Sentinel node identification using non-isotope means

[0002] This application claims priority from provisional U.S. Patent Application No. 60/065,491, filed Nov. 19, 1997.

[0003] This invention relates to methods, compositions and apparatuses for detecting sentinel nodes, and more particularly to means for transcutaneously identifying sentinel nodes, which do not employ radioactive isotope marking agents.

[0004] Due to the propensity of malignant tumors to metastasize through the lymphatic system, it has in the past been normal practice in some situations to remove all lymph nodes potentially harboring malignant cells metastasized from a tumor. Recently, the technique of interoperative lymphatic mapping has taken much of the guesswork out of determining which lymph nodes to remove. The at least one lymph node (typically 1-3 lymph nodes) which is the first to receive lymphatic drainage from the tumor (i.e., the sentinel node) is identified and biopsied. If the at least one sentinel node is free of malignant cells, then further lymph node biopsies can be avoided.

[0005] Sentinel nodes have been identified by injecting a marking agent into the tumor-bearing tissue and tracing the pathway of the marking agent through the lymphatic system. Visible marking agents have been employed to visually detect sentinel nodes with the naked eye, but such methods typically require significant surgical dissection to view the potential sentinel nodes and detect the presence of marking agent therein. Radioactive isotopes have also been employed as sentinel node marking agents. See, e.g., Kapteijn et al., “Localizing the sentinel node in cutaneous melanoma: gamma probe detection versus blue dye,” 4(2) Ann. Surg. Oncol. 156-60 (Mar. 1997) and U.S. Pat. No. 5,732,704 to Thurston et al. These techniques comprise injecting radioactive isotope compositions into the tumor bearing tissue and detecting the migration of the composition from the tumor and into the lymphatic system.

[0006] Although such radiochemistry techniques are an improvement over prior visible detection methods in that radioactive marking agents can be detected transcutaneously (regardless of the depth of the sentinel node within the tissue), radiochemistry techniques are less than ideal in a number of aspects. Patients and medical personnel are exposed to potentially harmful doses of ionizing radiation. Radioactive isotopes also pose environmental contamination and disposal issues.

[0007] Thus, there has been a need for a method of transcutaneously identifying a sentinel node without using radioactive isotopes.

[0008] All references cited herein are incorporated herein by reference in their entireties.

[0009] The invention addresses at least the foregoing deficiencies of the prior art in providing a method for identifying a sentinel node, comprising:

[0010] injecting tumor-bearing tissue with a marking composition comprising a marking agent;

[0011] radiating marking-agent-targeting energy into suspect tissues potentially harboring said sentinel node; and

[0012] detecting a lymph node first infiltrated by said marking agent to identify said sentinel node, said detecting being across a substantial thickness of said suspect tissues,

[0013] wherein said method is conducted without detecting radioactivity.

[0014] The invention also provides systems for performing the method of the invention and compositions for use in the method of the invention.

[0015] The invention provides methods and systems for identifying at least one sentinel node across a substantial thickness of tissue without using radioactive isotopes. The methods and systems employ marking agents that enable trans-tissue (e.g., transcutaneous) detection of sentinel nodes via ultrasonic detection, magnetic resonance detection and/or laser-enhanced detection.

[0016] The trans-tissue detection methods and systems of the invention do not require surgical dissection to reveal potential sentinel nodes to the naked eye. The invention enables noninvasive detection of sentinel nodes across a substantial thickness of tissue, e.g., substantially below the surface of the skin. A tissue is of substantial thickness if it is thick enough to conceal a dye-infiltrated sentinel node from the naked eye under ambient lighting conditions. Unlike prior art methods employing blue dyes, the invention enables noninvasive detection of sentinel nodes through tissue (including skin) at least 2 mm thick, and even at least 5 mm thick.

[0017] The invention enables ultrasound identification of the first lymph nodes to drain a solid tumor. A marking composition comprising an ultrasound contrast agent is subcutaneously injected adjacent the tumor-bearing tissue and allowed sufficient time to migrate to the sentinel node before detection begins. The marking composition can be, e.g., injected between the skin and the immediately underlying tumor, as suggested by the European Institute of Oncology. See, e.g., Paganelli “Sentinel node biopsy: role of nuclear medicine in conservative surgery of breast cancer.” European Journal of Nuclear Medicine 1998, 25: 99-100, and Veronesi et al. Lancet 1997, 349: 1864-67. In the United States, the National Cancer Institute has published studies of a technique whereby 1 ml volumes of lymphatic tracer are injected at 3-,6-,9-, and 12-o'clock positions into the breast surrounding the primary tumor or biopsy cavity. See, e.g., Krag et al., “The Sentinel Node in Breast Cancer, A Multicenter Validation Study.” New England Journal of Medicine 1998; 339: 941-946. A broad overview of the intraoperative use of gamma probes is presented in Gulec et al., “The Expanding Clinical Role for Intraoperative Gamma Probes.” Nuclear Medicine Annual 1997: 209-237.

[0018] The ultrasound marking composition is preferably a pharmaceutically acceptable composition containing an ultrasound contrast agent, preferably coated with a phagocytosis enhancing material, such as tufsin, and a carrier suitable for subcutaneous infection. The ultrasound contrast agent is sufficiently small to migrate from the tumor-bearing tissue to the sentinel node, and is sufficiently stable to survive the trip and remain within the sentinel node long enough to be detected. Ultrasound contrast agents of the invention are preferably about 10 to about 200 nanometers in diameter. In embodiments, the ultrasound contrast agents reflect sound a million-fold more than adjacent soft tissues. Ultrasound contrast agents and pharmaceutically acceptable compositions containing them are generally disclosed in, e.g., U.S. Pat. Nos. 5,707,607 and 5,611,344 and the references cited therein.

