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Sublethal Irradiation Induces Vascular Endothelial Growth Factor and Promotes Growth of Hepatoma Cells: Implications for Radiotherapy of Hepatocellular Carcinoma

Authors' Affiliations: Departments of ¹ Radiation Oncology, ² Radiology, ³ Internal Medicine, and ⁴ Clinical Protocol Office, Koo Foundation Sun Yat-Sen Cancer Center; and ⁵ School of Medicine, National Yang-Ming University, Taipei, Taiwan

Requests for reprints: Yih-Lin Chung, Department of Radiation Oncology, Koo Foundation Sun Yat-Sen Cancer Center, No. 125 Lih-Der Road, Taipei, Taiwan. Fax: 886-2-27020372; E-mail: ylchung{at}mail.kfcc.org.tw.

Purpose: To investigate the clinical benefit of additional radiotherapy to patients with unresectable hepatocellular carcinoma treated with transcatheter arterial chemoembolization (TACE) and the molecular effects of radiation on gene expression in hepatoma cells.

Experimental Design: Between August 1996 and August 2003, 276 and 64 patients with American Joint Committee on Cancer stage T₃N₀M₀ hepatocellular carcinoma receiving TACE alone and TACE followed by three-dimensional conformal radiotherapy, respectively, at our institution were studied. Clinical outcome and pattern of failure were analyzed for the association of survival benefit with radiotherapy. The molecular effects of radiotherapy were studied in vitro and in vivo using human hepatoma cells with different p53 mutation and hepatitis B virus infection status.

Results: Median follow-up and survival time in the TACE alone and TACE + radiotherapy groups were 39 and 19 months, and 51 and 17 months, respectively. Additional radiotherapy to TACE did not improve overall survival (P = 0.65). However, different failure patterns were noted after TACE and after radiotherapy. Although all irradiated tumors regressed substantially, radiotherapy rapidly enhanced both intrahepatic and extrahepatic tumor progression outside the radiotherapy treatment field in a significant portion of patients, which offset the benefit of radiotherapy on overall survival. In molecular analysis of the radiation effects on human hepatoma cells, radiotherapy rapidly induced p53-independent transcriptional up-regulation of vascular endothelial growth factor (VEGF), increased VEGF secretion in a dose-, time-, and cell type–dependent manner, and promoted hepatoma cell growth in vivo with enhanced intratumor angiogenesis, which correlated well with elevated levels of serum VEGF.

Conclusions: Radiotherapy to eradicate a primary hepatocellular carcinoma might result in the outgrowth of previously dormant microtumors not included in the radiotherapy treatment field. Radiotherapy-induced VEGF could be a paracrine proliferative stimulus. Therapeutic implications of the study justify the combination of three-dimensional conformal radiotherapy with anti-VEGF angiogenic modalities for the treatment of unresectable hepatocellular carcinoma to reduce relapses.

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