Axillary Staging in Pregnant Women with Breast Cancer

Sentinel lymph node biopsy (SLNB):
- Is the standard of care in patients with early stage, clinically node negative breast cancer
Compared to axillary lymph node dissection (ALND),:
- SLNB has lower morbidity, including a:
  - Lower risk of musculoskeletal limitations and lymphedema
In general, SLNB can be performed with the use of:
- Blue dye
- Technetium-99 (99mTc), or
- Dual agents
The role of SLNB in pregnancy is not clearly defined:
- Recently updated American Society of Clinical Oncology (ASCO) Guidelines:
  - Upholds its prior recommendation that SLNB should not be performed in pregnancy:
    - The strength of the recommendation, however;
      - Is described by the ASCO expert panel to be “weak,” as it is based on ”informal consensus” rather than quality evidence.
Several retrospective studies have described the safety of SLNB during pregnancy
- The majority of patients in these studies underwent SLNB with 99mTc alone:
  - However, methylene blue dye was used in some patients
- One recent retrospective review reported on 145 women with clinical node-negative disease who underwent SLNB during pregnancy:
  - The mapping agents utilized were:
    - 99mTc alone (66%), methylene blue dye alone (9.7%), dual agents (10.3%), and the remainder was unknown
  - Sentinel lymph nodes were identified in 99.3% of patients, with excellent gestational outcomes
- No neonatal adverse events related to the SLNB procedure were reported
Models of fetal radiation exposure have demonstrated that the use of 99mTc for SLNB:
- Leads to a negligible dose to the fetus of 0.014 mGy or less:
  - Whereas risk of fetal malformation is associated with levels > 100 mGy
- Lower doses of exposure can be achieved using a 1-day protocol rather than a 2-day protocol
The use of lymphazurin dye is not recommended:
- Due to the 1% to 2% risk of anaphylaxis
Historically, the use of direct intra-amniotic injection of methylene blue dye for identification of ruptured membranes led to significant neonatal complications:
- Recent pharmacokinetic data indicate that the absorption of methylene blue dye used during SLNB is minimal
- Although the use of methylene blue dye for SLNB has been described, the data are limited in comparison to that of 99mTc
Thus, with respect to axillary staging, the risks and benefits of ALND vs. SLNB must be discussed with the patient prior to surgery

References
- Giuliano AE, Kirgan DM, Guenther JM, Morton DL. Lymphatic mapping and sentinel lymphadenectomy for breast cancer. Ann Surg. 1994;220(3):391-398.
- Lyman GH, Somerfield MR, Bosserman LD, Perkins CL, Weaver DL, Giuliano AE. Sentinel lymph node biopsy for patients with early-stage breast cancer: American Society of Clinical Oncology Clinical Practice Guideline Update.J Clin Oncol. 2017;35(5):561-564.
- Han SN, Amant F, Cardonick EH, et al. Axillary staging for breast cancer during pregnancy: feasibility and safety of sentinel lymph node biopsy. Breast Cancer Res Treat. 2018;168(2):551-557.
- Gropper AB, Calvillo KZ, Dominici L, et al. Sentinel lymph node biopsy in pregnant women with breast cancer. Ann Surg Oncol. 2014;21(8):2506-2511.
- Gentilini O, Cremonesi M, Toesca A et al. Sentinel lymph node biopsy in pregnant patients with breast cancer. Eur J Nucl Med Mol Imaging. 2010;37(1):78-83.
- Pandit-Taskar N, Dauer LT, Montgomery L et al. Organ and fetal absorbed dose estimates from 99mTc-sulfur colloid lymphoscintigraphy and sentinel node localization in breast cancer patients. J Nucl Med. 2006;47(7):1202-1208.