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60 Gy Standard Radiotherapy for NSCLC Challenged

60 Gy Standard Radiotherapy for NSCLC Challenged

CHAPEL HILL, NC-"Local failure in inoperable non-smallcell lung cancer (NSCLC) is high, about 80%-and cure is impossible without local control. The radiotherapy community has not addressed this problem," said Julian C. Rosenman, MD, PhD, professor of radiation oncology at the University of North Carolina (UNC), Chapel Hill. "A 10-cm tumor compared with a 1-mm tumor has a 1-million-fold increase in size, but our response is to reduce dose." For example, he said, a T1c prostate tumor is treated with 75 Gy of radiation, whereas a vastly larger stage IIIa or IIIb NSCLC is typically treated with 60 Gy. Questioning 60 Gy
Dr. Rosenman discussed evidence that the 60 Gy dose is insufficient in this patient population, and reported on UNC data suggesting that dose escalation improves survival. The 60-Gy standard, he said, is based on a decades- old Radiation Therapy Oncology Group study (RTOG 73- 01) that was done before the availability of computed tomography scans and contemporary chemotherapy. This dose has been challenged in four randomized studies but not bested. For example, Johnson and col- leagues randomized 319 patients with locally advanced NSCLC to receive vindesine (Eldisine) 3 mg/ m2, standard thoracic radiotherapy of 60 Gy over a period of 6 weeks, or both vindesine and thoracic radiotherapy.[1] Median survival time was 8.6 months for radiotherapy alone, 9.4 months for radiotherapy plus vindesine, and 10.1 months for vindesine alone. "The investigators concluded that radiotherapy does not prolong survival over drug therapy, but an alternative interpretation is that 60 Gy is too low a dose for cure and too high for palliation," Dr. Rosenman said. "Most patients today are being treated with 55 to 60 Gy. Perhaps a million patients have been treated at these levels. Shame on us." Dose Pushed to 74 Gy
Dr. Rosenman and colleagues examined the radiotherapy dose in UNC study LCCC 9603 for inoperable stage IIIa/IIIb NSCLC patients with a performance status of 0 or 1. Patients were treated with induction carboplatin (Paraplatin) to AUC 6 and paclitaxel 225 mg/m2, with cycles starting on days 1 and 22. Beginning on day 43, patients received concurrent chemoradiotherapy weekly with carboplatin to AUC 2 and paclitaxel 45 mg/m2, and radiation doses were escalated from 60 to 74 Gy. This regimen produced 1-year survival of 71% and 5-year survival of 29% (see Figure 1). Median survival time was 24 months, at a median survivor-follow-up duration of 43 months. Dr. Rosenman said five other recent studies using 60 Gy reported median survival times of 15.6 to 19 months). He added that the radiation dose in the UNC study was escalated only to 74 Gy because it hit the "DCP- or Doctor Chicken Point" rather than because of adverse effects. Phase III Trial
Concurrent chemotherapy with radiotherapy has produced promising responses in NSCLC, perhaps owing to the radiosensitizing effects of chemotherapy. "There are also hints that better local control might improve survival," Dr. Rosenman said. Consequently, he and colleagues set about designing a multi-institutional, phase III trial to compare high-dose vs standarddose radiotherapy with concurrent chemotherapy in patients with stage IIIa or IIIb NSCLC. Each treatment regimen will be further randomized to amifostine (Ethyol) or no amifostine (see Figure 2).The hope is that amifostine will permit more tolerable radiotherapy dose-escalation, which might translate into longer survival. Dr. Rosenman reviewed a number of unanswered questions in treatment of NSCLC, including the question of what is considered a standard vs a high dose, what sizes radiation fields should be, what is the optimal chemotherapy, and questions about best study design, including the possibility of starting with a ramp-up phase II trial design.

References

1. Johnson DH, Einhorn LH, Bartolucci A, et al: Thoracic radiotherapy does not prolong survival in patients with locally advanced, unresectable non-small cell lung cancer. Ann Intern Med 113(1):33-38, 1990.
 
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