Fundamental questions in the combined use of radiation and chemicals in the treatment of cancer

A phase III randomized study of misonidazole plus radiation vs. radiation alone for cervix cancer

BACKGROUND AND PURPOSE

A randomized-controlled study of radical radiotherapy for cervical cancer with or without the hypoxic sensitizer, misonidazole was conducted from 1981 to 1984 to investigate its therapeutic benefit.

PATIENTS AND METHODS

Seventy-three patients were accrued from the Princess Margaret Hospital, and St John Regional Cancer Centre and randomized to either misonidazole (MISO, n = 39) or placebo (P, n = 34) in addition to radiotherapy. MISO was given orally each day 4 h prior to external beam radiation treatment (45Gy to midplane in 20 daily fractions) at a dose of 0.45 g/m(2), as well as during intra-uterine brachytherapy (40Gy).

RESULTS

The 10-year overall survival (OS) for the entire group was 46%, and the disease-free survival (DFS) was 39%. The 10-year OS for patients in the MISO arm was 45%, compared to 49% for the P arm (P = 0.89). The corresponding DFS figures were 36 and 43%, respectively, (P = 0.6). Ten patients (14%) developed severe late complications (grade 3 or 4). The 10-year serious late complication rate was 14% for MISO and 12% for P (P = 0.51).

CONCLUSIONS

Misonidazole failed to improve the outcome of patients with cervix cancer treated with radiotherapy.

Long-term toxicity and neuropathology associated with the sequencing of cranial irradiation and enhanced chemotherapy delivery

OBJECTIVE

The goal was to evaluate, at 1 year, 75 Long-Evans rats for survival rates and toxicity associated with the sequencing of cranial irradiation and enhanced chemotherapy delivery.

METHODS

Seventy-five Long-Evans rats were randomized into four groups and evaluated at 1 year for survival rates and toxicity associated with the sequencing of cranial irradiation and enhanced chemotherapy delivery. Radiation (2,000 cGy) was administered as a single fraction, by using parallel opposed portals, 30 days before chemotherapy (Group 1), 24 hours before chemotherapy (Group 2), 30 days after chemotherapy (Group 3), or without chemotherapy or without radiation (control group, Group 4). Five subgroups within each treatment group included rats receiving intra-arterially administered methotrexate (1 g/m2) or intravenously administered etoposide (200 mg/m2) combined with intra-arterially administered carboplatin (200 mg/m2), administered with or without osmotic blood-rain barrier disruption, and a group receiving normal saline solution after blood-brain barrier disruption.

RESULTS

There was a significant increase in total toxic effects when the three experimental groups were compared with the control group (P = 0.001, 0.006, and 0.013 for Groups 1, 2, and 3, respectively). All groups receiving radiation and chemotherapy (particularly carboplatin and etoposide) had an increased incidence of hind limb paralysis, resembling experimental allergic neuritis (P = 0.053). Statistical analysis showed a trend toward increased mortality rates in Group 1 (antecedent radiation), compared with the control group (P = 0.082), and an increased incidence of intracerebral calcification (P = 0.019). No differences in mortality rates were observed for Group 2 or 3, compared with the control group.

CONCLUSION

Radiation before chemotherapy was a more toxic sequence and, surprisingly, carboplatin/etoposide administered in combination with radiotherapy was more detrimental than methotrexate. Additional studies are in progress to evaluate the toxicity and efficacy of sequences of cranial irradiation and enhanced chemotherapy in tumor-bearing rats.

Radiation survival of two human cervical carcinoma cell lines after multifraction irradiation

PURPOSE

Multifraction irradiation may contribute to radiation therapy treatment failure if selection of radiation resistant subpopulations occurs. We sought to determine whether surviving cells following daily fraction irradiation of two human cervical squamous cell carcinoma lines would express different radiation survival characteristics compared to the unirradiated parent.

