Patients with stage IIa testicular seminoma experienced prolonged OS when they received radiotherapy rather than multi-agent chemotherapy, according to an analysis using the National Cancer Data Base presented at the European Society for Therapeutic Radiology and Oncology conference.
However, this benefit did not persist for patients with stage IIb disease, results showed.
“Testicular seminoma is a rare disease, [so] there is a lack of randomized data to guide treatment and many prior studies have been limited by small sample sizes,” Scott Glaser, MD, resident physician at University of Pittsburgh Cancer Institute, said in a press release. “It has, therefore, been difficult to tease out small differences in efficacy of radiation therapy versus chemotherapy.”
The National Comprehensive Cancer Network recommends radiotherapy for stage IIa disease, whereas the European Association of Urology guidelines recommend radiation or multi-agent chemotherapy. Both guidelines call for radiation or multi-agent chemotherapy for stage IIb disease and multi-agent chemotherapy for stage IIc disease.
In general, stage II testicular seminoma is highly curable with multi-agent chemotherapy or radiation, but the two modalities have never been prospectively compared.
“The trend away from radiation therapy may be due to a misperception that it is more toxic than three or four cycles of multi-agent chemotherapy,” Glaser said. “Across this large, national dataset, radiation therapy was associated with a better outcome for stage IIa patients and equivalent outcomes for stage IIb patients. However, potential explanations for these improved outcomes are less clear.”
Researchers used the National Cancer Data Base to analyze predictive factors for the use of radiation vs. multi-agent chemotherapy and determine their corresponding OS among 2,437 patients diagnosed between 1998 and 2012 with stage II testicular seminoma (IIa, n = 960; IIb, n = 812; IIIc, n = 665).
Median follow-up was 65 months.
Rates of radiation usage were higher than those of multi-agent chemotherapy among patients with stage IIa disease (78.1% vs. 21.9%) and stage IIb disease (54.4% vs. 45.6%), but lower among patients with stage IIc disease (4.2% vs. 95.8%).
Use of radiation decreased over time for patients with stage IIa (P = .0001) and IIb disease (P = .016), whereas use of multi-agent chemotherapy increased.
Among patients with IIa or IIb disease, those who were diagnosed in a later year, were treated at an academic facility, or underwent pathologic assessment of lymph nodes were more likely to receive multi-agent chemotherapy.
Charlson-Deyo comorbidity scores of 1 or higher and having non-private insurance also increased likelihood of receiving multi-agent chemotherapy among patients with stage IIa disease, whereas a T stage of 2 or higher increased the likelihood for patients with stage IIb disease.
Rates of unadjusted 5-year OS were 97.1% (95% CI, 96.1-98.1) for stage IIa disease, 93.9% (95% CI, 92.1-95.7) for stage IIb disease, and 92.6% (95% CI, 90.6-95.6) for stage IIc disease (P = .006).
Five-year OS was higher among patients with stage IIa disease treated with radiation vs. multi-agent chemotherapy (99% vs. 93%).
The data also showed a radiation advantage on multivariable analysis (HR = 0.22; 95% CI, 0.08-0.64) and propensity-adjusted analysis (HR = 0.28; 95% CI, 0.09-0.88).
Among patients with stage IIb disease, 5-year OS rates were 95.2% (95% CI, 92.8-97.6) for those who received radiation and 92.4% (95% CI, 89.2-95.6) for those who received multi-agent chemotherapy (P = .04).
However, multivariable (HR = 0.74; 95% CI, 0.32-1.7) and propensity-adjusted analyses (HR = 0.77; 95% CI, 0.33-1.8) were not statistically significant.
The researchers acknowledged that their analysis may be limited due to the lack of data on staging workup, specific chemotherapy regimen, number cycles for chemotherapy and nonadherence.
“We would advocate for radiotherapy continuing to be the preferred treatment for stage IIa patients and for a risk-adapted approach for stage IIb patients,” Glaser and colleagues wrote.
These data need confirmation, Philip Poortmans, MD, PhD, head of department of radiation oncology at Radboud University Medical Center in Nijmegen, the Netherlands and president of ESTRO, said in the press release.
“The movement away from radiation therapy in favor of chemotherapy, induced by the fear of a higher rate of late toxicity, is now suggested to be probably not the right one for patients with stage IIa testicular seminoma, with an OS benefit in favor of radiation therapy up to at least 10 years after treatment,” Poortmans said. “Ideally, these results should be confirmed in a prospective trial with a very long-term follow-up, including a thorough analysis of side effects. However, this might be difficult to achieve.” – by Nick Andrews
Glaser SM, et al. Clin Oncol.2016; doi:10.1016/j.clon.2016.02.008.
Glaser SM, et al. Abstract E35-0121. Presented at: ESTRO 35 Conference; April 29-May 3, 2016; Turin, Italy.
HemOnc Today was unable to confirm the researchers’ relevant financial disclosures at the time of reporting.