Karen L. Lindsley

Evaluation of oxygenation status during fractionated radiotherapy in human nonsmall cell lung cancers using [F-18]fluoromisonidazole positron emission tomography

PURPOSE Recent clinical investigations have shown a strong correlation between pretreatment tumor hypoxia and poor response to radiotherapy. These observations raise questions about standard assumptions of tumor reoxygenation during radiotherapy, which has been poorly studied in human cancers. Positron emission tomography (PET) imaging of [F-18]fluoromisonidazole (FMISO) uptake allows noninvasive assessment of tumor hypoxia, and is amenable for repeated studies during fractionated radiotherapy to systematically evaluate changes in tumor oxygenation. METHODS AND MATERIALS Seven patients with locally advanced nonsmall cell lung cancers underwent sequential [F-18]FMISO PET imaging while receiving primary radiotherapy. Computed tomograms were used to calculate tumor volumes, define tumor extent for PET image analysis, and assist in PET image registration between serial studies. Fractional hypoxic volume (FHV) was calculated for each study as the percentage of pixels within the analyzed imaged tumor volume with a tumor:blood [F-18]FMISO ratio > or = 1.4 by 120 min after injection. Serial FHVs were compared for each patient. RESULTS Pretreatment FHVs ranged from 20-84% (median 58%). Subsequent FHVs varied from 8-79% (median 29%) at midtreatment, and ranged from 3-65% (median 22%) by the end of radiotherapy. One patient had essentially no detectable residual tumor hypoxia by the end of radiation, while two others showed no apparent decrease in serial FHVs. There was no correlation between tumor size and pretreatment FHV. CONCLUSIONS Although there is a general tendency toward improved oxygenation in human tumors during fractionated radiotherapy, these changes are unpredictable and may be insufficient in extent and timing to overcome the negative effects of existing pretreatment hypoxia. Selection of patients for clinical trials addressing radioresistant hypoxic cancers can be appropriately achieved through single pretreatment evaluations of tumor hypoxia.

Tumor and target delineation: Current research and future challenges☆

In the past decade, significant progress has been made in the imaging of tumors, three dimensional (3D) treatment planning, and radiation treatment delivery. At this time one of the greatest challenges for conformal radiation therapy is the accurate delineation of tumor and target volumes. The physician encounters many uncertainties in the process of defining both tumor and target. The sources of these uncertainties are discussed, as well as the issues requiring study to reduce these uncertainties.

Impact of a multileaf collimator on treatment morbidity in localized carcinoma of the prostate

PURPOSE To evaluate the effectiveness of variable multileaf collimation, three-dimensional treatment planning, and computer-controlled conformal radiation therapy of prostate cancer. METHODS AND MATERIALS Two hundred and forty-five patients with locally advanced prostate cancer have completed treatment over a 9-year time span using a multileaf collimator and conformal treatment techniques on the University of Washington cyclotron. All patients had three-dimensional treatment planning with computed tomography scans in the treatment position, and had treatment fields individually shaped to the target volume with a continuously variable multileaf collimator. Treatment was delivered under computer control with network transfer of the multileaf collimator settings from the treatment planning computer to the cyclotron control system. RESULTS The multileaf collimator combined with three-dimensional treatment planning results in elegant dose distributions. These neuron dose distributions resulted in a reduced local/regional tumor failure rate with no increase in complications when compared to control treatment with photons in a randomized trial. Neutron treatment delivered at other institutions without conformal beam shaping resulted in the same improvement in local-regional tumor control rates, but was associated with a significantly higher normal tissue complication rate than seen with conformal neutron beam delivery techniques (grade 3 and 4 cumulative late normal tissue toxicity rates of 39% vs. 10%, p = 0.0007). CONCLUSIONS Conformal treatment of prostate cancer using a multileaf collimated neutron beam results in increased local/regional tumor control rates with low normal tissue toxicities. This experience is directly applicable to the conformal treatment of prostate cancer with photons.

