The British Journal of Radiology, 82 (2009), 595–599
Anatomical, clinical and radiological delineation of target volumes in breast cancer radiotherapy planning: individual variability, questions and answers P CASTRO PENA, MD, Y M KIROVA, MD, F CAMPANA, N FOURNIER-BIDOZ, PhD and A FOURQUET, MD
MD,
R DENDALE,
MD,
M A BOLLET,
MD,
Department of Radiation Oncology, Institut Curie, Paris, France
ABSTRACT. The purpose of the study was to evaluate the individual variability of anatomical and radiological delineation for breast cancer radiotherapy (RT) in preparation for new techniques and to propose practical solutions to improve delineation in everyday practice. In the first phase, a patient with stage T3N3M0 breast cancer and complete response after neoadjuvant chemotherapy was assessed by CT scan in the treatment position before RT. 11 radiation oncologists (5 breast cancer specialists and 6 residents) independently delineated the breast and lymph node (LN) regions before definition of target volumes. Organs at risk (heart, lung, thyroid and brachial plexus) were also delineated. All regions (breast, axilla, supraclavicular LN, infraclavicular LN and internal mammary chain) were delineated and compared in terms of volume. Comparative analysis was performed with Aquilab software. Differences in the clinical and radiological assessment were observed between the various radiation oncologists. Simplified rules of delineation were developed in the department. Using these rules, the second patient’s CT was delineated by the same physicians and better results were observed. Simplified rules of delineation were developed. In conclusion, major differences in anatomical and radiological delineation for breast cancer RT were observed among the physicians. This study led to the development of written delineation protocols. The study is ongoing with evaluation of the dosimetric impact and definition of different target volumes.
Breast-conserving radiotherapy (RT) is the standard treatment for breast cancer [1]. Over recent years, new techniques have been developed to obtain better target definition, dose homogeneity and conformity [2–7]. Radiation oncologists have three main objectives: definition of treatment volumes (breast, axilla, supraclavicular lymph nodes (SCLNs) and infraclavicular lymph nodes (ICLNs)), homogeneous coverage of these volumes [7– 11] and avoidance of organs at risk (OAR) to reduce early and late complications [12–17]. In view of the importance of these objectives and the development of new treatment techniques in our department, such as the use of whole breast intensity-modulated radiation therapy and/or helical tomotherapy, a simple small-scale study was conducted in the department. The aim of this study was to evaluate the individual variability of target and OAR delineation for breast cancer RT between various physicians and to standardise this procedure by preparing written protocols.
Methods and materials This pilot study was conducted in three phases: (i) lymph node, breast and OAR target volume delineation, Address correspondence to: Youlia Kirova, Radiation Oncology, Institut Curie, 26 Rue d’Ulm, 75005 Paris, France. E-mail:
[email protected]
The British Journal of Radiology, July 2009
Received 4 August 2008 Accepted 10 October 2008 DOI: 10.1259/bjr/96865511 ’ 2009 The British Institute of Radiology
performed by senior radiation oncologists and residents, followed by evaluation of variability between the various physicians; (ii) a training programme based on anatomical atlases and the literature following target delineation of LN and breast volumes in another patient by the same team of senior radiation oncologists and residents, and evaluation of the variability between the physicians; and (iii) evaluation of the dosimetric impact and definition of different target volumes. Phases one and two are reported in this study; phase three is ongoing and will be reported subsequently. Contrast-enhanced CT scans of the two patients in the treatment position were used for delineation and analysis. The patients were placed in the supine position on a MEDTEC inclined board (15˚) (CIVCO, IA, USA) with their ipsilateral arm raised above the head and the shoulder leaning on a dedicated arm rest. Before the CT scan, the radiation oncologist clinically determined the edge of all palpable breast tissues using a radio-opaque skin marker. CT scans encompassing the whole thorax were then performed with 5 mm slices every 5 mm. All images were then transferred to an Eclipse treatment planning system (Varian Medical Systems Inc, Palo Alto, CA). 11 radiation oncologists (5 breast cancer specialists and 6 residents in training) independently delineated the breast and LN regions before definition of the target volumes. The residents, classified as ‘‘junior’’, contoured the CT images in groups of two. All clinical target 595
P Castro Pena, Y M Kirova, F Campana et al
volumes (CTVs) (breast, axilla, SCLNs, ICLNs and internal mammary chain (IMC)) were delineated and compared in terms of volume. The procedure is given in Figure 1. The clinical breast volume corresponded to that of the whole breast. It was delineated on all transverse slices as the volume between the pectoralis major and 5 mm below the skin (for dosimetric considerations) within the space outlined by radio-opaque skin markers indicating the limits of the palpable breast tissue. The definition of SCLNs, ICLNs and the IMC has been reported previously [4]. The volume of the axilla was defined as the region along the lateral part of the latissimus dorsi muscle to the termination of the thoracoacromial vein [8]. All sources of information, such as breast cancer atlases and recent publications discussing the definition of treatment volumes, were used [4, 8–11]. The variability and the differences in the delineated volumes were quantified and the standard deviation was calculated. Evaluation of the results of the first phase was presented at the Department of Radiation Oncology Meeting (Figure 2), an open discussion between all participants in this study
supported by various examples from the literature. The training course was conducted in the anatomical setting. A new case was then used for the second phase of the study: contouring of a new patient with bilateral T1N0M0 breast cancer after breast-conserving surgery and chemotherapy before radiation therapy. The comparative analysis was realised using the Aquilab Program (Aquilab, Loos les Lille, France) using the formula (Figure 3): OV~
Cn\CR Cn|CR
ð1Þ
where OV is the overlap volume.
