Testosterone treatment and the risk of aggressive prostate cancer in men with low testosterone levels

<div><p>Purpose</p><p>Testosterone treatment of men with low testosterone is common and, although relatively short-term, has raised concern regarding an increased risk of prostate cancer (CaP). We investigated the association between modest-duration testosterone treatment and incident aggressive CaP.</p><p>Materials and methods</p><p>Retrospective inception cohort study of male Veterans aged 40 to 89 years with a laboratory-defined low testosterone measurement from 2002 to 2011 and recent prostate specific antigen (PSA) testing; excluding those with recent testosterone treatment, prostate or breast cancer, high PSA or prior prostate biopsy. Histologically-confirmed incident aggressive prostate cancer or any prostate cancer were the primary and secondary outcomes, respectively.</p><p>Results</p><p>Of the 147,593 men included, 58,617 were treated with testosterone. 313 aggressive CaPs were diagnosed, 190 among untreated men (incidence rate (IR) 0.57 per 1000 person years, 95% CI 0.49–0.65) and 123 among treated men (IR 0.58 per 1000 person years; 95% CI 0.48–0.69). After adjusting for age, race, hospitalization during year prior to cohort entry, geography, BMI, medical comorbidities, repeated testosterone and PSA testing, testosterone treatment was not associated with incident aggressive CaP (HR 0.89; 95% CI 0.70–1.13) or any CaP (HR 0.90; 95% CI 0.81–1.01). No association between cumulative testosterone dose or formulation and CaP was observed.</p><p>Conclusions</p><p>Among men with low testosterone levels and normal PSA, testosterone treatment was not associated with an increased risk of aggressive or any CaP. The clinical risks and benefits of testosterone treatment can only be fully addressed by large, longer-term randomized controlled trials.</p></div

Association between testosterone treatment and any prostate cancer with additional survival requirements.

<p>Association between testosterone treatment and any prostate cancer with additional survival requirements.</p

Mean total serum T levels at cohort entry and follow-up among men treated and not treated with T.

<p>Mean total serum T levels at cohort entry and follow-up among men treated and not treated with T.</p

Association between testosterone treatment and prostate cancer.

<p>Association between testosterone treatment and prostate cancer.</p

Person-years of follow-up and incidence of prostate cancer, per 1000 person years.

<p>Person-years of follow-up and incidence of prostate cancer, per 1000 person years.</p

Association between testosterone treatment and prostate cancer among individuals using single type of formulation.

<p>Association between testosterone treatment and prostate cancer among individuals using single type of formulation.</p

Tumor growth and androgen levels in prostate cancer xenografts treated with castration and dutasteride.

<p>Mean tumor volumes in mice bearing LuCaP35 (<b>A</b>) and LuCaP96 (<b>B</b>) xenografts. Intact male SCID mice were subcutaneously implanted with 30 mm³ pieces of the indicated xenograft. When tumors reached ∼300mm³, mice were castrated and randomly enrolled into cohorts treated with either vehicle (Cx) or dutasteride (Cx+Dut) for 8 weeks (denoted by black line above x-axis). Mean tumor volumes are depicted for each treatment group at the indicated days post enrollment (Cx, black squares; Cx+Dut, white circles).</p

Characterization of LuCaP35 and LuCaP96 prostate cancer xenografts and responses to systemic androgen suppression.

<p>(<b>A</b>) Representative FFPE samples of each xenograft were stained with hematoxylin and eosin (H&E) and for expression of the androgen receptor (AR) and PSA as indicated. The scale bar (depicted on the PSA figures for ease of visualization) are 50µm. Kaplan-Meier plots of progression free survival (defined as tumor size <750 mm³) in mice bearing LuCaP35 (<b>B</b>) or LuCaP96 (<b>C</b>) xenografts. Intact male SCID mice were implanted subcutaneously with 30 mm³ pieces of the indicated xenografts. When tumors reached ∼300 mm³, mice were randomly enrolled into cohorts that were either left intact (No Cx) or castrated (Cx). P-values for curve comparisons were generated using the Mantel-Haenszel logrank test. (<b>D</b>) Mean and standard deviation of tissue testosterone (T, black bar) and DHT (gray bar) levels measured by mass spectrometry in tumors of the indicated xenograft (passaged in intact mice). (<b>E</b>) Relative expression of transcripts for the indicated steroidogenic genes was calculated using the delta dCt method (fold change = 2∧ddCt). Genes differentially expressed in LuCaP35 vs. LuCaP96 within one order of magnitude are indicated within the gray lines. Significant differences (by Welch’s t test; p<0.05) are indicated by black circles; white circles indicate genes that were not significantly different between LuCaP35 and LuCaP96 (all values given in Supplementary Data 2).Upward triangles indicate highly differentially expressed genes specifically leading to increased T (AKR1C3, 40 fold) or increased DHT levels (SRD5A1, 5.0 fold; 17BHSD10 4.8 fold; RLHSD, 99 fold). Downward triangles indicate highly differentially expressed genes specifically mediating DHT catabolism (AKR1C2, 7 fold; UGT2B15, 3000 fold).</p

Androgen levels and AR expression in prostate cancer xenografts treated with castration and dutasteride.

<p>Tissue testosterone (T, black bars) and DHT (gray bars) levels were measured by mass spectrometry in LuCaP35 (<b>A</b>) and LuCap96 (<b>B</b>) tumors resected from intact mice (No Cx), and from mice treated with castration alone (Cx) or castration + dutasteride (Cx+Dut) at early time points (d3-21, while still on therapy, indicated by double-headed arrows), or at castration-resistant re-growth (defined as >750 mm³). P values computed from Welch’s two sample t test (p<0.05 were considered significant). Single stars indicate a statistically significant difference in DHT levels between Cx vs. Cx+Dut treated samples at d3-21 of treatment. Double stars indicate a significant difference in DHT levels between Cx vs. Cx+Dut treated samples even after castration-recurrent re-growth. No other comparisons between Cx vs. Cx + Dut treated groups were significant. Expression of full length (FL) AR and the AR variant 7 (ARV7) truncated splice variant was measured in LuCaP35 (<b>C</b>) and LuCaP96 (<b>D</b>) at the time of tumor re-growth to 750 mm³. Transcript expression was measured by qRT-PCR and normalized to expression of the housekeeping gene RPL13A within each sample to yield the delta cycle threshold (dCt). The relative difference in expression between the indicated treatment groups was calculated using the delta dCt method (fold change = 2∧ddCt). P values computed from Welch’s two sample t test (p<0.05 were considered significant).</p

Response to dutasteride by tumor size at enrollment in LuCaP35 xenografts.

<p>Kaplan-Meier plots of progression free survival (defined as tumor size <750 mm3) in all LuCaP35 tumors treated with castration alone (Cx) vs. castration + dutasteride (Cx + Dut) (<b>A</b>), and in tumors enrolled into treatment when tumors were <250 mm³ (<b>B</b>). P-values for curve comparisons were generated using the Mantel-Haenszel logrank test. Mean tumor volume growth curves at the indicated days post enrollment in LuCaP35 tumors enrolled into treatment when tumors were <250 mm³ (<b>C</b>), between 250–400 mm³ (<b>D</b>), and >400 mm³ (<b>E</b>). Dutasteride treatment was continued for 8 weeks (denoted by black line above x-axis) in the castration + dutasteride group.</p