrence requiring re-irradiation of the chest wall using bolus electron conformal therapy with image-guided treatment delivery. The patient was a 51-year-old woman who had undergone lumpectomy, axillary lymph node dissection, and adjuvant whole-breast radiation therapy for a stage I left breast cancer in June 1998. In March 2009, she presented at our institution with biopsy-proven recurrent inflammatory carcinoma and was aggressively treated with multi-agent chemotherapy followed by mastectomy that left a positive surgical margin. Given the patient’s prior irradiation and irregular chest wall anatomy, bolus electron conformal therapy was used to treat her chest wall and draining lymphatics while sparing the underlying soft tissue. The patient still had no evidence of disease 21 months after treatment. Our results indicate that bolus electron conformal therapy is an accessible, effective radiation treatment approach for recurrent breast cancer in patients with irregular chest wall anatomy as a result of surgery. This approach may complement standard techniques used to reduce locoregional recurrence in the postmastectomy setting. 䉷 2012 American Association of Medical Dosimetrists.
Introduction The treatment of locoregionally recurrent breast cancer in patients who have undergone previous radiation therapy is challenging. In breast cancer patients with resectable disease recurrence, adjuvant radiation therapy may confer greater locoregional control than surgery or chemotherapy alone.1, 2 However, the added toxicity of adjuvant radiation therapy in the retreatment setting mandates the use of a radiation delivery approach that accurately targets areas at risk for harboring residual disease and spares surrounding normal issue. One such approach is electron conformal radiation therapy. Several techniques, including abutting electron fields, electron arc therapy, and custom bolus electron conformal therapy, have variable properties. The highly conformal dose distribution of the custom bolus technique has been described previously in the postmastectomy setting for primary disease, with satisfactory short-term clinical outcomes.3 Herein, we report the case of a patient with recurrent, inflammatory breast
Reprint requests to: Michelle M. Kim, M.D., 1515 Holcombe Boulevard Unit 97, Houston, TX, 77030. E-mail: [email protected]
cancer treated with surgery and re-irradiation using 3D custom bolus electron conformal therapy. Case Report In March 2009, a 51-year-old premenopausal woman presented to our institution with rapid-onset skin thickening, heaviness, and nipple inversion of the left breast. Eleven years earlier, she had been diagnosed with stage T1N0M0 invasive ductal carcinoma of the left breast, for which she underwent a lumpectomy and levels I and II axillary lymph node dissection followed by adjuvant radiation therapy of the whole breast. At that time, a standard tangential technique had been used to deliver 50.4 Gy in 1.8-Gy daily fractions using 6-MV photon beams, followed by a field size reduction for a 10-Gy tumor bed boost using 9-MeV electrons. After 5 years of tamoxifen therapy for estrogen receptor (ER)-positive disease, the patient remained disease-free for 4 years until she presented at our institution, where a punch biopsy of the skin of the left breast confirmed an inflammatory-type recurrence. The staging workup revealed no evidence of regional or distant metastases. The patient received 4 cycles of doxorubicin-based chemotherapy, which resulted in a partial response. Following this, a modified radical mastectomy of the left breast revealed extensive, invasive carcinoma with dermal and lymphovascular invasion involving all 4 quadrants of the breast. No identifiable lymph nodes were recovered from the axilla. Despite resection down to and including the pectoralis fascia, the carcinoma invaded within 1 mm of the deep and superior lateral margins. After determining that additional resection was not feasible, the decision was made to proceed with adjuvant re-irradiation. Given the 10-year interval since the patient’s last course of radiation therapy and the near-total removal of her previously irradiated breast tissue, the patient was consid-
0958-3947/$ – see front matter Copyright 䉷 2012 American Association of Medical Dosimetrists doi:10.1016/j.meddos.2011.07.004
M.M. Kim et al. / Medical Dosimetry 37 (2012) 208-213
209
Fig. 1. Axial planning CT images show the marked irregularity of the patient’s chest wall anatomy from superior to inferior (A–D). Red indicates the radiation therapy target volume.
Fig. 2. Representative axial (A) and sagittal (B) CT images of radiation dose lines in the chest wall and underlying lung tissue from a comparison tangential field plan using 30⬚ wedges and 6-MV photons.
210
M.M. Kim et al. / Medical Dosimetry 37 (2012) 208-213
Fig. 3. Two-beam (A) and 3-beam (B) segmented electron fields plan. Using low-energy 4-MeV appositional electrons, significant dosing to underlying lung is seen.
Fig. 4. Two-beam (A) and 3-beam (B) segmented electron fields plan in a region of irregular chest wall anatomy. Significant underdosing of the target volume (light green) is seen using low-energy, 4-MeV electrons.
Fig. 5. Axial (A) and sagittal (B) CT images of isodose lines from the custom bolus plan using a single appositional 12-MeV electron field.
