Date of Award

3-2025

Degree Type

Dissertation

Degree Name

Master of Medicine (MMed)

First Advisor

Dr. Samuel Nguku

Second Advisor

Dr S. R. Samnakay

Department

Imaging and Diagnostic Radiology (East Africa)

Abstract

Background: Rising PSA levels following local therapy with curative intent are seen in about one third of men previously treated for prostate cancer, indicative of disease recurrence. This is usually not detectable through imaging modalities like computed tomography (CT) or magnetic resonance imaging (MRI). Several studies show high detection rates of recurrence with 18F-PSMA-1007 PET/CT, one of the novel PET imaging modalities for prostate cancer. No studies, however, have been done to show the patterns of recurrence in the Sub-Saharan African population in whom prostate cancer is known to occur earlier and be more aggressive. Biochemical recurrence almost always predates clinical symptoms, and early detection is paramount for better clinical outcomes.

Objective: To determine the detection rate and patterns of recurrence on 18F-PSMA-1007 PET/CT in patients with biochemical recurrence following definitive treatment for prostate cancer.

Materials and methods: This retrospective cross-sectional study reviewed 18F-PSMA-1007 PET/CT examinations in patients with rising PSA levels following definitive treatment of prostate cancer from June 2020 until February 2024. Data on the detection rates and disease recurrence sites as per 18F-PSMA-1007 PET/CT examinations was collected. The recurrence sites were grouped into prostatectomy bed/prostate gland, regional nodes, non-regional nodes, skeletal sites and visceral sites. Recurrence patterns were grouped into local, regional and distant. Descriptive analysis of data through frequencies and percentages was performed on categorical variables and for continuous variables, the mean was used. Group comparison was done using Fishers Exact test for categorical data and Kruskal Wallis test for continuous data. Logistic regression was used to compute the odds ratio and a p value of < 0.05 was considered statistically significant.

Results: Detection rate of recurrence of prostate cancer using 18F-PSMA-1007 PET/CT was 87.9%. The commonest recurrence site was the prostatectomy bed/prostate gland at 70.7%. There was an association between PSA levels at the time imaging was performed and scan positivity (OR 1.57 [0.93, 2.67] p=0.019) with higher PSA levels demonstrating greater scan positivity rates. Higher positivity rates were seen in patients treated with radiotherapy in comparison to radical prostatectomy (OR 10.6 [1.2, 93.86], P=0.034). Neither Gleason score nor ISUP grade at the time of primary staging demonstrated association with PET CT scan positivity.

Conclusion: 18F-PSMA-1007 PET/CT had a high rate of detection for sites of biochemical recurrence in Sub Saharan African men who received radical treatment for prostate cancer. The most common site of recurrence was locally in the prostatectomy bed/prostate gland. Patients treated with radiotherapy had higher PSA levels during the time of scanning and higher detection rate on PSMA PET/CT in comparison to those treated with radical prostatectomy.

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1

Last Page

35

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