Partial Breast Irradiation

The study presented by Dr. Grace Smith at the San Antonio Breast Cancer Symposium entitled Partial Breast Brachytherapy is Associated with Inferior Effectiveness and Increased Toxicity Compared with Whole Breast Irradiation in Older Patients 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 the breast surgery and radiation oncology fields, it has become necessary to try to clarify the data on APBI, discuss the 'information' in the abstract and the hyperbole in the lay press that is distressing our patients.

First and unequivocally, Acellerated 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 2 prospective randomized (the gold standard) studies have shown no difference in survival, local-regional recurrence rates or complications between APBI and Whole Breast Irradiation (WBI). The American Society of Breast Surgeons Mammosite Registry has published more than 16 papes showing the safety and efficacy (comparable to WBI) of Mammosite APBI.

The abstract and presentation is 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 NCI and sold to institutions to do research. The linked database has information about cancer type and treatments but no specific data on margin status, prognostic factors such as ER/PR and Her2Neu, or even local, regional or distant recurrence. The study stated that 'subsequent mastectomy' is a 'validated surrogate for local failure' although 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 Whole Breast Irradiation in their study). Both of these rates are quite small and questionable whether there is any clinical significance between the two. Not emphasized but equally (?more) important is the overall survival rates 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 antiobiotics and that is 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 or the fat necrosis or breast pain. Lastly, they state there was a 9.6% hospitalization rate for APBI patients vs 5.7% for WBI patients. This is quizzical since no diagnosis was given for hospitalization nor the time period over which they were hospitalized (was it APBI related[doubtful] or related to first chemotherapy cycle [perhaps] or other unrelated health issues [APBI often used in older, sicker patients who may not be candidates for 6-7 weeks of WBI]). In summary, this retrospective study of an inherently inacurate (no data on tumor characteristics and margin status - both known to be significant determiners of local recurrence) database 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 2 prospective randomized trial to the contrary.
Thanks for the question! The San Antonio Breast Cancer Symposium is one of the largest and most prestigious breast cancer conferences, and often exciting and innovative research is presented. However at the recent meeting, a study was presented by a group from MD Anderson, questioning the safety and effectiveness of accelerated partial breast irradiation (APBI) for early-stage breast cancer - specifically they noted that patients undergoing this treatment have a higher rate of complications and eventual mastectomy. Unfortunately before the study was even presented, it received national media attention, leading to significant anxiety and confusion among women. This stresses the importance of reading the study, not just listening to the sound bite - here are some facts:
- The study used retrospective (after the fact) "claims data" to do their evaluation. That means they took Medicare billing information, not actual patient data, and drew some conclusions. It is NOT possible to accurately determine complication rates from claims data as they are not always reported. It is also not possible (and the authors admitted this) to determine why the women treated with APBI subsequently underwent mastectomy - it could have been for an entirely different cancer, even one in the other breast!
- The absolute increased risk of mastectomy was 1.8% which is quite low, and again we have no way to know why the women underwent mastectomy
- APBI has been the subject of multiple prospective (going-forward) and peer-reviewed studies, and has been shown to have an equivalent or in some cases better rate of breast cancer control compared to whole-breast irradiation; the complication rate is also equivalent.

3 respected professional medical societies published responses critical of the MD Anderson study, and I expect more criticism will come. The responses are from the American Society of Breast Surgeons: https://www.breastsurgeons.org/news/article.php?id=122, the American Brachytherapy Society: http://campaign.r20.constantcontact.com/render?llr=kdofiegab&v=001rj64Pj8NTf4ISgwN4cSdZYtZBR53GjAi73j4En_qeygPzWmSUe1qgGI7U-jt8HRV7NouL9sMViv1IOOeGT2QHMAaDWrfEuOApREAHj-8Z60%3D and the American Society for Radiation Oncology: https://astro.org/News-and-Media/News-Releases/2011/ASTRO--APBI-safe,-effective-for-some-breast-cancer-patients.aspx

It is again unfortunate that this poorly designed study with no real valid clinical data was allowed to be presented at such a prestigious meeting, and that it received immense national media attention before the scientific community was allowed to interpret the study and respond. I am hopeful that this will not happen in the future, as many women (and many physicians) were caused unnecessary anxiety regarding their breast cancer treatment options.

There are currently two ways to do Accelerated Partial Breast Irradiation: AccuBoost (a precise form of high dose rate (HDR) brachytherapy done as part of a protocol or off-label use. It can be done twice a day for 5 days, or once daily for 10 consecutive days. The other form is done via external beam radiation therapy, typically intensity modulated radiation therapy, or IMRT. There are currently two ways to do Accelerated Partial Breast Irradiation: AccuBoost (a precise form of high dose rate (HDR) brachytherapy done as part of a protocol or off-label use. It can be done twice a day for 5 days, or once daily for 10 consecutive days. The other form is done via external beam radiation therapy, typically intensity modulated radiation therapy, or IMRT.

Partial breast techniques include: AccuBoost (as protocol or off-label) non-invasive high dose rate (HDR) brachytherapy technique, balloon-based invasive HDR: MammoSite, Contura, Savi, and external beam radiation therapy. Partial breast techniques include: AccuBoost (as protocol or off-label) non-invasive high dose rate (HDR) brachytherapy technique, balloon-based invasive HDR: MammoSite, Contura, Savi, and external beam radiation therapy.