ORLANDO – New treatment algorithms for breast cancer treatment accept the "no ink on tumor" standard as an acceptable pathological measure of negative margins for early stage invasive cancer in the breast conservation setting, doctors said here.
In outlining changes in the National Comprehensive Cancer Network guidelines for breast cancer treatment, Kilian Salerno, MD, associate professor of radiation oncology at the Roswell Park Cancer Institute, Buffalo, said, "No ink on tumor is considered adequate margin for stage I- II invasive carcinoma treated with whole breast radiation therapy." (The term derives from the use of ink markers to delineate edges of excised tissue during pathological analysis.)
The 31-member breast cancer guideline writing committee accepted the standard as part of the algorithm for treatment, following the approach put forth by the joint in treatment of ductal carcinoma in situ (DCIS) by the Society of Surgical Oncology, the American Society for Radiation Oncology and the American Society of Clinical Oncology.
Salerno said the new guidelines consider that a 2-mm margin reduces the risk of ipsilateral breast tumor recurrence among patients undergoing treatment for excision of pure DCIS relative to narrower widths in patients receiving whole breast radiation therapy.
"The updates are designed to deliver review of the appropriate targets for radiation therapy and to discuss some of the options to optimize our treatments," she said in her oral presentation before the 1,800 attendees at the meeting.
The new guidelines are a departure from earlier algorithms that discussed margins as wide as 10 mm as acceptable. The edited-out wording was, "margins greater than 10 mm are widely accepted as negative (but may be excessive and may lead to less optimal cosmetic outcome)."
The new wording in the updated guidelines state: "The routine practice of obtaining negative margins greater than 2 mm is not supported by the evidence. DCIS with micro-invasion (defined as no invasive focus greater than 1 mm in size) should be considered as DCIS when considering optimal margin width."
The committee also took into consideration the width of margins among women who opt to avoid whole body radiation or for women with certain mutations that can increase the risk of late complication with radiation. The updated guideline reads: "For patients treated with excision alone (without radiation), regardless of margin width, the risk of ipsilateral breast tumor recurrence is substantially higher than treatment with excision and whole breast radiation therapy (even in pre-defined, low-risk patients). The optimal margin width for treatment with excision alone is unknown, but should be at least 2 mm. Some evidence suggests lower rate of ipsilateral breast tumor recurrence with margin widths greater than 2 mm."
Radiation Regimens
Salerno also addressed radiation protocols, noting that the guidelines indicate that "a hypofractionated schedule for delivering whole breast radiation is really the preferred regimen for most patients receiving whole breast irradiation. The target of radiation is the entirety of the breast tissue."
The guidelines recommend: "The whole breast should receive a dose of 46-50 Gray in 23-25 fractions or 40-42.5 Gray in 15-16 fractions. All dose schedules are give 5 days a week. A boost to the tumor bed is recommended in patients at higher risk for recurrence. Typical booster doses are 10-16 Gray in 4-8 fractions."
Salerno said that the guidelines address accelerated partial breast irradiation. According to the updated guidelines, "Preliminary studies of accelerated partial breast irradiation suggest that rates of local control in selected patients with early-stage breast cancer may be comparable to those treated with whole breast radiation therapy. However, compared to standard whole breast radiation, several recent studies document an inferior cosmetic outcome with accelerated partial breast irradiation. Follow-up is limited and studies are ongoing. Patients are encouraged to participate in clinical trials."
The NCCN guideline accepts the ASTRO guidelines for accelerated partial breast irradiation, which defines suitable patients for the procedure as those patients over the age of 50 with invasive ductal carcinoma measuring 2 cm or less with negative margins of at least 2 mm, no lymphovascular invasion, estrogen-receptor positive cancer and BRCA negative or patients with a low/intermediate nuclear grade, screen-detected DCIS measuring 2.5 cm or less with negative margins greater than 3 mm.
All the recommendations are considered category 2A which means that randomized clinical trial data is lacking. The NCCN considers that participation in a randomized clinical trial is always one of the preferred options.
Disclosures
Salerno disclosed no relevant relationships with industry.
Primary Source
National Comprehensive Cancer Network
Salerno K, "Evolving radiation therapy recommendations for breast cancer," NCCN 2017.