Clinical use of radiation sensitizing agents

Combination of Electrochemotherapy with Radiotherapy: A Comprehensive, Systematic, PRISMA-Compliant Review of Efficacy and Potential Radiosensitizing Effects in Tumor Control

Radiotherapy (RT) and electrochemotherapy (ECT) are established local treatments for cancer. While effective, both therapies have limitations, especially in treating bulky and poorly oxygenated tumors. ECT has emerged as a promising palliative treatment, raising interest in exploring its combination with RT to enhance tumor response. However, the potential benefits and challenges of combining these treatments remain unclear. A systematic review was conducted following PRISMA guidelines. PubMed, Scopus, and Cochrane libraries were searched. Studies were screened and selected based on predefined inclusion and exclusion criteria. Ten studies were included, comprising in vitro and in vivo experiments. Different tumor types were treated with ECT alone or in combination with RT. ECT plus RT demonstrated superior tumor response compared to that under single therapies or other combinations, regardless of the cytotoxic agent and RT dose. However, no study demonstrated a clear superadditive effect in cell survival curves, suggesting inconclusive evidence of specific ECT-induced radiosensitization. Toxicity data were limited. In conclusion, the combination of ECT and RT consistently improved tumor response compared to that with individual therapies, supporting the potential benefit of their combination. However, evidence for a specific ECT-induced radiosensitization effect is currently lacking. Additional investigations are necessary to elucidate the potential benefits of this combination therapy.

Radiotherapy with concomitant continuous cisplatin infusion for unresectable tumors of the upper aerodigestive tract: results of a phase I study

A phase I-II study was initiated in February 1991 of concomitant radiation and cisplatin (CDDP) in the treatment of unresectable head and neck squamous cell carcinomas (n = 12). The first patient was treated palliatively for a cervical recurrence of laryngeal cancer. The 11 other patients had locally advanced (stage IV) previously untreated carcinomas of the oropharynx (n = 9), hypopharynx (n = 1), or cervical node with unknown primary site (n = 1). Standard external radiation was carried out up to a total dose of 60 Gy/6 weeks (7 MeV electron beam) for the first patient and 72 Gy/8 weeks (Co60 beam) for the other 11 patients. CDDP was infused continuously during the entire radiation treatment, 5 days/week. The starting dose was 4 mg/m2/day and was escalated by increments of 1 mg/m2/day; dose-limiting toxicity was observed at 7 mg/m2/day. Neutropenia (grade 4, one patient; grade 3, three patients) and thrombocytopenia (grade 3, one patient; grade 2, one patient) were the limiting factors. Therefore, the recommended dose of CDDP is 6 mg/m2/day. All patients but one completed the scheduled radiation. For the entire group, mucositis was not more severe than that observed with radiotherapy alone. There was no nephro-, oto-, or neurotoxicity. A complete response was obtained in eight (66%) patients. Of these, four were free of disease 12-34 months after completion of treatment and one had a total glossectomy for a tongue necrosis. For the whole series, the mean overall survival was 16 months posttreatment. Pharmacokinetic analysis indicated the total cisplatin accumulation at the end of treatment to be 743-1551 ng/ml. Accumulation of ultrafilterable platin was noted in only one patient (137 ng/ml at the end of treatment).

Cisplatin-ifosfamide as neoadjuvant chemotherapy in stage IIIB cervical uterine squamous-cell carcinoma

Survival in patients with advanced cervical cancer (stage III B) treated by radical radiotherapy is low. In this study we attempted to assess the efficacy of the cis-diamminedichloroplatinum(II) (CDDP)-ifosfamide combination as neoadjuvant chemotherapy in advanced cervical cancer. The treatment schedule was: 20 mg/m2 CDDP on days 1-5; 1.5 g/m2 ifosfamide on days 1-5; and 900 mg/m2 mesna on days 1-5. Courses were given every 28 days. Radiotherapy was given 15 days after the completion of chemotherapy. A total of 26 patients were entered in this trial. Of the 24 patients evaluable for response, 15 (62.5%) achieved at least a 50% reduction in tumor volume, 6 (25%) showed stable disease, and three (12.5%) had progressive disease. At 38 months (mean follow-up) after completion of radiotherapy, 13 of the 24 (54%) evaluable patients were disease-free; 73% of the patients responding to chemotherapy vs 22% of the nonresponders remained free of disease (Fisher's exact test: P less than 0.02). Major hematologic depression occurred in 2 of the 26 patients evaluable for toxicity. No CNS toxicity was detected. These results are superior to those obtained by radical radiotherapy alone. Future treatment should be directed toward improving response rates as the best way of increasing both local and distant long-term disease control in these patients.

Concomitant hydroxyurea, 5-fluorouracil, and radiation therapy for recurrent head and neck cancer: early results

We tested the combination of hydroxyurea (HU), 5-fluorouracil (5-FU), and concomitant radiotherapy (XRT) in a group of patients with advanced or recurrent head and neck cancer. Both drugs are effective single agents, have shown synergistic activity in vitro, and can act as radiation sensitizers. A 5-day course of radiotherapy, with simultaneous HU and continuous infusion 5-FU, was followed by a 9-day rest period; cycles were repeated until completion of XRT. Sixteen patients have completed their therapy. Eleven patients had recurrent disease after previous therapy with surgery (11 patients), radiotherapy (9 patients), and combination chemotherapy (4 patients). Five patients had not received previous local therapy. These patients had persistent disease after induction chemotherapy and/or were inoperable because of poor general medical condition. Of 15 patients evaluable for response, 9 had complete response, including 5 patients who had earlier local therapy; 5 had partial response; and 1 failed to respond. Toxicities included mild myelosuppression and mucositis. No unusual complication related to previous radiotherapy was observed. This regimen has shown impressive activity in a cohort of patients who are not usually responsive to other types of currently available therapy. We are continuing our investigation to further define efficacy, toxicity, and maximally tolerated doses of this regimen.

