There are few long-term studies of people who've had face transplants, and even the addition of another study of seven cases does not answer all questions about safety and efficacy of the procedure, say the authors of a new report.

"Ultimately, if one answers, 'yes' to the question, 'Should we continue performing face transplants?'" then the "ethical requirements" for going forward include meticulous patient selection, long-term monitoring, and strict oversight by the institutional review board, the authors wrote online August 24 in The Lancet.

There have been fewer than 40 face transplants since 2005. In the new study, the French research team followed outcomes for seven transplant patients who had the surgery at their hospital between 2000 and 2009. Four had self-inflicted gunshot wounds to the face, one was burned and two had an inherited facial tumour condition.

A study of seven people is relatively large when you consider that so few transplants have ever been done, lead author Laurent Lantieri of the Hopital Européen Georges Pompidou in Paris said.

Over an average of six years of follow-up, two patients died, one due to transplant failure and infection and one due to suicide more than three years after the transplant.

All of the recipients experienced period rejection episodes. The surviving patients continued to take high-dose steroids for years after surgery. None developed diabetes, but three developed hypertension and all had noticeably reduced kidney function.

Not all recipients experienced the same improvement in quality of life or social integration. Improvements in those areas seemed to depend on patients' quality of life before the transplant, and whether or not they had serious psychiatric comorbidities.

Mental health is an important predictor of the success or failure of a face transplant, and recipients should be carefully selected and have mental health and social work professionals in their multidisciplinary transplant teams, according to Dr J. Rodrigo Diaz-Siso and Dr Eduardo D. Rodriguez of New York University Langone Medical Center, one of the few facilities in the world where face transplants are performed. Diaz-Siso and Rodriguez coauthored a comment along with the new research in The Lancet.

Also critically important to the success of a face transplant is HLA matching, which can be difficult in highly sensitised burn patients, they say.

The authors of the study and of the comment agree that what long-term data we have so far does not yet answer the question, "Should we continue performing these procedures?"

"Face transplantation is not Face/Off," Lantieri said, referring to a 1990s science fiction movie. "These patients have no other options and face incredible risks just to improve their basic quality of life, unlike what has been shown in the media."

"Face transplants are appropriate for a select group of individuals, particularly for those for whom conventional plastic surgery options have been exhausted and function has not yet been restored," Rodriguez said. "These individuals must also understand the risks of these types of these procedures as well as the long-term effects of immunosuppression medication."