12. Objectives
• Quantify the changes in seroma volume over the course of RT for early
stage breast cancer patients eligible for RTOG 1005.
• Evaluate the dosimetric impact of these changes on sequential boost
planning in accordance with Arm I of RTOG 1005.
• Assess the need for adaptive planning and pre-boost CT acquisition for
sequentially boosted breast cancer patients based on evaluation with
RTOG 1005 criteria.
• Dosimetrically compare two hypofractioned boost methods, concurrent
electron versus concomitant tangential IMRT photon, with the
planning/evaluation criteria outlined in Arm II of RTOG 1005.
15. Reference 1 on Final Slide
• For Early Stage Breast Cancer Patients (Stage I-II)
• Post-Lumpectomy Breast Conservation Course
• Shorten Treatment Time
• Objectives of Study
• Primary: determine if accelerated hypofractionated WBI with
concomitant tumor bed boosting is non-inferior in local control to
Standard of Care sequential boost and fractionation scheme
• Secondary: determine if ARM II is non-inferior to the Standard of Care
in terms of cosmesis, treatment symptoms (3 weeks and at 3 years),
cardiac toxicity for left sided cases, and treatment costs
• If non-inferior, determine if ARM II hypofractionated scheme is superior
to Standard of Care fractionated in same criteria
17. • 2009 study, aimed to evaluate the change in seroma volume over WBRT
prior to boost planning.
• 24 patients with evident seroma on initial CT, received 42.4Gy/16fx with
9.6Gy/4fx boost or 50.4Gy/28fx WBRT with 10Gy/5fx boost
• Second CT acquired at 3-5 weeks, dependent upon fractionation schedule
• Mean CT1 seroma was 65.7 cc and CT2 was 35.6 cc. Mean reduction of
39.6% with an SD of 23.8%, p<0.001, 2 of 24 patients showed increase in
size with an increase or 9.7% and 10.7%
• Changes during WBRT found to be significant and group concluded boost
planning accuracy can be affected by these changes.
Reference 6 on Final Slide
18. Reference 7 on Final Slide
• 2009 study, aimed to determine if lumpectomy cavity decreases in volume
during whole breast radiotherapy and contributing factors.
• 43 patients, 44 breast lesions prospectively enrolled. Lumpectomy and CT
sim within 60 days of surgery. WBRT 45-50.4 Gy.
• CT2 acquired b/w 21-23 treatments, seroma contoured on new CT and
compared.
• Mean volume was 38.2 cc on CT1, 21.7 cc on CT2. Mean decrease of
32% and 11.2 delta cc. Decreased on 38 of 44 patients (86%), p<0.001
• Concluded that tracking change and acquiring a pre-boost CT can lead to
decreased doses of radiation to remaining breast and critical structures,
and should be considered in patients with larger cavities.
20. Summary of Methods
• 11 early stage breast cancer patients eligible for RTOG 1005
• Clinically evident seroma at time of initial simulation (CT1)
• Received second CT (CT2) prior to planning of sequential boost
• Seroma volume/Lumpectomy GTV delineated on both datasets
• PHASE I: Characteristics of both CT1 and CT2 seroma volumes recorded
• Fusion of CT2 dataset and contour onto CT1 dataset
• In accordance with RTOG 1005 Arm I, patients retrospectively re-planned
giving 50Gy/25fx to whole breast and boosting sequentially with 12Gy/6fx
given via electron boost to the cavity (Standard of Care Arm)
• Boost plans individually optimized for each volume (CT1 vs. CT2)
• Plans compared based on dose to Heart, Ipsilateral Lung, Breast PTV Eval
(Normal Breast), and coverage of Lumpectomy PTV Eval using specified
Arm I evaluation criteria
21. Summary of Methods
• PHASE II: Comparison of Concurrent Hypofractionated Boost Methods
• In accordance with RTOG 1005 Arm II, patients retrospectively re-planned
giving 40Gy/15fx to whole breast tangents and boosting concurrently with 8
Gy in the same 15 fx
• Boost plans individually optimized for CT1 target volumes
• Concurrent Electron Cavity Boost
• Concomitant IMRT Photon Cavity Boost
• Plans compared based on dose to Heart, Ipsilateral Lung, Breast PTV Eval
(Normal Breast), and coverage of Lumpectomy PTV Eval using specified
Arm II evaluation criteria
24. Lumpectomy CTV (per RTOG 1005)
• Lumpectomy GTV + 1 cm 3D Expansion, Limiting Borders: Pectoralis
and Serratus Anterior Muscles, Midline, and 5 mm from skin surface
25. Lumpectomy PTV (per RTOG 1005)
• Lumpectomy CTV + 7 mm uniform 3D Expansion (Excluding Heart)
26. Lumpectomy PTV Eval (per RTOG 1005)
• Lumpectomy PTV minus area outside of ipsilateral breast, first 5 mm
of skin, and the chest wall/pectoralis muscles/lungs.
