I met a new patient in clinic this week who has a solitary pulmonary nodule that has been followed with serial CT scans for a year, contains calcification, is FDG-PET-negative, and was biopsied with no evidence of malignant cells. It grew from 14mm to 17mm on the latest CT, and he came self-referred to me to have it ablated. He was quite miffed that I insisted he have another biopsy to prove that this was cancer before I would ablate him. His rationale was that if I ablated it, he wouldn’t have to worry about it anymore. The scary thing is that his local radiation oncologist was willing to Cyberknife him without a diagnosis.
Image-guided biopsy is an indispensable tool in oncology. As my chief of GI Oncology is fond of saying, “no meat -- no treat!”. An accurate histologic diagnosis provides important prognostic information and helps to guide therapy. In addition to cytologic grading, immunohistochemical staining and genetic analysis adds specificity to diagnosis, prognosis, and potential therapeutic targets. Biopsy tissue can be screened for susceptibility to specific chemotherapeutic drugs.
From the standpoint of the interventional oncologist, biopsies are time-consuming, can be technically tricky, and the reimbursement stinks. It is tempting to leave them to the diagnostic radiologists, who can make up the revenue reading dozens of CT and MR studies daily. As I discussed in a prior post, there are a number of downsides to abandoning biopsies (see “What is an Interventional Oncology Practice?”, September 24) First, diagnostic radiologists suck at them. They do wimpy fine-needle cytologic aspirates instead of definitive core biopsies, then coming running to us to manage their complications. More importantly, every request for a biopsy is a point of contact with a patient and a referring physician. This is a free invitation to insert an IO consultation into the patient’s care. A chance to biopsy is a chance to ablate, with negligible added morbidity -- but only if you meet the patient first and get to have that conversation.
So who really needs a biopsy?
10%-15% of resected renal masses are benign, and the proportion goes up as the tumor size gets smaller: from 25% for masses under 3 cm to 45% for masses under 1 cm. Markov modeling suggests that biopsy is the most cost-effective strategy for small renal masses. I usually biopsy and ablate at the same setting, for efficiency and safety, but others insist on a histologic diagnosis before doing an ablation. Even then, renal mass biopsies are non-diagnostic about 20% of the time, and compared to resected specimens turn out to be wrong 10% of the time.
Liver nodules present a similar conundrum. Despite our diagnostic colleagues’ best efforts, including the introduction of the LI-RADS classification to give the illusion of standardization to their reads, explant pathology reveals the high error rate of imaging diagnosis. Ten percent of primary intrahepatic tumors turn out to be cholangiocarcinoma or mixed histology, which changes the prognosis and therapy. Even liver metastases can fool you. I have several patients with primary adenocarcinomas whose metachronous liver lesions turned out to be neuroendocrine tumors on biopsy, again dramatically changing their prognosis and management.
All in all, biopsies are good for patients, and good for interventional oncologists.