Compared to sequential conventional fractionation schedule, Simultaneous integrated Boost provides increased dose homogeneity, with less unintended excessive dose outside the boost area; in combination with a higher dose per fraction to the tumour bed, resulting in a shorter overall treatment time spanning over 5 1⁄2 weeks. We compared cosmesis using the Harvard cosmesis scale and dosimetry of SIB IMRT versus sequential electron boost in breast cancer patients.
Patients in our Institute who have undergone breast-conserving surgery and received adjuvant chemotherapy, who are referred for adjuvant radiotherapy. The study period spanned from 1st May 2016 to 31st March 2018.
The baseline Harvard score for grading breast cosmesis in both the arms was excellent (84% in SIB and 81% in SEB) or good(16% in SIB and 19% in SEB). None of the patients in either arm had fair or poor cosmesis. Assessment of cosmesis at the end of radiation therapy showed a dip from excellent to good and fair in both the arms ( 34% versus 9% with excellent cosmesis, 53% versus 72% with good cosmesis and 13% versus 19% with poor cosmesis in SIB versus SEB arms) but the patients in the SEB arm had comparatively much lower cosmetic score. However, this difference was not statistically significant(p=0.045). Overall cosmesis at the end of 3 months was better in SIB arm compared to that of the SEB arm and was statistically significant (93% with excellent and good cosmesis in SIB vs 65% in SEB p<0.001). At 6 months of follow-up in SIB arm, there was an improvement of the cosmesis with a majority of the patients showing excellent(59%) and good (34%) cosmetic score.
In a selected cohort of patients who have undergone breast conservation surgery, a simultaneous integrated boost along with WBI is considered equivalent radiobiological to sequential electron boost after WBI. This study reports better cosmetic outcomes and favourable toxicity profile with SIB compared to SEB over short-term follow-up which is statistically significant.
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All authors have declared no conflicts of interest.