Effect of Low-level Laser Therapy on Salivary Flow, pH and Quality of Life in Irradiated Oropharyngeal Cancer Patients.

There are multiple treatment modalities the cancers of the head and neck. The main three major treatment options are surgery, radiation therapy and chemotherapy. Radiation therapy (RT) is used to control the growth of the tumor with limiting the damage to adjacent tissues. Surgery is the main treatment for oropharyngeal cancers, but if the cancer remains, radiation and chemotherapy is used in adjunct to surgery. Radiation therapy is a common treatment options for initial to mid stage malignancies.

A major complication of RT is that non neoplastic tissues of the head and neck are variably affected. The exact amount of damage to healthy tissues depends on factors such as fraction of radiation dose, the total amount of the radiation dose administered, volume of irradiated tissue, and how the dose is distributed in the tissue. The effect on the tissues may appear either during the treatment (acute) or once the treatment is complete (late).

For Oropharyngeal cancer, major and minor salivary glands are mostly affected by RT due to the fact that salivary glands fall in the radiation pathway. The mechanisms by which the tissues and cells are damaged due to radiation are still not very clear, but the features most commonly found histologically are atrophy of the tissues and degeneration of the acini. According to researchers, "the decrease in saliva and xerostomia that results from radiotherapy plays an important role in worsening Quality of Life (QoL) among patients who undergo radiotherapy for head and neck cancers". The normal flow rate of unstimulated saliva is 0.3-0.5 ml/min. If it decreases to less than 0.1-0.2 ml/min, it is then that one would experience xerostomia Xerostomia Inventory (XI) which was formulated by Thomson is a validated tool which will also be used to determine the amount of dryness based on the XI score. A higher score will be suggestive of worsening xerostomia.

The most commonly recommended treatment for xerostomia currently is intraoral topical agents. These include salivary stimulants, chewing gums, topical sprays containing malic acid. Also used for xerostomia are medicines such has pilocarpine and cevimeline but both medicines are parasympathomimetic and need to be administered with extreme caution. The effectiveness of there medicines is short lived and only provide symptomatic relief.

Generally, the mechanism by which Low level laser Therapy(LLLT) works is that photons are generated through the light energy and these photons produce cellular responses in the cell. The photons of light are readily absorbed by the cytochromes and the porphyrins present in the mitochondria of the cell.