Since time immemorial, physicians have attempted to tailor the treatments of their patients to suit the individual – from Hippocrates, who prescribed drugs based on the individual's age, physique and constitution, to Prakriti based Ayurvedic medicine, to the Persian sage Avicenna.
Whereas previously, treatment was based on broader characteristics, we are now delving into minutia- at the molecular and genomic level, aiming to treat the individual, not the group.
Modern Personalized Medicine is the use of specific characteristics unique to the individual, creating a biomedical profile of the individual using a combination of genetic and other information, to predict disease susceptibility, disease prognosis, or treatment response and to provide then right patient with the right treatment at the right dose at the right time.
Table 1. Some definitions
Biomarkers constitute one of the most important sources of information that treatment in personalized medicine is based on.While the spectrum of definition is vast, the National Institutes of Health Biomarkers Definitions Working Group defines a biomarker as “a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention”. Vital signs, basic lab work, complex lab data, imaging, molecular and genetic data, all fall under the purview of biomarkers, but it is the molecular and genetic data that now chiefly influence treatment options – currently predominantly in oncology. About 15% of patients undergoing nephrectomy are found to have benign kidney disease at final histological diagnosis. Image guided needle biopsy and DNA analysis could eliminate the need for unnecessary surgery, as commonly seen in renal and thyroid diseases. Even cancers of the same histologic subtype show vast heterogeneity in response to treatment, determined largely by their genetic makeup. This makes the identification of the genetic and molecular makeup of tissue a necessity – increasing the need for minimally invasive tissue sampling.
The utility of biospecimens for just obtaining a histologic diagnosis is a thing of the past. Molecular and genetic analysis of tissue is now necessary to guide therapy in a number of cancers such as lung, breast, melanoma and colon, necessitating increased sampling of larger tissue volume. The requirement of tumor tissue, often repeated multiple times for molecular analysis, has been shown to be a common cause of ineligibility in trials. It has also been found in lung cancer trials that molecular and biomarker targeted therapies have a much higher chance of clinical success, making this the focus of future drug development. It is, thus, of paramount importance that sufficient sample be obtained to enable histological, genetic and molecular analysis. The NCI-MATCH Trial, part of ex-President Obama’s Precision Medicine Initiative, discovered in its interim survey that 1 in 5 biopsy samples were inadequate for genetic analysis and proved to be a major impediment in the treatment of patients for whom this trial was the last resort. Moreover, repeat tissue analysis is now also necessary for the detection of disease progression, prognostication and guiding further treatment in the event of drug resistance.
Current methods of tissue acquisition remain rather variable, however, as biomarker based treatment works its way to becoming standard of care, this must change. The radiologist is in the unique position of identifying which site would be ideal for a biopsy and the best way of easily accessing it, while keeping in mind the risks and benefits of the procedure. Whether it is the study of imaging biomarkers, the acquisition of tissue biopsy specimens or, in the near future, liquid biopsy specimens, the radiologist has a crucial role to play.
Image-guided Needle Biopsies: Modalities and Equipment
Percutaneous needle biopsy is now a commonly used technique for obtaining tissue for both oncologic and non-oncologic diagnoses. The critical element of the procedure is image guidance – which allows one to see where you should be, but more importantly, where you shouldn’t be, making it safer and more effective. It has made it possible to access tissue that was once unreachable by augmenting the physician’s understudying of spatial anatomy. The choice of imaging modality is depends upon a number of factors – lesion characteristics like size, location, depth, surrounding tissue, patient characteristics like built, suitability of ionizing radiation, contrast and physician preference to name a few.
Various navigation systems have been developed to enhance target visibility. In any image guided procedure, the physician must first identify the patient’s anatomy within the images – a process called segmentation- and mentally construct the patient’s anatomy utilizing the images – registration. The use of multiple image data sets is of special use in lesions that are indistinct, heterogeneous, have challenging access angles or are only visible on PET-CT as they improve visualization. Image fusion is the overlay of different imaging datasets together, and image co-registration is the spatial alignment or matching of the two separate imaging datasets, which may be rigid, allowing only rotation and panning or elastic, allowing rotation, panning and localized stretching, as may be caused by a probe or stent for example. This obviates the need for the physical presence of CT/MRI/PET equipment but yields the additional information they provide which can be used along with the intra-procedural image, however, they are rather bulky systems. Tracking is another component of the navigation system which allows the visualization of the position of a device in real time.