Changing role of chemotherapy in treatment of head and neck cancer

The role of chemotherapy in the management of head and neck cancer includes treatment for recurrent disease and as an adjunct to conventional therapy with radiation and/or surgery in the primary treatment program. The best single agents, methotrexate and cisplatin, used for recurrent disease give response rates of 20 to 50 percent but of short duration. Results may be improved with combination chemotherapy, but often with increased toxicity. Prognostic factors that influence response are discussed. A newer role of chemotherapy in this disease is in the initial treatment program. Pretreatment chemotherapy can debulk these lesions prior to surgery and/or irradiation in up to 80 percent of patients. Controlled trials are in progress to determine the effect on cure rates. Chemotherapy utilized during radiotherapy has resulted in survival benefit in several studies. Post-treatment adjuvant chemotherapy still needs to be evaluated. The potential advantages and disadvantages of chemotherapy used in the initial treatment are discussed. Major strides have been made in the last decade in the treatment of head and neck cancer, and chemotherapy is assuming an increasingly important role.

Radiobiology of the skin: review of some effects on epidermis and hair

Significant doses of ionizing radiation produce an acute skin reaction characterized by erythema, epilation, and dry or moist desquamation with or without erosions. These early acute changes are dose-dependent and reflect damage to the germinative cells of the epidermis and to the cutaneous vasculature. Studies in the pig, for example, have shown that the degenerative phase of cell loss (2-3 weeks) results from reproductive failure in germinative cells and a sharp reduction in the proliferation rate of basal cell "survivors." D0 values for epidermal cells in different species generally range from 100-140 rads. Cell maturation and ascension rates in the suprabasilar layers are largely unaffected. A regenerative phase of cell replacement, characterized by sharply increased cell replication rates, occurs from the 3rd to 5th postradiation weeks. The postregenerative phase of hyperplasia reflects a temporary overshoot of cell density above control levels; a subsequent decrease in hyperplasia indicates feedback control of cellular proliferation. Postradiation changes in the highly proliferative anagen hair matrix cell populations result in hair dysplasia, slowed growth rates, impaired metabolic processes, and alopecia. Dosages of 700-800 rads or more induce some degree of permanent hair loss. G0 telogen matrix cells are 2-3 times more radioresistant than proliferating anagen matrix cells, but may "store" radiation damage for prolonged periods. Altered matrix cell uptake of amino acids, the incidence of dysplasia, and the degree of alopecia occurring after irradiation have all been used as quantitative biological end-points for the general study of cellular radiation effects, as well as studies on the enhancement of or protection against radiation damage provided by certain pharmacologic or physical agents.

Simultaneous combination radiotherapy and multidrug chemotherapy for stage III and stage IV squamous cell carcinoma of the head and neck

Combined simultaneous radiotherapy and multidrug chemotherapy have been utilized in an attempt to eradicate or shrink tumors of the head and neck area in advanced stages to allow subsequent surgical extirpation. Thirty-six patients (1 stage II; 11 stage III; 24 stage IV; 1 unknown primary) were treated with simultaneous radiotherapy and fractionalized doses of bleomycin, adriamycin, and 5-fluorouracil. Thirty of 36 patients completed the treatment schedule. Twenty-nine of 30 (97%) had a 75% or greater response to treatment; 20/30 (66%) had 100% response; 9/30 (30%) had 75% response; and 1/30 had 50% response. Of the 30 patients completing the regimen, 19/30 (63%) are alive three to 27 months later, and 12 (40%) of these have no evidence of disease. Six patients died within four months of initiation of therapy, mostly from complications of their disease. This treatment regimen appears effective in the control of locoregional disease or to produce enough shrinkage of tumor to allow subsequent surgical extirpation.

Comparison of radiotherapy with and without razoxane (ICRF 159) in the treatment of soft tissue sarcomas

Comparison of the recurrence rates of soft tissue sarcomas treated by radiotherapy (14 patients) or radiotherapy and synchronous administration of razoxane (19 patients) has shown a statistically significant benefit for those patients treated by the combination. No increase in tissue reactions or adverse side-effects (apart from a readily reversible leukopenia) was observed. The implication is that razoxane acts as a well tolerated adjuvant for radiotherapy.

The role of chemotherapy in the management of cancer of the head and neck: a review

Although experience with drug therapy of advanced or recurrent squamous cell carcinoma of the head and neck is limited, several agents have produced convincing and reproducible tumor regression in these patients. Methotrexate has had the widest usage, and produces 30-50% response rates; bleomycin, hydroxyurea, and adriamycin appear to be somewhat less effective. Location of the malignancy and previous x-ray treatment appear to be important determinants of responsiveness to methotrexate, while degree of differentiation has not yet been shown to be an important factor for response to this drug. Attempts to improve the response rate and duration of chemotherapeutic response by utilizing combinations of drugs, or use of drugs to sensitize the tumor to x-ray treatment, or to reduce the bulk of tumor before x-ray treatment, are reviewed; they have been only moderately encouraging. Intra-arterial chemotherapy appears to have a therapeutic advantage over intravenous treatment; however, the morbidity associated with the former approach limits its usefulness for routine usage. The use of drugs as adjuncts following surgery and/or radiation therapy or immunotherapy are newer approaches that have not been investigated sufficiently, but are promising areas for investigation.