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Partial-breast radiotherapy may spare women of ‘physical discomfort, emotional distress’
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Targeted partial-breast radiotherapy at reduced doses did not appear inferior to standard whole-breast radiotherapy for early-stage breast cancer, according to a randomized, phase 3 study published in The Lancet.
Partial-breast and reduced-dose radiotherapy also resulted in fewer adverse events.
“One of the challenges when treating early-stage breast cancer is trying to minimize the side effects that can have a real impact on a woman’s life, without affecting the chances of curing her,” Arnie Purushotham, MD, professor of breast cancer and director of King’s Health Partners Comprehensive Cancer Centre, who was not involved in the study, told HemOnc Today. “This approach could spare many women significant physical discomfort and emotional distress.”
The rate of relapse following breast conservation surgery and radiotherapy has fallen sharply in many countries where whole-breast radiotherapy is standard treatment. Guidelines allow partial-breast radiotherapy for selected women at low risk for recurrence based on age, small tumor size and early stage.
One challenge in treating women with early breast cancer, according to researchers, is to reduce the morbidity of radiotherapy without compromising its ability to cure the cancer.
“We started this trial because there was evidence that if someone’s cancer returns, it tends to do so close to the site of the original tumor, suggesting that some women receive unnecessary radiation to the whole breast,” Charlotte E. Coles, MD, honorary consultant in clinical oncology at University of Cambridge, said in a press release. “Now we have evidence to support the use of less, but equally effective radiotherapy for selected patients.”
Coles and colleagues of the IMPORT LOW trial recruited 2,016 women aged 50 years or older who had breast-conserving surgery for unifocal invasive ductal adenocarcinoma of any grade. Patients had tumor size of 3 cm or smaller (pT1-2), axillary node-negative disease or one to three positive nodes (pN0-1), and minimum microscopic margins of noncancerous tissue of 2 mm or larger.
Between May 3, 2007, and Oct. 5, 2010, researchers randomly assigned 674 women (median age 62 years; 90% grade 1 or 2) to the control group of 40 Gy whole-breast radiotherapy, 673 women (median age, 63 years; 89% grade 1 or 2) to the reduced-dose group of 36 Gy to the whole breast and 40 Gy to the partial breast, and 669 women (median age, 62 years; 91% grade 1 or 2) to the partial-breast group with 40 Gy to the partial breast only. Women received treatment from 30 radiotherapy centers in the United Kingdom in 15 daily treatment fractions.
Standard tangential beams delivered field-in-field intensity-modulated radiotherapy, which were reduced in length for the partial-breast group.
Ipsilateral local relapse served as the primary endpoint.
Median follow-up was 72.2 months (interquartile range, 61.7-83.2).
Researchers estimated 5-year local relapse cumulative incidence rates of 1.1% (95% CI, 0.5-2.3) in the control group, 0.2% (95% CI, 0.02-1.2) in the reduced-dose group and 0.5% (95% CI, 0.2-1.4) in the partial-breast group.
Compared with the control group, researchers estimated 5-year absolute differences in local relapse of –0.73% (95% CI, –0.99 to 0.22) for the reduced-dose group and –0.38% (95% CI, –0.84 to 0.9) for the partial-breast group. These data met criteria for noninferiority, with the critical HR at more than 2.03 (reduced-dose group, P = .003; partial-breast group, P = .016).
Adverse events appeared similar after reduced-dose or partial-breast radiotherapy according to photographic, patient and clinical assessments. Researchers observed significantly lower incidence of change in breast appearance in the partial-breast group (P = .007) and breast being harder or firmer in both groups (reduced-dose group, P = .002; partial-breast group, P < .0001) than in women treated with whole-breast radiotherapy.
“We’re delighted that the results of this trial have the potential to lead to a real change in the way selected [patients with breast cancer] are treated,” Judith Bliss, MD, study researcher and professor of clinical trials at The Institute of Cancer Research, said in a press release. “The technique used here can be carried out on standard radiotherapy machines, so we anticipate these results will lead to further uptake of this treatment at centers across [the UK] and worldwide.”
The most striking finding of the IMPORT LOW trial might be the extremely low absolute recurrence rates observed across all groups, which appeared markedly lower than in previous trials, Reshma Jagsi, MD, DPhil, associate professor and deputy chair of radiation oncology at University of Michigan Medical School, wrote in an accompanying editorial.
“Although previous trials have not identified a subgroup of women in whom adjuvant radiotherapy might safely be omitted altogether — with the exception of older women with small hormone-sensitive tumors — the remarkably low recurrence rates observed in this trial prompt yet again the question of whether some other patients might also reasonably omit radiotherapy,” Jagsi wrote.
Although longer follow-up is needed, particularly for patients with favorable disease who may experience late recurrence, the findings of IMPORT LOW support ongoing efforts to establish whether improvements in areas such as imaging, pathology, surgery and systemic therapy might render adjuvant radiotherapy immediately after breast-conserving surgery to be optional for an even larger, identifiable subgroup of women.
“Future generations of women diagnosed with breast cancer will benefit not only from the findings of the IMPORT LOW trial itself, but also from the advances that will build on its foundational efforts,” Jagsi wrote. – by Chuck Gormley
For more information:
Arnie Purushotham, MD, can be reached at arnie.purushotham@kcl.ac.uk,
Disclosures: Coles, Bliss and the other study authors report no relevant financial disclosures. Jagsi reports grants from the NIH, the Doris Duke Foundation and the Greenwall Foundation. Purushotham reports no relevant financial disclosures.
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