Results The first patient weighed 55 kg for a height of 158 cm. No residual tumour or suspicious LNs were found on CT scan after completion of chemotherapy. The results of target volume delineation are shown in Table 1. Differences in the clinical and radiological
(a)
(b)
(c)
(d)
Figure 1. (a–d) Examples of simplified volumes delineation (limits). SCLN, supraclavicular lymph node; ICLN, infraclavicular lymph node; IMC, internal mammary chain.
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Delineation of lymph node volumes in breast cancer
assessment were observed between the various radiation oncologists. Examples of delineation are shown in Figure 1. Figure 2 shows the three-dimensional reconstruction of target volumes. Figure 3 and Table 2 show the differences in delineation of breast and axilla CTVs in Patient 1 (Figure 3a) and Patient 2 (Figure 3b). An improvement of the delineation procedure was observed in Patient 2. After this experience, new simplified rules were developed in our department and training courses for new residents are now organised every 6 months. A practical atlas for everyday use has been developed for internal use. This study is ongoing and the last phase is designed to compare dosimetries performed on the various volumes and determine whether these individual variations in CTV definition have any impact on the patient’s treatment.
Figure 2. Three-dimensional reconstruction of defined volumes using TPS Eclipse: supraclavicular lymph nodes (red); infraclavicular lymph nodes (sky blue); left breast (transparent light green); axilla (magenta); internal mammary chain (yellow); Rotter lymph node (blue); brachial plexus (green) between supra/infraclavicular nodes and axilla; sternum, clavicle and humeral bone (white); thyroid gland (pink); left lung (brown) and heart (dark blue).
Discussion This study shows the importance of CTV definition in breast cancer treatment and the individual variations in delineation despite the use of various standard sources. A more uniform target volume delineation of the breast and regional LNs constitutes a real challenge. Over recent years, many teams have studied volume definition and the corresponding dosimetric coverage [4, 7–10, 18–
(a)
Figure 3. Comparison of the deli-
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neation of breast (intersection), axillary (orange) and internal mammary chain (magenta) volumes in Patients 1 and 2. This comparative analysis was performed using Aquilab/ Artiview software. It shows improvement in the delineation of volumes. The intersection of all physicians in the contoured volume is shown in red. (a) First patient: contouring before training programme. (b) Second patient: contouring after training programme. It is clearly shown that there is a better homogeneity between the delineation of volumes by different physicians.
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P Castro Pena, Y M Kirova, F Campana et al Table 1. Patient 1: variations in CTV of the breast, axilla, SCLNs, ICLNs and IMC (performed before the training programme) Target region (CTV)
Number of delineation specialists
Minimum CTV (cm3)
Median CTV (cm3)
Maximum CTV (cm3)
Mean CTV (cm3)
SD (cm3)
Breast Axilla SCLN ICLN IMC
11 11 11 10 9
348.7 26.8 5.7 8.1 3.2
407 70.7 31.1 16.6 5.8
443.5 127.7 76.9 45.7 13.7
404.5 64.5 33 19.7 7.1
35 34 23.2 12 3.6
(5+362) (5+362) (5+362) (4+362) (5+262)
CTV, clinical target volume; SCLN, supraclavicular lymph node; ICLN, infraclavicular lymph node; IMC, internal mammary chain; SD, standard deviation.
Table 2. Patient 2: variations in CTV of the breast, axilla, SCLNs, ICLNs and IMC (performed after the training programme by the same team of radiation oncologists) Target region (CTV)
Number of delineation specialists
Minimum CTV (cm3)
Median CTV (cm3)
Maximum CTV (cm3)
Mean CTV (cm3)
SD (cm3)
Breast Axilla SCLN ICLN IMC
11 11 11 11 11
733.1 55.6 16 8.6 1.3
785.8 135.2 29.6 17.1 3.4
849.3 171.2 61.2 46.2 9.3
778.5 130.9 33.6 19.3 4.2
39.6 34 13.4 10.3 2.8
(5+362) (5+362) (5+362) (5+362) (5+362)
CTV, clinical target volume; SCLN, supraclavicular lymph node; ICLN, infraclavicular lymph node; IMC, internal mammary chain; SD, standard deviation.
20]. Conformal RT requires definition of target volumes by anatomical limits based on delineation on CT slices. Some authors have proposed anatomically based landmarks specific for breast cancer RT to delineate all regional LNs [8, 18]. Despite these recommendations, major individual variability was observed in our study. The breast and its lymphatic drainage remain essentially ‘‘clinical’’ targets and it is difficult to ensure standardised delineation by all physicians in the same department. Open discussion of the results and comparison between various radiation oncologists using the literature as a guide is useful and improves the results. This ongoing study will evaluate a third question: the impact of these differences in treatment planning and dose distribution. In conclusion, this study showed major differences in the anatomical and radiological delineation of breast cancer target volumes for breast cancer RT among physicians. Written delineation protocols and training courses need to be developed. This study showed that open discussion of results and comparison with the literature is useful and improves the results.
2.
3.
4.
5.
6. 7.
Acknowledgments We thank Drs O Berges, Z Bourhaleb, V Marchand, L Oberic and V Passerat for their valuable work in volume contouring and to Dr A G Pollet for his help in anatomical definitions. This study was presented in part as an oral presentation at the RSNA Annual Meeting 2007, Chicago, USA.
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