Clinical Utility of the AJCC 8th Edition pT1 Subclassification and Impact on Practice Patterns in Stage I Seminoma




Badia, Rohit Reddy

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BACKGROUND: The American Joint Committee on Cancer 8th edition staging guidelines for testicular cancer established a 3 cm cutoff to subclassify stage T1 seminomas (<3 cm = pT1a and ≥3 cm = pT1b). The efficacy of this cutoff in predicting metastatic disease and impact on treatment patterns have not been studied. METHODS: We retrospectively reviewed patients with pT1 testicular seminoma in the National Cancer Database from 2004-2016. Receiver operating curves (ROC) were used to determine the efficacy of the 3 cm tumor cutoff in identifying metastatic disease, and multivariable regression was used to compute the effect of tumor size on the rate of adjuvant therapy among Stage I patients. RESULTS: 10,134 patients with pT1 seminoma were evaluated. The current size cutoff of 3 cm for subclassification did not exhibit high discrimination in identifying metastatic disease (area under ROC: 0.546). Surveillance has grown as the preferred treatment after orchiectomy - 32.1% in 2004 to 81.2% in 2015. However, the rate of adjuvant therapy for pT1, Stage I seminomas associated positively with tumor size even with adjustment for year of diagnosis. For tumors above 3 cm, the odds ratio stabilized around 1.9. By using the 3cm cutoff to guide adjuvant therapy, up to 85% of T1b patients may be overtreated. CONCLUSION: The 3 cm cutoff for subclassification of Stage I seminoma does not predict metastatic recurrence but is associated with increased receipt of adjuvant therapy. A 3 cm cutoff and the pT1a/b classification may therefore contribute to overtreatment in many young patients with a long life expectancy for whom minimizing adverse effects should be prioritized.

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