Table 2. Commonly Used Imaging Modalities for Needle Biopsy
Needle Types
The choice of the needle is also determined by a variety of factors considering the target lesion, area to be traversed, amount of sample required, physician preference and the clinical setting. Broadly, there are two major sampling techniques – single needle, and two needle which includes Tandem and Coaxial sampling.
The single needle technique is generally used for more superficial targets, for example, the thyroid. A single needle is placed into position and the lesions is sampled, glowing sampling of different areas of the lesion but multiple needle tracks. In two needle sampling, one needle is placed in proximity to the target and acts as a guide for the other needle, either in tandem or coaxially. The use of a coaxial needle is common and allows the capsule or pleura to be punctured only once while allowing the biopsy needle many passes. However, the biopsy needle remains limited by the track of the guiding needle.
The methods of procuring a tissue sample include Fine Needle Aspiration (FNA), Fine Needle Capillary Sampling (FNCS), Core Needle Biopsy (CNB), and Large Needle Aspiration (LNA).
In an FNA, a sample is acquired by applying gentle suction until tissue collected in the syringe. FNCS is essentially FNA without without aspiration, the needle is gently rotated within the target until sample gets pulled up into the needle hub by capillary action. An LNB is similar to an FNA but done with a larger bore needle. A CNB procures a large core or piece of tissue. It is usually done with an 18-21 (more commonly18)-gauge needle with an automated spring-loaded biopsy gun. Needles with a throw between 5-30mm may be chosen depending on the target. The needle length should be chosen as per the depth required, keeping in mind that the longer the needle, the more difficult it is to control.
FNA is less traumatic and safer, while a CNB has the advantages of providing larger samples. CNB, with an automated 18–21 gauge spring loaded needle with a short excursion, has high diagnostic results and increased sensitivity and specificity, but also carries higher risk of complications. However, the yield of both is sufficient for histological as well as molecular diagnosis.
Pre-procedure Planning and Evaluation
Knowledge of the patient’s relevant medical history and physical examination are essential prerequisites before any further progression. The vitals must be controlled. The indication of the procedure and viable alternatives must be considered and discussed with the patient. The patient should be explained the procedure in its entirety in order to mitigate patient anxiety, ideally by the person performing the procedure. Informed consent must always be obtained after discussing the indication, benefits, risks, and alternatives to the procedure. Ensure that the patient is able to follow basic instructions.
One of the most important considerations is a complete bleeding history, including family history of any bleeding/coagulative disorders, and review of all medications, especially anticoagulants, dietary or herbal supplements and their temporary discontinuation, if deemed necessary. Case-by-case considerations should be made, especially in patients with prosthetic valves, stents etc. and a consultation with the patient’s Cardiologist would be beneficial so as to optimise care. Recent lab work including CBC, PT/INR, aPTT, preferably within 4-6 weeks, should be reviewed. It may also be reasonable to obtain KFTs as most commonly used anticoagulants are eliminated renally – Dabigatran, in particular, is most influenced by renal function. Any coagulation abnormalities should be corrected before the procedure. However, multiple studies show the low predictive value of lab tests in predicting bleeds. It is important to remember that guidelines usually vary from organisation to organisation and should not be generalised to all patients. There is no substitute for clinical judgement and care must be individualised.
Table 3: Acceptable lab values at our institution
Table 4 : Guidelines for peri-procedure anticoagulant management
*Indicates no data. Consider measuring agent-specific anti Xa level and/or withholding ≥ 48 hours ** Indicates no data. Consider measuring agent-specific anti Xa level and/or withholding ≥ 72 hours
Approach to Bridging Anticoagulant Use
Table 5 : Bleeding Risks of Procedures
Table 6 : Risk of TE vs Reason of Anticoagulation
Prophylactic antibiotic use is not recommended for biopsy procedures with the exception of prostate biopsy. Fluroquinolones and cephalosporins are commonly used first line drugs with TMP-SMX and aminoglycosides as second line options . The antibiotic regime and duration vary, and do not appear to have significant impact. However, in some cases, multiple dose regimes have been found to have lower rates of bacteriuria and antibiotic resistance.
It is of the utmost importance to rule out any contraindication to the procedure before proceeding with it.
Technique
Most image guided biopsies are performed on an outpatient basis under local anesthesia with mild sedation and analgesics if needed with the patient in a comfortable position that allows easy access to the lesion. An IV line is in place and vitals are continuously monitored. A disposable biopsy tray is used, with sterile paper drapes, lidocaine, syringes, needles, and a syringe holder if needed, or the automated device, and appropriate fixatives. The entry site should be sterilized. With few exceptions, as discussed in systemic considerations, the shortest path to the lesion is preferred.