M.M. Kim et al. / Medical Dosimetry 37 (2012) 208-213
211
Fig. 6. Dose distribution from the custom bolus plan in regions of dynamic and irregular chest wall anatomy. Purple indicates 90% of the prescribed radiation dose.
ered a candidate for adjuvant re-irradiation. However, her recent surgery had resulted in a highly irregular chest wall anatomy, with areas of the midchest wall that were thin enough to pose a substantial risk of overtreating previously irradiated structures (including the ribs, intercostal musculature, pleural surface, and lung), which were not at risk for harboring disease. Representative computed axial tomography (CT) images of the irregular radiation therapy target volume (shown in red) are depicted in Fig. 1 from superior to inferior (Fig. 1A–D). Several radiation therapy techniques were considered, including a standard medial and lateral tangential technique using 6-MV photon beams and 30⬚ wedges matched to a medial electron field to cover the internal mammary chain. Figure 2 shows representative axial (Fig. 2A) and sagittal (Fig. 2B) CT images of this plan. In Fig. 3, comparison 2-field (Fig. 3A) and 3-field (Fig. 3B) segmented electron field plans are shown using appositional 4-MeV electrons. A significant overdosing of the underlying lung is seen in the thinner areas of the chest wall. In contrast, a significant underdosing of the target volume (shown in light green) is apparent in areas of irregular chest wall anatomy for both the 2-field (Fig. 4A) and 3-field (Fig. 4B) plans. Figure 5 depicts axial (Fig. 5A) and sagittal (Fig. 5B) images from the 3D custom bolus plan. Using a single, appositional 12-MeV electron field, the 3D custom bolus technique permitted conformal coverage of the areas of surgical change while sparing the deepest part of the rib cage and intrathoracic organs from high-dose radiation (Fig. 6). In Figs. 2–6, the 90% isodose line is depicted in purple.
As per standard radiation treatment planning, a noncontrast, free-breathing CT scan was acquired using 1.25-mm thickness slices. The CT images were imported into a standard treatment planning system (Pinnacle, Philips Medical Systems, Andover, MA), and the at-risk soft tissue of the operative bed was carefully delineated with a margin and designated as the planning target volume (PTV). The images were then exported into the bolus-design planning software (p.d. version 4.0., decimal, Inc., Sanford, FL) to create a virtual custom bolus that conformed to the distal contours of the PTV and the external contours of the patient’s chest wall. The bolus parameters were then exported back into the treatment planning system for dose calculation. After the treatment plan was carefully reviewed to ensure coverage of the PTV, the bolus specifications were sent to a custom bolus manufacturer (.decimal, Inc.) that fabricated a custom wax bolus with radiation properties defined previously.4 The bolus was manufactured from machinable wax (Machinable Wax, Inc., Lake Ann, MI), which has a density of 0.93 g/cm3. After extensive quality assurance testing, the completed custom bolus was returned. The turnaround time for the entire process was 23 hours. After receiving the custom bolus from the manufacturer, a noncontrast CT scan was repeated with the custom bolus in place to verify its fit on the patient’s chest wall. The resultant CT images were used to calculate the final planned radiation dose. For daily treatment, routine imaging with either kilovoltage x-rays or cone-beam CT was acquired to ensure proper daily setup, positioning, and alignment of the custom
212
M.M. Kim et al. / Medical Dosimetry 37 (2012) 208-213
Fig. 7. Representative cone-beam CT image from actual treatment and reference image demonstrating optimal fit to the patient’s chest wall with minimal air gaps.
bolus. In Fig. 7, reference and representative daily cone-beam CT images from a treatment session demonstrate a good fit of the custom bolus with minimal air gaps. A single appositional field using 12-MeV electrons was used to deliver 50 Gy in 2-Gy daily fractions, with the distal 90% isodose line covering the chest wall and internal mammary nodal chain. A subsequent 10-Gy boost in 2-Gy daily fractions was delivered to the superolateral quadrant of the primary field in the area with close surgical margins using the same bolus technique. These techniques permitted coverage of the area of surgical change in the chest wall with the 90% isodose line, along with maximal sparing of the left lung from low and high dose (V20 approximately 23%, V40 approximately 4%). A 6-MV oblique photon field was matched to the primary electron field using a half-beam block technique to deliver 54 Gy in 2-Gy daily fractions to the supraclavicular nodal basin—slightly dose-escalated in keeping with previously established guidelines for recurrent disease.5 Figure 8 shows axial (Fig. 8A) and 3D skin rendering (Fig. 8B) images of the supraclavicular field with target coverage by the 90% isodose line. As expected, the patient developed grade 2 erythema and hyperpigmentation in areas of the treatment field that did not cause desquamation. Mild pruritus was effectively treated with 1% hydrocortisone cream, and the patient did not require any treatment breaks. Six months after completing radiation therapy, the patient was noted to have an erythematous, maculopapular rash conforming to the areas of high-dose radiation therapy. A punch biopsy revealed eosinophils and spongiosis consistent with the inflammatory effects of radiation treatment (Fig. 9). Twenty-one months after completing bolus electron conformal therapy, the patient had no evidence of disease.
