Multimodal imaging for clinical target volume definition in prone whole-breast irradiation: a single institution experience

62 Background: A relatively newer algorithm for surgical management of axilla, where axillary node dissection (ALND) is avoided in cN0 EBC patients with 1 to 2 metastatic sentinel nodes (SLN) is now widely practiced in North America. ASCO & NCCN guidelines, and St Gallen consensus statement too have endorsed this strategy. This algorithm, based on the ACOSOG-Z0011 trial results has evoked quite a debate in India too. Concerns relating the quality of Z0011 data and its wide applicability persist. On the other hand, avoidance of ALND and its morbidity seems attractive to the oncologists and patients. In a single institution validation SLN Biopsy (SLNB) data-set, we evaluated the applicability of the “Z0011 strategy” to know its impact on an Indian patient cohort. Methods: In a prospective data-set of 120 cN0 EBC patients (mean age 51.1 years, T1 = 14, T2 = 106, mean tumor size 3.8 cm, 51.7% ER/PR+) who underwent validation SLNB (ALND irrespective of SLNB histology), such patients who fulfilled the selection criteria of ACOSOG-Z0011, i.e. those who underwent BCS and tangential field whole breast irradiation, and 1-2 metastatic SLNs were identified. Results: 66 (55%) of the 120 patients underwent BCS and tangential field whole breast irradiation. Of the 25 out of 66 patients with metastatic SLNs, 5 patients had 3 or more metastatic SLNs, and 2 had extra-nodal spread, thus not fitting the Z0011 criteria. Thus only 18 patients (15% of entire study cohort, and 27.3% of those undergoing BCS) with 1 to 2 metastatic SLNs were eligible for avoidance of ALND based Z0011 criteria. Of these 18 eligible patients, 7 (38.9%) had non-sentinel metastatic nodes. These 7, and the 3 with false negative SLNs could be seen as being left with undertreated axillae. Conclusions: In Indian context, where the majority of patients have large tumors and many opt for mastectomy, avoidance of ALND in presence of metastatic SLNs can be offered to a small proportion of patients. In a single institution validation SLNB data-set, only 15% patients qualified for avoidance of ALND using the Z0011 trial criteria. Besides, avoidance of ALND would have left 8.3% patients potentially undertreated in the axilla.

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Dosimetric study of three-dimensional conformal radiotherapy, electronic compensator technique, intensity-modulated radiation therapy and volumetric-modulated arc therapy in whole breast irradiation

Journal of Radiotherapy in Practice ◽

10.1017/s1460396917000243 ◽

2017 ◽

Vol 16 (4) ◽

pp. 431-443 ◽

Cited By ~ 2

Author(s):

Chonnipa Nantavithya ◽

Kitwadee Saksornchai ◽

Puntiwa Oonsiri ◽

Kanjana Shotelersuk

Keyword(s):

Radiation Therapy ◽

Volumetric Modulated Arc Therapy ◽

Three Dimensional ◽

Intensity Modulated Radiation Therapy ◽

Conformal Radiotherapy ◽

Target Volume ◽

Whole Breast Irradiation ◽

Breast Irradiation ◽

Lung Dose ◽

3D Crt

AbstractBackgroundWhole breast irradiation is an essential treatment after breast-conserving surgery (BCS). However, there are some adverse effects from inhomogeneity and dose to adjacent normal tissues.ObjectiveAim of this study was to compare dosimetry among standard technique, three-dimensional conformal radiotherapy (3D-CRT), and advanced techniques, electronic compensator (ECOMP), inverse intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT).MethodsWhole breast irradiation treatment plans of patients who had underwent BCS and whole breast irradiation were re-planned with all four techniques. Clinical target volume was contoured according to the Radiation Therapy Oncology Group atlas for breast only in patients who had negative node or ductal carcinoma in situ and breast with chest wall for patients with positive node. Planning target volume was non-uniformly expanded. Dose prescription was 50 Gy in 25 fractions with 6 MV photon energy.ResultsIn total, 25 patients underwent whole breast irradiation with computed tomography simulation from November 2013 to November 2014 were included. Six patients with positive nodes were re-planned for breast with chest wall irradiation and 19 patients with negative nodes were re-planned for breast only irradiation. Primary outcome, radical dose homogeneity index (HI) of 3D-CRT, ECOMP, IMRT and VMAT were 0·865, 0·889, 0·890 and 0·866, respectively. ECOMP and IMRT showed significant higher HI than 3D-CRT (p-value<0·001). Secondary outcome, conformity index (CI) of advanced technique were significantly better than 3D-CRT. Lung V20, mean ipsilateral lung dose (MILD), mean heart dose (MHD), heart V25, heart V30 of advanced techniques were also lower than 3D-CRT. ECOMP had better mean lung dose (MLD), mean contralateral lung dose (MCLD) and mean contralateral breast dose (MCBD) when compared with 3D-CRT. Monitor units of advanced techniques were significantly higher than 3D-CRT.ConclusionsHI of ECOMP and IMRT were significantly higher than 3D-CRT technique. All advanced techniques showed statistically better in CI. Lung V20, MILD, heart V25 and heart V30 of advanced techniques were lower than 3D-CRT. However, only ECOMP showed decreased MLD, MHD, MCLD and MCBD when compared with 3D-CRT.

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