Bayesian survival analysis of time-to-remission of prostate cancer and associated prognostic factors in a health-based institute, South-West Nigeria

Background: Prostate cancer (CaP) develops when healthy cells in the prostate gland change and grow out of place, forming a tumour. In Nigeria, this disease is on an upward trajectory, despite the availability of screening services. This study seeks to estimate the time-to-remission and to determine the prognostic factors for prostate cancer remission. Method: A retrospective analytical study design was employed, through the extraction of case files of patients diagnosed and treated for CaP from January 2010 to December 2017 at the University College Hospital, Ibadan. The extracted data were further divided into two cohorts 2010 to 2014 and 2015 to 2017 to account for non-treatment months. Kaplan Meier method was used to estimate the time-to-remission. Bayesian parametric (Weibull) Accelerated Failure Time (AFT) model was used to determine the factors associated with time-to-remission. Results: : The average age(SD) of the patients was 72(3.65) years, with peak incidence among those aged 70 – 79 years. Most CaP patients (87.3%) were diagnosed at stage IV, with many having metastasis to the spine. Among the patients, (33.6%) received chemotherapy and surgery. Patients from Northcentral part of Nigeria had the highest Median Time to Remission (MTR) of 3.7 months in the (2015 - 2017) cohort. The MTR for the 2010 - 2014 cohort was 2.9 months, 3.3 months for the 2015 - 2017 cohort while the overall MTR for the study was 3.2 months. Ages 60 – 69 years and 79 years and above in the 2010 – 2014 cohort decelerated time-to-remission by 30% (adjusted Time Ratio (aTR) = 1.3; 95% CrI (Credible Interval): 1.1 – 1.5) and 40% (aTR = 1.4; 95% CrI: 1.1 – 1.8) respectively. Time-to-remission was significantly delayed by 40% (aTR = 1.4; 95% CrI: 1.1 – 1.7), and 230% (aTR = 3.3; 95% CrI: 2.1 – 4.9) for patients from the south-south and north-central respectively for the 2015 – 2017 cohort compared to patients from the south-west. Conclusion: We found that patients age, location, marital status, occupation, stage, method of diagnosis, Gleason group, site and treatment received significantly influence the time to CaP remission. Stakeholders should therefore sensitize men well advanced in age to take up regular prostate examination as well as emphasize early presentation.