A pilot study of endorectal magnetic resonance imaging and magnetic resonance spectroscopic imaging changes with dutasteride in patients with low risk prostate cancer

Study Type – Therapy (case series) Level of Evidence 4 What’s known on the subject? and What does the study add? While not approved by the Food and Drug Administration (FDA) for chemoprevention, dutasteride has been shown in a large randomized trial to reduce the overall risk of developing prostate cancer. In our pilot study, one third of patients demonstrated a significant reduction in the volume of their prostate cancer as measured by magnetic resonance spectroscopic imaging. OBJECTIVE • To evaluate the effects of dutasteride on treatment‐naïve prostate cancer in men using serial magnetic resonance imaging (MRI) and magnetic resonance spectroscopic imaging (MRSI) in this pilot study. PATIENTS AND METHODS • This investigator‐initiated prospective single‐arm study was approved by the institutional committee on human research ethics board. • The target accrual was 10 patients. Newly diagnosed prostate cancer patients with low risk disease either with symptomatic benign prostatic hypertrophy or deemed to require pre‐brachytherapy androgen suppression therapy were eligible. In the latter group, dutasteride was used to achieve cytoreduction. • All patients received 6 months of dutasteride 3.5 mg daily and underwent baseline blood work, health‐related quality of life indices and MRI/MRSI, which were repeated at 1, 3 and 6 months. • MRSI spectra were examined and scored as healthy or cancerous. The change in cancerous volumes over time was evaluated. RESULTS • Of the 10 patients enrolled, nine patients completed the entire study. One patient withdrew after 3 months because of drug‐related toxicity. • Because a significant decrease in citrate and polyamines on MRSI spectra was noted at 1 month compared with baseline, healthy tissue appeared to be more like cancer and thus created a false impression that the cancer had grown after 1 month. To reduce this bias, comparisons were made between the 1‐month and 6‐month scans. • The median MR cancer volumes at 6 months and 3 months were 100% and 101% of the 1‐month value, respectively. Three of the nine patients had a 30–45% decrease in cancer volume at 6 months relative to 1‐month measures. Of the others, two had no change in cancer volume and four had an increase (range 65–167% of the 1‐month value). • The median cancer volume (range) at baseline was only 0.5 (0.1–5.6) mL. CONCLUSIONS • The inclusion of only men with low volume disease may have limited our ability to accurately assess response rates after dutasteride due to the background effects on normal prostate metabolism. Despite this, one‐third of patients had a 30–45% reduction in cancer volume at 6 months. • Future studies including men with larger volume disease may enable estimates of response rates to be made more accurately.

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