Fewer adverse events with reduced dose, partial radiation for low-risk breast cancer
Women with invasive breast cancer who received hypofractionated intensity modulated radiotherapy (IMRT) at a reduced dose or to only the tumour site (partial radiation) were less likely to report adverse events (AEs) than those who received standard dose IMRT to the whole breast, according to findings of the phase III, UK-based IMPORT LOW* trial.
Study participants were 2,016 women aged ≥50 years with invasive ductal carcinoma (grade 1–3, primary tumour size ≤3 cm, axillary lymph node metastasis [pN0–1]) who had undergone breast conservation surgery with resection margins of ≥2 mm. They were randomized to receive IMRT at either the standard dose to the whole breast (40 Gy; control group), reduced dose to the whole breast (36 Gy) plus standard dose to the partial breast (40 Gy), or standard dose to the partial breast (40 Gy). Treatments were administered as 15 daily fractions. The results were based on the analysis of 1,265 women who provided patient-reported outcomes at 6 months, 1, 2, and 5 years after receiving therapy.
The number of AEs reported decreased with time with significantly fewer reports among women who received reduced dose or partial breast radiation compared with those who received standard dose radiation to the entire breast (p<0.001). [EBCC 2018, abstract 3]
Younger women, those with larger breasts, those with lymph node metastasis, those with a larger amount of breast tissue excised during surgery, and those who experienced anxiety or depression at study onset were more likely to report AEs (p<0.001).
Women who received a reduced dose of radiation or partial breast radiation reported a reduction in induration, pain in the arm or shoulder, oedema, oversensitivity, and changes in appearance of skin of the breast over time (p<0.001).
“Now that we can identify these patients who are at higher risk of reporting side effects, this knowledge can be discussed with patients, may modify treatment, and enable doctors to put in place more personalized and frequent monitoring if necessary,” said Dr Indrani Bhattacharya from the Institute of Cancer Research in London, England, who presented the findings at EBCC 2018.
“For example, patients with higher levels of anxiety and depression could be offered psychosocial support at the start of treatment,” she said, cautioning that it remains to be seen whether this reduces AE reporting.
While AE incidence was associated with reduced quality of life at 5 years, there were no significant differences in overall quality of life between the treatment groups.
Together with previous results of the IMPORT LOW trial which demonstrated noninferiority of the reduced dose and partial breast IMRT regimens compared with standard dose whole breast IMRT in preventing local relapse in low-risk breast cancer, [Lancet 2017;390:1048-1060] these findings add to the knowledge of the risks and benefits of IMRT and position this method as a potential treatment option for certain low-risk patients, said Bhattacharya.
“Patient-reported outcomes are among the most important factors that we have added to assessments of outcomes in breast cancer in recent years,” said EBCC 2018 co-chair, Professor Isabel Rubio from Clinica Universidad de Navarra, Spain, who was not involved in the study.
“These latest results from the IMPORT LOW trial provide important and reassuring information for clinicians and patients about side effects after partial or reduced dose radiotherapy, and will help them to make the best choices in each individual case,” she said.