The Composite Planning Technique in Left Sided Breast Cancer Radiotherapy: A Dosimetric Study.

Original Article Eur J Breast Health 2020; 16(2): 137-145 DOI: 10.5152/ejbh.2020.5370 The Composite Planning Technique in Left Sided Breast Cancer Radiotherapy: A Dosimetric Study Naveen Kumawat1 , Anil Kumar Shrotriya2 , Malhotra Singh Heigrujam1 , Satendra Kumar1 , Manoj Kumar Semwal3 Anil Kumar Bansal1 , Ram Kishan Munjal1 , Deepak Kumar Mittal1 , Charu Garg1 , Anil Kumar Anand1 , Department of Radiation Oncology; Max Super Speciality Hospital, New Delhi, India Department of Physics, SPSB Govt. PG College, Shahpura, India 3 Department of Radiotherapy, Radiotherapy Army Hospital (Research and Referral), New Delhi, India 1 2 ABSTRACT Objective: The aim of this retrospective study is to reduce the dose of heart, both lung and opposite breast and left anterior descending artery (LAD) and avoid long term complication and radiation induced secondary malignancies in radiotherapy left breast/chest wall without losing homogeneity and conformity of the Planning Target Volume (PTV), contoured using Radiotherapy Oncology Group (RTOG 1005) guideline. Materials and Methods: The treatment plans were generated retrospectively by TFIF, VMAT and Composite techniques for 30 patients. DoseVolume Histograms (DVHs) were evaluated for PTV and organs at risk (OAR’s) and analyzed in two groups BCS and MRM using Wilcoxon signed rank test. Results: The homogeneity index (HI) was improved in Composite technique by 32.72% and 21.81% of VMAT, 50.66% and 49.41% of TFIF in BCS and MRM group respectively. The Conformity Index (CI) for composite plan was statistically same as VMAT and superior by 27.94% and 41.37% of TFIF in BCS and MRM group respectively. The low dose volume V5Gy and V10Gy of the heart were improved in Composite plan by 47.9% and 26.1% of VMAT respectively in BCS group and in MRM group, improved by 21.2% and 45.6% of VMAT. The V5Gy and V10Gy of ipsilateral lung were improved in Composite plan by 16% and 13.7% of VMAT respectively in BCS and 8.4% and 3% of VMAT respectively in MRM group. Conclusion: The Composite plan consisting of VMAT and TFIF plan with an optimum selection of fractions can achieve lower low dose exposure to the OAR’s without compromising coverage compared to VMAT. Keywords: BCS, composite plan, breast, dosimetric comparison, MRM Cite this articles as: Kumawat N, Shrotriya AK, Heigrujam MS, Kumar S, Semwal MK, Bansal AK, et al. The Composite Planning Technique in Left Sided Breast Cancer Radiotherapy: A Dosimetric Study. Eur J Breast Health 2020; 16(2): 137-145. Introduction Breast cancer or carcinoma of the breast (Ca-Breast) is the most common malignancy among women and the second most commonly occurring cancer overall in the world (1). In breast cancer, the most common treatment is conservative surgery or mastectomy followed by adjuvant chemotherapy and radiotherapy with or without hormonal therapy (2). Several prospective studies have shown that radiotherapy in Ca-Breast improved the disease free survival by almost 15% at 10 years and reduced the15-year risk of Ca-Breast death by 4% (3). Thus making the chronic sequelae of the breast cancer radiotherapy more important (4). But it has been shown that patients treated with radiation to chest wall or breast alone developed pneumonitis in 1% cases which increased to 4% in patients treated with loco-regional irradiation including draining lymph node (5). Oie et al. (6) reported that radiation pneumonitis (RP) mostly developed in ipsilateral lung and arose next to the rapidly decreasing dose area. Previous reports have shown that irradiation of the breast/chest wall with supraclavicular field led to an increased incidence of symptomatic radiation pneumonitis (7, 8) (SRP). Wen et al. (9) have suggested that the volume receiving 20Gy and 30Gy (V20Gy, V30Gy) were Corresponding Author : Naveen Kumawat; Received: 05.01.2020 Accepted: 09.02.2020 137 Eur J Breast Health 2020; 16(2): 137-145 the main predictors for SRP and also suggested that with new technologies such as IMRT and hypo-fractionated RT additional studies of corresponding dose-volume parameters should be performed for better guidance in practice. Shaikh et al. (10) studied radiation pneumonitis in patients receiving taxane-based trimodality therapy for locally advanced esophageal cancer. In their study the authors concluded that the volumes covered by 5Gy (V5Gy), 10Gy (V10Gy), 20Gy (V20Gy) and 30Gy (V30Gy) were associated with risk of RP grade 2 plus and V5Gy≤ 65% was the optimal threshold to prevent it. Other studies have also supported that the low dose volume of lung was associated with an increase in risk of RP (11, 12). In the 1930’s, the heart was considered as a radio-resistant organ below a dose of 30Gy (13), but current studies have shown that the cardiovascular disease could occur with mean doses as low as 3 to 17 Gy (14). However, at low doses the typical latent period for cardiac related problems is often long. The risk of myocardial infarction after post lumpectomy radiation treatment for left sided breast cancer (15) is more than right sided breast cancer and it has also been found that increase in radiation dose to heart leads to increased cardiac related mortality (16, 17). Darby et al. (18) reported that 1 Gy added to the mean heart dose could increase the rate of ischemic heart disease by 7.4%, regardless of the threshold dose. Also, there is a relationship reported between low-radiation doses (∼5 Gy) and cardiac mortality (19). Data published by authors such as Hortobagyi et al. (20) on anthracycline and trastuzumab in Ca-breast showed that patients who had received anthracycline based chemotherapy were at a higher risk for developing cardiac toxicity. In long-term survivors, second malignancy is also a cause of non-breast cancer mortality. Stovall et al. (21) found that women who were less than 40 years of age and received a radiation dose more than 10 Gy to the contralateral breast had a 2.5 times higher long-term risk of developing a second primary in contralateral breast. 138 Radiotherapy planning of the breast cancer has challenges in balancing delivery of adequate radiation dose to the breast and internal mammary chain (IMC) nodes with sparing of heart, lungs and contra lateral breast mainly due to large tissue in-homogeneity (22). There are several guidelines available for breast contouring like Radiotherapy Oncology Group (23) (RTOG), European Society for Radiotherapy and Oncology (24) (ESTRO) and Project on Cancer of the Breast (25) (PROCAB) guidelines. The planning target volume (PTV) with RTOG-1005 guidelines for intact breast or post modified radical mastectomy (MRM) chest wall is very irregular and with conventional 3 dimensional (3D) planning, it is not possible to conform the dose distribution to this shape. The Tangential Field in Field (TFIF) technique is often not able to achieve the desired coverage of the PTV, and ipsilateral lung and heart dose volume constraints are also violated. But Intensity Modulated (...truncated)