Head and Neck cancer -7- Radiotherapy

HEAD & NECK CANCER PART-7

(All the articles published in past are available at www.shyamhemoncclinic.com/blog/)

Question: Thank you for explaining role of neck dissection, various types of neck dissection in last part. You also made some important points about radiotherapy – radiotherapy alone is sufficient for only very small tumors, but radiotherapy plus chemotherapy has replaced surgery in few sites, radiotherapy after surgery is important in many patients, and some things about how modern radiation is delivered.
Can you clarify more about modern radiotherapy use? Every few years we hear about latest radiotherapy machine in a new hospital, and that is supposed to be the Best.
How much detail is important for our readers?
Ans: A good question indeed. Your readers need to know some basics as they are patient advocates and they should be able to guide patient reasonably well, to ensure their life is not compromised.
All modern radiotherapy machines are linear accelerators, not cobalt. As the machine advances, there is higher precision and convenience, for both patient and the operator i.e. the radiation oncology team.
You can compare this with increasing features in our laptop or phones or even surgical instruments. Every situation does not need all new features or all new instruments. A good and experienced surgeon can operate well with a reasonable set of instruments. Few surgeries do need additional very specific instruments. Most important however is the surgeon, and his team.
Same is true for Radiotherapy. Additionally, different companies make different types of machines. This can be compared with various computers again, for example some people are more comfortable with Microsoft and some people with Mac. More important matter is your knowledge of all the features of what you are using, and your basic training, rather than features of the computer or machine.
First level one can say is 3-D conformal radiotherapy i.e. using CT scan to plan radiation field rather than x-rays. More advanced systems have CT scan images integrated with radiation machine, making it more precise and convenient both.
Second level is IMRT (intensity modulated radiotherapy). This is a significant advance in radiotherapy and is increasingly being used. High end software allows optimal dose distribution. Hence, maximum dose goes to the tumor whereas normal organs are spared.
However IMRT is not required or recommended for all sites in body as of now. Like any new technique, it has specific advantages and disadvantages. Importantly, it is not easy for the radiation oncologist (and physicist etc team members), is time consuming to plan, and requires certain training and experience. Thus it is not sufficient just to have IMRT facility in the machine. If not properly planned and delivered, it can actually harm patient, like any other new modality in other fields as well. IMRT is important for most head and neck sites. It allows sparing of some important normal structures, giving dual advantage: allows higher radiation dose delivery AND less side effects. Most important such organ to spare in head and neck region is “salivary glands”.
One of the biggest long term concerns with radiotherapy in this region is Xerostomia – dryness of mouth due to reduced or complete lack of saliva production, a result of permanent damage to salivary glands. This can be quite distressing for patient, making it difficult to eat, poor dental hygiene and sometimes even worse.
Reduction in xerostomia is one of the biggest achievements of IMRT. This technique is also useful in reducing dose to rectum thus avoiding some important side effects, in case of prostate cancer or cervix cancer treatment. About 40-50% of head and neck cancer patients need repeat radiation due to relapse. This is not possible if initial radiation was done using older methods, as the normal organs are not spared adequately. However if initial method used was IMRT, repeat radiation is often feasible.
Third level is IGRT etc. IGRT improves accuracy of radiation delivery, by ensuring that radiation is actually delivered as per plan made by the radiation oncologist. Daily imaging like x rays or CT scan done on treatment machine ensures that the IMRT plans are delivered at the right place with precision. In fact this is significant advancement in delivery of radiotherapy since all errors are corrected daily. This type of precision is more important now as we are reducing size of radiation field and giving higher doses. Tumor position may change by few to several millimeters in body, every day, due to gas, respiration etc. IGRT ensures that radiation delivery will remain precise in spite of such factors.
July 12th 2015. Dr. Chirag A. Shah; M.D. Oncology/Hematology (USA), 079 26754001. Diplomate American Board of Oncology and Hematology. Ahmedabad. drchiragashah@gmail.com Shyam Hem-Onc Clinic. 402 Galaxy, Near Shivranjani, Opp Jhansi ki Rani BRTS, Ahmedabad. www.shyamhemoncclinic.com
I AM INDEBTED TO DR VIVEK BANSAL, FOR HIS SUGGESTIONS.