Most of the other disease sites and 90% of cancer treatments employ photons, says Evans. "Some energy spectrums on your photon beam go up as high as 23 MV. Six is an IMRT beam and you might treat the breast with 10 or 15 MV. With the liver it could be an 18 MV beam." The higher energy and absorbed radiation dose is permissible because far less healthy tissue is affected and risk of toxicity is lower with IMRT and stereotactic procedures.

"Radiotherapy typically delivers 2 gray fractions, so every day the patient comes in and receives 2 grays of [radiation] dose," says Zankowski. "That setup involves image guidance, positioning of the patient and then the treatment occurs in about a 15-minute time slot. When you're doing stereotactic applications you're giving very high doses in a single fraction or very few fractions, which can take 20 minutes to several hours...One of the trends we've been seeing over the past three to five years is that a lot of what was standard radiotherapy is starting to migrate toward hypofractionated radiotherapy so that instead of seeing the same patient 30 to 45 times and delivering small doses each time, these regimens are starting to become more and more compressed and in some instances it's as extreme as doing it all in five fractions."


Significant success rates with IMRT and IGRT

Dr. David Parda is chairman of the West Penn Allegheny Health System Radiation Oncology Network. Allegheny General Hospital's Radiation Oncology Department is among several rising stars in the field and one of the larger programs in the American College of Radiology. Allegheny offers a dedicated radiation oncology residency program and provides tertiary care for 300 patients a day throughout the network. Dr. Parda estimates that the lifetime incidence of life-threatening cancer is one in two for men and one in three for women, which makes cancer-fighting technologies like linear accelerators all the more relevant. According to recent data, advanced and highly personalized therapies delivered by linear accelerators have led to some staggering cure rates and a dive in toxicity levels.

"For lung cancer treatment - if you have a 2 cm lung nodule that is non-small cell lung cancer and if you treat it with conventional radiation treatment techniques you are able to eradicate that local tumor anywhere from 15% to 30% of the time," says Dr. Parda. "If you use stereotactic radiosurgery and radiotherapy approaches, eradicating the tumor has been shown to occur 90% of the time." Dr. Parda stated that dose escalation procedures combined with IMRT and IGRT showed cure rates also at or exceeding 90% for prostate cancer patients.

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