January 31, 2013

$PVCT: Refractory scalp #Sarcoma

I wanted to dig deeper into Tan and Nehaus’ letter to the editor about the “Novel use of Rose Bengal (PV-10) in two cases of refractory scalp sarcoma.”

Refractory means “resistant to treatment or cure.” So, refractory scalp sarcoma means a sarcoma already shown to be resistant to other treatments. “A sarcoma is is a cancer that arises from transformed cells of mesenchymal origin. Sarcomas are quite rare. Common malignancies, such as breast, colon, and lung cancer, are almost always carcinoma.”

The article in ANZ Journal of Surgery is just another example of PV-10 have a positive effect on tumors.

The first patient previously underwent surgery, which was followed by radiotherapy to combat his sarcoma. Nodules, however, appeared afterwards in the area to which radiotherapy was applied. Rose Bengal (PV-10) was used, and a complete clinical response was attained.

The second patient also underwent, first, surgery and, second, radiotherapy. Rose Bengal was used with good clinical effect; however, he subsequently developed pulmonary metastases, which is being combated with a systemic chemotherapy. It does not appear from reading the letter that the pulmonary mets was challenged with PV-10.

Some would say, quickly: one success and one failure. More substantively and intellectually honestly: one complete success and one near success. After all, only two patients were treated, with limited frequency (once per patient) and amount of Rose Bengal treatment, with stunning success given sarcomas are rare. I doubt much successful clinical work has been done on patients with fibrous histiocytoma. Yet, here Rose Bengal is with near complete success (both patientdespite limited application.

Both patients were treated with PV-10 after first being treated with surgery and then with radiotherapy, an immunosuppressive therapy.

What happened with the second patient? Maybe surgery removed a certain antigenic type, and the pulmonary mets are another type that does not match. Tumor heterogeneity might be interfering (a topic of a blog entry that I will post in a bit). Maybe all of the high-affinity monoclonal antibodies capable of killing the tumor were killed by the radiotherapy treatment. How the patient was first treated (i.e., surgery, radiotherapy) might precipitate the failure of immune system to ultimately help in the removal of the tumor.

Maybe the patients’ parents didn’t give their now elderly son the proper genes for his immune system to respond. There are a number of these folks in any population, and saving them with any kind of treatment is a near impossibility.

As Craig has long said, and I expect Moffitt to confirm, using PV-10 first, followed if necessary by other treatments is the way to go. In the two cases highlighted by the authors, the approach was backwards. Yet, the “backwards” approach yielded good results on refractory sarcoma. Why backwards? Recall Foote et al.’s past and current work: PV-10 first, followed by radiotherapy. That appears to be the right treatment order.

Still, and to be intellectually honest, we’re talking about only two patients. There is much more to do and much more to learn.

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