(RxWiki News) After breast conserving surgery, radiation therapy is given to reduce the chances of the breast cancer returning. External beam radiation therapy (EBRT) is the standard therapy and it is performed over multiple sessions, typically daily for four to five weeks.
Two recently published studies looked at two forms of single-dose radiation techniques given at the time of surgery or shortly thereafter.
One of the methods — TARGIT — resulted in slightly higher breast cancer recurrence (return) rates than traditional EBRT, which beams intense X-ray energy to the entire breast. However, the women who received TARGIT had higher overall survival rates than women who got EBRT.
The second method — ELIOT — uses electrons to target the tumor site in a single dose. Recurrence rates were higher in the women who received ELIOT than in women who underwent EBRT. Overall survival, though, was similar among both groups.
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For the first study, Professor Michael Baum and Professor Jayant Vaidya, of University College London in the UK, led an international team of researchers to compare the performance of TARGIT, in which radiation is delivered with a miniature X-ray device, and EBRT therapy given over a three to six-week period.
A total of 1,721 women received the TARGIT treatment, and 1,730 women received EBRT during the 12-year study.
Two trials were performed during the study, with one group of 1,140 women receiving TARGIT at the time of their lumpectomy (removal of the tumor and surrounding tissue) and another group of 1,158 participants receiving EBRT.
After requests from clinicians, additional women were added to the study, 562 of whom had EBRT, and 581 of whom received TARGIT an average five weeks after surgery.
Some women at high risk of cancer recurrence received both radiation therapies.
After five years, the risk of recurrence in the TARGIT group was 3.3 percent, compared to 1.3 percent in the EBRT group.
The researchers had determined at the start of the trial that if the recurrence rates were within 2.5 percent, then the TARGIT should be considered as good as (non-inferior) standard EBRT. This metric was achieved.
At five years, fewer deaths from all causes occurred in TARGIT group than in the EBRT group — 3.9 percent versus 5.3 percent.
The survival difference was seen in fewer cardiovascular-related deaths and deaths caused by other cancers, the researchers reported.
When TARGIT was given during the lumpectomy surgery, local recurrence was similar between the groups, but overall survival was significantly lower in the TARGIT group — 1.3 percent versus 4.4 for EBRT.
Breast cancer-specific survival (deaths caused by breast cancer) were the same for both groups.
Dr. Vaidya said of the results, “Our research supports the use of TARGIT concurrent with lumpectomy, provided patients are selected carefully, and should allow patients and their clinicians to make a more informed choice about individualising their treatment, saving time, money, breasts, and lives."
The second trial was led Professor Umberto Veronesi, of the European Institute of Oncology in Milan, Italy, and compared electron intraoperative radiotherapy (ELIOT) with standard EBRT.
A total of 1,305 women between the ages of 48 and 75 were enrolled from the European Institute of Oncology in Milan.
Half of the women received ELIOT (651) and half (654) under EBRT after lumpectomy.
Researchers compared the rates of local recurrence, where the breast cancer returns to the same site as the original tumor, and ipsilateral recurrence, in which the cancer returns to the same breast.
Higher recurrence rates — both local (2.5 percent) and ipsilateral (4.4 percent) — were seen in the ELIOT group after five years than in the EBRT group, 0.4 percent of whom experienced any recurrence.
Upon examination, the researchers found that the tumors that returned were larger than 2 cm and were estrogen-receptor negative, meaning that the hormone estrogen did not fuel the breast cancer.
Cancer specific-mortality and all-cause mortality rates were similar between the groups, the researchers found.
“Unfortunately, these two studies add little to the scientific question as to whether or not single-fraction intraoperative radiation therapy is adequate treatment in some patients," Frank Vicini, MD, FACR, radiation oncologist at 21st Century Oncology in Royal Oak, MI, told dailyRx News.
"The techniques utilized in both trials cannot establish formally whether or not an effective dose of radiation was delivered to the target tissues at risk. As a result, it's impossible to determine (1) that a sufficient dose of radiation was delivered to the area that requires it, (2) if results are due to the treatment delivered or merely to the selection of very low risk patients who may not require radiation at all, and/or (3) whether or not partial breast irradiation (i.e., confining the radiation only to the tumor bed region) is as effective as whole breast irradiation," Dr. Vicini said.
"Fortunately, this last question will be answered by ongoing phase III trials within the next few years. Until then, these results cannot be used to suggest that a change in the current standard of care is warranted and that single-fraction intraoperative radiation therapy should still be considered investigational,” Dr. Vicini said.
Both studies were published November 10. The TARGIT study appeared in The Lancet, and the ELIOT trial was published in The Lancet Oncology.
The TARGIT research was funded by the University College London Hospitals (UCLH)/UCL Comprehensive Biomedical Research Centre, UCLH Charities, National Institute for Health Research Health Technology Assessment programme, Ninewells Cancer Campaign, National Health and Medical Research Council and the German Federal Ministry of Education and Research.
Several of the authors of the TARGIT study reported having various types of financial relationships with Carl Zeiss and other commercial entities.
The ELIOT trial was funded by the Italian Association for Cancer Research, Jacqueline Seroussi Memorial Foundation for Cancer Research and Umberto Veronesi Foundation. No conflicts of interest were reported.