by ecancer reporter Janet Fricker

In patients with metastatic melanoma combining intralesional injections of PV10 with radiotherapy (RT) delivered additive benefits over historic data using PV-10 alone, reported an abstract presented at the American Society of Clinical Oncology meeting.

“This combination approach may be best for clustered (melanoma) recurrence in sensitive sites such as the face or scalp,” said Mark Smithers, the lead investigator from The University of Queensland, Brisbane.

The idea for the study came out of a case report, published 2010, showing ‘impressive results’ in three metastatic melanoma patients treated with PV-10 and external beam RT.

PV-10, a 10% solution of Rose Bengal originally used as an agent to stain necrotic tissue in the cornea, has been developed to selectively target and destroy cancer cells without harming surrounding healthy tissue.

In the current phase 2 open level, single arm study, 15 melanoma patients with stage IIIb/IIIc ‘clustered recurrence’ were treated with PV-10 injections and reviewed at one and four weeks.

To be eligible, patients had to have lesions treatable within a localised radiotherapy field.

There were 13 patients with disease still present, who did not have disease at other sites, who were treated with 3D conformal radiotherapy (photons or electrons) (30 Gy, six fractions of 5 Gy twice weekly over three weeks).

RT was started six to 10 weeks after PV-10.

Results at a median follow-up of 19.3 months showed the overall response rate was 87% (complete response 33%; partial response 53%), with a 12.2 month mean duration of complete responses.

The latest data can be compared to a series of 80 patients with diffuse transmit recurrent melanoma treated with PV-10 alone showing overall response rates of 51 % (complete 26%; partial 25%).

The data was reported in 2014. In the current study investigators observed complete responses were more likely with metastases smaller than 10mm.

Treatment was well tolerated, with no treatment associated grade 4 or 5 adverse events.

“Our hypothesis is that PV-10 may sensitize the malignant cells to be more likely to respond to radiotherapy,” said Smithers. Previous studies, he added, have identified groups responding to second injections of PV-10. “So it may be that the addition of RT selects out this group,” he said.

The observation metastases less than 10mm showed greater potential for complete response, he added, was likely due to larger lesions being more biologically active and resistant to treatment.

Source: ASCO 2016