Originally published 2/16/2015
More than six years ago, we published the blog below in hopes of reducing patient fears that a needle biopsy of the prostate could spread prostate cancer (PCa). The concept is called “track seeding” or “needle tracking”. Back then, we referred to occurrence of track seeding in prostate biopsies as exceedingly rare, and we continue to stand by that.
In the intervening years since 2015, we found only two published individual case studies that cited evidence of post-biopsy track seeding, and one case study of what appeared to be track seeding after brachytherapy radioactive pellets implanted with needles similar to biopsy needles:
- A 2015 case study (Garcia-Bennett, et al.) reporting a needle track recurrence detected by 18F-Choline PET-CT, following a transrectal prostate biopsy.[i]
- A 2021 case study (DiLizia, et al.) of patient whose small post-biopsy mass in the rectal wall was surgically removed following track seeding.[ii]
- A 2021 case (Sidibe, et al.) of a patient with a PCa recurrence in the perineal area (where brachytherapy needles are inserted) following implantation of radioactive pellets.[iii]
The DiLizia paper describing the removal of the rectal wall mass offers further discussion. After citing the same Volanis article that we used below to demonstrate how rare track seeding is, the authors write, “Several proposed risk factors for seeding include tumor size, grade, biopsy needle type, and biopsy technique, though these remain to be definitively proven. … Given the recent advantages of ultrasensitive PSA and improved imaging capabilities for detecting biochemical recurrence in prostate cancer, it is possible that more future cases of local recurrence from prostate biopsy seeding may be detected.”[iv] Keep in mind, however, two important points. First, over the past 2 decades, there has been an increase in the number of prostate biopsies performed annually, but no evidence of an increase in reports of seeding. Second, seeding does not mean spreading; there is no persuasive evidence that tumor cells left in the soft tissue along a needle tract pose a serious threat of metastasis.
We want to underscore that at our Center, we further shrink the infinitesimally small odds of track seeding by significantly reducing the number of needles we use for prostate biopsies. Thanks to our real time in-bore MRI targeting, we selectively sample suspicious lesions identified during the scan. This means we achieve incredibly accurate diagnosis using a minimal number of needles. Fewer needless, less risk. Please take a few extra minutes to review the original blog, and the data it contains.
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.[v] 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[vi], 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, while 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.”[vii] 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 0.1 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.”[viii]
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.”[ix]
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.”[x] 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.
NOTE: This content is solely for purposes of information and does not substitute for diagnostic or medical advice. Talk to your doctor if you are experiencing pelvic pain, or have any other health concerns or questions of a personal medical nature.
[i] J Garcia-Bennett, I Henríquez, A Zugazaga Cortazar, J Fuertes. Needle track recurrence after transrectal prostate biopsy detected by ¹?F-Choline PET-CT. Rev Esp Med Nucl Imagen Mol. Mar-Apr 2015;34(2):128-9.
[ii] E Matthew DiLizia, Michael Ahdoot, Michael Daneshvar, et al. Metastasectomy for rectal wall seeding of prostate adenocarcinoma after transrectal prostate biopsy. Urol Case Rep. 2021 Jan; 34: 101445.
[iii] I Sidibe, M Le Blanc-Onfroy, G Delpon, E Rio et al. Perineal recurrence of prostate cancer along a brachytherapy needle track: A case report. Cancer Radiother. 2021 Jul;25(5):476-479.
[iv] DiLizia, ibid.
[vii] 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]
[ix] Loughran C, Keeling C. Seeding of tumour cells following breast biopsy: a literature review. Br J Radiol. 2011 Oct; 84(1006): 869–874.