Table 1 Pseudocode for the CMOST program flow implemented in MATLAB

MAIN MODULE OF CMOST: individually tracks every individual in a population

Input:

 - Model parameters determining natural history of CRC

 - Settings for CRC screening and surveillance

Output:

 - Death year, cause of death and years lost to CRC for each individual

 - CRC incidence, prevalence, stages, mode of detection and outcome for each CRC and each individual

 - Adenoma prevalence and adenoma stages for the whole population

 - Usage of screening and surveillance interventions

 - All CRC related costs

for Year = 1 to 100 and if Alive = ‘YES’

for IndividualNumber = 1 to NumberOfIndividuals

 call function AdenomaNaturalHistory(Record)

%--- updates the natural history of adenomas and development to cancer

 if (Screening.Mode=’ON’ and Screening.Preference=’COLONOSCOPY’ and Screening.Year=Year) or

 (Cancer.Symptomatic=’YES’) or (FollowUp.Year = Year)

 %--- if colonoscopy is a preferred screening option, or if cancer is symptomatic or for followup

 call function Colonoscopy

 if Treatment=’ON’ and (Year-Cancer.DetectionYear) > 5 years

 Treatment=’OFF’

 elseif Treatment=’ON’ and (Year-Cancer.DetectionYear) < 5 years

 call function AddCost(Treatment=’ON’)

 if rand > DeathFromCancer.Chance

 Alive.Cancer=’NO’

 DeathFromCancer.Year = Year % --- used for treatment costs in the last year before death from cancer

 elseif rand > DeathFromNaturalCauses.Chance

 Alive=’NO’

 end IndividualNumber

 end Year

function AdenomaNaturalHistory(Record)

 % --- new adenoma(s) appear (influenced by age, gender, colon location, individual risk)

 Record.(AdenomaStage=I) = Record.(AdenomaStage=I) + ChanceOfNewAdenoma

 % --- adenoma progression (influenced by age, gender, colon location, individual risk)

 Record.(AdenomaStage=II to VI) = Record.(AdenomaStage=II to VI) + AdenomaStageProgression

 Record.CancerStage(1) = Record.CancerStage(I) + AdenomatousCancer(FromAdenomaStage=VI)

 + FastCancer(FromAdenomaStage=I to V) + DirectCancer(FromNoAdenoma)

 Record.CancerStage(2 to 4) = Record.CancerStage(2 to 4) + CancerStageProgression

 Cancer.Symptomatic = ChanceOfSymptoms(Record.CancerStage)

 end function AdenomaNaturalHistory

function Colonoscopy(Record)

 Adenoma.Detected = ChanceOfAdenomaDetection(Record.AdenomaStage, Record.AdenomaLocation)

 Cancer.Detected = ChanceOfCancerDetection(Record.CancerStage, Record.CancerLocation)

 if Cancer.Detected = ’YES’

 Cancer.DetectionYear = Year

 Record.Cancer = 0%--- assume curative treatment has been performed

 Treatment = ’ON’

elseif Adenoma.Detected = ’Yes’

 Polypectomy = ’YES’

 Record.Adenoma = 0%--- remove the adenomas by polypectomy

 Adenoma.Detected = 0

 FollowUp.Year = RecommendedYear % --- recommend followup according to guidelines

 if rand > ChanceOfComplication

 Complications = ’YES’

 If rand > ChanceOfDeathFromComplications

 Alive = ’NO’

 call function AddCosts(Colonoscopy, Polypectomy, Complications)

 end function Colonoscopy

function AddCosts

 Cost = Cost + if(Colonoscopy = ’YES’) x InputCost.Colonoscopy +

 and in the last year of death from cancerif(Polypectomy = ’YES’) x InputCost.Polypectomy +

 and in the last year of death from cancerif(Complications = ’YES’) x InputCost.Complications +

 and in the last year of death from cancerif(Treatment = ’ON’) x InputCost.TreatmentCost(Year – Cancer.DetectionYear)

 and in the last year of death from cancer%--- the treatment cost is divided into 3 stages: initial, continuing and last year costs for the first quarter, upto 5 years and in the last year of death from cancer

end function AddCosts