Studies on the Effects of the Prophylactic Radiation
I have limited-stage small cell lung cancer. I had four cycles of chemotherapy with carboplatin and etoposide, which was extremely effective. I will complete 30 treatments of radiation therapy next week to my lung area. My oncologist wants me to have 10 prophylactic cranial irradiation (PCI) treatments to my head. My mother also has lung cancer (mixed small and large cell) and had radiation to get rid of two small cerebellum brain tumors. I feel that the radiation therapy that she had significantly affected her mental functioning. My oncologist sent me links to literature on toxicity and statistical studies on the effects of the prophylactic cranial irradiation, and I was not convinced. The studies are small, old, and not conclusive about toxicity. Do you recommend PCI? By the way, my mother's side of the family has a history of early onset Alzheimer's disease.
Are there any new studies with larger samples?
Mitch Machtay, MD, Radiation Oncologist, responds:
The downside of PCI is the potential risk of permanent radiation damage to the brain. Radiation therapy to any part of the body usually causes side effects, some of which are temporary and some of which can be permanent. Radiation therapy to the brain can cause the gradual loss of brain cells (neurons) over months to years that can lead to problems with memory, coordination, strength and/or other brain functions. This has been well demonstrated among survivors of childhood cancers who received brain radiation therapy. In rare cases, these neurologic problems can progress to very serious stroke-like episodes and/or "dementia" similar to Alzheimer's disease. These "anecdotal" risks have led some physicians and patients to refuse any consideration of PCI for small cell lung cancer.
The medical literature on brain problems after PCI for small cell lung cancer is admittedly poor, with few well-controlled modern studies. However, several points have emerged from these data:
In summary, as with any cancer treatment, one must weigh the benefits of that treatment against its risks. While some physicians call the use of PCI a "no-brainer" due to the clear survival benefit associated with this therapy that has a relatively well-tolerated side-effect profile, I can understand the continued reluctance of some patients and physicians to undergo this frightening treatment. However, I personally recommend PCI for most patients without pre-PCI neurocognitive problems who have successfully completed treatment for limited-stage small cell lung cancer and are in a complete remission or extensive-stage small cell lung cancer and are in complete remission or who have had a partial response or stable disease. In my practice, this typically consists of 10 daily fractions of 250 cGy each to the whole brain given at least 3 weeks after the last dose of any chemotherapy. A brain MRI should be performed prior to starting PCI to be sure that the cancer has not already shown up in the brain.