27. Breast PTV Eval (per RTOG 1005)
• Breast CTV (palpable breast volume – CW and 5mm skin) + 7 mm PTV
expansions in same Manner as Lumpectomy PTV Eval (avoid CW, 5mm)
28. Critical Normal Structures (per RTOG 1005)
• In this study: Ipsilateral Lung, Heart (Split of Pulmonary trunk into
Pulmonary Arteries superiorly to apex inferiorly), and Contralateral Lung.
31. GTV Delineation (RTOG 1005) and Image Fusion
Box-Based Fusion using chest wall and
Ipsilateral Breast
CT-CT Fusion done in PhilipsTM
Pinnacle® SyntegraTM
33. Results – Table 1 Seroma Volume Changes
Max Percent Decrease = 77.3%
Min Decrease = 46.1%
34. Planning for Phase I: Sequential
Electron Boost for CT1 and CT2
(RTOG Arm I)
35. Phase I of Study, Sequential Boosting (Arm I)
• 11 patients, retrospectively re-planned for 50 Gy in 25 fractions
tangentially to the whole breast.
36. • Sequential Electron boosts given 12 Gy in 6 fractions to
Lumpectomy GTV using Lumpectomy PTV as Block Margin
• Optimized for both CT1 and CT2 Scans for the 11 patients
(Available MEV 6, 9, 12, 15, 18, 21)
Phase I of Study, Sequential Boosting (Arm I)
Boost BEV for CT1 Volume Boost BEV for new CT2 Volume
45. Comparison
(Phase I)
For Phase I, the lung
and heart dose are
comparable for both
plans.
However, V56 of
Breast PTV Eval
drops by 6.8% for
boost plan optimized
to new volume
46. Phase I of Study, Sequential Boosting (Arm I)
• Comparison of Sequential Electron Boosts
Boost Plan for Lumpectomy PTV Eval CT1 Boost Plan for Lumpectomy PTV Eval CT2
Reduced V56 for Re-
CT Optimized Plan
59.8 Gy
56 Gy
47.5 Gy
20 Gy
48. Comparison of V58.9 of Lumpectomy PTV Eval
Old Plan still maintains
coverage of re-scan
Lumpectomy PTV Eval
49. Planning for Phase II:
Hypofractionated Concurrent Electron versus
Concomitant IMRT Photon
(RTOG Arm II)
50. Phase II of Study, Hypofractionated Course
with Concurrent Boosting (Arm II)
• 11 patients, retrospectively re-planned for 40 Gy in 15 fractions
tangentially to the whole breast.
