Monitoring Response to Thermodox using Optical Spectroscopy

Greg Palmer Ph.D. present his post-doc work in Dr. Dewhirst's Lab:

Optical spectoscopy involves measuring the reflectance, and fluorescence of tissue, and looking to provide structural and functional information. This is a non-invasive, near real-time, non-destructive measurement.

Three properties are measured: absorbance, scattering, and fluorescence.

Measurable Quantities:
Hb concentrations and saturation
NAD, NADPH
Collagen
Amino Acids
Extrinsic Fluorecence (doxorubicin and other drugs or contrast agents)
Size and density of scattering centers (collagen structure)

Depth may be done up to 5cm when utilizing infrared wavelengths (though with shorter wavelengths, we may be limited to millimeters).

Measurement within 10% can be arrived at via monte carlo model fit for hemoglobin concentrations. PO2 can thereby also be estimated. This contrasts to BOLD imaging which only measures relative change.

Note that the measurements are volume averaged, thus less sensitive to positition than an ependorf electrode.

Thermodox is doxorubicin encapsulated within a thermally sensitive liposome. This is given in combination with regional hyperthermia for directed chemotherapy delivery. As doxorubicin is fluorescent (593nm), measurements with optical spectroscopy can estimate in real time, regional drug concentrations may be estimated.

Concentrations as estimated by optical spectroscopy and correlated to HPLC assay as reference resulted in excellent correlation r=0.9, p=1e-20.

Hb saturation and concetration both are seen to increase after hyperthermia. In the setting of liposomal doxorubin, these do not increase, which may be a result of doxorubicin's direct affect on vasculature. One can see a dramatic increase in doxorubicin after application of hyperthermia to liposomal doxorubicin, much greater than free dox +HT, or free dox alone.

Ongoing clinical work is progressing in Head and Neck, Breast, and Cervical Cancer... stay tuned.

Hyperthermia Symposium 4/9/09

These talks were part of a symposium hosted by Dr. Dewhirst at Duke.

Timo L.M. ten Hagen, PhD

Laboratory Experimental Surgical Oncology

Department of Surgery

Rotterdam, the Netherlands

“Manipulation of Tumor Response with Vaso-active Agents”

The problem is poor perfusion in regions with viable tumor. This causes both hypoxia and poor drug delivery.

Isolated limb profusion with high dose melphalan, TNF or other vasoactive drugs was the strategy used. Hyperthermia may also be used. Used in both melanoma and sarcoma of the extremities.

TNF, Histamine, IL-2, hyperthermia, and MMP antagonists (matrix metalloproteases) all act on tumor vasculature. At this time he showed images of a TNF treated patient with a lower extremity sarcoma, with normalization of the angiogram. TNF alone doesn't seem to cause any regression on its own, but in combination with melphalan, an additional effect on tumor is seen in animal models. Interestingly, interstitial pressure is not significantly changed.

Addition of Melfalan + TNF or doxorubcin +TNF one sees an improvement in drug accumulation in tumor. Distribution is also more homogeneous. In either TNF or histamine hemorrhage is also seen in the tumor specimens (increasing the vascular permeability?).

One problem is that chemotherapy agents such as melphalan, even with isolated perfusion, pharmacokinetics remain poor. Efforts now directed towards liposomal drugs.

TNF + doxil (liposomal doxorubicin) resulted in an increase in tumor response rate, as well as growth delay. In normal tissues, concentrations were low, except for the spleen (TNF may be activating macrophages in this organ). 100nm liposomes seem to give the best localization into tumor.

Side note – it is fortunately easy to image doxorubicin because it fluoresces. One can use liposomes labeled with DIO to demonstrate differential concentrations of the intact liposomes and free doxorubicin. One issue is that many liposomes hold onto their doxorubicin, and the drug is not release to the target – the nucleus. (Can Res 2007)

TNF is also a toxic systemic agent, also termed cachectin due to it's role in cancer associated cachexia. At high doses it can lead to hypotensive shock and multi-system organ failure.

The second talk of the day was:

Lars Lindner, PhD

Department of Internal Medicine III

University Hospital Grosshadern

Munich, Germany

“Title: Potential of phosphatidyloligoglycerols in temperature sensitive liposomes”

Temperature sensitive liposomes are engineered to release contents at mild hyperthermic temperatures 40degrees.

Two Strategies for delivery

Interstitial drug release: Specificity controlled by increased vascular permeability in tumors, and which can be improved by the application of targeted heat. The cons to this approach include inefficient entrapment process, and high systemic drug load due to uptake by the reticular endothelial system (RES). In this approach, there is no need for quick drug release as the drug is within the interstitial compartment.

Intravascular drug release: has the potential to have a 100% drug delivery to the tumor region, however systemic recirculation is a limitation of this approach. It is important to have efficient drug release in this setting to maximize the targeting.

Phosphatidyloligoglycerols: three subtypes, and with PG2 and PG3 there are much more linear pharmacokinetics. By increasing the concentrations of PG2 and PG3, one can increase the rate of release with increase in temperature. These are development currently awaiting clinical applications.

Hyperthermia in the Netherlands

Dr. Maarten Paulides from Erasmus in the Netherlands - an engineer associated with their Hyperthermia project - spoke about their current clinical efforts.

Background

12- year update of the netherlands deep ht trail

doi:10.1016/j.ijrobp.2007.07.2348    

114 pts with locally advanced cervical cancer

1990-1996

ebrt + brachytherapy in all patients to 68-70Gy to point A

randomized to ht once weekly with heating goal of 42 degrees C for 60 minutes

local control 37% rt vs 56% rtht (p=0.001)

overall survival 20% rt vs 37% rtht (p=0.03)

actuarial > grade ii late toxicity was no different between arms

This is one of the strongest trials supporting a clinical benefit to hyperthermia with radiation therapy in the curative settting.  The primary weakness is that this trial occurred prior to the NCI alert in 1999 supporting the use of concurrent cisplatin based chemotherapy.

This weakness is addressed in an ongoing multi-institutional trial, currently open at Duke, exploring radiation therapy with concurrent cddp based chemo, plus or minus hyperthermia.

Current HT Clinic load at Erasmus:

deep ht - ~100 patients/year - 1.5 hour treatment time (0.5 hours of this is warm up), treated once weekly.

superficial ht - ~60 patients/year - 1 hour treatment times (0.25 hours for warmup), treated once weekly.

Ongoing ht trials at erasmus:

phase iii cervix trial (noted above)

recurrent rectal cancer: capcetabine + HT in previously irradiated patients

developing head and neck applicator

Head and Neck

Dr. Paulides referenced the below as backgound.

valdagni ijrobp 1994 (PMID: 8270437) 

small randomized trial of RT +/- HT in locally advanced head and neck cancers

in 44 nodes (41 patients) the response rate was 41% rt vs 83% rtht

this trial also reported improve nodal control and overall survival at 5 years, though one must take the number of patients into account.

With this backdrop, the physicists and engineers at Erasmus have been developing a head and neck collar applicator for hyperthermia delivery, which has now been used for treating patients.  Monitoring is a bit of a problem as many of these sites are not accessible or amenable to invasive thermometry.  Addtitionally cooling from vasculature and respiration may confound attempts for homogeneous heating of the target.  However, he was able to show that this could be done, and I for one was quite surprised that they were implementing this in patients already, including a nasopharyngeal patient which he showed the thermometry for.  

Link to an Abstract describing the applicator (the Hypercollar): http://www.esho.info/esho2007/pdf/paulides1_esho2007.pdf