HOLLYWOOD, FLA. – No huge surprises here, but newly revised National Comprehensive Cancer Network guidelines for locoregional therapy of breast cancer help clarify the optimal use of adjuvant radiation.
For example, updates to the pages on principles of radiation therapy in invasive breast cancer contain new information on optimal dosing, fractionation, treatment planning, and techniques for minimizing radiation of surrounding normal tissues, noted Dr. Kilian E. Salerno, director of breast radiation and soft tissue/melanoma radiation at the Roswell Park Cancer Institute in Buffalo, New York.
“There are a number of treatment options, many more now than ever before,” she said at the annual conference of the National Comprehensive Cancer Network.
The guidelines emphasize the importance of individualized radiation therapy planning and delivery. A CT-based treatment plan can help clinicians choose target volumes and identify adjacent organs and tissues that may be at risk for radiation spill.
Recommended options for reducing radiation doses to adjacent tissues include deep breath holds and prone positioning so that the treated breast hangs down, helping to isolate it from the heart and lungs.
Whole breast irradiation
Whole breast irradiation is the standard for radiation therapy of early breast cancer following breast-conserving surgery, although partial breast irradiation, typically of lumpectomy cavities, is also commonly performed, Dr. Salerno said.
Boost radiation in conjunction with breast conserving therapy can be delivered via en face electron fields, photons, or brachytherapy; boost dosing to chest wall scar is usually treated with photons or electrons, the guidelines note.
The guidelines recommend weekly imaging to ensure that daily treatment setup is consistent, but caution against routine use of daily imaging.
For whole breast irradiation, the guidelines recommend either doses of 46-50 Gy divided into 23-25 fractions (conventional fractionation), or, preferably, hypofractionated radiation delivered in doses of 40-42.5 Gy over 15-16 fractions, with all doses given 5 days per week. Patients at higher risk for recurrence should receive boost doses to the tumor bed, typically at doses of 10-16 Gy delivered in 4-8 fractions.
The guidelines now favor hypofractionation based on long-term results from clinical trials conducted in Ontario, Canada, and in London.
In the Canadian trial (N Engl J Med. 2010;362:513-20), patients were treated with whole-breast irradiation at doses of 42.5 Gy in 16 fractions, with no boost dose.
In the Standardisation of Breast Radiotherapy B (START B) trial (Lancet Oncol. 14;11:1086-94), in London, patients received 40 Gy in 15 fractions without a boost dose.
Both trials showed that hypofractionation was associated with disease outcomes that were equivalent or better to those seen with conventional fractionation schedules, as well as equivalent or better cosmesis and adverse event profiles, Dr. Salerno said.
“This is for whole breast radiation; it is not to be routinely used in the post-mastectomy setting or when you’re treating regional nodes,” she said.
Accelerated partial breast irradiation
For accelerated partial breast irradiation (APBI), the guidelines recommend a hypofractionated schedule of 34 Gy divided into 10 fractions delivered twice daily for 5 days for brachytherapy, or 38.5 Gy in 10 twice daily fractions with external beam therapy to the tumor bed.
The NCCN guidelines for APBI are based on the American Society of Radiation Oncology (ASTRO) consensus statement for APBI. An updated statement is planned for 2017.
Results from the CALGB 9343 trial and other studies suggest that in selected women with lower risk for recurrence, radiation can be omitted without compromising survival. These include women aged 70 or older with small primary breast cancers, negative nodes, negative surgical margins, and hormone-receptor-positive disease who are treated with breast conserving surgery and go on to tamoxifen maintenance.
Following total mastectomy with surgical axillary staging, with our without reconstruction, the guidelines recommend specific steps based on the number of nodes involved and the tumor size and/or margin status.
Thus, women with four or more positive axillary nodes should receive radiation to the chest wall and infraclavicular region, supraclavicular area, internal mammary nodes, and any at-risk part of the axillary bed. If adjuvant chemotherapy is prescribed, radiation usually is given following chemotherapy completion.
For women with one to three positive axillary nodes, the guidelines urge clinicians to “strongly consider” treating them as they would women with four or more positive nodes. The same advice applies to women with negative nodes but tumors larger than 5 cm or positive surgical margins as defined by ink on tumor.
For patients with negative nodes, tumors 5 cm or smaller and negative but narrow margins (less than 1 mm), the guidelines recommend consideration of radiation to the chest wall. Patients with small tumors, no nodal involvement, and margins 1 mm or greater can be spared radiation therapy.