You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Outcome of patients with differentiated thyroid cancer risk stratified according to the American Thyroid Association and Latin American Thyroid Society risk of recurrence classification systems. Objective: To validate the proposed Latin-American Thyroid Society (LATS) risk of recurrence stratification system and to compare the findings with those of the American Thyroid Association (ATA) risk of recurrence stratification system. Subjects and Methods: Retrospective review of papillary thyroid cancer patients treated with total thyroidectomy and RAI at a single experienced thyroid cancer center and followed according to the LATS management guidelines. Each patient was risk stratified using both the LATS and ATA staging systems. The primary endpoints were (1) the best response to initial therapy defined as either remission (stimulated Tg < 1 ng/mL, negative US), or persistent disease (biochemical and/or structural) and (2) clinical status at final follow-up defined as either no evidence of disease (suppressed Tg <1 ng/mL, negative US), biochemical persistent disease (suppressed Tg > 1 ng/mL in the absence of structural disease), structural persistent disease (loco-regional or distant metastases) or recurrence (biochemical or structural disease identified after a period of no evidence of disease, NED). Results: One hundred and seventy one papillary thyroid cancer patients were included (mean age 45±16 yrs, followed for a median of 4 yrs after initial treatment). Both the ATA and LATS risk stratification systems provided clinically meaningful graded estimates with regard to the (1) likelihood of achieving remission in response to initial therapy, (2) the likelihood of having persistent structural disease in response to initial therapy and at final follow-up, (3) the likely locations of the persistent structural disease (loco-regional vs. distant metastases), (4) the likelihood of recurrence and (5) the likelihood of being NED at final follow-up. The likelihood of having persistent biochemical evidence of disease was not significantly different across the staging categories. Conclusions: Both the ATA and LATS risk of recurrence systems effectively risk stratify patients with regard to multiple important clinical outcomes. When used in conjunction with a staging system that predicts disease specific mortality, either of these systems can be used to guide risk adapted individualized initial management recommendations.
{"Chemical": []}