Phototherapy is the use of light in the treatment of physical or mental illness.
The new approach uses a single chemical compound, silicon naphthalocyanine, that has both diagnostic and therapeutic value, the researchers said.
At the same time, this compound creates heat within any remaining cancer cells, killing them in the process.
In tests completed with laboratory animals, tumours were completely eradicated without side effects, and did not return, the researchers said
"This system that can make cancer cells glow is like giving the surgeon an extra pair of eyes," said lead author of the study Olena Taratula, research assistant professor at Oregon State University in the US.
"And the compound we are working with now is inexpensive and appears effective at killing any cancer cells that remain," she said.
When perfected, researchers believe that the evolving field of phototherapy may become a new and promising addition to the three primary ways that most cancer is treated today: surgery, radiation and/or chemotherapy.
Phototherapy clearly has the potential to make some of those approaches more effective than they already are, the study said.
Research so far has studied ovarian cancers in laboratory animals, but the researchers said that conceptually the treatment may also be useful for other solid tumours.
The findings were published in the journal Chemistry of Materials, a publication of the American Chemical Society.