Stem cell sparing radiotherapy preserves salivary gland function
MedWire News: The response of the parotid gland to radiation critically depends on the dose to its stem cells, which are located in the major ducts, study findings indicate.
Speaking at the 31st Conference of the European Society for Radiotherapy and Oncology, in Barcelona, Spain, Peter van Luijk (University Medical Center Groningen, the Netherlands) said that these stem cells can easily be spared with current treatment modalities, which may result in significantly reduced complications in radiotherapy for head and neck cancer.
"Parotid gland dysfunction after radiotherapy for head and neck cancer was, and still is, a major clinical problem. During radiotherapy, attempts to minimise the risk of this complication have been aimed at reducing the average dose to the salivary gland, on the assumption that it would not make a difference where in the gland the radiation dose was reduced," said van Luijk in a statement to the press.
"However, this does not seem logical according to the anatomy of the salivary gland and, in previous work, we discovered that reductions in the radiotherapy dose to some parts of the gland allowed the parotid gland to regenerate, whereas a dose to other parts did not."
The relationship between the location of parotid gland stem cells, which are necessary for the long-term maintenance of organ function, and late parotid gland dysfunction after irradiation was therefore investigated by van Luijk and team.
They found that in mouse, rat, and human tissue, the stem cells were predominately located in the central part of the major ducts of the parotid gland.
Furthermore, high-precision proton irradiation to this central part of the gland resulted in a significant reduction in saliva production in rats. By contrast, minimal effects were observed after irradiating other parts of the gland.
To test whether this local sensitivity is also observed in patients with head and neck cancer, the team compared saliva production at 1 year after radiotherapy with the radiotherapy dose received at specific subvolumes of the parotid gland in 36 patients.
"Excitingly, dose to the cranio-ventral extension of the gland containing the major ducts was most predictive of damage to saliva production," said van Luijk.
In addition, the team used a mathematical model to show that it would be possible to reduce the radiation dose by approximately 50% to this part of the gland, without compromising adequate target coverage.
"Using the mathematical model, we estimated that with such dose reduction none of the patients would have developed parotid gland dysfunction."
The researchers caution, however, that further prospective studies comparing stem cell sparing radiotherapy with standard treatment are required before the technique is recommended.
If the findings of such studies are positive, the stem cell sparing technique could "improve quality of life of 500,000 patients treated with radiotherapy for head and neck cancer worldwide every year," van Luijk concluded.
MedWire (www.medwire-news.md) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2012
By Laura Cowen