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Karmanos physicians present research on efficacy of photon, neutron radiotherapy

Two Barbara Ann Karmanos Cancer Center resident physicians recently presented findings that demonstrate the efficacy of photon and neutron radiotherapy to treat two types of cancer, a technique available at few medical centers other Karmanos and Wayne State University.


Dr. Peter Paximades

Peter Paximadis, M.D., and Michael Christensen, M.D., both resident physicians in the Department of Radiation Oncology, presented their findings at the 2011 American Society of Clinical Oncology GI Conference in San Francisco, Calif.
 
“The significance of these projects is the unique type of radiotherapy (neutrons) that was delivered,” Dr. Paximadis said. “Wayne State University/Karmanos Cancer Center is one of only two centers in the United States with the capability of treating tumors with fast neutron radiotherapy.”
 
The poster presented by Dr. Paximadis, “High Linear Energy Transfer Radiation Therapy in Recurrent, Metastatic, or Unresectable Rectal Cancer,” sought to retrospectively analyze the outcomes of patients with recurrent, metastatic or unresectable rectal adenocarcinoma treated with mixed beam photon and high LET radiotherapy.
 
The database containing all patients treated with fast neutron radiotherapy from 1995 to 2005 was reviewed to identify patients treated for rectal adenocarcinoma, calculating local control of the initial cancer site and the overall survival rate, toxicities and the photon and neutron dose.
 
Dr. Paximades reviewed the High Linear Energy Transfer database from 1995 to 2005 to identify patients treated for rectal adenocarcinoma, calculating local control of the initial cancer site and the overall survival rate, toxicities, and the photon and neutron dose.
 
In all, Dr. Paximadis identified 11 patients with recurrent, metastatic or unresectable rectal adenocarcinoma who were treated with mixed photon-neutron radiation, the median age of which was 58. The median survival rate was 16 months (ranging from four to 76 months), with one- and two-year survival rates of 56 percent. Local control of the cancer was achieved in nine – or 82 percent – of the patients.
 
“Our experience demonstrates that treatment of unresectable rectal tumors with mixed photon-neutron achieved excellent local control,” Dr. Paximadis said. “With the added capabilities of intensity modulated neutron radiation therapy, the incidence of treatment-related morbidity may be improved while taking advantage of the superior tumor control that high-LET radiation can impart.”
 
Dr. Christensen’s presentation, “Mixed Photon and Neutron Radiotherapy Given Concurrently with Chemotherapy in Unresectable Pancreatic Cancer,” investigated one of the most difficult sites to treat, despite the use of targeted radiotherapy and modern chemotherapeutic agents.
 
Previous randomized trials exploring the efficacy of chemotherapy and radiation to treat these cancers, he explained, have demonstrated median survival of nine to 11 months. These survival times for what many consider the most deadly form of cancer have not improved appreciably in the modern era. Dr. Christensen sought to review the Karmanos/Wayne State University experience with unresectable pancreatic cancer treated with mixed photon-neutron radiotherapy given concurrently with chemotherapy.
 
Dr. Christensen also used the LET database to find 13 patients treated with high LET radiotherapy for unresectable tumors of the pancreas between 1993 and 2001. Each received mixed photo-neutron radiotherapy and chemotherapy.
 
The median age of the patients was 65 years. Twelve were diagnosed with adenocarcinoma; the other had islet cell carcinoma. The median survival was 11.5 months (ranging from three to 25.6 months). The one- and 2-year overall survival rate was 46.2 percent. Local control of the primary tumor was excellent at 92.3 percent, Dr. Christensen found.
 
The findings, Dr. Christensen said, “demonstrate that treatment of unresectable pancreatic tumors with mixed photon-neutron radiotherapy given concurrently with chemotherapy results in excellent local control, with survival time equivalent to or exceeding that demonstrated in previous series. With the added capability of intensity modulated neutron radiation therapy the incidence of treatment-related morbidity may be improved while taking advantage of the superior tumor control that high-LET radiation may impart.
 
“I would add that our Physics and Engineering staff has developed the capability to perform intensity modulated neutron radiotherapy for use in the future, which would allow for superior conformality of radiation delivery and potentially sparing of normal structures. This capability is unique to Wayne State University worldwide.”
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