USG Guided: While guides are available to direct needle depth, most prefer a free hand approach that allows more control over the needle. Higher frequency transducers are used for more superficial structures and lower frequencies for deeper. The head of the transducer probe must be covered with a sterile cover, or cleaned with betadine/alcohol/cydex. There is no need for gel if 10% povidone-iodine solution is used to clean the area as it acts as the coupling agent between the probe and skin. Injecting 1-2ml of 1% lidocaine hydrochloride solution into the skin and superficial subcutaneous tissue is useful if repeated aspirations are to be taken. The lesion is localized by scanning in multiple planes and the relationship between the lesions and major vessels is mapped to avoid vascular injury. The target nodule is centered in the imaging field. A more acute angle of insertion is used for superficial lesions, and a larger angle for deeper lesions. The needle may be inserted parallel to the transducer, which allows visualization of a larger length of the needle, or perpendicular, generally with a shorter needle, which minimizes risk of injury to major vessels but visualizes only the tip. If the needle isn’t visualized, it is probably due to misalignment between the probe and the needle. Slight oscillation of the needle during insertion allows visualization of the path of the needle. Larger gauge needles are better visualized on USG. Hypoechoic structures such as the liver, spleen, kidney, and subcutaneous fat layers allow easier visualization of the needle, but a gas-filled bowel or hyperechoic abdominal fat can make it difficult.
CT Guided: A scan of the target area is first taken with a marking device in place on the skin close to the predicted entry site. Using the marker and the scan, the cephalocaudal location of the target lesion is determined. The depth to the lesion is measured, optimum angle of insertion and the path to be traversed is planned. The needle is inserted as vertically as possible, as, if it is at an angle, multiple CT slices are necessary to visualize the tip and is more difficult to correctly localize. The needle is gradually advanced in stages for the distance calculated earlier, with serial scans being done to monitor its progression until the target is reached.
Sampling: Sampling is done when the needle is seen to be in the correct position.
For an FNA, when the target is reached, suction is applied and rotatory motions are made in the target area until material is seen filling the hub. Suction is released just before the needle is withdrawn. Specimens must be taken from different areas of the lesion. If a non-aspiration technique is preferred, the needle is rapidly moved to and fro through the nodule. It has been seen that multiple passes with smaller gauge needles have a better yield than fewer passes with larger bore needles.
When performing a CNB, it is advisable to perform a test deployment of the device beforehand, and to inform the patient of the sound of the device to ensure they don’t get startled. A small nick is made over the target site. In a semi-automated system, the inner tracer is first advanced manually through the lesion, allowing greater control and safety. The automated spring loaded outer cutting cannula with a preset excursion is then deployed. However, this may be difficult if the lesion is too hard to penetrate by manual force or is easily displaceable, in which cases, more rapid firing is desired. Fully automated systems forcefully plunge both the inner tracer and cutting cannula together on firing. It is important to keep in mind the initial position of the needle tip and the excursion length of the needle to ensure that no surrounding vasculature is damaged, especially with fully automated systems.
Lastly, it is important to remember that for larger lesions, attempts should be made to take tissue form the periphery as the center may be necrotic. It is also important to ensure that cores are being taken from different areas within the mass when cancer is suspected, due to significant intra-tumor heterogeneity in terms of both their molecular signatures and morphology, which may lead to the development of drug resistance.
Systemic considerations along with complications and their management are discussed later.
Sample Adequacy and Analysis
A small specimen yield may often pay the price for the advantages of increased patient safety, decreased procedure time and cost. It becomes of paramount importance that specimen yield is sufficient for both histopathological and biomarker analysis when needed, minimizing the need for repeat biopsies.
For biomarker testing, there are no established guidelines on the amount of tissue needed due to the vast number of unknowns in this field: no objective criteria for biopsy site selection, or device and technique used, evolving techniques of analysis with different techniques requiring differing amounts of tissue and none established as gold standard, and inherent tumor factors the effect yield. Usually, each lab follows its own protocols for the amount of tissue or proportion of tumor cells needed to establish a diagnosis. Guidelines from the College of American Pathologists, International Association for the Study of Lung Cancer, and Association for Molecular Pathology state “ultimately, any specimen that meets the laboratory's requirements for tumor content, fixation, and quality, as established during validation, may be chosen for analysis”. For biomarker analysis, inadequate sample amounts are associated with a higher rate of false negatives. Limited tissue is also a deterrent to rapid and complete analysis of all necessary markers, which can prove to be detrimental to patient care. As demonstrated with NSCLC, a delay in obtaining biomarker attributes delays treatment decisions and can lead to inferior outcomes due to the initiation of inappropriate chemotherapy.
