Results of the PROSPECT trial provide compelling evidence that high-quality preoperative MRI in combination with postoperative analysis of pathologic features can identify a substantial subset of women with localized early breast cancer who could safely skip radiation therapy.
(1%) at 5 years, reported lead investigator Gregory Bruce Mann, MBBS, PhD, of The Royal Women’s Hospital, Melbourne, Australia, at the San Antonio Breast Cancer Symposium (abstract PS02-03).
Additionally, women who skipped radiation had superior health-related quality of life relative to peers who underwent the treatment and, quite unexpectedly, their fear of cancer recurrence was “dramatically reduced,” Dr, Mann said in an interview.
“The hypothesis was that less treatment [would] lead to more fear of cancer recurrence” because patients would worry that they hadn’t received standard treatment, “but patients who omitted RT actually had less fear of cancer recurrence,” he said.
This may come down to positive perceptions about tailored care and trust, he explained. “If the patient got the impression that the doctor wasn’t worried about recurrence, then the patient wasn’t worried. If they trusted you and you had that relationship with the patient, they were less likely to experience a fear of recurrence.”
Results of the PROSPECT trial were published online on December 5 in The Lancet.
PROSPECT was a prospective, nonrandomized study that evaluated whether preoperative bilateral contrast-enhanced 3-Tesla breast MRI and postoperative tumor pathology could identify patients with “truly localized” disease who might feasibly skip radiation therapy after breast-conserving surgery.
The researchers hypothesised that radiation therapy reduces local recurrence risk by treating occult synchronous disease that has not been identified by conventional imaging techniques. Exclusion of such occult disease using preoperative MRI, in association with low-risk pathology, could define a group of patients with early breast cancer in whom radiation can be omitted without substantially compromising local recurrence rates.
Women aged 50 years or older with cT1N0 non–triple-negative breast cancer were eligible for the trial. Among 443 patients, preoperative MRI detected 61 malignant occult lesions separate from the index cancer in 48 patients (11%) of the total cohort.
Patients with apparently unifocal cancer had breast-conserving surgery and, if pT1N0 or N1mi, did not undergo radiation therapy (group 1: 201 women). Standard treatment including radiation therapy was offered to the others (group 2: 242 women). All women were recommended for systemic therapy. The primary endpoint was the ipsilateral invasive recurrence rate at 5 years, with follow-up to continue to 10 years.
At a median follow-up of 5.4 years, the ipsilateral invasive recurrence rate in group 1 was exceedingly low — just 1.0% (upper 95% CI, 5.4%) — with one local recurrence at 4.5 years and a second at 7.5 years. In group 2, local recurrence at 5 years was also low, at 1.7% (upper 95% CI, 6.1%).
The only case of distant metastasis in the entire cohort was genetically distinct from the index cancer.
Omitting radiation therapy led to better health-related quality of life and functional and cosmetic outcomes, and the women viewed not having radiation as highly acceptable and appropriate treatment, not undertreatment.
PROSPECT has defined a role for “very high quality” preoperative MRI in identifying patients who can be considered for deintensified treatment, Dr. Mann said.
The findings need to be replicated in multicenter, international trials, “and that’s what we are working on,” he added.