Discussion The effective control of locally recurrent breast cancer must be balanced against the risks of retreatment. Several studies have sug-
gested that particle beam radiation therapy for local breast cancer recurrence after mastectomy may confer durable local control with acceptable toxicity, with reports of locoregional control ranging from 62–74% at 5 years.6 – 8 The median cumulative dose delivered in these studies ranged from 59.3–100 Gy with acceptable rates of morbidity and no instances of skin necrosis. However, significant dose heterogeneity may occur after surgery in patients with irregular chest wall anatomy who are treated with conventional radiation therapy. The variable densities of the target volume and underlying tissue also may result in incidental overtreatment. Electron conformal therapy capitalizes on the physical properties of electron beams, permitting the treatment of irregular target volumes at limited depths. Several such techniques have been described. In contrast to radiation delivery techniques that use abutting electron fields of different energies, bolus electron conformal therapy avoids the characteristic hot and cold spots created at the junctions of segmented fields.9 In addition, techniques such as electron arc therapy that are used for improved dose uniformity in areas at high risk for recurrence are not available at most institutions, whereas bolus electron conformal therapy is readily available through commercial software and bolus manufacturing companies. Finally, because it can achieve a higher skin surface dose than conventional techniques,
Fig. 8. Matched oblique supraclavicular field using 6-MV photons. Representative axial CT image (A); yellow indicates 90% of prescribed radiation dose. Three-dimensional skin rendering (B) of nondivergent, supraclavicular field.
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Conclusion Electron conformal therapy using 3D custom bolus enables the spatial modulation of an electron field that is appropriate for individual patient anatomy. It is an accessible, effective treatment technique for the irradiation of irregular chest wall anatomy in the setting of primary or recurrent disease. Bolus electron conformal therapy may complement standard radiation therapy techniques used in the postmastectomy setting. References
Fig. 9. Ten months after treatment, an erythematous, maculopapular rash conforming to the areas of high-dose radiation therapy was evident. A prior punch biopsy revealed eosinophils and spongiosis consistent with inflammation and the effects of radiation treatment, but no evidence of recurrent disease.
bolus electron conformal therapy enables the treatment of the dermal lymphatics, which were at risk in the case of our patient. The highly conformal properties of this technique make treatment well tolerated, with satisfactory immediate results in a range of clinical settings.3, 10
1. Deutsch, M.; Parsons, J.A.; Mittal, B.B. Radiation therapy for local-regional recurrent breast carcinoma. Int. J. Radiat. Oncol. Biol. Phys. 12:2061–5; 1986. 2. Schwaibold, F.; Fowble, B.L.; Solin, L.J.; et al. The results of radiation therapy for isolated local regional recurrence after mastectomy. Int. J. Radiat. Oncol. Biol. Phys. 21:299 –310; 1991. 3. Perkins, G.H.; McNeese, M.D.; Antolak, J.A.; et al.A custom three-dimensional electron bolus technique for optimization of postmastectomy irradiation. Int. J. Radiat. Oncol. Biol. Phys. 51:1142–51; 2001. 4. Low, D.A.; Starkschall, G.; Bujnowski, S.W.; et al. Electron bolus design for radiotherapy treatment planning: Bolus design algorithms. Med. Phys. 19:115–24; 1992. 5. Liao, Z.; Strom, E.A.; Buzdar, A.U.; et al. Locoregional irradiation for inflammatory breast cancer: Effectiveness of dose escalation in decreasing recurrence. Int. J. Radiat. Oncol. Biol. Phys. 47:1191–200; 2000. 6. Gaffney, D.K.; Lee, C.M.; Leavitt, D.D.; et al. Electron arc irradiation of the postmastectomy chest wall in locally recurrent and metastatic breast cancer. Am. J. Clin. Oncol. 26:241– 6; 2003. 7. Janjan, N.A.; McNeese, M.D.; Buzdar, A.U.; et al. Management of locoregional recurrent breast cancer. Cancer 58:1552– 6; 1986. 8. Laramore, G.E.; Griffin, T.W.; Parker, R.G.; et al. The use of electron beams in treating local recurrence of breast cancer in previously irradiated fields. Cancer 41:991–5; 1978. 9. Tapley, N.D.; Montague, E.D. Elective irradiation with the electron beam after mastectomy for breast cancer. AJR Am. J. Roentgenol. 126:127–34; 1976. 10. Low, D.A.; Starkschall, G.; Sherman, N.E.; et al. Computer-aided design and fabrication of an electron bolus for treatment of the paraspinal muscles. Int. J. Radiat. Oncol. Biol. Phys. 33:1127–38; 1995.