There have been a number of questions on the Johns Hopkins pancreatic website regarding stereotactic radiosurgery for pancreatic cancer. Therefore, we thought it is important to review the literature on stereotactic radiosurgery and help patients better understand the risks and benefits of this treatment and clarify some of the misconceptions. Stereotactic radiosurgery (SRS) can also be called stereotactic body radiotherapy (SBRT) or CyberKnife. It is important to stress that all of these modalities use radiation and that there is no actual surgery done.
The theory is that the radiation doses are high enough to cause ablation of the pancreatic tumor. While the data suggests that SBRT and/or CyberKnife can ablate certain tumors (brain metastasis and lung tumors) there is no prospective data showing that SBRT and/or CyberKnife can effectively ablate pancreatic tumors or shrink them to the point where they can be resectable. As you can see by the two prospective trials posted on this blog, SBRT and CyberKnife appear to prevent pancreatic tumors from progressing (grow) but there is no evidence that it causes pancreatic tumors to shrink or improve survival. Further, the data suggests that high doses of radiation given by SBRT or CyberKnife can cause some unacceptable acute (within 2-3 months of treatment) and chronic side effects from treatment when compared to conventional radiation treatment delivered over 2-6 weeks of treatment. Specifically, approximately 30-40% of all patients treated with SBRT/CyberKnife develop gastrointestinal side effects including a small number of patients who developed ulcers which required surgical repair. The authors suggest that this may be because the duodenum and small bowel is adjacent to the pancreatic tumors and it is hard to treat the pancreatic tumor and avoid irradiating these areas.
It is important that almost all patients in these studies developed metastatic disease, clearly demonstrating a need for better drugs to control pancreatic tumor spread. Finally, the survival in both of these studies unfortunately were very similar to conventional radiation and chemotherapy. While SBRT and CyberKnife are more convenient for patients (1-5 days of treatment) compared with 25 treatments (conventional), the increased risk of side effects with shorter course radiation with no improved survival make us question whether these treatments in their CURRENT FORM are clearly benefiting patients with pancreatic cancer.
It is important to note that the doses of radiation used in these studies are high. In the Stanford CyberKnife study (Koong et al.) the dose was 25 Gy given in one fraction and in the SBRT (Denmark) trial the total dose was 45 Gy. It is possible that lower doses (15-25) delivered over 3-5 fractions may be better tolerated than the doses given in these two studies, however this data has not been published in a prospective controlled fashion. In summary, SBRT/CyberKnife does appear to result in good local control of pancreatic tumors, however it is unlikely that it will shrink a majority of pancreatic tumors enough for surgical resection and patients are likely to have increased chronic (long term) side effects when compared to conventional treatment.
Additional prospective (patients treated on a clinical trial and followed for side effects) studies are needed to test the true benefit and safety of SBRT and Cyberknife treatment for patients with unresectable pancreatic cancer. While SBRT and CyberKnife therapy does hold promise we have to be careful not to tell patients that it is likely to cure them of their cancer….the data simply isn’t there.
The theory is that the radiation doses are high enough to cause ablation of the pancreatic tumor. While the data suggests that SBRT and/or CyberKnife can ablate certain tumors (brain metastasis and lung tumors) there is no prospective data showing that SBRT and/or CyberKnife can effectively ablate pancreatic tumors or shrink them to the point where they can be resectable. As you can see by the two prospective trials posted on this blog, SBRT and CyberKnife appear to prevent pancreatic tumors from progressing (grow) but there is no evidence that it causes pancreatic tumors to shrink or improve survival. Further, the data suggests that high doses of radiation given by SBRT or CyberKnife can cause some unacceptable acute (within 2-3 months of treatment) and chronic side effects from treatment when compared to conventional radiation treatment delivered over 2-6 weeks of treatment. Specifically, approximately 30-40% of all patients treated with SBRT/CyberKnife develop gastrointestinal side effects including a small number of patients who developed ulcers which required surgical repair. The authors suggest that this may be because the duodenum and small bowel is adjacent to the pancreatic tumors and it is hard to treat the pancreatic tumor and avoid irradiating these areas.
It is important that almost all patients in these studies developed metastatic disease, clearly demonstrating a need for better drugs to control pancreatic tumor spread. Finally, the survival in both of these studies unfortunately were very similar to conventional radiation and chemotherapy. While SBRT and CyberKnife are more convenient for patients (1-5 days of treatment) compared with 25 treatments (conventional), the increased risk of side effects with shorter course radiation with no improved survival make us question whether these treatments in their CURRENT FORM are clearly benefiting patients with pancreatic cancer.
It is important to note that the doses of radiation used in these studies are high. In the Stanford CyberKnife study (Koong et al.) the dose was 25 Gy given in one fraction and in the SBRT (Denmark) trial the total dose was 45 Gy. It is possible that lower doses (15-25) delivered over 3-5 fractions may be better tolerated than the doses given in these two studies, however this data has not been published in a prospective controlled fashion. In summary, SBRT/CyberKnife does appear to result in good local control of pancreatic tumors, however it is unlikely that it will shrink a majority of pancreatic tumors enough for surgical resection and patients are likely to have increased chronic (long term) side effects when compared to conventional treatment.
Additional prospective (patients treated on a clinical trial and followed for side effects) studies are needed to test the true benefit and safety of SBRT and Cyberknife treatment for patients with unresectable pancreatic cancer. While SBRT and CyberKnife therapy does hold promise we have to be careful not to tell patients that it is likely to cure them of their cancer….the data simply isn’t there
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