Response to Letter: Radiosurgery for Colloid Cyst – Surgeon Patriarchy or Patient Autonomy?

Abstract

Dear Editor,We want to thank Dr. Tripathi and Dr. Verma for their interest in our paper. We appreciate the feedback they provided and consequently would like to clarify some issues they raised in their letter.There remains controversy on the minimum number of patients that make a study eligible to be classified as a clinical series. However, our series is by definition the first clinical series on treating third ventricle colloid cysts with gamma knife radiosurgery. According to Esene et al. [1] a clinical series should include at least 5 patients. Morgan et al. [2] included only 4 patients. In the mentioned study, the first MRI was done after 6 weeks. Only a CT was done immediately post aspiration, which does not qualify as a reliable imaging modality for assessing residual cyst. In addition, the authors report that at 6 months of follow-up MRI, the tumor diameter had regressed to 7.3 mm while at 6 weeks post aspiration it was only 5.5 mm. This means that at the time of radiosurgical treatment the cyst had progressed, although size was not mentioned, which we consider the time of recurrence.The treatment of 13 patients with colloid cysts over 12 years hardly represents overzealous use of gamma knife radiosurgery. When it comes to cyst size, the authors overemphasize this factor, while insisting on placing a size cut-off, which is in fact of no benefit to the patient and may be misleading. This is because the main factors in the development of neurological complications from colloid cyst progression are cranial compliance, brain tissue volume, and ventricular plasticity and not only cyst size of itself. A smaller cyst may cause sudden death, while a larger cyst may present first with neurological deterioration because of hydrocephalus.As for the interval range between the presentation and intervention, it was because of the 2 patients that showed progressive growth on observation by serial imaging before gamma knife radiosurgery. They were eventually treated at 60 months and 99 months.Our firm belief is that in benign and rare entities such as colloid cysts, where management is controversial and surgery is not low risk, the patient should be counseled appropriately without leading him/her to the surgeon’s personal preference. The patient should be presented with all the relevant data, and gamma knife should be included as a treatment option, which as our data suggest, is safer than observation. The decision to put in a shunt or not is the treating physician’s decision, especially if the patient is not clinically manifesting. Also, we are a stand-alone center at the risk of being redundant.The cyst diameter can be easily calculated from the volume of a sphere with a relevant formula. In addition, volume measurements are more accurate [3], and the relevant volume measurement software is non-costly and easily available.We agree that a prospective study on the long-term effect of gamma knife radiosurgery on memory should be conducted, while the rarity of these lesions makes this practically impossible. However, previous studies reporting on treating other lesions in the same region with gamma knife radiosurgery, report no effect on neurocognitive functions [4, 5].Lastly, I have often wondered why the question of natural history is always raised when radiosurgery is mentioned but seldom questioned when the topic is surgery-related. Natural history is basically unknown for each individual, so why put the patient at risk of the unknown when we have the option of the virtually risk-free known?All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript.No funding was received for this research.Amr Mohamed Nageeb El-Shehaby: concept and design, article writing, critical review, and revision and acceptance of final manuscript. Wael Abdel Halim Reda, Khaled Mohamed Abdel Karim, Ahmed Nabeel, Reem Mohamed Emad Eldin, and Sameh Roshdy Tawadros: critical review and revision and acceptance of final manuscript.