Radiation therapy for hepatocellular carcinoma: current status and perspectives from our experience

Abstract

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide and is accompanied by a poor prognosis. We had reported that radiation therapy has great potential, in a wide spectrum of primary liver cancers, from local advanced stage of the disease to the more advanced stages, with regional nodal metastases, tumor thrombosis, and for palliation of distant metastases. Following the initial observation that HCC is radiosensitive and with the development of radiation technology, radiotherapy has become a feasible and promising treatment modality for HCC, particularly for advanced forms of the disease. Here, we review the substantial amount of available data on radiotherapy for HCC, report on the current status of this application of radiotherapy, and propose future avenues of research. Current status Hepatocellular carcinoma (HCC) is radiation-sensitiveThis conclusion is based primarily on the results of experimental study and clinical observation. Experimental resultsIn radiation biology, we determined that the a/b ratio of HCC is 11.2 Gy. This is equivalent to the value of poorly differentiated squamous cell carcinoma, with the survival curves of clonogenic cell assay applying the linear-quadratic (L-Q) model [1]. Clinical observationIt has been possible to deliver 70 Gy or higher doses directly to the HCC tumor with the availability of threedimensional conformal radiation therapy (3DCRT). It has been reported that a dose of 70 Gy results in complete remission of an intrahepatic tumor of more than 10 cm in diameter. As we had observed in the clinic, the objective response rate was 76% for a dose range of 50-60 Gy [2]. In patients with lymph node (LN) metastases of HCC, partial or complete responses were observed in 90% of those treated with 54 Gy and when the radiation dose was increased to 60 Gy, complete remission of the LN metastases was observed [3]. Tai et al. [4] estimated an a/b value of 15 ± 2 Gy, based on clinical data and using the Lyman model, which is consistent with the results of our clonogenic assay. These findings suggest that the radiosensitivity of HCC is similar to that of a poorly differentiated squamous cell carcinoma, such as nasopharyngeal carcinoma.Radiotherapy is effective for different stages of HCC, although higher level evidence-based medicine (EBM) is lackingTranscatheter arterial chemoembolization (TACE) combined with radiotherapy constitutes an improved therapeutic strategy for unresectable but confined intrahepatic HCC Transcatheter arterial chemoembolization does not induce complete or massive necrosis of HCC tumors greater than