Clips. First We Pleaded for Them. Now, Not So Much: A Radiation Oncologist’s Perspective
Henry J. Lee, M.D.,PhD
Department of Radiation Oncology
NYP Lawrence Hospital/Columbia University
Bronxville/New York, NY
It’s always been distressing to explain to surgeons that their meticulously placed lumpectomy clips are much less useful to radiation oncologists than they originally perceived. Maybe it’s because of the desperate appreciation that radiation oncologists express when even one clip is left behind. In this current era of de-escalating therapies, patients receiving breast radiation therapy, especially a boost, are known to have the very highest risk of local failure. In other words: if there’s a group that needs their radiation therapy to be accurately delivered to the operative bed, it’s today’s patients. Accurately is the operative word, yet study after study evaluating clips as markers concludes they are inaccurate in depicting the precise location of the tumor site. It bears mentioning that clips improve only consistency among observers in drawing a boost target, but clip-based targeting is known to be inaccurate.
Since few surgeons have labored in the arcane world of radiation oncology, perhaps an everyday analogy might help in understanding our predicament to accurately deliver radiation therapy to a missing or suboptimal target. Consider 3 clips left for a radiation oncologist for postoperative radiation image planning and treatment. Now imagine instead if a surgeon relied on 3 calcifications on mammography or tomosynthesis as a guide while performing a tight lumpectomy. However, in this scenario, the surgeon would have no wire, tactile feedback, sonography, or architectural distortion. Just 3 measly calcifications on a series of 2D mammographic images and a favorite diathermy device.
It’s hard enough with a wire and all the normal guides to do a good lumpectomy. It’s almost impossible to accurately remove a 3D tumor using limited 2D information from a few points. Now imagine if someone didn’t leave a localization wire for you to follow but instead was kind enough to spiral or wind a filament around the outside edges of the entire tumor. You’d be able to easily follow that continuous filament around the tumor, dissecting in its entirety with an appropriate margin. While I realize that surgeons don’t need that level of hand-holding, radiation oncologists certainly wouldn’t mind it. And what if the knowledge gleaned from the preop imaging could be combined with the surgeon’s intraop observations to localize the tumor bed in the most accurate way possible for the radiation oncologist? That’s the point of VeraForm®, a 3D, continuous, multi-planar radiopaque filament marker that allows the radiation oncologist to follow the radiopaque track completely around the tumor bed precisely because it is continuous. What’s further unique is that our treatment planning systems enable computers to automatically follow the VeraForm filament around a tumor bed, generating a continuous contour in only a few seconds. What’s created is a cage that accurately delineates the tumor bed as defined by the surgeon, not imagined by the radiation oncologist.
Going back to clips, remember that each clip represents only a single point at the tumor bed and thus requires the radiation oncologist to interpolate the space between clips, somehow re-creating the location and shape of the original tumor bed. Geometrically, it’s an incredibly difficult task since it’s using just a few points. Clips create only a 2D-plane/area, not a 3D-structure or volume designed to be the target of an XRT boost or APBI. Incidentally, it’s the number of clip locations that helps, not the sheer number of clips. The data shows that the more locations of clips the better, although even 4 or 5 isn't much more helpful than 2 or 3 clips.
Critical studies have repeatedly demonstrated that seromas, preop CT’s, MRI-base radiation planning, and various iterations of fiducial markers (seed, 3D) don’t provide a satisfactory method to help radiation oncologists accurately deliver postoperative radiation therapy to the tumor bed, especially after oncoplastic surgery. What’s the common deficit? They all share the fact that they are missing the opportunity to utilize knowledge from the most important element of the equation: the person who knows more about the gross location of the tumor than anyone else – the breast surgeon – and at the time that they know it best – during the operation.
VeraForm is unique in its ability to permit the surgeon to communicate their knowledge to radiation oncologists in a manner that is complete in its accuracy and reliability. Yes, it requires the surgeon to encapsulate the tumor bed, not entirely, but just the location of the gross disease. That small effort ensures integrity to the entire process and is a major leap forward in providing the radiation oncologist with the best possible information to avoid under or over treatment of radiation therapy for the patient.
Standard surgical clips representing a few points in the operative field
VeraForm, a 3D, continuous radiopaque
filament accurately outlining an entire tumor bed