Application of light at plural treatment sites within a tumor to increase the efficacy of light therapy

Abstract

Light is administered during photodynamic therapy (PDT) for an extended period of time at a plurality of sites distributed within the abnormal tissue of a tumor. A clinical study has shown that a substantially greater volume of abnormal tissue in a tumor is destroyed by the extended administration of light therapy from a plurality of probes than would have been expected based upon the teaching of the prior art. In this process, a plurality of light emitting optical fibers or probes are deployed in a spaced-apart array. After a photoreactive agent is absorbed by the abnormal tissue, the light therapy is administered for at least three hours. The greater volume of necrosis in the tumor is achieved due to one or more concomitant effects, including: the inflammation of damaged abnormal tissue and resultant immunological response of the patient's body; the diffusion and circulation of activated photoreactive agent outside the expected fluence zone, which is believed to destroy the abnormal tissue; a retrograde thrombosis or vascular occlusion outside of the expected fluence zone; and, the collapse of the vascular system that provides oxygenated blood to portions of the tumor outside the expected fluence zone. In addition, is possible that molecular oxygen diffusing and circulating into the expected fluence zone is converted to singlet oxygen during the extended light therapy, causing a gradient of hypoxia and anoxia that destroys the abnormal tissue outside the expected fluence zone.

Description

FIELD OF THE INVENTION[0001] The present invention generally relates to the use of light therapy to destroy abnormal tissue in a tumor, and more specifically, to the use of multiple light sources disposed at spaced-apart treatment sites within a tumor to render the therapy.BACKGROUND OF THE INVENTION[0002] Abnormal tissue in the body is known to selectively absorb certain dyes that have been perfused into a treatment site to a much greater extent than surrounding tissue. For example, tumors of the pancreas and colon may absorb two to three times the volume of these dyes, compared to normal tissue. Once pre-sensitized by dye tagging in this manner, the cancerous or abnormal tissue can be destroyed by irradiation with light of an appropriate wavelength or waveband corresponding to an absorbing wavelength or waveband of the dye, with minimal damage to normal tissue. This procedure, which is known as photodynamic therapy (PDT), has been clinically used to treat metastatic breast cancer,...

AI Technical Summary

Benefits of technology

[0013] In accord with the present invention, a method is defined for destroying abnormal tissue in a tumor within a patient's body using an extended light therapy and at least one concomitant effect thereof. The method includes the step of administering a photoreactive agent to the abnormal tissue. The photoreactive agent, which has a characteristic absorption waveband, is preferably absorbed by the abnormal tissue rather than by normal tissue in the patient's body. Light having a waveband corresponding to the absorption waveband of the photoreactive agent is administered to a treatment zone in the tumor. A pattern in which the light is administered to the tumor defines the treatment zone, and this zone preferably encompasses a substantial portion of the tumor not penetrated by the light being administered. The method provides for continuing to administer the light to the treatment zone for at least three hours of extended light therapy. The light destroys the abnormal tissue that it illuminates by activating the photoreactive agent absorbed thereby. Furthermore, the extended period of light therapy indirectly destroys the substantial portion of the tumor that is not penetrated by the light being administered by inducing at least one concomitant effect that destroys the abnormal tissue comprising the substantial portion of the tumor.

[0020] The method may include further steps. Specifically, in one embodiment, the light is emitted into the tumor in a first direction from each of the plurality of probes, relative to the probe from which the light is emitted. Next, the method provides for terminating emission of light into the tumor in the first direction and emitting light into the tumor in a second direction from each of the plurality of probes. The second direction is substantially different from the first direction for each of the probes. Preferably, in one embodiment, the first direction is directed toward a perimeter of the tumor, and the second direction is directed toward an interior of the tumor. By first destroying the perimeter of the tumor, the interior portion of the tumor is more readily destroyed due to the one or more concomitant effects.

Problems solved by technology

Furthermore, the extended period of light therapy indirectly destroys the substantial portion of the tumor that is not penetrated by the light being administered by inducing at least one concomitant effect that destroys the abnormal tissue comprising the substantial portion of the tumor.

In one case, the concomitant effect arises because the destruction of the abnormal tissue in the treatment zone deprives the substantial portion of the tumor from receiving oxygen.

In another instance, the concomitant effect arises because the photoreactive agent within the treatment zone that is activated by the light being administered diffuses into the substantial portion of the tumor that is not penetrated by the light.

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