Investigators have studied whether a slow decline in hCG and AFP during chemotherapy could single out patients likely to fail conventional therapy [7, 12–14]. A subgroup of patients with poor-prognosis NSGCT with a better outcome was identified based on a tumour marker decline assessed 3 weeks after the start of chemotherapy [14]. Baseline and days 18–21 tumour marker values are introduced into a logarithmic formula, which defines a favourable and an unfavourable decline pattern in serum tumour markers. A decline is defined as favourable only if both AFP and hCG declines are considered favourable by the formula. The calculator tool is available online at http://​www.​gustaveroussy.​fr/​calculation-tumor/​NSGCT.​html. Using this method, patients with an unfavourable decrease and those with a favourable decrease had a 3-year PFS rate of 46 and 73 % (p = 0.01) and an overall survival (OS) rate of 59 % and 81 % (p = 0.02), respectively [14]. These data were prospectively confirmed in a separate set: 48 % [95 %CI: 38; 59 %] versus 70 % [95 %CI: 57–81 %] for 3-year PFS (p = 0.01) and 65 % [95 %CI: 55–75 %] versus 84 % [95 %CI: 71–92 %] for OS (p = 0.02) in patients with poor-risk NSGCT and an unfavourable and a favourable decline, respectively [15].