Disclaimer: This is the second installment of a quarterly series featuring Foundation Chief Scientific Officer Dr. Kim Hunter-Schaedle (to view the first article please click here). These responses are for general informational purposes only and are not intended to be a substitute for medical advice, diagnosis or treatment by a physician who is aware of personal medical history. Do not rely on these responses in place of seeking professional medical advice.
Q: Do any of the following affect NF tumor growth: sunbathing; galvanic (electrical) stimulation for pain relief; the female menstrual cycle; stress?
A: Sunbathing carries risks for all of us, whether we are have NF or not. It is well known that sun exposure can cause ultraviolet damage to DNA in the skin. This can cause genetic changes and increase the risk of skin cancer. In NF, genetic differences are present from the time of birth, but NF tumors will form only once additional specific genetic changes occur. In theory, this could be caused by sunbathing. Overall as a general rule, you should limit sunbathing and you ALWAYS use high SPF sunscreen and reapply this often especially after swimming.
Electrical stimulation: This is not well studied in NF. From other areas of research, the information we have is mixed. Electrical stimulation has been shown to promote the local growth of new blood vessels to aid wound healing; and new blood vessels could potentially help promote tumor growth. However it has also been reported that electrical stimulation can increase the production of tumor-killing enzymes called caspases; and another study suggests ‘electric shock’ of drug-resistant tumor cells can make them sensitive to drug again. In brief this is an area where limited information means we don’t have a clear picture.
Menstrual cycle: As tumors can be responsive to the female hormone estrogen, times of life when estrogen levels significantly change – notably puberty and pregnancy – can be times when NF tumors can show an increase in growth. However there is no evidence that NF tumors increase in growth during the regular menstrual cycle.
Stress: There is no evidence that stress promotes tumor growth in NF. And research studies attempting to link stress and cancer have yielded conflicting results.
Q: Is the progression of NF tumors the same for subcutaneous and plexiform tumors? Are there certain areas of the human body, when affected with dermal neurofibromas or plexiform tumors, are more prone to malignancies? When there are many tumors and it is difficult to tell which tumor is causing pain, are there any diagnostic tests that might help determine which tumor is causing pain?
A: Subcutaneous (dermal) neurofibromas and plexiform neurofibromas are both caused by tumors developing from nerve cells. For both tumor types, it is difficult to predict when or where they will appear in the body or how big they will grow. For both tumor types too, they are unfortunately likely to re-grow in the same location after surgical removal. There is however a major difference between the two tumor types in the way they may progress which relates to the risk of malignancy.
While dermal neurofibromas will, except in very exceptional cases, remain non-cancerous, plexiform neurofibromas run the risk of turning into malignant cancers in around 10% of cases. Unfortunately today it cannot be predicted if a person is at risk of developing one of these malignancies or which tumor in which region of the body might become malignant. For this reason plexiform neurofibromas should be monitored annually by your NF physician, and if you have any pain in the plexiform tumor you must report this to your doctor immediately. If pain is felt the doctor can perform a PET scan which can reveal through imaging areas of the tumor that are ‘metabolic hotspots’ – the areas that may be early stage malignancies.
Q: What can you tell us about long term use of the drugs Avastin and vinblastine for NF in children?
A: Vinblastine is widely used drug for cancers and is used in children as well as adults. It is not intended to be used as a long-term therapy but rather for short term drug regimes. Your physician should carefully explain to you potential benefits and risks.
Avastin is now widely used in many cancer regimes following chemotherapy. It is of increasing interest in NF2 where it has shown early promise for the treatment of vestibular schwannomas. Use of Avastin in NF1 has been more limited to date. Avastin has been given to children as a treatment for different cancers, but generally is still in an early stage of investigation. One concern is based on the fact that Avastin works by preventing the growth of new blood vessels; and as children are still growing, they need new blood vessels. In NF1, there is one recent report that a young boy treated with Avastin for an NF1-related glioblastoma (brain tumor) went on to develop vascular problems in the brain. It emerged that he had a pre-existing complication that can occur in NF1 called moyamoya where the brain blood vessels are not developed properly.
Q: How hard is it to remove a large plexiform in the upper part of the leg without losing the leg?
Every plexiform tumor is different and some can be complicated to remove. Your doctor should carefully explain to you the options to treat or remove it and any associated risks. There are a number of skilled surgeons who can remove very complicated NF1 tumors; CTF has an NF Clinic Network through which you can identify such a surgeon if needed.
Q: What is the link between heart conditions and NF?
A: It is widely recognized that persons with NF1 have an increased risk of cardiovascular disease. However in the past few years this has become an area of significant interest and a focus of study by both scientists and clinicians. Scientists are figuring out the mechanisms that cause this heart disease and finding that these have a lot in common with the mechanisms that for example cause plexiform neurofibromas. Down the line this will help develop effective treatments for NF1 related heart disease and help the doctors to understand how to predict whether this heart disease might occur in specific individuals with NF1.
If you have any questions about NF1, NF2, or schwannomatosis you would like to ask Dr. Kim please register at ctf.org and submit them to the discussion board.
