After a 10 minute intravenous infusion of padeliporfin, an ultrasound probe is driven up the patient’s rectum.  Images from the probe show the doctor where to stick needles through the perineum and into the prostate.  Fiber optic cables are threaded into these openings and then are lit up to emit 753 nanometer laser light into the tissue for about 22 minutes.1,2 The light shines through normal tissue3 to reach and excite padeliporfin, which lingers in tumors longer than in normal tissue.  Upon activation the drug generates reactive oxygen species (ROS) that directly kill cells, cause oxidative stress, and stimulate an immune response.  This is photodynamic therapy (PDT) for prostate cancer with padeliporfin.1,2

therapy
Image from Ref. 2.

Phase III results were released for this investigational drug in mid-December.  European men were enrolled at 47 study centers.  None had prior treatment for their localized, low-risk prostate cancer.  The treatment arm patients received the photodynamic therapy described above and the control arm patients received the standard of care, which includes regular imaging and check-ups.  The co-primary endpoints were progression of disease and negative biopsy at 24 months follow-up.  Fifty-eight (28%) of 206 treated patients had disease progression, compared to 120 (58%) of 207 patients in the control arm (p<0.0001).  One hundred one (49%) in the padeliporfin-treated group had a negative biopsy, but only 28 (14%) in the control arm did (p<0.0001).  The most common serious adverse event in the treatment group was retention of urine (n=15), although this resolved within two months for all patients.1

PDT has been slow to catch on due to problems with first-generation treatments, like porfimer sodium.3 But it may become a popular focal therapy for prostate cancer, like cryoablation or high-intensity focused ultrasound,4,5 because it could control low-risk cancer and prevent or put off radical surgery.1

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References:

1. http://www.thelancet.com/journals/lanonc/article/PIIS1470-2045(16)30661-1/abstract

2. Nature Clinical Practice Urology, 2009, 6, 18-30.

3. Photochem. Photobiol. Sci., 2015,14, 1765-1780.

4. Nature Reviews Urology, 2010, 7, 562-571.

5. http://www.harvardprostateknowledge.org/promising-technologies-for-the-treatment-of-prostate-cancer (accessed Jan. 1, 2017)

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