Breast cancer patients reported fewer moderate or marked side effects if they were treated with radiotherapy to part of the breast or a reduced dose to the whole breast, according to new findings from a major study presented at the 11th European Breast Cancer Conference.

The IMPORT LOW study of 2,016 women in 41 centers in the UK has already shown that partial-breast and reduced-dose radiotherapy was as effective as whole breast radiotherapy in controlling the cancer at 5 years, and women in the partial-breast and reduced-dose groups reported fewer side effects, including less change in the appearance of the breast.

These latest results, which focus predominantly on side effects affecting the breast and also body image reported during the 5 years following radiotherapy, show that over half of patients in the study did not report moderate or marked side effects at any point and that most side effects reduced over time.

The number of side effects reported per person were fewer in the partial-breast and reduced-dose groups compared with the whole-breast radiotherapy group.

The IMPORT LOW trial was coordinated by the Clinical Trials and Statistics Unit at The Institute of Cancer Research, London, and funded by Cancer Research UK.

Simple to deliver and available worldwide

Professor Judith Bliss, director of the ICR-CTSU co-leads the trial with Dr. Charlotte Coles, from the University of Cambridge and Addenbrookes Hospital, who is the chief investigator of the trial. Professor John Yarnold at the ICR was the previous chief investigator between 2008 and 2013.

Dr. Indrani Bhattacharya, a Clinical Research Fellow at the ICR, told the conference:

“The findings from this study are reassuring for women who are offered either whole-breast or partial-breast radiotherapy using this technique of radiotherapy, which is simple to deliver and already available in centers worldwide.”

“This new information will help doctors discuss the risks and benefits of this type of radiotherapy with patients and may improve shared decision-making, as well as enabling them to tailor treatment for individual patients.”

Reduced dose vs partial breast

The IMPORT LOW study randomized women to receive standard radiotherapy at a dose of 40 Gy to the whole breast (the control group), or 36 Gy to the whole breast and 40 Gy to the part of the breast that contained the original tumor (reduced-dose group), or 40 Gy only to the site of the original tumor (partial-breast group).

The radiotherapy was given using hypofractionated intensity modulated radiotherapy (IMRT)—a technique that can deliver an even dose of radiation, minimizing the chances of hotspots of unwanted high doses and reducing the cosmetic problems that can occur after breast radiotherapy.

More than half of the women (1,265) took part in the sub-study that looked at patient-reported outcomes (PROMs).

Side effects measured for up to 5 years

The women were asked about adverse side effects, such as a hardening of tissue, pain, over-sensitivity of the treated area, and build-up of fluid, at the start of the study, after 6 months, and 1, 2, and 5 years after radiotherapy.

Most of the side effects reported by the women related to changes affecting the breast, and the commonest reported side effect was “overall change in breast appearance”.

The researchers found that women were more likely to report adverse side effects if they were younger, had larger breasts, had a larger volume of breast tissue removed at surgery, if the cancer had spread to any of their lymph nodes, and if, at the start of the study, they were feeling anxious or depressed.

Reassurance of the low risk of side effects

Commenting on the potential impact of these findings, Dr. Bhattacharya said:

“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.”

“For example, patients with higher levels of anxiety and depression could be offered psychosocial support at the start of treatment, although we do not know from this study whether this would reduce the reporting of side effects.”

“We have previously reported that partial-breast radiotherapy is as effective as whole breast radiotherapy with similar or fewer side effects over 5 years and can be safely delivered in a selected group of patients with low-risk breast cancers.”

“This new analysis shows that patients requiring whole-breast radiotherapy can be reassured about the low risk of side effects affecting the breast and body image.

“The technique of radiotherapy used in IMPORT LOW is easy to implement and deliver as the equipment and expertise is available in all centers worldwide.”