METHODS AND MATERIALS

A late-passage line (HTB35) and an early-passage line (RECA) received daily 2 Gy x-irradiation. Two new stable HTB35 cell lines were established after 40 and 60 Gy (HTB35-40 and HTB35-60). A single line was established from RECA after 30 Gy (RECA-30). High dose rate (74 cGy/min) acute radiation survival curves were prepared from the three new lines and the unirradiated parents. Potentially lethal damage repair (PLDR) and sublethal damage repair (SLDR) responses were detailed for HTB35, HTB35-40 and HTB35-60. Low dose rate (1.27 cGy/min) survival was measured for HTB35 and HTB35-60. Clones were derived from HTB35 and from HTB35-60 and the surviving fraction at 2 Gy (SF2) values were determined.

RESULTS

The two parent lines (HTB35 and RECA) differed in acute radiation survival. The surviving lines following multifraction irradiation (HTB35-40, HTB35-60, and RECA-30) showed no change in acute radiation response compared to the appropriate parent. HTB35-40 and HTB35-60 were repair proficient, demonstrating similar PLDR and SLDR recovery ratios as the parent. Likewise, acute, low dose rate survival of HTB35 and HTB35-60 was similar. Nine clones derived from HTB35 lacked a consistent difference in SF2 compared to the original culture. A single clone of seven derived from HTB35-60 was consistently radiation resistant (SF2 = 0.81 +/- 0.06) compared to the original culture (SF2 = 0.50 +/- 0.09).

CONCLUSION

No evidence was obtained that cell lines generated following multiple daily fractions of x-irradiation in vitro possessed acute radiation survival or repair characteristics that were different from the unirradiated parent.

Chemotherapy-radiation interactions in human cervix carcinoma xenografts

The combination of irradiation and four agents of clinical interest in the treatment of cervix carcinoma (bleomycin, etoposide, cisplatin and ifosfamide) have been investigated using two human cervix carcinoma xenografts in nude mice. As a model of clinical brachytherapy regimes, radiation was administered at a continuous low dose rate of 5 cGy min-1 to a total dose of 9 or 12 Gy. No substantial enhancement in tumour growth delay over that observed for radiation alone was observed with bleomycin, etoposide or cisplatin. Ifosfamide, however, led to substantial additional growth delay, an effect which was lost when irradiation was administered at a higher dose rate of 70 cGy min-1. As dose-rates of around 5 cGy min-1 allow greater repair of radiation damage than at the higher dose-rate without significant cell cycling or repopulation, it is possible that ifosfamide may act as an inhibitor of repair processes in this model. It would be of interest to evaluate the role of ifosfamide and brachytherapy regimes in the clinical treatment of carcinoma of the cervix.

Prediction of the relative in vitro sensitivity of 9L rat brain tumor cells to nitrosoureas by the sister chromatid exchange assay

In an earlier study we showed that there is a good correlation between sister chromatid exchange induction and cell kill in 9L cells treated with certain nitrosoureas. In the study reported here, we treated four 9L cell lines that have different sensitivities to chloroethylnitrosoureas with 1,3-bis (2-chloroethyl)-1-nitrosourea, chlorozotocin, and ethylnitrosourea and determined the number of sister chromatid exchanges induced. Cell lines that were most sensitive to the drugs with respect to cell kill were also most sensitive to induction of sister chromatid exchanges for a given drug, and the assay based on sister chromatid exchange is therefore predictive of the relative sensitivity of these cells to the drugs used.

Detection of heterogeneity in the chemosensitivity of 9L brain tumor cell lines to 1,3-bis (2-chloroethyl)-1-nitrosourea by the sister chromatid exchange assay

To investigate the potential use of the sister chromatid exchange assay to analyze the heterogeneity of drug response among tumor cell subpopulations, mixtures of 1,3-bis (2-chloroethyl)-1-nitrosourea-sensitive (9L) and -resistant (9L2) rat brain tumor cells were treated in vitro with 2 microM 1,3-bis (2-chloroethyl)-1-nitrosourea. When data were plotted as histograms representing the number of cells vs sister chromatid exchanges/metaphase, two regions corresponding to the 9L and 9L2 populations were obtained. The approximate percentages of 9L and 9L2 in each mixture could be predicted from these histograms. While these results were obtained with a limited model chosen for its simplicity, they suggest that the sister chromatid exchange assay may be useful in the analysis of heterogeneity in drug sensitivity among cell subpopulations in a tumor.