It is often a good idea to have an onsite pathologist who may be able to confirm the amount of tissue needed and has been shown to minimize false negatives and improve diagnostic accuracy. Telepathology may also be considered when feasible. Most recommend 4-6 cores at least if biomarker analysis is required. At least 50 viable cells per tissue section are required for fluorescent in situ hybridization (FISH) testing, and a minimum of ~200ng of DNA or about 500 cells per histology section for DNA extraction for genotyping. Newer genotyping techniques may need as low as 10ng of DNA extracted from formalin-fixed and paraffin-embedded (FFPE) tissue samples, and cytology specimens. Mutation analysis requires at least at least 10% malignant cell content. 21 gauge needle aspirates yield about 100 cells. The samples need to be preserved in appropriate fixatives as per the investigation required.
Table 7: Some Commonly Used Fixatives
SYSTEMIC CONSIDERATIONS
Head and Neck
Thyroid Biopsy
The main indication for a thyroid biopsy is a thyroid nodule. Thyroid nodules may be discovered by the patient, during a routine physical exam, or during another imaging investigation. There is a high prevalence of thyroid nodules in the general population : 2–6 % (palpation), 19–35 % (ultrasound) and 8–65 % (autopsy data). The incidence increases with age and is more common in women. While the risk of a nodule being malignant remains low -4.0 to 6.5%- it is important to rule out cancer.
A nodule discovered by palpation with an elevated or normal TSH is first evaluated by USG, along with an evaluation of cervical lymph nodes. If USG criteria for FNA are met, a biopsy is carried out. FDG-PET avid lesions, and hot nodules on sestamibi scans should undergo an FNA. Incidentaloms with a maximum diameter greater than 1.0–1.5 cm should be considered for FNA. Other incidentaloms detected on CT/MRI or USG should undergo a dedicated thyroid USG evaluation.
Aside from nodules, a biopsy may also be needed in case of rapid, diffuse enlargement of the gland, especially in those older than 50 years to rule out aplastic carcinoma or lymphoma. In patients of Hashimoto’s with goiter presenting with a prominent nodular lesion, a biopsy is necessary to rule out concurrent lymphoma or papillary carcinoma.
Pre-procedure planning remains the same as for any other biopsy, except fasting is not required.It is an outpatient procedure performed with the patient in supine position with the neck extended. The patient should be told that most nodules are benign and is instructed to not swallow, speak or breathe during the procedure. A thyroid biopsy may be done both with and without USG guidance, however, a guided biopsy has been shown to have a higher accuracy.
The American Thyroid Association recommends FNA as the procedure of choice in the evaluation of thyroid nodules, when clinically indicated. Done with 27–22 g needles, most commonly 25–27 g, it is more likely to yield more diagnostically adequate samples especially in lesions with lower cellularity. FNC, has the benefit of causing less pain and bleeding. It has also been shown to have lesser number of unsatisfactory samples and allows better preservation of cellular architecture, with less bleeding and degeneration. A combination of FNAB and FNC may have higher diagnostic accuracy, and is usually recommended as both are complementary. While there is no consensus among guidelines, a CNB, with an automated 18–21 gauge spring loaded needle with a short excursion is usually recommended for previous nondiagnostic FNA results or atypia of undetermined significance, suspected lymphoma, anaplastic carcinoma, medullary carcinoma, and metastasis to the thyroid, and for calcified and degenerating thyroid nodules. LNB is usually not used, but is another alternative in case of non-diagnostic FNA.
Table 8: Palpation vs. USG guided Thyroid Biopsy
The procedure remains the same as any USG guided biopsy but care is taken to inject Lidocaine directly over the capsule as it significantly reduces patient discomfort. 2-5 passes are usually performed.
The presence of colloid and epithelial cells usually indicates sample adequacy. When an FNA is found to be inadequate, a repeat FNA is usually performed in different areas of the nodule with
3-4 more aspirates, but a CNB may also be considered.
Molecular analysis is complementary to histological diagnosis may be considered in the case of indeterminate results (Bethesda III-V) and helps avoid unnecessary thyroidectomies and guides treatment.
