Photodynamic therapy (PDT) is FDA approved for the treatment of both early stage lung cancer and the palliation of advance stage lung cancer. Off label lung applications have included augmentation of fluorescence bronchoscopy, ablation of granulation tissue causing airway obstruction and as a radiosensitizer prior to brachytherapy. Photofrin® tissue levels have been documented to clear from mucosa and skin in 4-10 weeks. Drug activation within the airway has been with laser light transmitted through diffusing fibers or micro-lens at red-light frequencies.
47 yo WF w/o any significant PMHx was diagnosis with adenoid cystic lung cancer in 2000. Pneumonectomy was not offered because of extensive main carinal involvement. Treatments included XRT, neutron beam radiation, left main stem and left lower lobe stents placed for palliative care. Stent function was complicated by granulation tissue in-growth. She received APC, electrocautery, and PDT to ablate the stent-granulation stenosis. PDT was performed on January 7th, 2005, 2 mg/kg IV was given, drug uptake into the granulation tissue was documented by optical biopsies employing green and blue light point spectroscopy. Initial complete response was seen with exposure of 90% of the stent wires. At the 3-month surveillance WLB, a large left main stem proximal granulation response was again noted; a 2.5-hour procedure using electrocautery, cryotherapy and balloon dilation was used to clear the proximal tissue. A 25% stenosis from granulation re-growth within the distal 3 cm of the left main stem stent and LLL stent was observed but un-treated. Follow-up bronchoscopy was performed 2 weeks later to plan therapy and surprisingly 100% of the left main stem and LLL stents were visible. Optical biopsies of skin and oral mucosa at the time of the follow-up bronchoscopy unexpectedly showed photosensitizer at significant levels.
Photofrin® has 5 significant absorption peaks, clinically we employ the absorption peak at 632nm (red-light); the highest absorption peaks are in the blue-green spectrum (500-600nm). WLB has a typical measured output of 3 mW in the visible light spectrum, with the preponderance of the total energy delivered in the 500-600nm ranges. The total bronchoscopy time was 9000 seconds in an area defined by a 1.4 x 4cm stent. The total power delivered was approximately 18-20 J/cm2, in a frequency range that interacted with the highest absorption peak of Photofrin®. Drug levels in the granulation tissue may have been significant, based on the optical biopsies from skin and oral mucosa done later. Drug-light dosimetry, done in retrospect, supports an ablative response.
WLB may have the ability to activate a PDT response in some patients. This potential should be taken into consideration when treatment-planning post PDT salvage procedures. Point spectroscopy is a vital tool for identification of clinically significant residual photosensitizer.
Franklin McGuire, None.