Preliminary report on "one-time" and high dose irradiation of the upper and lower half-body in patients with small cell lung cancer

Forty-two patients with histologically confirmed inoperable small (oat) cell lung cancer were treated with local tumor irradiation (approximately 4,000 cGy) combined with "one-time" irradiation of the upper and lower half of the body. Twenty-five patients (Group I) received the irradiation in lateral position first to the upper half-body, and six weeks later to the lower half-body, the midplane dose averaging 880 cGy (not corrected for lung tissue). In 17 patients, lethal pneumonitis occurred. The mean time of survival was 8.2 months for 22 patients having the disease limited to one thorax-side and 4.0 months for three patients having distant metastases, stated by conventional clinical and X ray investigations. Seventeen patients (Group II) received the two half-body irradiation treatments through anterior-posterior fields. The average dose had been reduced to 800 cGy (uncorrected) and was given on one day in two fractions (600 and 200 cGy, separated by an interval of 5 hours). Furthermore, the forearms and the lower legs had been left outside the fields. Only one patient showed pneumonitis. The mean time of survival was 14.3 months for 12 patients having the disease limited to one thorax-side and 6.6 months for five patients having distant metastases. In both groups, serious reactions of the bone marrow were not observed. In Group II, leucocytes and lymphocytes had reached their original values three months after the end of irradiation. For all 42 patients, X ray films showed complete regression of the primary tumor. In 12 out of 35 autopsy specimens, the primary tumor could not be detected histologically, but only five of these were free of metastases. Presently, additional irradiation of the two halves of the body with lower and fractionated doses are being tested in order to achieve the further reduction of tumor cell numbers.

A pilot study with ethyl bis (2,2-dimethyl-1-aziridinyl) phosphinate (AB-163) and radiation therapy

Ethyl bis (2,2 dimethyl-1-aziridinyl) phosphinate (AB-163), a TEPA analogue, was used with radiation therapy in treating 18 patients with advanced malignancies. There were 12 patients with esophageal carcinoma; 3 with adenocarcinomas of the gastrointestinal tract; one, squamous carcinoma of the cervix; and one, adenocarcinoma of the ovary. One hundred mg/M2 AB-163 was given by rapid i.v. drip one half-hour before conventional radiation therapy. The majority of patients received 10 combined treatments. Three of those with squamous cell carcinomas (two in the esophagus and one in the cervix) remained disease-free for more than 2 years. One with liver metastasis and unresectable carcinoma of the stomach survived for 9 months. The drug causes side effects mainly involving the central nervous system and gastrointestinal tract. Drug-related myelosuppression has not been observed. The mode of action is speculated to be a result of active intermediate hydrolysis products which appear capable of phosphorylating X ray induced DNA strand damage. However, much additional investigation is required, both in vitro and clinically, before its efficacy and safety can be demonstrated.

Modifiers of radiation response in tumor therapy: strategies and expectations

The administration of two (or more) cytotoxic agents to widen the differential between the responses of tumor and normal tissues depends upon the biological properties of the agents in the cells and tissue, their interactive potential, and the strategy employed in their administration. Assuming that one agent is ionizing radiation and considering response modification in broad terms, the qualitative features of various strategies are developed for physical as well as chemical modifiers. The heterogeneity of human tumor cells and the compensatory mechanisms of normal tissues following injury are identified as topical areas requiring sustained research effort. Finally, estimates are developed for the degree of improvement required from a response modifier to effect significant improvements in tumor cure rates.