In the management of stage I testicular cancer, a persistent clinical dilemma is the identification of patients who truly need adjuvant treatment after orchiectomy rather than active surveillance alone. Interim results from the CLIMATE study found post-orchiectomy Plasma miR-371a-3p (miR-371), a measure of measurable residual disease (MRD), to be superior to existing biomarkers of recurrence. The prospective cohort trial enrolled 200 patients across Australia and New Zealand, and the findings were presented at the 2026 ASCO Genitourinary Cancers Symposium.1
“Post-orchiectomy miR-371 has the potential to optimize patient selection for adjuvant chemotherapy,” said Ben Tran, MD, MBBS, FRACP, a medical oncologist at Peter MacCallum Cancer Centre in Melbourne, Australia.
Addressing the Clinical Problem: Finding the Right Tool
Stage I testicular cancer is highly curable. Orchiectomy alone is sufficient for many patients, making active surveillance the preferred management strategy for the majority. A subset of patients will relapse, however, and adjuvant chemotherapy with one or two cycles of bleomycin, etoposide, and cisplatin (BEP) significantly reduces recurrence risk in those deemed high-risk. The problem is that the available tools for defining “high-risk” are imprecise.
“Adjuvant chemotherapy is considered for those at high risk of recurrence. However, its use can lead to unnecessary treatment and toxicity for the majority of patients who may be cured by orchiectomy alone,” Dr. Tran said. “Improved biomarkers that identify patients at very high risk of recurrence are needed so that we can optimize the use of adjuvant chemotherapy and minimize treatment while maximizing outcomes.”
miR-371 is a small non-coding RNA that is highly expressed in germ cell tumors and detectable in circulating blood. Its theoretical appeal as an MRD marker is considerable: it is germ cell tumor-specific, has high sensitivity and specificity in prior diagnostic work, and, crucially, has a very short half-life (3-7 hours), meaning that a positive post-orchiectomy signal likely reflects residual viable tumor rather than clearance kinetics. Despite this promise, retrospective data have been conflicting, and no prospective head-to-head comparison had been conducted before the CLIMATE study was designed, in part, to resolve this question directly.
Study Design
CLIMATE is a prospective cohort study assessing the clinical utility of miR-371 as a marker of MRD in clinical stage I testicular germ cell tumors. The trial, conducted by the Australian and New Zealand Urogenital and Prostate Cancer Trials Group (ANZUP), enrolled 200 patients with stage I testicular cancer (both seminoma and non-seminoma) from centers across Australia and New Zealand. Patients were enrolled within 6 weeks of orchiectomy and all were managed with active surveillance per ANZUP surveillance recommendations; no upfront adjuvant therapy was permitted at enrollment.
Blood samples, both serum and plasma, were collected at baseline (post-orchiectomy) and then every 3 months for 2 years, with an additional sample collected at documented recurrence if it occurred within 3 years. Samples were processed and frozen within 3 hours of collection. All clinical data were entered into the iTestis registry, Australia’s national testicular cancer database. The samples were assayed using a quantitative polymerase chain reaction (PCR) method, with strict protocol controls.
The primary objective was to determine the positive predictive value (PPV) and negative predictive value (NPV) of a post-orchiectomy miR-371 result in forecasting recurrence. Key secondary objectives included comparing serum vs plasma performance, and prospective validation in collaboration with international study partners. The interim analysis reported focuses exclusively on the baseline (post-orchiectomy) sample.
Positive MRD Predicts Recurrence
The cohort of 200 patients, median age 33, comprised 117 patients with pure seminoma and 79 with non-seminoma tumors. Baseline (post-orchiectomy) samples were available for 196, collected at a median of 29 days postsurgery. At the time of data cutoff, there were 40 recurrences—8% in the seminoma group (median time to recurrence 6.7 months) and 38% in the non-seminoma group (median time to recurrence 4.0 months), with an overall median follow-up of 18.9 months.
The findings confirmed what retrospective data had suggested: plasma significantly outperforms serum. Overall concordance between the two matrices was 89%, but their performance characteristics diverged meaningfully. The serum assay identified 34 positive samples, yielding a PPV of 56% and NPV of 87%; the plasma assay identified 42 positives, with a PPV of 62% and NPV of 91%. In receiver operating curve analysis, plasma achieved an area under the curve (AUC) of 0.77 vs 0.69 for serum (P = .04). All subsequent analyses in the interim report, therefore, focused on plasma.
Plasma baseline miR-371 were robustly associated with recurrence, with a hazard ratio (HR) of 10.3 (P < .001) for a positive result. At 24 months, the recurrence-free survival rate was 32% for patients with a positive baseline result vs 89% for those who tested negative. Among the 40 patients who recurred, 14 had a negative baseline miR-371. This group had a longer median time to recurrence (6.9 months), with eight recurrences noted beyond 6 months; most were of nonseminomatous histology. Two patients had a negative miR-371 even at the time of recurrence; one had a pure teratoma (which does not express miR-371), and the second had isolated nodal positivity at recurrence without clear metastatic disease—highlighting the known biological limitations of the assay in teratoma-predominant disease, he said.
Of the 156 patients who had not recurred at data cutoff, 16 had a positive baseline miR-371. Dr. Tran noted that five of these patients had less than 12 months of follow-up, suggesting that some recurrences may emerge with additional surveillance time.
Outperforms Existing Risk Factors
Of clinical significance, according to Dr. Tran, miR-371 outperformed the established risk stratification tools in both histologies. In the 117 patients with pure seminoma, the AUC was 0.86, compared to 0.63 for Boormans risk group (P = .022) and 0.60 for tumor size > 40 mm (P = .013). In non-seminoma, baseline plasma miR-371 demonstrated an AUC 0.72, an improvement over 0.58 for lymphovascular invasion (P = .035) and 0.53 for embryonal carcinoma (P < .001).
