Compensation pursuant to cancer suffered by a firefighter shall only be to those firefighters who have served four or more years in continuous firefighting duties, who can establish direct exposure to a carcinogen referred to in section 108(r)¹ relating to cancer by a firefighter and have successfully passed a physical examination prior to asserting a claim under this subsection² or prior to engaging in firefighting duties and the examination failed to reveal any evidence of the condition of cancer. The presumption of this subsection may be rebutted by substantial competent evidence that shows that the firefighter's cancer was not caused by the occupation of firefighting. Any claim made by a member of a volunteer fire company shall be based on evidence of direct exposure to a carcinogen referred to in section 108(r) as documented by reports filed pursuant to the Pennsylvania Fire Information Reporting System and provided that the member's claim is based on direct exposure to a carcinogen referred to in section 108(r). Notwithstanding the limitation under subsection (c)(2)³ with respect to disability or death resulting from an occupational disease having to occur within three hundred weeks after the last date of employment in an occupation or industry to which a claimant was exposed to the hazards of disease, claims filed pursuant to cancer suffered by the firefighter under section 108(r) may be made within six hundred weeks after the last date of employment in an occupation or industry to which a claimant was exposed to the hazards of disease. The presumption provided for under this subsection shall only apply to claims made within the first three hundred weeks.