Conflicting test results


My father was diagnosed with stage IVA carcinoma esophagus cancer on Feb 2011. He underwent 35 days of radiation and 4 rounds of chemo. After 2 months of his treatment, he got his pet scan and endoscopy done. His pet scan results shows positive results (SUV 9) but his biopsy is negative. We got another biopsy done whose result also was negative. Chemo Doctor is of an opinion that we should get another biopsy done as he suspects that the disease still exists and biopsy may have missed it. But radiologist believes that repeated biopsies will damage the esophagus area and may rupture the esophagus. Has anyone faced the same issue and what can be done in such situation when the opinion of the two doctors differ.