By: Dan Sperling, MD
In February, 2008 a “breaking news” press release (“Prostate Biopsy Spreads Prostate Cancer Cells”) was issued from a Sarasota, FL clinic headed by Dr. Ron Wheeler.[i] It appeared as an article in the website Medical News Today. Although a prompt refutation was posted by Dr. Richard Whittington (U. of Pennsylvania School of Medicine) on OncoLink.org[ii], the original article alarmed prostate cancer patients as word spread like bad gossip. This led to an unfortunate fear of biopsy that is not in the best interests of men who need an accurate diagnosis of what’s going on in their bodies. While Dr. Wheeler and others have claimed to be able to diagnose prostate cancer without a needle biopsy, the only way to gain information on the true nature of a tumor’s cell line—and some are potentially life-threatening—is by sampling the tumor’s core. In fact, track seeding in prostate biopsies is exceedingly rare, and the risks are greatly exaggerated and overblown.
Most solid tumor cancers are diagnosed by using hollow needles to obtain tissue samples from suspicious masses revealed by imaging such as ultrasound, CT scans, MRI scans, etc. The needles can be very small in diameter, which is called fine needle aspiration biopsy (FNAB), or larger in diameter, which is called core sampling. As the names imply, FNAB is able to capture only very small amounts of cells, whole core sampling extracts a larger thread of tissue that yields more information about the tumor and surrounding tissue. The path of the needle is called the track or tract, and many articles in the medical literature describe instances of new tumor activity that appears to implant and grow along the track. This is called various names: track seeding, tract seeding, needle seeding, or neoplastic seeding. In all cases, track seeding as a cause of cancer spread is considered a rare occurrence.
Incidence of track seeding in prostate biopsies
An article published by Volanis, et al. in the prestigious British Journal of Urology (June, 2014) reports a literature review conducted earlier that year. The authors systematically examined the huge PubMed literature database for research evidence “with emphasis on the incidence of seeding, clinical presentation and on risk factors including type of needle used, transrectal vs. transperineal approach, as well as tumour grade and stage.”[iii] They identified 26 articles reporting instances of needle tracking, for a total of 42 cases (9 cases occurred after transrectal biopsy, 33 following transperineal biopsy). Considering a conservative figure of 220,000 cases of prostate cancer diagnosed per year, the fraction of needle tracking is astonishingly small. According to a review of the 2014 article, “There were probably well in excess of 2 million prostate biopsies conducted in America last year. Even if as many as half of the 42 identified cases of seeding had occurred last year in America (which they most certainly did not), this means that the individual risk for seeding at the time of a specific biopsy is certainly no higher than 21 × 100 ÷ 2,000,000 or 0.001 percent (i.e., 1 in 1,000), and it may be a lot lower than that. Furthermore, even when such seeding does occur, there is no evidence to suggest that such seeding is associated with any increase in risk for clinically significant prostate cancer.”[iv]
Volanis et al. observed that the number of prostate biopsies conducted each year has continued to increase, yet there is no apparent proportionate increase in the rate of track seeding resulting from prostate biopsies. Furthermore, there is evidence (from breast cancer track seeding) that displaced cells that escape into surrounding tissue have slim chances of survival. Once isolated from the parent tumor, where they are nourished by the tumor’s own new blood supply (angiogenesis) they are not viable. “Clinical recurrence at the site of a needle biopsy is uncommon and the relationship between biopsy and later recurrence is difficult to confirm.”[v]
However, one type of prostate cancer called neuroendocrine prostate cancer (NEPC) is highly aggressive. Whittington states, “Most of the described cases of seeding involve neuroendocrine tumors of the prostate, which are <1% of prostate tumors and don’t make PSA, so PSA levels are not elevated.”[vi] NEPC is uncommon; most cases occur when patients with advanced metastatic prostate cancer are put on hormone therapy, which somehow seems to trigger the development of NEPC proliferation. While this is not fully understood, it should be reassuring to know that newly diagnosed prostate cancer almost always have a form called adenocarcinoma.
Preventing track seeding
Track seeding does not occur in the vast majority of biopsies, but it is more commonly reported in breast, liver, lung, and aggressive cancers such as pancreatic cancer. Because of the risk, new technologies are being developed to preemptively kill any cancer cells that might escape along the needle track during a biopsy. These methods involve some form of ablation (destruction) along the path of the needle. By using radiofrequency, high intensity focused ultrasound, or microwaves, they are designed to preserve the living cells within the needle while inflicting permanent damage on the stray cells in the track.
In regard to prostate cancer, reducing the number of biopsy needles is a way to lower the risk of track seeding. Targeted biopsies guided by real-time 3T multiparametric MRI offer the dual advantage of 1) requiring a minimal number of needles, because the imaging clearly depicts the size, shape and location of the tumor, and 2) taking samples from the core of the tumor where the most dangerous cells are likely to exist. In short, the risk is minimized and the accuracy of the diagnosis is maximized.
Prostate cancer patients should put to rest any fears they have that tumor cells will be implanted along the tracks of biopsy needles. 3T multiparametric MRI and targeted biopsy go hand-in-hand to equip a patient and his doctor with the optimum information needed to develop the best treatment plan.
[iii] Volanis D1, Neal DE, Warren AY, Gnanapragasam VJ. Incidence of needle-tract seeding following prostate biopsy for suspected cancer: a review of the literature. BJU Int. 2014 Jun 23. doi: 10.1111/bju.12849. [Epub ahead of print]
[v] Loughran C, Keeling C. Seeding of tumour cells following breast biopsy: a literature review. Br J Radiol. 2011 Oct; 84(1006): 869–874.