IMRT appears safe, effective at 5-year follow-up in early-stage breast cancer

Intensity-modulated radiotherapy appeared associated with good local control and few side effects in women with early-stage breast cancer at 5-year follow-up, according to first results of the phase 3 IMPORT LOW trial presented at the 10th European Breast Cancer Conference.

“We hope that the evidence of benefit we have shown in this trial will bring about a change in practice worldwide, and enable very many more women with early breast cancer to undergo this treatment,” Charlotte Coles, MD, consultant clinical oncologist at Cambridge University Hospitals NHS Trust, in Cambridge, UK, said in a press release. “At a time when breast cancer mortality rates are falling and more women are surviving their cancer, we believe it is particularly important to keep any treatment toxicity to the absolute minimum.”

Radiotherapy to the whole breast is standard after breast-conserving surgery for early-stage breast cancer; however, this treatment can cause physical changes and psychological distress.

Intensity-modulated radiotherapy (IMRT) delivers an even dose of radiation to the tumor bed, minimizing areas of unwanted high-dose radiation and reducing the risk for cosmetic problems.

Coles and colleagues evaluated the use of partial-breast radiotherapy using IMRT in 2,018 women (median age, 63 years; interquartile range, 58-68) who underwent breast-conserving surgery for invasive adenocarcinoma to assess whether full-dose radiotherapy to the whole breast is necessary in patients with low-risk early breast cancer. Forty-three percent of tumors were grade 1, 47% were grade 2 and 10% were grade 3.

Researchers randomly assigned women 1:1:1 to whole-breast radiotherapy at standard 40-Gy dose to the whole breast (controls; n = 675), 40 Gy radiotherapy to the tumor bed and 36 Gy to the rest of the breast (n = 674) or 40 Gy to the tumor bed only (n = 669).

Local tumor control in the ipsilateral breast served as the primary endpoint. Secondary outcomes included late adverse effects measured with a combination of clinical, photographic and patient self-assessments.

After a median follow-up of 68.3 months, the rates for local recurrence were 1.1% (95%CI, 0.5-2.3) in the control arm, 0.2% (95%CI, 0.02-1.2) in women assigned 40 Gy radiotherapy to the tumor bed and 36 Gy to the rest of the breast, and 0.5% (95%CI, 0.2-1.4) among women assigned 40 Gy to the tumor bed only.

When compared with controls, the absolute treatment difference in local recurrence for women assigned radiotherapy at 40 Gy to the tumor bed and 36 Gy to the rest of the breast was –0.83% (95%CI, –1.04 to 0.18). The difference was –0.69% (95% CI, –0.99 to 0.44) among women in the control arm vs. those assigned 40 Gy to the tumor bed only.

A significantly smaller proportion of women assigned 40 Gy radiation to the tumor bed only reported marked (4% vs. 7%) and moderate (11% vs. 20%; P = .005 for both) changes in appearance of the breast.

“Five years after treatment, we found very low rates of local recurrence and minimal side effects across all the groups,” Coles said in the release. “We also found evidence of benefit to patients in the 'test' groups in terms of satisfaction with overall breast appearance as reported by patients themselves, particularly for those receiving no radiotherapy outside of the tumor bed. However, we intend to continue to follow up the trial patients for at least 10 years because we know that cancer recurrence can still occur more than 5 years after completion of treatment.” – by Jennifer Southall

Reference:

Coles C, et al. Abstract 4LBA. Presented at: 10th European Breast Cancer Conference; March 9-11, 2016; Amsterdam.

Disclosure: The researchers report no relevant financial disclosures.