A Swiss pharmaceutical company presented a clinical study of patients with solid tumors who were given a combination treatment of the company's best-selling cancer drug with an experimental immune-booster, but experts say the results are unclear.

Reuters reported that Roche used Avastin, the cancer drug, along with the experimental MPDL3280A drug, and presented the data of the trials at the European Society of Medical Oncology annual congress in Madrid, which showed a possible effect but no conclusive results.

Avastin accounts for 13 percent of Roche's sales, so the pairing of two of the companies drugs is important to its business.

New immunotherapy medicines like MPDL3280A could potentially kill the cancer drug industry if the pairing isn't pushed, Reuters reported.

Avastin is well-known for its ability to stop tumors from developing new blood vessels. The new immune-boosting drug is designed to help the body's immune system fight cancer cells.

Oncologists and investors are waiting to see more conclusive data that the two drugs compliment each other.

Christopher Lieu of the University of Colorado Cancer Center reported results for patients, both with and without chemotherapy.

Various cancer types, including kidney and colorectal cancers, saw tumor shrinkage as a result of the combination of drugs, Reuters reported. One patient with kidney cancer given the two drugs with chemotherapy experienced a complete response, or disappearance of disease.

Some of the results have doctors suggesting that the combination might play a role in kidney cancer

Response rates of 10 kidney cancer patients given MPDL3280A and Avastin without chemotherapy was 40 percent but only 8 percent in 13 colorectal patients, Reuters reported. A different group of colorectal patients had about a 40 percent response rate when they added chemotherapy.

"There may be synergies but we can't draw any firm conclusions from the data so far," said Eric Van Cutsem of the University of Leuven, who was not involved in the research, according to Reuters. "We don't know if it is due to the chemotherapy or due to the other drugs."

The experimental drug is on a list of closely watched drugs, which are supposed to help in blocking a tumor's ability to evade the immune system's defenses.