Response to Growth Hormone Treatment after Radiation Therapy Depends on Location of Irradiation.

OBJECTIVES Cancer survivors with GH deficiency (GHD) receive GH therapy (GHT) after 1+ year(y) observation to ensure stable tumor status/resolution. Hypothesis: radiation therapy (RT) to brain, spine, or extremities alters growth response to GHT. Aim: identify differences in growth response to GHT according to type/location of RT. METHODS KIGS (Pfizer International Growth Database) was searched for cancer survivors on GHT for ≥5y. Patient data, grouped by tumor type, were analyzed for therapy (surgery, chemotherapy, RT--focal CNS, cranial, craniospinal, or total body RT [TBI] as part of bone marrow transplantation), gender, peak stimulated GH, age at GHT start, and duration from RT to GHT start. Kruskal-Wallis test and Quantile regression modeling were performed. RESULTS Of 1149 GHD survivors on GHT for ≥5y (male 733; median age 8.4y; GH peak 2.8 ng/mL), 431 had craniopharyngioma (251, cranial RT), 224 medulloblastoma (craniospinal RT), 134 leukemia (72, TBI), and 360 other tumors. Median age differed by tumor group (P<0.001). Five-year delta height SDS (5y ∆HtSDS; median [10th-90th %ile]) was greatest for craniopharyngioma, 1.6 (0.3-3.0); for medulloblastoma, 5y ∆HtSDS 0.9 (0.0-1.9); for leukemia 5y ∆HtSDS, after TBI (0.3, 0-0.7) versus without RT (0.5, 0-0.9), direct comparison P<0.001. Adverse events (AEs) included 40 treatment-related, but none unexpected. CONCLUSIONS TBI for leukemia had significant impact on growth response to GHT. Medulloblastoma survivors had intermediate GHT response, while craniopharyngioma cranial RT did not alter GHT response. Both craniospinal and epiphyseal irradiation negatively affect growth response to GH therapy, compared to only cranial RT or no radiation therapy.