The effect of combined treatment with a platinum complex and ionizing radiation on chinese hamster ovary cells in vitro

Biological Mechanisms to Reduce Radioresistance and Increase the Efficacy of Radiotherapy: State of the Art

Cancer treatment with ionizing radiation (IR) is a well-established and effective clinical method to fight different types of tumors and is a palliative treatment to cure metastatic stages. Approximately half of all cancer patients undergo radiotherapy (RT) according to clinical protocols that employ two types of ionizing radiation: sparsely IR (i.e., X-rays) and densely IR (i.e., protons). Most cancer cells irradiated with therapeutic doses exhibit radio-induced cytotoxicity in terms of cell proliferation arrest and cell death by apoptosis. Nevertheless, despite the more tailored advances in RT protocols in the last few years, several tumors show a relatively high percentage of RT failure and tumor relapse due to their radioresistance. To counteract this extremely complex phenomenon and improve clinical protocols, several factors associated with radioresistance, of both a molecular and cellular nature, must be considered. Tumor genetics/epigenetics, tumor microenvironment, tumor metabolism, and the presence of non-malignant cells (i.e., fibroblast-associated cancer cells, macrophage-associated cancer cells, tumor-infiltrating lymphocytes, endothelial cells, cancer stem cells) are the main factors important in determining the tumor response to IR. Here, we attempt to provide an overview of how such factors can be taken advantage of in clinical strategies targeting radioresistant tumors.

Pemetrexed (Alimta, LY231514) demonstrates clinical activity in chemonaive patients with cervical cancer in a phase II single-agent trial

The objective of this study was to determine the response rate in chemonaive patients with inoperable, locally advanced, recurrent, or metastatic cervical cancer treated with pemetrexed (Alimta, LY231514), a multitargeted antifolate. The patients were treated with either 500 mg/m(2) (11 patients) or 600 mg/m(2) (24 patients) of pemetrexed, administered as a 10-min infusion on day 1 of a 21-day cycle. Patients receiving 500 mg/m(2) dose also received 5 mg/day oral folic acid supplementation beginning 2 days prior and ending on day 3 of each cycle. Of the 34 patients evaluable for efficacy, six patients (18%) had partial response, with median response duration of 3.8 months (range, 3.3-6.6 months). Twenty-four patients (71%) had stable disease, one patient (3%) had progressive disease, and three patients could not be assessed. Median overall survival was 15.2 months (range, 2.9-35.3+ months). Grade 4 hematologic toxicities consisted of neutropenia (37%), leukopenia (9%), anemia (6%), and thrombocytopenia (3%). One patient died of hypotensive shock associated with frank rectal hemorrhage that was considered to be related to the study drug. We conclude that pemetrexed therapy showed moderate activity, similar to other active agents, in the treatment of locally advanced or metastatic cervical cancer.

Does the evidence support the use of concurrent chemoradiotherapy as a standard in the management of locally advanced cancer of the cervix, especially in developing countries?

Locally advanced cancer of the cervix (FIGO stages III and IVA) is one of the most common malignancies in developing countries. Conventional treatment has been a judicious combination of external radiotherapy and intracavitary brachytherapy. However, prompted by the results of five randomised-controlled trials (RCTs) published in close succession, The National Cancer Institute (NCI) alert in 1999, and two meta-analyses, the management of cancer of the cervix has gradually changed. Concurrent chemoradiotherapy with cisplatin alone, or in combination, is gradually being favoured for the treatment of cancer of the cervix. This overview examines whether the published evidence is sufficiently adequate to justify the use of chemoradiotherapy using cisplatin as standard care in the management of cancer of the cervix, especially in developing countries, where most women present with locally advanced cancer of the cervix. A critical review of the various phase III randomised trials and meta-analyses indicates that, although chemoradiotherapy could be a standard form of treatment for early cancer of the cervix, its role in advanced stages needs further exploration before this could be incorporated into routine clinical care.

