The objective of the study was to explore the impact of the surgery volume on the course and outcome of the papillary thyroid cancer depending on the risk factors. This is a retrospective study with 3,266 successive cases of papillary thyroid cancer registered from 1990 till 2005 in subjects residing in Minsk or Minsk Region at the moment of diagnosing, with a medium observation of 10.2 years. In the group of postoperative patients, 5-, 10- and 20-year cause-specific survival was 99.0±0.2％, 98.0±0.2％, 97.3±0.6％, and cumulative relapse rate was 6.0±0.5％, 8.2±0.6％, 14.3±1.5％, respectively. Life expectancy of patients with papillary thyroid cancer is mainly established by the independent prognostic factors, and not by the volume of surgical intervention, which is related to the early diagnosing of a relapse and timely performed repeated surgery. The key factors defining the risk of death due to cancer are age over 55 years in women (PR＝30.08, p＜0.0001) , and 35 years (PR＝22.15, p＜0.0001) in men, presence of distant metastasis (p＜0.0001) , and massive extrathyroidal extension of a tumour (p＜0.0001) . Metastatic involvement of regional lymph nodes 7.26-fold increases the risk of relapse (p＜0.0001) and is a key prognostic factor. Organ preservation surgeries 3.3-fold increase the risk of relapse (p＜0.0001) , and absence of lymph node dissection - 2.85-fold (p＜0.0001) .

Conclusions:

1. Age, distant metastasis, and massive extrathyroidal extension are the key independent prognostic factors, which define the risk of death due to papillary thyroid cancer. The age of 55 years for women and of 35 years for men can be more accurately used for division of patients between the prognostic groups.

2. Thyroidectomy and bilateral lymph node dissection significantly reduce the risk of relapse, but statistically do not influence the cause-specific survival.

3. Presence of metastasis in the regional lymph nodes is a decisive factor of relapse. It testifies to insufficiently removed level III and level IV lymph nodes in case of any signs of their metastatic affection, and requires an extension of the lymph node dissection volume in such patients.