The potential role of external beam radiation in preventing restenosis after coronary angioplasty

The potential role of radiation in the prevention of coronary artery restenosis after angioplasty has generated much recent interest. Animal research and pilot clinical efforts have focused primarily on intraluminal methods of radiation delivery. This article reviews the experience to date with external beam radiation in restenosis prevention and suggests issues that should be considered from the standpoint of both external beam and intravascular radiotherapy. External beam radiation can certainly play an effective role in clinical studies of coronary artery restenosis, and a multicenter randomized trial of external beam radiation after coronary angioplasty has been initiated.

Very intensive, short-term chemotherapy for children and adolescents with metastatic sarcomas

BACKGROUND To improve the prognosis for pediatric patients with metastatic sarcomas, including the Ewing sarcoma family of tumors (ESFT), rhabdomyosarcoma (RMS), and undifferentiated sarcoma (UDS), we tested the feasibility of a brief, intensive regimen of chemotherapy that maximizes dose intensity. PROCEDURE Twenty-four children and adolescents with metastatic sarcomas received VACIME chemotherapy, consisting of eight courses of vincristine 2 mg/m(2) on day 0; doxorubicin 20 mg/m(2)/day on days 0-3; cyclophosphamide 360 mg/m(2)/day on days 0-4; ifosfamide 1,800 mg/m(2)/day on days 0-4; mesna 2,400 mg/m(2)/day; and etoposide 100 mg/m(2)/day on days 0-4. Doxorubicin was omitted in courses 7 and 8. Granulocyte colony-stimulating factor (G-CSF) was used routinely following each course of therapy. Courses of therapy were repeated every 21 days or as soon as hematopoietic recovery and resolution of nonhematopoietic toxicities permitted. Surgical resection followed course 6, and radiotherapy followed the completion of all therapy. RESULTS Thirteen patients achieved a complete response (CR) with chemotherapy alone, and seven more achieved a CR following surgical resection after course 6 (overall CR rate 83%). There was one toxic death. Thirteen patients developed progressive disease, with 2- and 4-year event-free survivals (95% confidence interval) of 50% (30-70%) and 45% (25-65%), respectively. Myelosuppression was severe and cumulative, leading to dose reductions and chemotherapy interval delays. Mucositis was the most common nonhematopoietic toxicity. CONCLUSIONS VACIME chemotherapy was a feasible dose-intensive regimen for pediatric patients with metastatic sarcomas. Cumulative hematopoietic toxicity and severe mucositis limited the delivery of chemotherapy as prescribed. The CR and 2-year event-free survival rates were superior to those of most previously reported regimens.

Phase I topotecan preparative regimen for high-risk neuroblastoma, high-grade glioma, and refractory/recurrent pediatric solid tumors.

We evaluated the toxicity and maximum tolerated dose of topotecan in a novel myeloablative regimen as treatment for high-risk pediatric tumors. Patients received an assigned topotecan dosage in combination with fixed doses of carboplatin and thiotepa, followed by autologous hematopoietic stem cells infusion. Topotecan dose was escalated in cohorts of four patients until the maximum tolerated dose of topotecan was defined or until accrual of 30 patients. Pharmacokinetics of topotecan were examined, and event-free survival was estimated. We describe preliminary results following treatment of 25 pediatric patients with high-risk solid tumors.

Digital radiotherapy simulator

We describe a prototype digital radiotherapy simulator which consists of a conventional simulator gantry, digital spot imager, and image correction and reconstruction software. The ability of the digital spot imager to acquire a diagnostic quality image directly in digital format during simulation offers unique possibilities in clinical practice. Applications include prescription of multileaf collimator, on-line patient setup verification, remote consultation and treatment planning. In addition, we discuss the possibility of using the digital simulator as a volume-CT scanner capable of obtaining three-dimensional anatomical information in a single scan.