Prognostic Factors and Outcomes in Clinical Stage II Testicular Seminoma Treated with Radiation Therapy at Two Institutions

Abstract

<h3>Purpose/Objective(s)</h3> Clinical stage II (CS2) testicular seminoma has been historically treated with chemotherapy or radiation (RT). Limited data exists reporting outcomes with contemporary RT dose and fields, and between de novo CS2 vs. relapsed stage I seminoma. We investigated recurrences in CS2 seminoma patients treated in the modern era across two institutions. <h3>Materials/Methods</h3> A retrospective review was performed of 71 patients who received RT for CS2 seminoma between 2001-2021. Recurrence-free survival (RFS) was determined using the Kaplan-Meier method. Univariate analysis for recurrence was calculated using Cox proportional hazard regression. Recurrence was defined as a new lymph node or mass, biopsy-proven to be seminoma, after RT completion. Covariates tested included: CS2 at orchiectomy (de novo) or CS2 diagnosed on surveillance after orchiectomy (relapsed), lymphovascular invasion (LVI), lymph node (LN) size at CS2 diagnosis, AJCC staging, RT modality, and treatment decade (2000s vs 2010s). Second malignancies were recorded as a biopsy-proven malignancy originating in the prior RT field. <h3>Results</h3> The median age at diagnosis was 39 years (IQR: 34, 46). Thirty-six (51%) patients presented with de novo CS2 while 35 (49%) patients had relapsed CS2. Staging was: IIA = 38, IIB = 33. Patients were treated with AP/PA (n = 45), or other (3D/conformal, VMAT or protons (n = 20)). Median follow-up time was 4.3 years (IQR: 1.9 – 7.1). Overall RFS was 91% at 1 year, 89% at 2 years, and 82% at 5 years. All recurrences were outside the RT field. De novo CS2 and patients treated in the second decade (2012-2021) exhibited a trend towards decreased recurrence (Table 1). RFS of the de novo cohort was 86%, 83%, and 74% at 1, 2, and 5 years, respectively. RFS of the relapsed cohort was 97%, 97%, and 91%, at 1, 2, and 5 years, respectively. Nine of the recurrences were salvaged with chemotherapy and one was salvaged with RT. There were no deaths due to seminoma. Two second malignancies occurred, a prostate cancer and a colorectal cancer (from which the patient died). <h3>Conclusion</h3> In this contemporary cohort of patients with stage II seminoma treated with modern RT, recurrence was uncommon, particularly for patients with relapsed CS2 and those treated in most recent decade, and exclusively occurred outside the RT field. All patients were successfully salvaged, and disease-specific survival was 100%. De novo CS2 approached statistical significance as a negative prognostic factor and may portend more aggressive or already metastatic disease.