The Radiation Therapy Oncology Group: an update of clinical research activities.

This paper provides an introduction into the clinical activities of the RTOG (Radiation Therapy Oncology Group), its goals, its organization, its format for protocol development, and presents major areas of achievement. It provides an organizational chart of the group, a disease site modality cross-reference for protocols, and appendices which provide the key published results of the Group's clinical activities. This paper presents an important overview of the RTOG clinical research activities, which are designed to improve the role of radiation therapy.

Hyperthermia in combination with definitive radiation therapy: results of a Phase I/II RTOG Study.

Between August 1981 and April 1986, 133 patients with superficial malignant tumors not previously treated with radiotherapy were entered on a Phase I/II RTOG study evaluating hyperthermia plus definitive radiotherapy. Eligible patients included those with superficial epithelial or mesenchymal tumors less than 4 cm in depth. Protocol radiotherapy specified a tumor dose of 60 Gy delivered in 1.8-2.0 Gy fractions 5 times/week with a boost of 5-10 Gy through reduced portals to residual tumor. Protocol hyperthermia, delivered twice weekly, was to start within 15 minutes following irradiation and to consist of 60 minutes of heat to a tumor temperature of 43 degrees C. Sixteen patients were excluded. Of the 117 eligible patients, the treated lesions had site/histologies which were 35% head & neck/squamous, 46% breast/adenocarcinoma, and 19% other site/histologies. Lesions were 3 cm or larger for 77% of patients. Of the 41 patients with head & neck/squamous lesions, skin or subcutaneous necrosis occurred within 6 months for 2% of the patients; 12% experienced thermal blisters. Fourteen patients were followed for 6 months or more following start of treatment; none of these experienced late toxicities more severe than telangiectasis. Complete responses were observed in 51% of these patients. Of the 54 patients with breast/adenocarcinoma lesions, skin or subcutaneous necrosis occurred within 6 months for 13% of the patients; 17% experienced thermal blisters. Thirty-seven patients were followed for 6 months or more following start of treatment; complications observed during this period included 13% with ulceration and one case of skin necrosis. Complete responses were observed in 85% of these patients. Local control was maintained at nearly this level for at least 2 years. Logistic regression analyses showed site/histology, greatest tumor diameter and average tumor temperature to be significantly related to response. Based on these promising findings, the RTOG has instituted a randomized Phase III study evaluating radiation therapy with or without hyperthermia in this patient population.

Radiotherapy with or without misonidazole for patients with stage IIIB or stage IVA squamous cell carcinoma of the uterine cervix: preliminary report of a Radiation Therapy Oncology Group randomized trial.

Between August 1980 and November 1984, 119 patients with FIGO Stage IIIB or IVA squamous cell carcinoma of the uterine cervix were randomized to receive radiation therapy (4600 cGy pelvis plus 1000 cGy parametrial boost) followed by intracavitary or external boost to the primary with or without misonidazole (MISO) (400 mg/m2 daily 2 to 4 hours prior to radiation therapy). Patients in the two treatment groups were evenly distributed with respect to stratification variables including stage, Karnofsky Performance score, and positivity of para-aortic nodes. Eighty-nine percent of patients had Stage IIIB disease and 88% had a Karnofsky score of 80 or better. Seventy-five percent of patients treated with radiation therapy alone and 79% of patients treated with radiation therapy plus MISO received a boost via intracavitary application. Life threatening (Grade 4) complications occurred in 5 patients receiving radiation therapy alone and one patient receiving radiation therapy plus MISO. MISO toxicity (Grade 3) was limited to severe nausea and vomiting in two patients. With 119 evaluable patients and a median follow-up of 33 months, 64% of patients receiving radiation therapy alone are alive at 18 months compared with 54% for patients assigned to radiation therapy plus MISO. The median survival for patients treated with radiation therapy alone and radiation therapy plus MISO was 1.9 years and 1.6 respectively. At this point in the study the difference in survival is inconsistent with the hypothesis of an improvement associated with MISO. There have been 23 deaths among the 49 patients treated with radiation therapy plus MISO who have been followed for at least 18 months compared with 17 deaths in 48 patients treated with radiation therapy alone. The chance of observing this number of deaths with radiation therapy plus MISO if the addition of MISO improves survival by 10 to 20% is 0.003 and less than 0.001, respectively. The addition of MISO to radiation failed to improve survival for these patients. The results cannot be explained by an uncharacteristically high survival on the radiation therapy alone arm or by an imbalance in the distribution of prognostic factors. Local-regional control remains a problem in the management of patients with advanced cervical carcinoma. More effective and less toxic radiosensitizing agents are needed.

Pulmonary toxicity of carmustine in patients treated for malignant glioma.

Carmustine (BCNU) was employed as the only chemotherapeutic agent in a Radiation Therapy Oncology Group multimodality study comparing misonidazole-radiosensitized radiation therapy to conventional radiation therapy in 318 patients with malignant glioma. In 289 patients evaluable for BCNU pulmonary toxicity, there were no clinical manifestations of toxicity in patients receiving less than 902-mg/m2 total BCNU dose. Ten of 107 patients receiving more than this dose developed detectable pulmonary toxicity. Results of a multivariate regression analysis of risk factors, which corrects for survival time bias, suggested increased risk of pulmonary toxicity when total dose exceeds 1400 mg/m2. The risk of pulmonary toxicity was not increased by the administration of misonidazole and does not appear to be related to age.

Effect of misonidazole dose on survival in patients with stage IIIB-IVA squamous cell carcinoma of the uterine cervix: an RTOG randomized trial.

Between August 1980 and November 1984, 120 patients with FIGO Stage IIIB or IVA squamous cell carcinoma of the uterine cervix were randomized to receive radiation therapy (RT) (46 Gy pelvis + 10 Gy parametrial boost) followed by intracavitary or external boost to the primary +/- misonidazole (MISO) (400 mg/M2 2-4 hours prior to RT daily, maximum 12 gm/M2). The median at 24-28 hr misonidazole plasma level was 20 micrograms/ml 2-6 hr and 3.5 micrograms/ml. Approximately 60% of the patients on RT + MISO received 100% of expected total Misonidazole dose; peripheral neurologic toxicity was reported for nine patients receiving misonidazole (8 with mild and 1 with moderate paresthesia or pain). Time-dependent regression analyses found that actual cumulative misonidazole dose was not related to duration of survival from start of treatment (p = 0.5). MISO dose expressed as a percent of expected dose was marginally related to increased survival measured from 14 weeks on on study (p = 0.1). No improvement in survival was observed with the addition of misonidazole to RT (64% of the patients on RT alone were alive at 18 months versus 54% of those on RT + MISO).