**8. Active Surveillance of PTMC**

Having established that PTMC can be treated conservatively does not mean that the individuals diagnosed with a usually indolent benign behaving thyroid lesion stop being patients. Indeed, avoiding surgery in PTMC may actually be more expensive than surgery as it is replaced by "active surveillance (AS)".

Japanese data have explored AS for the management of incidentally identified uncomplicated PTMC. Long-term longitudinal follow-up studies in Japan have demonstrated that PTMC can safely be treated conservatively with no significant morbidity and no increase in disease-specific mortality [84–86]. Following 1235 patients for up to 227 months with biopsy-confirmed thyroid malignancy showed 0% distant metastatic rates and the small percentage of patients with tumour progression or new lymph node metastases showed excellent outcomes with rescue surgery [35,46]. Given the absence of reliable predictors of which PTMC will remain dormant and which will develop into clinically significant disease, the active surveillance patients are monitored radiologically at variable intervals indefinitely. The cost implication of identifying an indolent thyroid cancer whether followed by surgery or AS is rarely considered, nor indeed the psychological impact of a "cancer" diagnosis that stays with the patient indefinitely.

It has been shown that in an American and Canadian context nonoperative management of PTMC is associated with a modest decrement in QoL. Indeed, a thyroid lobectomy appeared cost-effective and is associated with an ICER of £3192/QALY, well below the study's willingness-to-pay threshold [87]. Deterministic sensitivity analysis revealed that the cost-effectiveness was highly dependent on the relative disutility of AS, meaning the patient-specific QoL decrement due to AS, as well as on the remaining life expectancy after diagnosis. It remains clear that the diagnosis of PTMC is undesirable both for the patient and the healthcare system except for the minority that develops a true PTC. A recent meta-analysis demonstrated tumour growth in 4.4% of 4156 patients with AS for low-risk PTMC, with only 1.0% developing cervical lymph node metastasis, and 0.04% developing metastatic disease over a pooled mean period of 44 months [88].