51. Phase II of Study, Hypofractionated Course
with Concurrent Boosting (Arm II)
• Concurrent Electron Boost (Same blocking as Initial Sequential Phase I)
given concurrently 8 Gy over 15 fractions for 11 patients
• 8 Gy Concomitant IMRT Photon Boost “mini-tangents” for same 11 patients
52. Evaluation of Concurrent Boost on
Hypofractionated Course
(RTOG Arm II)
Phase II: Electron versus Concomitant IMRT
Photon
59. Results for Concurrent Boost on
Hypofractionated Course
(RTOG Arm II)
Phase II: Electron versus Concomitant IMRT
Photon
60. For Phase II, the
ipsilateral lung and
heart dose are
comparable for both
plans.
However, V44.8 of
Breast PTV Eval
dropped by 28.1% for
Electron Boost vs.
IMRT Photon Boosts
Comparison
(Phase II)
61. 45.6 Gy
44.8 Gy
38 Gy
16 Gy
Phase II of Study, Concurrent Hypofractionated
Boosting (Arm II)
Much higher V44.8 for
Concomitant IMRT
Photon Boost Plan
Concurrent 8 Gy Electron Boost Concomitant 8 Gy Photon IMRT Boost
• Comparison of Boost Methods
64. Discussion
• Average seroma volume decrease of 57.1% +/- 8.96% from CT1 to CT2
• Time elapsed between CT acquisition was 33.6 days +/- 5.1 days
• ARM I SEQUENTIAL: V56 for Breast PTV Eval decreased by an
average of 9.2% +/- 3.3% by optimizing the boost plan on a 2nd CT for
the current standard of care WB + Boost (50 Gy + 12 Gy Boost)
• Lung and Heart Dose discrepancies were minimal b/w plans
• Coverage of Lumpectomy PTV Eval CT2 volume maintained using
CT1-optimized plan
• Under-treating not found to be a concern in this study
• ARM II Hypofractionated: V44.8 for Breast PTV Eval decreased by an
average of 16.2% +/- 8.1% on all Electron Boosts when compared to
concomitant IMRT photon boost methods
• Lung and Heart Dose discrepancies were minimal b/w plans
65. Discussion
• Findings showed significant dose differences to the Breast PTV Eval
• Reduced by re-planning sequential boost using pre-boost CT
• Reduced using electron boost versus IMRT photon
• Significance of findings?
• Beyond WB prescription, breast tissue deemed to be normal tissue
• Reducing amount of normal breast tissue in boost field could potentially
decrease some of the acute side effects associated with treatment of the
site4,5
• Potential also exists to reduce late effects from breast irradiation, such
as the development of fibrosis4,5
• RTOG 1005 does not currently allow planning from a pre-boost CT
66. • 2008 trial to investigate predictors of long-term risk of fibrosis
• Between 1989 and 1996, 5318 patients receive 50 Gy/25 fx WBRT
• 2661 not boosted, 2657 boosted w/ 16 Gy/8fx with electrons to tumor bed
• Median Follow-up 10.7 years in both, 1079 pt (20.8%) had developed
moderate or severe fibrosis, 482 (9.3%) local recurrences, and 1013 (19.6% )
died
• Development dataset: 26.9% in boost arm had moderate or severe fibrosis
versus 12.6% in non-boosted
• Boost reduced the risk of local recurrence by 41%
Reference 4 on Final Slide
69. Take Home Message
• Breast volume beyond tangential prescription should be treated as normal
tissue and should be spared as much as possible
• Potential to minimize both acute and late RT effects
• Adaptive Planning, or optimizing using a pre-boost CT showed to
significantly decrease excess irradiation to normal breast tissue
• Electron cavity boosting also showed to be significantly superior to photon
mini-tangents
• Lung and Heart dose discrepancies minimal between respective comparisons
• Simply acquiring one CT and adaptively optimizing a new boost plan has
the potential to significantly decrease excess dose to normal breast tissue
• 4th or so week of treatment, ample time for dosimetry to generate boost plan
• In a world of CBCT and IGRT, the simple acquisition of one additional CT
may be considered worthwhile in terms of potential to better patient
outcomes