The role of chemotherapy in locally advanced, metastatic and recurrent cervical cancer

Cervical cancer is among the major health problems world-wide although advances in screening programs. Surgery and radiotherapy are the treatment modalities of choice for early and locally advanced cervical cancer. However, the role of chemotherapy in this setting has been better investigated in the latest years. To improve loco-regional control in locally advanced disease, authors have tested both neo-adjuvant chemotherapy and concurrent chemoradiotherapy. From 1999 NCI clinical announcement, concurrent cisplatin-based chemoradiation is considered the treatment of choice for cervical cancer patients requiring radiation therapy. Neo-adjuvant chemotherapy is reaching encouraging results in IB bulky-IIA cervical cancer, but further investigation are ongoing in locally advanced cervical setting. The optimal treatment for patients with metastatic or recurrent cervical cancer is still undefined and chemotherapy is used with palliation intent. Cisplatin remains the most active cytotoxic agents, although combinations of cisplatin with paclitaxel, topotecan, vinorelbine, have shown encouraging results in phase II and in early phase III studies. This paper reviews the role of chemotherapy in the management of patients with locally advanced, metastatic and recurrent cervical cancer. Studies discussed in this paper were selected trough a search in the med-line database performed in October 2003.

Radiosensitizing properties of novel hydroxydicarboxylatoplatinum(II) complexes with high or low reactivity with thiols: two modes of action

We examined radiosensitizing properties of two novel platinum complexes (ethylenediamine(L-malato)platinum(II)), Pt1 and bis(1-ethylimidazole(L-malato)platinum(II)), Pt4. Initial double strand break (DSB) level and DSB rejoining were measured, using pulse field gel electrophoresis (PFGE) in human G1 phase lymphocytes subjected to Pt complex treatment alone and in combination with 10Gy of X-rays. Effects of Pt complex pre-treatment followed by X-irradiation were examined on survival (clonogenic ability) and growth (48 h growth tests) in Chinese hamster ovary (CHO-K1), xrs6 and L5178Y (LY) cells (LY-R and LY-S sublines). Cell cycle distributions of CHO cells after drug treatment were determined with the use of flow cytometry. Pt1 slowed down rejoining of X-ray induced DSB. It exerted a more than additive lethal effect on CHO-K1 cells but not on L5178Y cells subjected to combined Pt complex treatment and X-irradiation. In xrs6 cells the effect of combined Pt1+X treatment was additive. We conclude that, as earlier proposed for other Pt complexes, the radiosensitizing effect of Pt1 is connected with converting repairable DNA damage into irrepairable one (mode (i) of action). The requirements for this mode of sensitization are functional DNA repair systems (nucleotide excision repair (NER) and non-homologous end-joining (NHEJ)). Pt4 does not slow down DSB rejoining. It shows a considerable ability to arrest cells in G2 phase. We assume that Pt4 pre-treatment arrests cells in G2 phase and thus sensitizes to X-rays these cells that have a radiosensitive G2 phase (mode (ii) of action).

Phase III trial comparing radical radiotherapy with and without cisplatin chemotherapy in patients with advanced squamous cell cancer of the cervix

PURPOSE

To test the hypothesis that cisplatin (CDDP) administered concurrently with standard radiotherapy (RT) would improve pelvic control and survival in patients with advanced squamous cell cancer of the cervix.

PATIENTS AND METHODS

A total of 259 patients with International Federation of Gynecology and Obstetrics stage IB to IVA squamous cell cervical cancer with central disease greater-than-or-equal 5 cm or histologically confirmed pelvic lymph node involvement were randomized to receive RT (external-beam RT plus brachytherapy) plus weekly CDDP chemotherapy (40 mg/m(2)) (arm 1) or the same RT without chemotherapy (arm 2).

RESULTS

A total of 253 patients were available for analysis. Median follow-up was 82 months. No significant difference was found in progression-free survival (P =.33). No significant difference in 3- and 5-year survival rates was found (69% v 66% and 62% v 58%, respectively; P =.42). The hazard ratio for survival (arm 2 to arm 1) was 1.10 (95% confidence interval, 0.75 to 1.62).

CONCLUSION

This study did not show a benefit to either pelvic control or survival by adding concurrent weekly CDDP chemotherapy in a dose of 40 mg/m(2) to radical RT as given in this trial. Careful attention to RT details is important for achieving optimum outcome for patients with this disease.

Nasopharyngeal cancer

The current standards of treatment for nasopharyngeal cancer include 1. In early disease (stage I and stage II), radiotherapy is the treatment of choice, and the chance for cure is usually high. 2. In locally advanced disease (stage III and stage IV) combination chemotherapy and radiation therapy is indicated. Further clinical trials are warranted, which may include the newer active chemotherapeutic agents. 3. Patients with distant metastases may be treated with chemotherapy alone or other palliative measures.

