Table 3:

Results of Key One-way Sensitivity Analyses

Variable Description	Preferred strategy	T1a N0	T1a N1	T1a N2	T1b-T2 N0	T1b-T2 N1	T1b-T2 N2	Population-level model
Cost of SLNB	Observation	$13-$96,593	$13-$96,593		$13-$96,593	$13-$96,593	$52,100-$96,593	NA2
	SLNB			$13-$96,593			$13-$52,000	NA2
Probability of lymphedema after SLNB	Observation	0.005–0.10	0.005–0.10		0.005–0.10	0.005–0.10		NA2
	SLNB			0.005–0.10			0.005–0.10	NA2
Utility of lymphedema	Observation	0.4–0.99	0.4–0.99		0.4–0.99	0.4–0.99	0.4–0.5	NA2
	SLNB			0.4–0.99			0.5–0.99	NA2
Probability: regional recurrence	Observation	0.001 −0.20	0.001 −0.20		0.001 −0.20	0.001 −0.20		NA2
	SLNB			0.001 −0.20			0.001 −0.20	NA2
Multiplier for probability of regional recurrence in patients with unrecognized nodal disease	Observation	NA1	1–5.9		NA1	1–4.3	1–7.6	NA2
	SLNB	NA1	6.0–20	1–20	NA1	4.4–20	7.7–20	NA2
Multiplier for probability of distant recurrence in patients with unrecognized nodal disease	Observation	NA1	1–1.6	1–2.8	NA1	1–1.3	1–2.3	NA2
	SLNB	NA1	1.7–20	2.9–20	NA1	1.4–20	2.4–20	NA2
Utility of regional recurrence	Observation	0.2–0.9	0.2–0.9	0.2–0.9	0.2–0.9	0.2–0.9		NA2
	SLNB						0.2–0.9	NA2
Utility of metastatic recurrence	Observation	0.2–0.9	0.2–0.9	0.2–0.9	0.2–0.9	0.2–0.9		NA2
	SLNB						0.2–0.9	NA2
False negative rate AUS for N1 disease	Observation	NA3	NA3	NA3	NA3	NA3	NA3	0.1–0.8
	SLNB	NA3	NA3	NA3	NA3	NA3	NA3
False negative rate AUS for N2+ disease	Observation	NA3	NA3	NA3	NA3	NA3	NA3	0.1–0.6
	SLNB	NA3	NA3	NA3	NA3	NA3	NA3
Willingness-to-pay threshold	Observation	$50,000-$150,000	$50,000-$150,000	<$50,000	$50,000-$150,000	$50,000-$150,000	$50,000-$65000	$50,000-$150,000
	SLNB			$50,000-$150,000			$65,000-$150,000

Key variables were presented based on their clinical relevance and notable impact on the model (variables not included in the figure did not have a significant impact on model results). Results of key 1-way sensitivity analyses shown above: each input variable varied within the range of values specified in Table 1, keeping all other variables at their baseline value. In the green cells, all input values listed resulted in NMB observation > NMB SLNB, i.e., observation was superior to SLNB. In the red cells, all input values listed resulted in NMB observation < NMB SLNB, i.e., SLNB was superior to observation. For a majority of variables, the conclusion was consistent: observation after negative AUS is the optimal strategy for axillary staging.

NA₁: Multipliers for breast cancer recurrence given unrecognized nodal disease (false-negative AUS or SLNB) were not applicable to N0 models.

NA₂: Variables in the stage-specific models were not used in the population-level model, and therefore not applicable for sensitivity analyses at the population level.

NA₃: The false-negative rates of axillary ultrasound were used only in the population-level model, and therefore not applicable for sensitivity analyses in the stage-specific models.

NMB: Net monetary benefit, SLNB: sentinel lymph node biopsy, AUS: axillary ultrasound, $: US dollars

NMB Observation > NMB SLNB (Observation preferred) for the range of values listed

NMB Observation < NMB SLNB (SLNB preferred) for the range of values listed