Table 3. Subgroup analysis for hazard ratio for recurrence based on change in cancer antigen 15-3.

Change between previous examination and current examination		Adjusted HR (95% CI)
		Elevated	Elevated 1 SD*
Pathologic N stage
	N0	1.43 (1.17–1.75)	5.31 (4.05–6.95)
	N+	2.12 (1.73–2.60)	8.82 (6.72–10.31)
	p-value for interaction	< 0.01	0.01
Subtype
	Luminal A (ER or PR+/HER2−)	2.07 (1.69–2.53)	8.00 (6.38–10.02)
	Luminal B (ER or PR+/HER2+)	1.58 (1.05–2.38)	6.53 (3.95–10.79)
	HER2+ (ER and PR−/HER2+)	1.32 (0.85–2.07)	4.52 (2.57–7.94)
	TNBC (ER and PR−/HER2−)	1.47 (1.09–1.98)	6.00 (4.21–8.55)
	p-value for interaction	0.22	0.34

Adjusted for age, pathological N stage, hormone receptor, HER2, chemotherapy, radiation therapy, and hormone therapy.

HR = hazard ratio; CI = confidence interval; SD = standard deviation; ER = estrogen receptor; PR = progesterone receptor; HER2 = human epidermal growth factor 2; TNBC = triple negative breast cancer.

^*Elevated ≥ 1 SD of baseline CA15-3 (4.5).