Dose Coverage Of Axillary And Sentinel Lymph Node Area During Breast Intensity Modulated Radiation Therapy In Early Stage Breast Cancer Patients

PART IDose Coverage of Axillary Levels Ⅰ-Ⅲ during Whole Breast Irradiation with Intensity Modulated Radiation Therapy in Early Stage Breast Cancer Patients Purpose:To evaluate and compare the incidental radiation dose to axillary levels Ⅰ-Ⅲ during whole breast irradiation with inverse-planned intensity modulated radiation therapy (inv-IMRT) and forward-planned intensity modulated radiation therapy (for-IMRT) in early stage breast cancer patients.Methods and Materials:We retrospectively reviewed 61 patients with early stage breast cancer treated in Fudan University Shanghai Cancer Center From February 2007 to May 2013. All patients underwent breast-conserving surgery and sentinel lymph node dissection by a senior experienced surgeon. Whole breast irradiation with inv-IMRT was applied in the patients. The prescription dose was 50 Gy in 25 fractions. Meantime, a for-IMRT technique was planned for each patient. The axillary levels Ⅰ-Ⅲ were delineated according to the RTOG. Dose-volume-histograms (DVHs) were used to calculate the dose delivered to these lymph node areas in both plans. At same time, we tried to select some potential anatomic parameters that might influence the dose distribution of axilla.Results:The average of mean dose delivered to level I using inv-IMRT technique versus for-IMRT technique were 27.7Gy (95%CI 26.1-29.4Gy) and 29.1 Gy (95%CI 27.2-31.0Gy) (p=0.011), respectively. The mean percent volume of axilla receiving > 95% of the prescribed dose (V95)was 16.9%(95%CI 14.1-20.0%) and 27.6% (95%CI 24.6-30.7%) (p=0.000), respectively. The average of mean dose delivered to level Ⅱ using inv-IMRT technique versus for-IMRT technique were 10.6Gy(95%CI 为8.9-12.3Gy) and 10.9Gy(95%CI为9.2-12.6Gy) (p=0.403), respectively. V95 were 1.7%(0.8-2.9%) and 1.8%(0.8～2.9%) (p=0.909), respectively. The average of mean dose delivered to level 、 using inv-IMRT technique versus for-IMRT technique were 2.5Gy(95%CI% 2.1-3.1Gy) and 2.8Gy(95%CI 为 2.3-3.4Gy) (p=0.089),, respectively, respectively.V95 were both 0. Patients with breast separation> 19.3cm\ body width>31.9cm、the distance between axillary cranial edge>0cm、the distance between tangential cranial edge and the humeral head<2cm received significantly higher mean dose in the axillay level I than patients with breast separation≤19.3cm、 body width<31.9cm、the distance between axillary cranial edge<0cm、the distance between tangential cranial edge and the humeral head> 2cm(p=0.007,0.001,0.023,0.002,respectively). Patients with breast PTV volume≥ 415 cm3 also had the trend of receiving higher mean dose (p=0.06).Conclusion:Both inv-IMRT and for-IMRT techniques provide limited dose coverage to axillary levels Ⅰ-Ⅲ., but further reduced with the inv-IMRT technique in axillary level Ⅰ. the height of radiation fields and anatomical factors of the patients impacts the dose distribution of axilla level Ⅰ. The choice of optimal radiation technique and patients’ anatomical features should take into considerations when applying Z0011 criteria to early stage breast patients with 1～2 positive sentinel lymph nodes. PART IIDose Distribution Analysis of the Sentinel Lymph Node Area during Intensity Modulated Radiation Therapy to BreastPurpose:The aim of this study was to analyze dose distribution of sentinel lymph node area during intensity modulated radiation therapy (IMRT) to breast in early stage breast cancer patients with breast-conservative surgery(BCS) and sentinel lymph node biopsy(SLNB).Methods and Materials:From May 2009 to February 2013, we retrospectively analyzed 39 early stage breast cancer patients with clips positioned at the site of the SLN during surgery by a senior experienced surgeon in Fudan University Shanghai Cancer Center. All patients underwent breast-conserving surgery and SLN biopsy followed by whole breast irradiation with inverse-planned intensity modulated radiation therapy (inv-IMRT). The prescription dose was 50 Gy in 25 fractions. Meantime, a forward-planned intensity-modulated radiotherapy (for-IMRT) technique was planned for each patient. The SLN CTV was defined as 2 cm in diameter around the clip with the lateral border not exceeding 0.5cm under skin. Dose-volume-histograms (DVHs) were used to calculate the dose delivered to these lymph node areas in both plans. The relationship between the SLN area and the tangential fields in the for-IMRT plan was also studied.Results:The median age was 49 years old (rang,28-77 years old).The median number of SLN per patients was 2(rang, 1-5).The median diameter of the SLN was 0.5cm (rang,0.2-1.6cm). There were 49 clips with 1 clip in 29 patients,2 in7 patients,3 in 2 patients. The mean dose delivered to SLN-CTV was 42.4Gy (95%CI:37.7-44.0Gy) in inv-IMRT plan and 41.3Gy (95%CI:39.0-45.4Gy) in for-IMRT plan, respectively. There was no significant between these two plans (p=0.429).27(55.1%),30(61.2%) of all SLN-CTVs had a mean dose greater than 45.0Gy, only 7(14.3%),5(10.2%)SLN-CTVs received a mean dose less than 30.0Gy in inv-IMRT plan and for-IMRT plan, respectively. The D40Gy-D50Gy of SLN-CTV in inv-IMRT plan was significant higher than that in for-IMRT. All SLN volumes were contained within axillary level I area. During the for-IMRT plan,31 of 49 SLN volumes were located within the radiation fields completely,18 SLN volumes that were partially covered by the radiation fields, none SLN volumes fell out of the radiation fields completely.Conclusions:Using whole breast irradiation with IMRT technique, the SLN area received a considerable amount of dose coverage. The majority of SLN volumes were located within radiation fields. Withholding SLNB may be safe in selected patients if disease is confined to the sentinel lymph nodes.