Appendix A4.

Results on select variables from analyses testing pre-integration trends in outcomes

	Estimate (Robust Standard Errors)
Outcome	Integrated group*year10†	Integrated group*year11†	Integrated group*year12†
Quantity
Log(Frequency of chemotherapy drug claims)	−0.02(0.03)	−0.03(0.03)	−0.07(0.04)
Log(Frequency of chemotherapy administration claims)‡	−0.02(0.03)	−0.04(0.03)	−0.12(0.05)**
Spending ($)
Log(Chemotherapy drug spending)	−0.03(0.06)	0.02(0.05)	0.00(0.08)
Log(Chemotherapy administration spending)	0.03(0.05)	0.06(0.05)	−0.01(0.07)
Treatment mix
Log(Chemotherapy drug spending per claim)	−0.00(0.05)	0.05(0.05)	0.08(0.07)

Notes:

^†These variables are the interaction terms between the integrated group indicator and year dummy. The integrated group includes oncologists who became integrated during the study period. Years include only pre-integration periods;

^‡The interaction between the integration group and year 2012 indicators was significant for this analysis. This appears to be due to a deviation in the trend in the non-integrated group in 2012: the number of administration claims in this group was 2.36 from 2009 through 2012, 2.38 in 2012, and 2.32 in 2013. In the integration group, it was 2.29 in 2009, 2.23 in 2010, 2.22 in 2011, and 2.21 in 2012 (pre-integration years). It dropped to 2.11 in 2013 when all doctors in this group were integrated.