Evaluation of cross-resistance between responses to cisplatin, hyperthermia, and radiation in human glioma cells and eight clones selected for cisplatin resistance

Human glioma cells were exposed to stepwise increasing concentrations of cisplatin and given a final, acute, high concentration treatment of cisplatin. From the surviving cells, eight cisplatin resistant clones were selected. These clones demonstrated a range of cisplatin sensitivities that were retained in the absence of cisplatin when cells were continually passaged. These cells were tested for cross-resistance to radiation and hyperthermia at 42 and 45 degrees C. The data showed that seven of the eight clones were also more radioresistant than the parental line, while one was more radiosensitive. The degree of cisplatin resistance was not related to the degree of radiation resistance. For hyperthermia at 42 and 45 degrees C, some of the clones were slightly more resistant than the parental line, while one clone was much more sensitive. This was not the same clone that was radiosensitive. In conclusion, there was no direct correlation between cisplatin resistance, radiation resistance, and hyperthermia response, although some of the clones were resistant to all three treatments.

Treatment of carcinoma of the uterine cervix with concomitant cisplatin, 5-fluorouracil and split course hyperfractionated radiotherapy

To improve local and systemic control of bulky (>4 cm) and/or advanced primary cancer of the uterine cervix, 35 patients were treated with concomitant cisplatin (CDDP), 5-fluorouracil (5-FU) and split course hyperfractionated radiotherapy. Radiation was administered to the pelvis in five-day courses at a dose of 1.5 Gy twice daily every 21 days until a median dose of 45 Gy was reached. 15 Gy more were administered to involved parametrium or central tumor by external radiotherapy or brachytherapy. The irradiated zone was extended to include paraaortic lymph nodes if necessary. CDDP was administered at a dose of 20 mg m(-2) and 5 FU at a dose of 500 mg m(-2) from day one to day five of each course. The median number of combined treatment courses per patient was four (1-6). Local responses were obtained in 19 out of 24 patients in whom evaluation was feasible (i.e. who did not undergo surgery prior to combined therapy). Median survival was not attained with a median follow up of 33 months, three year overall survival was 62% and 52% in patients with local control and in the whole population respectively. Several patients with stage III and IV tumors achieved a very long survival. Acute toxicity was manageable but three patients required surgical repair of late radiation complications. This combined chemotherapy and radiotherapy resulted in good local control and did not rule out surgery.

Cisplatin, hyperthermia and radiation treatment in human cisplatin-sensitive and resistant glioma cell lines

In this study, the effects of mild protracted hyperthermia, combined with prolonged exposure to cisplatin and low dose-rate irradiation (LDRI), were examined in two human cell lines. The cell lines are human glioma parental and cisplatin-resistant variant cells. The results show that mild hyperthermia at 40 degrees C was able to sensitize both the parental and the variant cisplatin-resistant cells to cisplatin treatments (1 microgram/ml for up to 20 h) when the two treatments were given concurrently. When mild hyperthermia and cisplatin were given with LDRI concurrently, additional enhanced cell killing was observed in both the parental and the cisplatin-resistant variant cells. Further analysis of the results showed that when the effects of the trimodality treatment were normalized to the effects of the combined treatment of mild hyperthermia with cisplatin, the residual cell killing was still greater than that observed for radiation alone, indicating a synergistic interaction. This synergistic interaction was greater for the parental line compared to the cisplatin-resistant line. Thus, these data show that the concurrent application of mild hyperthermia, low concentration, long duration, cisplatin and low-dose rate irradiation may be an effective form of treatment in both normally responding and cisplatin-resistant variant human tumour cell lines.

Concomitant low dose-rate irradiation and cisplatin treatment in ovarian carcinoma cell lines sensitive and resistant to cisplatin treatment

Human ovarian carcinoma parental and cisplatin-resistant cells were evaluated for their radiation sensitivity to high and low dose-rate irradiation and for the effectiveness of cisplatin in radiosensitization. The cisplatin resistant variant A2780cp showed increased radiation resistance for both low dose-rate (LDRI) and high dose-rate irradiation. For cisplatin treatment for 1 h before and after HDRI there was radiosensitization in only the cisplatin-resistant variant. Concomitant cisplatin treatment during LDRI resulted in radiosensitization in both cell lines with dose-modifying factors ranging from 1.6 to 5.8. In this case greater radiosensitization was achieved in the parental cell line. In both cell lines the dose-modifying factors were larger when the cisplatin was refreshed every 6 h instead of 12 h during LDRI. These data show that cisplatin may be a very effective radiosensitizer when given during LDRI which is used in brachytherapy.

