Table 2:

Association between breast cancer tumor stage & treatment time-related factors and recency of last childbirth among premenopausal women <50 years of age in the Carolina Breast Cancer Study, 2008–2013 (N=1179)

	Nulliparous (N=210)	0–5 postpartum (N=160)	5.1–10 postpartum (N=207)	10.1–20 postpartum (N=438)	20.1–30 postpartum (N=164)
Stage
I-II	181 (86.2)	119 (74.4)	175 (84.5)	365 (83.3)	135 (82.3)
III	29 (13.8)	41 (25.6)	32 (15.5)	73 (16.7)	29 (17.7)
III vs. I-II, Age & Race-Adjusted RFD (95% CI)	Ref.	12.6% (4.0%, 21.1%)	2.6% (−4.2%, 9.3%)	3.4% (−2.4%, 9.1%)	2.8% (−4.7%, 10.4%)
Fully Adjusted RFD (95% CI)a	Ref.	12.2% (3.6%, 20.8%)	1.8% (−4.8%, 8.5%)	2.3% (−3.5%, 8.1%)	1.1% (−6.5%, 8.7%)
Delayed Initiation
≤30 days	122 (58.1)	115 (71.9)	130 (62.8)	284 (64.8)	91 (55.5)
>30 days	88 (41.9)	45 (28.1)	77 (37.2)	154 (35.2)	73 (44.5)
>30 vs. ≤30 days, Age & Race-Adjusted RFD (95% CI)	Ref.	−14.6% (−25.1%, −4.2%)	−5.0% (−14.8%, 4.8%)	−8.4% (−16.9%, 0.1%)	−0.2% (−11.2%, 10.9%)
Fully Adjusted RFD (95% CI)b	Ref.	−11.2% (−21.4%, −1.0%)	−3.2% (−13.0%, 6.5%)	−7.1% (−15.4%, 1.3%)	1.0% (−10.2%, 12.1%)
Prolonged Treatment Duration
No	113 (53.8)	112 (70.0)	104 (50.2)	259 (59.1)	88 (53.7)
Yes	97 (46.2)	48 (30.0)	103 (49.8)	179 (40.9)	76 (46.3)
Yes vs. No, Age & Race-Adjusted RFD (95% CI)	Ref.	−17.2% (−27.8%, −6.6%)	4.8% (−5.3%, 14.8%)	−6.0% (−14.7%, 2.6%)	−3.1% (−14.1%, 7.9%)
Fully Adjusted RFD (95% CI) b	Ref.	−17.5% (−28.0%, −7.1%)	4.6% (−5.4%, 14.6%)	−5.8% (−14.5%, 2.8%)	−1.1% (−12.3%, 10.1%)

Abbreviations: RFD, relative frequency difference; CI, confidence interval

^aAdjusted for age, race, income, education, marital status, and health insurance status at baseline

^bAdjusted for age, race, tumor stage, size, grade, lymph node status, hormone receptor status and human epidermal growth factor receptor 2 status