Methylene blue sentinel lymph node biopsy for breast cancer learning curve in the COVID-19 era: How many cases are enough?

Background: Sentinel lymph node biopsy (SLNB) is now the gold standard for early breast cancer with clinically negative lymph nodes (N0). According to the Indonesian Board-Certified oncologist surgeon, the learning curve for evaluating fellow breast surgeons to achieve this competency could have been shorter due to the COVID-19 pandemic. This study aims to see if the learning curve for sentinel lymph node (SLN) identification can be shortened. Methods: Trainee breast surgeons were taught to perform SLNB on breast cancer patients. Intraoperative assessment and completion of axillary lymph node dissection (ALND) were performed in the first setting for standardization with the attending surgeon. Sentinel lymph node identification was plotted on cumulative sum chart (CUSUM) limitations for evaluating the variability competency between the attending and trainee surgeons based on a target identification rate of 85%. Results: We concluded that CUSUM charts are the best tools currently available for assessing psychomotor learning SLNB. According to a CUSUM chart based on a reasonable set of parameters, the learning curve for SLNB using methylene blue dye is reached after 4-5 consecutive positively detected SLN. Conclusion: CUSUM Chart showed that experienced breast surgeons have completed the SLNB learning curve after 4-5 successful methylene blue attempts. In the future, this learning curve analysis can be applied to trainee breast surgeons by utilizing a proxy measure for failure, such as failure to identify the SLN.