DO THE METASTATIC PATTERNS OF SEMINOMA SUPPORT PRIMARY RPLND AS THE TREATMENT OF CHOICE IN STAGE II SEMINOMA COMPARED TO NON-SEMINOMA?

Abstract

Introduction

Primary RPLND is one treatment modality for stage II seminoma germ cell tumor (SGCT) cases. In theory, the success of the procedure relies on having the disease confined within the dissected lymph nodes with no presence of any undetected organ metastatic disease outside the surgical margins. While SGCT characteristics and behavior have been well described in comparison to non-seminoma germ cell tumors (NSGCT), quantifying the probability and absolute causal effect of SGCT subtype in having advanced metastatic disease (i.e., Stage III) compared to NSGCT has not been described using large national dataset yet. Therefore, we aim to quantify and describe this relationship using the National Cancer Database (NCDB).

Methods

We utilized inverse propensity score weights (IPTW) calculated by age, primary tumor characteristics, patient sociodemographic, regional and facility level, and year of diagnosis to run a multivariable IPTW-weighted logistic regression model (MVA) for the outcome of stage III (vs. stage I/II) to estimate the odds ratio of SGCT presenting with stage III. Then, we utilized IPTW to estimate the absolute average causal effect of SGCT v.s. NSGCT in developing stage III in our balanced IPTW-matched study sample.

Results

We identified 62,329 testicular germ call cancer patients between 2004 and 2016 (details available in Table 1). Our IPTW-MVA showed that SGCT is significantly less likely to present with stage III disease compared to NSGCT after accounting for all available covariates (OR: 0.303, [95%CI; 0.278 – 0.330], p<0.0001), based of the same model we estimated the mean causal effect of presenting as stage III to be significantly less likely in SGCT compared to NSGCT by 66.41% if all other patients parameters and variables were the same (- 62.41% [95%CI: - 65.00%, -59.82%], p<0.0001).

Conclusions

Our results strongly validate the use of primary-RPLND in SGCT as opposed to NSGCT, as SGCT are 62.41% less likely to present with advanced stage given the same parameters in NSGCT. In addition torecent favorable clinical trial results, primary RPLND in carefully selected SGCT patients should be highly considered to avoid long-term complications associated with other treatment modalities.