(The Boormans risk model is a validated prognostic tool for patients with clinical stage I testicular seminoma, using tumor size, rete testis invasion, and lymphovascular invasion to define low-, intermediate-, and high-risk groups for relapse.)
Additionally, in patients with high-risk clinical factors, baseline miR-371 positivity further informed recurrence risk. In Boormans intermediate/high-risk patients, positive miR-371 at baseline was associated with a HR of 21.9 for recurrence; in patients with lymphovascular invasion, baseline positivity carried a HR of 4.2, he noted.
Findings Supported by Sensitivity Analysis
A sensitivity analysis accounted for the short follow up in the interim analysis by enriching for long-term follow up, including only those patients who did not recur and who have had at least 24 months of follow-up. In this enriched subgroup, the performance characteristics remained robust: PPV 93%, NPV 75%, AUC 0.80,and the recurrence-free survival curve was consistent with the overall cohort analysis.
External validation is also ongoing. The final analysis will include complete follow-up across all 200 patients as well as longitudinal sample data, which should help inform how serial miR-371s map onto clinical recurrence patterns and whether rising or persistently positive measurements can prompt earlier intervention.
DISCLOSURE: Dr. Tran had disclosures for Amgen, Astellas, AstraZeneca, Bayer, BMS, Ipsen, IQVIA, Janssen, Merck, MSD, Novartis, Pfizer, Roche, Sanofi, Tolmar, and Vir Biotech.
REFERENCE
1. Tran B, Lewin JH, O’Haire S, et al: Initial results from CLIMATE, a prospective cohort study assessing the clinical utility of miR-371a-3p as a marker of minimal residual disease in clinical stage 1 testicular germ cell tumour: ANZUP 1906. 2026 ASCO Genitourinary Cancers Symposium. Abstract 596. Presented February 28, 2026.
EXPERT POINT OF VIEW
“The CLIMATE study demonstrated that post-orchiectomy plasma microRNA-371a-3p (miR-371) positivity was a strong predictor of relapse in patients with clinical stage I testis cancer and outperformed our existing risk stratification strategies. However, there are too many barriers, questions, and potential pitfalls to support its routine use in clinic today,” said invited discussant Samuel A. Funt, MD, of the Genitourinary Oncology Service at Memorial Sloan Kettering Cancer Center, New York.
“The data from CLIMATE and other studies do, however, justify the timely design of interventional trials to determine the role of this biomarker in the management of testis cancer,” Dr. Funt added.
Among the issues of concern, he said, are the variable testing methodologies across institutions, the unclear natural history of miR-371-positive disease, potential patient anxiety triggered by a positive result, and importantly, the lack of data to guide when and how to intervene after a positive test.
But clearly, better biomarkers for risk are needed, Dr. Funt acknowledged. “The high curability of metastatic disease informs the management of patients with clinical stage I disease. We feel more comfortable offering surveillance, because we can cure them when and if they recur,” he said. “But we haven’t seen a new treatment incorporated for the management of testis cancer since the 1990s and cisplatin-based chemotherapy, albeit extremely effective in curing disease, has acute toxicities and also late toxicities, which are very important to consider.… I think we can all agree that we can begin developing new biomarkers to better personalize treatment and to avoid overtreatment and undertreatment in our patients.”
Dr. Funt called miR-371 “the most promising lead to date,” as it is pathognomonic for germ cell tumors. It has superior sensitivity compared to alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) and a much shorter half-life, meaning that patients can be spared weeks of serial tumor marker testing that currently follow orchiectomy. How miR-371 stacks up to circulating tumor DNA, for which there is much more limited data in GCTs, is an important question for the field. There are pros and cons of each test: ctDNA is more expensive, requires tissue and takes longer to obtain initial results, though it is widely available with an established role in other tumor types. Neither test is known to detect teratoma at this point, and this is an active area of investigation, he added.
As efficacy data for miR-371 had been conflicting, the CLIMATE study was rigorously designed and conducted to determine how well miR-371 can measure MRD and predict recurrence. The interim results achieved with plasma were “striking,” in that a positive result identified a 10-fold risk of recurrence, he commented. Relapse-free survival at 2 years was only 31.4% in miR-371-positive patients but rose to 88.9% for patients with a negative result.
“miR-371 is a marker of residual disease, specifically for clinical stage I testis cancer. The results suggest that it’s a strong predictor of relapse. But this was an interim analysis with somewhat limited follow up, and we eagerly anticipate the serial sample data to answer the question of whether or not miR-371 relapse predicts clinical relapse,” Dr. Funt concluded.
He maintained it is too soon to use miR-371 to guide the management of stage I testis cancer in the clinic; it is time to start incorporating this robust biomarker into intervention trials to firm up its role. “I think we’ve come to a fork in the road with this biomarker, and I agree with the late Yogi Berra that ‘when you come to a fork in the road, take it,’ but we should take it with collaboration and rigor, to do better for our patients.”
DISCLOSURE: Dr. Funt had personal disclosures for Allogene Therapeutics, Doximity, Urogen, Daiichi Sankyo, Generate Biomedicines, AstraZeneca/MedImmune, Genetech, Merck, and ALX Oncology.
REFERENCE
1. Tran B, Lewin JH, O’Haire S, et al: Initial results from CLIMATE, a prospective cohort study assessing the clinical utility of miR-371a-3p as a marker of minimal residual disease in clinical stage 1 testicular germ cell tumour: ANZUP 1906. 2026 ASCO Genitourinary Cancers Symposium. Abstract 596. Presented February 28, 2026.
