A member who qualifies for disability retirement under this part pursuant to this chapter because of a disabling impairment that is amenable to treatment that could be expected to restore the member’s ability to perform service in the member’s former position of employment or in a comparable level position shall participate in a treatment program prescribed by the member’s primary treating physician. Willful failure to initiate and continue participation in the program shall cause the disability retirement allowance to be terminated. In determining whether a member has good cause for failure to follow that treatment, the board shall take into account whether the treatment would abridge the member’s right to the free exercise of religion or whether the member’s physical or mental condition has worsened as determined by the member’s treating physician and substantiated by medical evidence.