Post Biopsy Care and Complications: The area is bandaged and manual compression is applied for at least 2-3 minutes post FNA and 20-30 minutes post CNB. Pain at the site, that may radiate up to the ear, is the most common complication and is usually minor. Hematomas are the most feared complication and may occur even hours after the procedure. The patient should be advised to seek care in the event of a neck swelling that doesn’t decrease with pressure. Small-to-moderate hematomas usually resolve spontaneously within days with cold compresses. Massive hematomas are rare but may be life threatening due to airway obstruction and require urgent care.
Table 9: Rare complications post thyroid biopsy
Thorax
Lung Biopsy
A lung biopsy may be required for the evaluation of a focal nodule, or diffuse disease. Usually, a percutaneous biopsy, also known as closed, transthoracic, or needle biopsy, is done for the evaluation of focal nodules and is considered for:
New or enlarging solitary nodule or mass on the chest radiograph which is not amenable to diagnosis by bronchoscopy or CT shows it is unlikely to be accessible by bronchoscopy.
Multiple nodules in a patient not known to have malignancy or who has had a prolonged remission or more than one primary malignancy.
Persistent focal infiltrates, either single or multiple, for which no diagnosis has been made by sputum or blood culture, serology, or bronchoscopy.
Hilar mass.
The pre-procedure planning and evaluation remains the same as for other biopsies. Additionally, PFTs may be considered on a case-by-case basis. A recent diagnostic CT should be available. The patient must be educated about the breathing technique required during the procedure and told to not cough. The patient lies supine or prone depending on the entry site required. A sitting position is not recommended due to the potential risk of air embolism or syncope.
CT is the preferred modality due to higher sensitivity, but fluoroscopy may be used and takes lesser time or USG for more superficial lesions. All interventions are done via the superior aspect of the rib in order to avoid injury to the neuromuscular bundle. Care is taken to ensure that Lidocaine is not injected directly into the pleura. While the shortest path to the lesion is generally preferred, it is more important in this case to minimize passing through pleura. Hence, if a fissure lies in the path of the shortest course, another course is advised. The patient should suspend all breathing when the needle is being advanced or withdrawn. Either CNB or aspiration biopsy may be done.
Injection of an autologous blood patch may prove to be beneficial in preventing pneumothorax, and is commonly practiced at our institute.
Post-Biopsy Care and Complications
Immediately after the procedure is done, and the wound is cleaned and closed, a repeat scan is taken to rule out the presence of a pneumothorax followed by post biopsy chest radiography. The patients are observed for at least 1, preferably 2 hours post biopsy as most complications develop within that time, lying with biopsy side down, with oxygen if needed. The patient is advised to seek care in case of sudden or increased shortness of breath, fullness/heaviness in chest, excessive hemoptysis, dizziness, chills or high fever.
Pneumothorax :The most common complication, it has been seen to occur in 61% of all lung biopsies. Acute pneumothoraces may develop at the time of the procedure, but delayed pneumothoraces have also been reported, post normal radiographs unto 24h after biopsy. Patient age, history of tobacco use and underlying smoking-related lung disease, lesion size (higher risk with lesions < 2cm), deeper lesions >4cm, needle gauge and experience of the radiologst, all impact the rate of pneumothorax development and need for chest tube. However, no difference has been found in conventional biopsies or biopsies for molecular analysis requiring more sample volume. It may be necessary to rule out a pulmonary hemorrhage in an acutely ill patient. 3.3–15% of all patients undergoing lung biopsy require a chest tube. After the placement of a chest tube, usually 8 Fr, recurrent pneumothoraces can also be managed on an outpatient basis. Hospitalization is necessary in cases of present leaks. Management is as per figures 1 and 2.
Pulmonary hemorrhage and hemoptysis: Hemorrhage has been observed in 5–16.9% and hemoptysis in 1.25–5% of patients. The risk is higher in sampling lesions deeper than 2cm.
Hemoptysis usually simply requires reassurance and the patient lying in a lateral position with the biopsy side down. Patients must be advised of this possibility. Pulmonary hemorrhage by itself is often asymptomatic and minor or may cause some chest pain.
Air embolism, the development of a hemothorax and tumor seeding of the pleura or chest wall are other possible, but rare complications.
Pleural Biopsy
A pleura biopsy is indicated for recurrent effusions of unknown etiology or any pleural masses or thickenings. The procedure is similar to that of lung biopsy, but it is usually done under USG guidance. Complications are also similar to that of lung biopsy with the addition of empyema, puncture of surrounding tissue like lungs, liver or spleen, or any major vessel. Sampling error may also occur due to extensive fibrosis or empyema.