[0019] In embodiments, a simple non-imaging ultrasound contrast agent detecting tissue penetrable probe is used in conjunction with conventional transcutaneous ultrasound imaging devices to provide probe surgical guidance to and probe confirmation of the identity of the sentinel lymph node in the context of an ultrasound image of the node and adjacent blood vessels.

[0020] Penetrable combined tissue imaging and signal intensity measuring ultrasound probes modeled on existing trans-vaginal imaging probes (some of which incorporate Doppler technology) provide visualization of adjacent anatomical structures, a critical improvement over gamma detecting probes which only indicate the direction in which labeled tissue may be found by careful tissue dissection.

[0021] Ultrasound contrast agent detecting probes avoid patient and staff exposure to potentially harmful doses of ionizing radiation. Avoiding radioactive isotopes also avoids environmental contamination and disposal issues.

[0022] The invention enables simple magnetic or paramagnetic detection or more complex magnetic resonance identification of the first lymph nodes to drain a solid tumor. A marking composition comprising a magnetic or para-magnetic compound, such as a species of gadolinium, iron, manganese, rhenium, europium, lanthanum, holmium, or fermium, is subcutaneously injected adjacent the tumor-bearing tissue and allowed sufficient time to migrate to the sentinel node before detection begins. The marking composition is preferably injected between the skin and the immediately underlying tumor, as suggested by the European Oncology Institute's studies discussed above.

[0023] The marking composition is preferably a pharmaceutically acceptable composition containing a magnetic or paramagnetic compound such as a species of gadolinium, iron, manganese, rhenium, europium, lanthanum, holmium, or fermium marking agent, preferably coated with a phagocytosis enhancing material, such as tufsin, and a carrier suitable for subcutaneous injection. The magnetic or paramagnetic marking agent is sufficiently small to migrate from the tumor-bearing tissue to the sentinel node, and is sufficiently stable to survive the trip and remain within the sentinel node long enough to be detected. Magnetic or paramagnetic marking agents of the invention are preferably about 10 to about 200 nanometers in diameter. Magnetic or paramagnetic marking agents and pharmaceutically acceptable compositions containing them are generally disclosed in, e.g., U.S. Pat. Nos. 5,776,094, 5,582,172 and 5,101,827, and the references cited therein. Particularly preferred are compositions containing 10 to 200 nanometer iron, ferrite, gadolinium or other ferromagnetic, paramagnetic or magnetic resonance marking agent particles, which migrate to lymphatics when injected in the periphery of the tumor.

[0024] Magnetic resonance imaging probes and coils can provide an image of the sentinel lymph node in the context of an image of the adjacent blood vessels, a critical improvement over gamma detecting probes which only indicate the direction in which labeled tissue may be found by careful tissue dissection. Embodiments of the magnetic resonance detection systems of the invention comprise a transducer coil, signal processing electronics, reporting devices, and a power source.

[0025] Metal detecting and para-magnetic contrast agent detecting probes avoid patient and staff exposure to potentially harmful doses of ionizing radiation. Avoiding radioactive isotopes also avoids environmental contamination and disposal issues.

[0026] Sentinel node localization can also proceed using ultraviolet, visible or infrared light illumination, complementary marking agents and complementary visualization means. The patient can be irradiated with ultraviolet, visible and/or infrared light subcutaneously injected or transcutaneously transmitted. The light source can be, e.g., a monochromatic laser, whose wavelength is dictated by the nature of the marking agent. The detection of reflected or fluorescing light with the naked eye and/or electronic imaging means noninvasively identifies the sentinel node without the need for pre-localization surgical dissection.

[0027] A marking composition comprising a marking agent is subcutaneously injected adjacent the tumor-bearing tissue and allowed sufficient time to migrate to the sentinel node before detection begins. The marking composition is preferably injected according to the European Institute of Oncology protocol between the skin and the immediately underlying tumor, or according to the National Cancer Institute protocol whereby 1 ml volumes of lymphatic tracer are injected at 3-, 6-, 9-, and 12-o'clock positions into the breast surrounding the primary tumor or biopsy cavity.

[0028] The marking composition is preferably a pharmaceutically acceptable composition containing marking agent and a carrier suitable for subcutaneous injection. The marking agent is sufficiently small to migrate from the tumor-bearing tissue to the sentinel node, and is sufficiently stable to survive the trip and remain within the sentinel node long enough to be detected. Marking agents of the invention are preferably about 10 to about 200 nanometers in diameter. Suitable marking agents include, e.g., lymphazurin blue dye, colloidal carbon particles, lymphazurin blue dye filled liposomes, other dye filled liposomes, dye containing colloids and dye containing microspheres, preferably coated with a phagocytosis enhancing material, such as tufsin.

[0029] Human or electronic observation can be through a disposable low resolution rigid penetrable fiberoptic device, with {fraction (1/16)}″ central fibers occupying ⅜″, and ⅛″ peripheral fibers occupying the remainder of the visualization field. However, the sentinel node and its signal can be detected without the use of fiberoptics. Embodiments of the detection systems of the invention comprise a light source (preferably a laser) that emits infrared, visible, ultraviolet and/or other light, a light sensor, signal processing electronics, reporting devices and a power source.

[0030] While the invention has been described in detail and with reference to specific examples thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.