concurring.
In determining that this case presents a mirror image of the issue before us in Hebden v. Workmen’s Compensation Appeal Board (Bethenergy Mines, Inc.), 142 Pa.Cmwlth. 176, 597 A.2d 182 (1991), reversed on other grounds, 534 Pa. 327, 632 A.2d 1302 (1993), I respectfully suggest that the majority is misguided. (See Op. at 1330-1331.) Our supreme court expressly stated in Hebden that, once a claimant proves that he is disabled as a result of an occupational disease, the disability and its cause may not be relit-igated. This is because, as Justice Cappy stated, despite modern medicine, occupational diseases are progressive; thus, the claimant’s medical condition and loss of earning power do not improve. Clearly, this reasoning is not applicable in a nonoccupational disease scenario.1 However, because I do *1332not believe that Larry R. Lowe (Claimant) presented competent medical evidence to show that his work-related back injury recurred on June 1,1992,1 concur in the result reached by the Majority.
Where an expert’s opinion is based upon assumptions which are contrary to the established facts, the opinion is worthless. State Workmen’s Insurance Fund v. Workmen’s Compensation Appeal Board (Wagner), 677 A.2d 892 (Pa.Cmwlth.1996).
Here, in the initial proceeding, the referee found that Claimant sustained a work-related injury in the nature of an acute lumbosacral sprain. Because Claimant did not appeal that finding, it is final. Section 418 of the Workers’ Compensation Act, Act of June 2, 1915, P.L. 736, os amended, 77 P.S. § 833. However, in the present controversy, Joseph R. Sabo, M.D., Claimant’s medical expert, testified that he diagnosed Claimant’s work-related injury as “nerve root irritation with sciatica with radicular pain, severe LS [sic] sprain.” (O.R., Dr. Sabo’s Deposition of April 29,1993 at 10.) Dr. Sabo’s opinion that Claimant’s work-related injury recurred as of June 1, 1992 was based on that assumption, which is contrary to the established facts of this case.
Because Claimant failed to prove by competent medical testimony that his work-related injury recurred on June 1, 1992, I would affirm.
SMITH and PELLEGRINI, JJ., join in this concurring opinion.
. Moreover, I question whether the doctrine of res judicata applies here. Res judicata requires, inter alia, an identity of causes of action. Heb-den. Such an identity exists where the subject *1332matter and ultimate issues in both the old and new proceedings are the same. Id. That is not the case here.
The ultimate issue in the initial proceeding was whether Claimant had fully recovered from his work-related injury as of September 7, 1988. In the present controversy, however, Claimant alleges that his work-related injury recurred as of June 1, 1992. It is obvious to me that the two proceedings involve totally different questions relating to two completely unrelated time periods.