Simultaneous integrated boost by Intensity Modulated Radiotherapy (SIB-IMRT) in patients undergoing breast conserving surgery – A clinical and dosimetric perspective

Abstract

Aim: To study feasibility of simultaneous integrated boost by intensity modulated radiotherapy (SIB-IMRT) in patients undergoing breast conserving surgery and its impact on cosmesis and dosimetry. Patients and methods: Between January 2014 and June 2017, all breast cancer patients fulfilling inclusion and exclusion criteria were enrolled in a prospective study conducted at a tertiary cancer centre in North India. All patients received adjuvant radiotherapy by simultaneous integrated boost technique following breast conserving surgery. Clinical information including patient and pathological characteristics, observed acute and chronic toxicities along with cosmesis using Harvard score were recorded and analysed. Univariate analysis and multivariate logistic regression analysis were performed for those variables which were found to be significant (p < 0.050) to study the influence of clinicopathological and dosimetric factors on toxicity and cosmetic outcome. Results: Maximum acute skin toxicity during treatment was Grade 0–1 in 68.2% and Grade 2–3 in 31.8% of cases, respectively. Fibrosis was the commonest late toxicity with ≥Grade II fibrosis being noted in 16.3% of cases. Assessment of global cosmesis at 12 months follow-up showed good/excellent cosmesis in 88.4% of cases. Mean age, tumor size and homogeneity index (HI) were the significant factors associated with fair or poor cosmetic outcome and ≥Grade 2 fibrosis on multivariate analysis. Telengectasia and breast edema were more frequent in patients with larger tumor size/GTV volume. There were 5 recurrences including 1 ipsilateral local breast tumor recurrence. Conclusion: SIB-IMRT is a dosimetrically feasible option in patients undergoing breast conserving surgery and provides good/excellent cosmetic outcome. Keywords: Breast conserving treatment, Lumpectomy cavity boost, SIB-IMRT, Harvard score, Cosmesis