L-[1-C-11]-tyrosine PET to evaluate response to hyperthermic isolated limbperfusion for locally advanced soft-tissue sarcoma and skin cancer

PET with L-[1-C-11]-tyrosine (TYR) was investigated in patients undergoing hyperthermic isolated limb perfusion (HILP) with recombinant tumor necrosis factor alpha (rTNF-alpha) and melphalan for locally advanced soft-tissue s arcoma and skin cancer of the lower limb. Methods: Seventeen patients (5 wo men, 12 men; age range 24-75 y; mean age 52 y) were studied. TYR PET studie s were performed before HILP and 2 and 8 wk afterwards. The protein synthes is rates (PSRs) in nanomoles per milliliter per minute were calculated. Aft er final PET studies, tumors were resected and pathologically examined. Pat ients with pathologically complete responses (pCR) showed no viable tumors after treatment. Those with pathologically partial responses (pPR) showed v arious amounts of viable tumors in the resected tumor specimens, Results: S ix patients (35%) showed a pcR and 11 patients (65%) showed a pPR. All tumo rs were depicted as hot spots on PET studies before HILP. The PSR in the pC R group at 2 and 8 wk after perfusion had decreased significantly (P < 0.05 ) in comparison to the PSR before HILP, A significant difference was found in PSR between the pCR and pPR groups at 2 and at 8 wk (P < 0.05). Median P SR in nonviable tumor tissue was 0.62 and ranged from 0.22 to 0.91. With a threshold PSR of 0.91, sensitivity and specificity of TYR PET were 82% and 100%, respectively. The predictive value of a PSR > 0.91 for having viable tumor after HILP was 100%, whereas the predictive value of a PSR less than or equal to 0.91 for having nonviable tumor tissue after HILP was 75%, The 2 patients in the pPR groups with a PSR < 0.91 showed microscopic islets of tumor cells surrounded by extensive necrosis on pathological examination, Conclusion: Based on the calculated PSR after HILP, TYR PET gave a good ind ication of the pathological outcome. Inflammatory tissue after treatment di d not interfere with viable tumor on the images, suggesting that it may be worthwhile to pursue TYR PET in other therapy evaluation settings.