Candidate for the Lee B. Lusted Student Prize Competition
Purpose: Bladder cancer has a heterogeneous natural history and a substantial plurality (40%) of incident cases are low grade non-muscle-invasive (NMIBC), with comparatively low risk of progression to life-threatening disease. Practice guidelines for NMIBC suggest intensive surveillance cystoscopy schedules with a limited evidence base, and there is a lack of consensus among the different guidelines for low risk NMIBC.
Method: We use a Partially Observable Markov Decision Process (POMDP) to investigate the optimal schedule of cystoscopies that maximizes expected quality adjusted life years (QALYs). Our model classifies patients into three risk levels with transition probabilities for health states taken from the EORTC risk calculator’s recurrence and progression probabilities. Mortality rates are taken from the CDC Vital Statistics Report, and parameters for utility of health states, and disutility of cystoscopy are drawn from the medical literature. Model validation is based on comparison of outputs to published survival data for patients diagnosed with bladder cancer.
Result: We compared the optimal schedule of cystoscopies from our model with the American Urology Association (AUA) and the European Association of Urology (EAU) guidelines for male and female patients aged 50 to 70. The optimal schedule for the base case scenario results in a 0.4 gain in expected QALYs over EAU and AUA guidelines for a 50 year old low risk male patient. Base case results indicate that older patients should receive less intensive surveillance than younger patients and female patients should undergo slightly more intensive surveillance than similar male patients. Optimal schedules are more intensive than EAU, and less intensive than AUA in the first 5 years of surveillance. Sensitivity analysis indicates that the optimal schedule is highly sensitive to the disutiltity of cystoscopy. For example, the total number of cystoscopies in the first 10 years increases from 10 to 40 when the disutility of cystoscopy drops from 0.05 to 0.01.
Conclusion: Whereas current American guidelines recommend a one-size-fits-all regimen, current European guidelines are based on explicit risk stratification, underscoring uncertainty in this area. We find that surveillance for low risk NMIBC patients should consider patient age, gender, co-morbidity and most of all, disutility of cystoscopy. Optimal schedules can result in considerable QALY gains, particularly for younger patients, compared to current guidelines