Table 10.

Alternative scenarios

Description	Alternative model inputs	Explanation
1. Fewer large and small polyps	Apply a 0.80 adjustment factor to the probability of large and small polyps and increase the probability of diminutive size polyps by the same amount so that the probability of finding a polyp of any size remains unchanged	Our base scenario, using data centered at approximately 2005, produces an approximately 18% aggregate probability of a large or small polyp finding. We have found smaller studies that indicate an aggregate probability in the 13–15% range [47–49]. Since the probability of finding a polyp of any size, however, uses recent data we left the total probability unchanged
2. Add costs for OC and CTC complications and CTC extra-colonic findings	OC costs: add $20 and $96 to OC without and with biopsy costs, respectively, for OC complications	We used published literature [50], trended to 2015, to estimate the costs of complications and the follow-up diagnosis costs of CTC extra-colonic findings. OC has more complications than CTC and within OC, OCs with biopsies have substantially more complications than OCs without biopsies [47, 49, 51]. See Appendix in supplementary material for more details. The ACR currently recommends the reporting of potentially significant extra-colonic findings [23]
	CTC costs: add $131 to CTC for CTC complications and extra-colonic findings
3. Increase anesthesia use for OC	Assume that 80% of OCs will have separately billed anesthesia, a 40% increase in use and costs from the 57% base scenario assumption	In 2013 separately billed anesthesia was subject to Medicare cost sharing; as of January 1, 2015 it is no longer subject to cost sharing [52]. Anesthesia use may therefore increase over the next couple of years
4. Add costs for CTC shared decision making	Add a $20 cost to all CTCs and another $20 cost to CTCs with small polyps	Medicare covers CT lung cancer screening with the provision that the first screening must include a documented shared decision making consultation [53]. If Medicare adopts a similar approach for CTC screening, two consultations may be required: the first for the screening and the second for the decision for follow-up OC if the patient has small polyps. See the Appendix in supplementary material for more details
5. Decrease maximum screening age	Decrease maximum screening age from age 84 to age 74	UPSTF recommends CRC screening until age 75. Medicare, however, currently pays for screening for all ages 50 and over
6. Decrease OC follow-up rate for CTCs with small polyp findings	Decrease OC follow-up rate for CTCs with small polyp findings from 50% to 25%	No one knows how many patients with small polyps will opt for OC polypectomy vs. CTC surveillance. The percentage will likely vary substantially by clinic and physician
7. Increase OC follow-up rate for CTCs with small polyp findings	Increase OC follow-up rate for CTCs with small polyp findings from 50% to 75%
8. Decrease rescreen years for both OC and CTC for screenings with small polyps	Rescreen in 3 years instead of the 6 years for OC and 5 for CTC	Literature indicates that many OC patients rescreen sooner than recommended by guidelines [46]
9. Increase rescreen years for CTC to match OC	Rescreen in 3, 6, 7, and 10 years for large, small, diminutive, and no polyps, respectively	By removing the rescreen time differential, this scenario compares the per-screen costs of CTC and OC