Purpose:This study aims at comparing the treatment quality of breast conformal radiotherapy (CRT) with sequential boost to tumor bed against intensity-modulated radiation therapy (IMRT) with simultaneously integrated boost to tumor bed by analyzing their corresponding dosimetric and radiobiological metrics.
Subjects and Methods:This work includes 20 primary left-sided breast cancer patients (10 with superclavicular node involvement (SCV) and 10 without SCV). In total 20 CRT plans and 20 IMRT plans were created. In the CRT plans, the whole breast with or without SCV irradiation receives a dose of 50Gy in 25 fractions with a sequential boost to the tumour bed of 10Gy in 5 fractions. In the IMRT plans, the whole breast receives 50Gy and the tumor bed 60Gy in 25 fractions. Each plan was evaluated in terms of PTV coverage, primary tumour conformity index, maximum plan dose, ipsilateral lung dose (D mean , V 20Gy , V 10Gy , V 5Gy ), heart dose (D mean, D max , V 15Gy ), contralateral lung dose (V 5Gy ) contralateral breast dose (max, D 5% ) and spinal cord dose (D 0.03cc ). The tumor control and normal tissues complication probabilities (TCP and NTCP) were calculated for each plan.Results: IMRT created more conformal plans in all cases, (conformity index: CRT=0.35, IMRT=0.75 with SCV and CRT=0.33, IMRT=0.76 without SCV). CRT plans delivered higher heart V 15Gy (CRT=6.5%, IMRT=5.2% with SCV and CRT=1.6%, IMRT=0.7% without SCV). CRT plans delivered higher V 20Gy ipsilateral lung doses with SCV (CRT=15.0%, IMRT=12.8%). Also, IMRT plans delivered lower D 0.3cc spinal cord doses (CRT=17.3Gy, IMRT=7.1Gy with SCV and CRT=2.6Gy, IMRT=0.5Gy without SCV). The NTCP values of heart and ipsilateral lung were lower for IMRT (0.03% and 1.87%) than CRT (1.10% and 4.70%) with SCV, respectively.Conclusions: IMRT plans showed superior dose conformity, lower NTCP values and shorter treatment duration. Especially, when there is SCV node involvement, it should be considered as the treatment of choice.