The use of the marker tumor concept in Ta, T1 bladder cancer: is it justified?

Abstract

Adjuvant instillations with chemo- or immunotherapy agents after transurethral resection of Ta, T1 bladder tumors are administered on non-measurable non-visible disease. To know whether adjuvant therapies are efficacious the marker tumor concept has been developed. The use of marker lesions has been questioned by many as dangerous and/or unethical because a deliberately left-behind tumor might be invasive or become invasive if the adjuvant therapy is not effective. However, 4 EORTC, 2 British, and one Japanese study using different drugs have shown that it is safe and ethically justified to use the marker tumor concept in clinical phase II studies. Data from six trials indicate the the risk of leaving an invasive tumor behind or that a tumor might progress while being treated with instillations is 0.8% (3/383). Marker lesion studies should be limited to intermediate risk patients. Expensive and inefficient long term phase III trials may be avoided by marker tumor trials. Exposing patients to ineffective drugs in prophylactic trials also jeopardizes the patient with regard to recurrence and/or progression of their bladder tumors.