Intensity-modulated radiation therapy with simultaneously integrated boost leads to shorter treatment time with similar outcomes as conventional radiotherapy after surgery for breast cancer

This study compared the effects of intensity-modulated radiation therapy (IMRT) with a simultaneously integrated boost (SIB) to conventional radiotherapy (CRT) with a sequential boost (SeqB) following breast-conserving surgery (BCS) in patients with breast cancer. The data showed that both radiotherapy techniques led to similar outcomes, while IMRT-SIB shortens treatment times.

BCS involves the removal of the tumor only, with the preservation of the breast. Radiation therapy (RT) is commonly used following BCS to destroy any remaining cancer cells. After the RT, an extra radiation dose is delivered to the place where the tumor was to prevent the recurrence of cancer. This is called a sequential RT boost (SeqB). However, recent evidence showed that the boos can also be given at the same time as the RT treatment. This is called a simultaneously integrated boost (SIB).

Conventional RT also affects healthy tissues surrounding the tumor. This leads to side effects, even years after treatment. IMRT is a type of RT where the radiation is aimed directly at the tumor from different directions. This way healthy tissues/organs are preserved it causes fewer side effects. This can help improve a patient’s quality of life.

IMRT with SIB is thought to reduce the length of treatment time after BCS while reducing the risk of complications. However, whether IMRT-SIB after BCS leads to similar outcomes compared to CRT-SeqB in patients with breast cancer remains unclear. 

This study involved 502 patients with breast cancer. These patients previously underwent BCS and were recommended RT. Patients were randomly put in 2 groups. Group 1 included patients who received IMRT-SIB. Group 2 included those who received CRT-SeqB. The average follow-up time was 5.1 years.

After 2 years, 99.6% in both groups had local control (the cancer does not grow or progress). The cosmetic evaluation (the physical aspect of the breast after treatment including skin retraction, size, shape of the breast) also showed similar outcomes between groups after both 6 months and 2 years. 

After 2 years, 99.6% of the patients in each group were alive. 

This study showed that IMRT-SIB led to similar outcomes compared to CRT-SeqB in patients with breast cancer who had BCS while reducing the total treatment time. 

The follow-up period was rather short to fully evaluate long-term complications. IMRT involves more radiation beams than CRT and this may lead to second cancers which could not be evaluated in this study.