A controversial study on breast brachytherapy (APBI) presented last week at the San Antionio Breast Cancer Symposium has prompted deep concern among APBI experts. They worry that breast cancer patients who are good candidates for APBI modalities such as SAVI, MammoSite and IORT will be scared off the therapy, by what the experts say is an inaccurate and misleading study.
Below are statements by three of these internationally know experts, prepared for a Dec. 13, 2011 teleconference they organized to challenge the study findings.
“Shortcomings of the New Study on Breast Cancer
Brachytherapy (APBI): What Women Need to Know Now”
Robert Kuske, MD, FAACE:
— Co-Principal Investigator, NSABP B-39 study comparing five-day APBI to six-week whole breast irradiation.
Partial breast irradiation (PBI) was begun in New Orleans in 1991 by myself and colleagues at the Ochsner Clinic, and has been one of the most studied treatments for breast cancer over the past 20 years. Numerous publications have shown PBI to be safe and effective for select early stage breast cancer patients. As a result of promising phase 2 clinical trials and two favorable randomized prospective clinical trials (scientifically the “Gold Standard”), there has been growing interest in using PBI. Accelerated PBI (APBI) treats only the part of the breast affected by cancer and the treatment time is decreased from several weeks to four or five days. For decades, whole-breast irradiation (WBI), where radiation is delivered every day for five to eight weeks, has been the standard treatment for patients with early breast cancer treated with breast conserving surgery.
APBI has several benefits, including a decreased overall treatment time and a decrease in the radiation delivered to healthy tissue and adjacent organs. To document its long-term safety and effectiveness compared to WBI, we await the results of the other 7 randomized trials comparing APBI with WBI.
I am concerned about the potential misinterpretation of data presented last week at the 2011 CTRC-AACR San Antonio Breast Cancer Symposium regarding breast cancer patients who received brachytherapy, or accelerated partial breast irradiation (APBI). These data have serious limitations, and should not influence current treatment recommendations for women with early stage breast cancer fitting current eligibility criteria for PBI.
This study, based on Medicare claims data, demonstrated a small 1.8% increase in the rate of mastectomies in patients treated with APBI compared with those treated with conventional whole breast external beam irradiation. Note that the rate of documented recurrences of breast cancer after treatment is not reported. In either case the rate of mastectomy is still very low (2.2 to 4%), and should be contrasted with the 35 to 40% recurrence rate after lumpectomy without any radiotherapy.
The data presented in San Antonio was drawn from records of patients varying risk factors and stage treated between 2000 and 2007. Doctors choose treatments for their patients based on cancer extent, grade, surgical margins, and other factors such as obesity, diabetes, and age. This study failed to take these important tumor and patient issues into account, and is therefore biased. This study is a good example of why it is important to be selective in choosing which patients receive the accelerated treatment.
The PBI treatment given in this study is an antiquated balloon catheter with a single channel. Since that time, technology has dramatically improved including the use of newer multichannel applicators with tighter dose constraints. The side effects and toxicity seen with these modern technological advances are far better than the results presented in this study.
This study should encourage enrollment in clinical trials, especially NSABP B-39/RTOG 0413, a National Cancer Institute-sponsored, randomized prospective phase 3 trial. In the meantime, doctors and patients should not limit their options, and should continue to consider a 5-day alternative to conventional 6-7 weeks of whole breast irradiation to conserve the breast.
Peter Beitsch, MD, FACS:
— Co-Principal Investigator of the American Society of Breast Surgeons’ MammoSite Registry.
The study presented by at the San Antonio Breast Cancer Symposium has garnered a tremendous amount of print and Internet media attention. After reading the abstract (paper not in press yet), seeing the talk live in San Antonio, and discussing the study with many colleagues in breast surgery and radiation oncology, I want to try to clarify the data on APBI, and discuss the “information” in the abstract and the hyperbole in the lay press that is distressing our patients.
First and unequivocally, accelerated partial breast irradiation is a safe and effective form of treating the breast after appropriately performed lumpectomy in patients over age 45-50 with early-stage invasive (typically <3cm primaries and lymph node negative) and non-invasive breast cancer. Numerous retrospective studies and two prospective randomized studies (the gold standard) have shown no difference in survival, local-regional cancer recurrence rates and complications between APBI and whole breast irradiation (WBI). The American Society of Breast Surgeons’ MammoSite Registry has published more than 16 papers showing the safety and efficacy (comparable to WBI) of MammoSite APBI.
The San Antonio abstract and presentation were drawn from the Medicare claims-SEER database, which is a large database with cancer-patient data linked to Medicare claims data. The database is managed by the National Cancer Institute and sold to institutions to do research. The linked database has information about cancer type and treatments, but it has no specific data on margin status, prognostic factors such as estrogen receptor/progesterone receptor (ER/PR) and HER2/Neu receptor — or even local, regional or distant recurrence.
The study stated that “subsequent mastectomy” is a “validated surrogate for local failure,” but I am unaware of any literature that states this. The “two-fold increased risk for subsequent mastectomy” is misleading and inaccurate. (It s 4.0% for APBI vs. 2.2% for WBI in their study). Both of these rates are quite small, and it is questionable whether there is any clinical significance between the two. Not emphasized but equally important are the overall survival rates for APBI vs. WBI, which were equivalent.
The study also stated that infections were higher for APBI (not surprising since it involves the insertion of one or more catheters in the breast), but there is no statement regarding severity (were the APBI patients just placed on prophylactic antibiotics and is that how an infection was defined?). Fat necrosis and breast pain were also significantly higher in the APBI group, although there is absolutely no uniform definition of what fat necrosis is nor a statement about the severity of the fat necrosis or breast pain.
Lastly, the researchers state there was a 9.6% hospitalization rate for APBI patients vs. 5.7% for WBI patients. This is puzzling since no diagnosis was given for hospitalization nor was there information on the time period over which patients were hospitalized. Was hospitalization APBI-related (doubtful) or related to first chemotherapy cycle (perhaps) or other unrelated health issues? (It’s worth noting that APBI is often used in older, sicker patients who may not be candidates for six to seven weeks of WBI).
In summary, this retrospective study of an inherently inaccurate database (no data on tumor characteristics and margin status — both known to be significant determiners of local recurrence), with questionable outcomes (admission rate) and non-validated “surrogate endpoints” (subsequent mastectomy=local recurrence) should be looked at with appropriate skepticism in the face of 20 years of retrospective studies and two prospective randomized trials to the contrary.
Jayant Vaidya, MD:
— Pioneer of targeted intraoperative radiotherapy (IORT).
We have performed a prospective randomized phase III trial, which is considered the highest level of scientific evidence.
We have shown with the TARGIT approach (risk-adapted partial breast radiotherapy with a single dose of radiotherapy during breast conserving surgery) that the local recurrence rate is very low (about 1% after 4 years). This rate is non-inferior to the standard approach, which was used in half of the more than 2000 patients.
This supports the concept of PBI in selected (e.g., older) patients with small tumors.
Also important was that the toxicity was not higher with the new approach. The rates of clinically relevant toxicity were about 3% in both treatment arms. Toxicity is highly dependent on how radiation is delivered, i.e. treatment device, dose, dose rate, fractionation and target volume concept.
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