77 Pa. Stat. § 1513
The board, or a referee designated by the board, may, at any time, review and modify or set aside an existing original or existing supplemental agreement, upon petition filed by either party with the board or in the course of the proceedings under any petition pending before such board or referee, if it be proved that such agreement was in any material respect incorrect.
The board or referee designated by the board, may, at any time, modify, reinstate, suspend, or terminate an original or supplemental agreement or an award, upon petition filed by either party with such board, upon proof that the disability of the employe has increased, decreased, recurred, or has temporarily or finally ceased, or that the status of any dependent has changed. Such modification, reinstatement, suspension, or termination shall be made as of date upon which it is shown that the disability of the employe has increased, decreased, recurred, or has temporarily or finally ceased, or upon which it is shown that the status of any dependent has changed: Provided, That an agreement or an award can only be reviewed, modified, or reinstated during the time such agreement or award has to run, if for a definite period; and no agreement or award shall be reviewed, or modified, or reinstated, unless a petition is filed with the board within two years after the date of the most recent payment of compensation made prior to the date of filing such petition. Where, however, a person is receiving benefits pursuant to the act of June 28, 1935 (P.L. 477, No. 193), referred to as the Heart and Lung Act, the two-year period in which a petition to review, modify, or reinstate a notice of compensation, agreement, or award must be filed, shall not begin to run until the expiration of the receipt of benefits pursuant to said Heart and Lung Act. Where compensation has been suspended because the employe's earnings are equal to or in excess of his wages prior to the disability payments under the agreement or award may be resumed at any time during the period for which compensation for partial disability is payable, unless it be shown that the loss of earnings does not result from the disability due to the exposure.
The board or referee to whom any such petition has been assigned may subpoena witnesses, hear evidence, make findings of fact, and award, or disallow compensation in the same manner and with the same effect and subject to the same right of appeal, as if such petition were an original claim petition.
The filing of a petition to terminate or modify a compensation agreement or award as provided in this section shall operate as a supersedeas, and shall suspend the payment of compensation fixed in the agreement or by the award, in whole or to such extent as the facts alleged in the petition would if proved, require.
77 P.S. § 1513