Cancer Treatment Today

Post mastectomy radiation of the left chest wall causes scatter radiation to the hear and left lung. IMRT refers to a technique of conformal radiation planning and delivery, in which non-uniform intensity beams produce unique radiation dose distributions that are designed to better target the lesion with better sparing of surrounding normal tissue than with conventional radiation therapy, thereby limiting side effects. IMRT also allows for dose escalation, when clinically appropriate, which can improve local control of a tumor.

The Ontario Evidence based review concluded that IMRT can be used if toxicity of external beam radiation is the concern but the evidence does not show improvement in treatment-related outcomes of freedom from contralateral breast cancer recurrence, clinical recurrence-free survival, or disease-specific survival. Authored by Dayes et la, it fudges the issue by stating the following:

•If acute toxic effects are the main outcomes of interest, then intensity-modulated radiation therapy (IMRT) is the recommended treatment option over tangential radiation therapy (TanRT) to patients undergoing adjuvant radiotherapy following breast-conserving surgery.
•If treatment-related outcomes are the main outcomes of interest, there is no evidence to support or refute a recommendation of IMRT over TanRT to patients undergoing adjuvant RT following breast-conserving surgery.

Special Report TEC Assessment from Blue Cross Blue Shield concluded: “Available data are insufficient to determine whether IMRT is superior to 3D-CRT for improving health outcomes of patients with breast or lung cancer.” It is superior to standard external beam radiation. More recently, NCCN 2012, on p. BINV-1 seems to accept IMRT for whole breast irradiation but not for post-lumpectomy or post-mastectomy irradiation. I must point out that the advantage of IMRT for whole breast radiation would seem to be smaller than post-mastectomy. However, this recommendation may be based on the interpretation of the available evidence, which is scant for the post-mastectomy setting. There are a few papers demonstrating an advantage in dose distribution for IMRT.

It comes down to this: IMRT causes less toxicity but it is not known whether this translates into better efficacy or prolonged survival. At least, it can be confidently stated that IMRT is supported by credible scientific evidence published in peer-reviewed medical literature generally recognized by the relevant medical community to be less toxic and that it is  clinically appropriate in terms of type, frequency, extent, site and duration and considered effective for the condition in question;

While it is logical that by further reducing treatment-related morbidity post-mastectomy, gains in survival will be realized, outcome studies are needed to validate these assumptions, and they have not been performed.

CE, Moody AM, Wilson CB, et al. Reduction of radiotherapy-induced late complications in early breast cancer: The role of intensity-modulated radiation therapy and partial breast irradiation. Part II – Radiotherapy strategies to reduce radiation-induced late effects. Clin Oncol. (R Coll Radiol). 2005; 17(2):98-110.

Bruce G. HafftyRobert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Cancer Institute of New Jersey, New Brunswick, NJ
Thomas A. BuchholzM.D. Anderson Cancer Center, Houston, TX
Beryl McCormick
Should Intensity-Modulated Radiation Therapy Be the Standard of Care in the Conservatively Managed Breast Cancer Patient?
Evidence-Based Series 21-3-2
The Role of IMRT in Breast Cancer
I. Dayes, R.B. Rumble, J. Bowen, P. Dixon, P. Warde,
and members of the IMRT Indications Expert Panel
A Quality Initiative of the
Program in Evidence-Based Care (PEBC), Cancer Care Ontario (CCO),
and the Radiation Treatment Program (RTP), CCO
Report Date: October 27, 2010

Bruce G. HafftyRobert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Cancer Institute of New Jersey, New Brunswick, NJ
Thomas A. BuchholzM.D. Anderson Cancer Center, Houston, TX. Should Intensity-Modulated Radiation Therapy Be the Standard of Care in the Conservatively Managed Breast Cancer Patient?
Beryl McCormick. JCO May 1, 2008 vol. 26 no. 13 2072-2074

Tony C S Woo , Jean-Philippe Pignol , Eileen Rakovitch , Toni Vu , Deanna Hicks , Peter O’brien , Kathleen Pritchard Body radiation exposure in breast cancer radiotherapy: impact of breast IMRT and virtual wedge compensation techniques. Int J Radiat Oncol Biol Phys. 2006 Jan 31;

ASTRO IMRT guidelines, 2011 http://www.acr.org/~/media/eabb986bc4ff4a78b53b001a059f27b3.pdf