TPMT and cancer: Nevertheless, the BAD guidelines caution about the prolonged use of azathioprine in part because of uncertainty over cancer risk.22 Reassuringly, 95% of respondents were aware that thiopurine methyltransferase status should be checked prior to initiating azathioprine therapy.22 The factors reported as influencing respondents’ choice of systemic agent provide evidence that consultant dermatologists are aware of the risks and benefits involved with specific treatment modalities.