Cisplatin induced cell killing and chromosomal aberrations in CHO cells: treated during G1 or S phase

Variation in sensitivity to cisplatin during the cell cycle was studied in synchronous CHO cells treated during G1 or late S phase. The cells were assayed for cell killing, cell-cycle delay, and chromosomal aberrations after they were treated with cisplatin (1-12 micrograms/ml) for 1 h at 37 degrees C. They were either plated for colony survival, or colcemid was added from 12 to 40 h after plating followed by fixation 4 h later for analysis of chromosomal aberrations after the cells completed 1 or 2 cycles (i.e. first or second mitosis). Cells treated with 6 micrograms/ml exhibited about a 10-h delay during the first cycle after treatment during G1 compared with about 3 h during the first cycle and 6 h during the second cycle after treatment during late S. In both cases, cells entering metaphase exhibited predominantly chromatid-type breaks and exchanges. For both cell killing and chromosomal aberrations, the cells in G1 were 1.5-1.6 times more sensitive than those treated in late S, with 1 aberration per cell corresponding to about 37% survival. However, the exchanges and breaks were observed primarily in the first mitosis when cells were treated in G1 compared with the second mitosis when cells were treated in late S. These results suggest that DNA replication opposite cisplatin cross-links in the DNA results in lethal chromosomal aberrations.

New concepts in radiotherapy for advanced squamous cell carcinoma of the head and neck

This paper reviews two of the newer concepts - multiple daily fractions of radiotherapy - in improving the treatment of squamous cell carcinoma of the head and neck.

Concurrent cisplatin and 5-fluorouracil chemotherapy and radiation therapy for advanced-stage squamous carcinoma of the vulva

A phase II trial of concurrent cisplatin and 5-fluorouracil (5-FU) chemotherapy and radiation therapy (CT + RT) was conducted for the primary treatment of 12 patients with retrospective surgical FIGO stages III-IV squamous carcinoma of the vulva. Eight patients were stage III and four were stage IV. Chemotherapy was used as a radiation sensitizer and it was administered in two 5-day cycles 28 days apart. Cisplatin, 50 mg/m2/day iv on Days 1 and 2 or 100 mg/m2 on Day 1 or 2, plus continuous-infusion 5-FU, 1000 mg/m2/day for 4-5 days commencing on Days 1 and 28 of external-beam radiation therapy, are given. The pelvic radiation to a dose of 4400-5400 cGy is administered AP and PA to treat the primary tumor, the groin nodes, and the iliac vessels to the level below the common iliac nodes. Complete tumor responses were seen in 8 of 12 (67%) patients. Responses were observed in 6 of 8 (75%) stage III patients and 2 of 4 (50%) stage IV patients. Partial response were observed in 3 patients, and 1 patient had persistent disease. At the completion of concurrent chemoradiation therapy, radical vulvectomy or excision was used in 3 patients and posterior exenteration in 1. With a median follow-up of 37 months (range, 7-60 months), 10 patients are alive and free of disease, and 2 patients died at 12 and 15 months. There were no treatment-related deaths and no grade 4 toxicity. The morbidity included moist desquamation of the vulva in all patients, with grade 2 toxicity in 10 and grade 3 in 2. One patient had a deep venous thrombosis that responded to anticoagulation therapy. These data support the use of concurrent cisplatin and 5-FU chemotherapy and radiation therapy as an alternative to primary radical surgery to treat advanced-stage squamous carcinoma of the vulva.

Time- and sequence-dependent responses to cisplatin and radiation in the rat kidney

The influence of time interval and sequence between administration of cisplatin and a radiation dose was studied in the rat kidney. A dose of 10.5 Gy X-rays was given to both kidneys, preceded or followed by a single dose of cisplatin. Two separate experiments were performed. In the first experiment 6.0 mg/kg cisplatin was given, in the second experiment the drug dose was 5.5 mg/kg. A range of time intervals was introduced between administration of drug and radiation, from 7 to 1 days, 12 to 1 h, and 30 to 0 min. Control animals received either modality alone, or were left untreated. Cisplatin alone caused tubular function to decrease very quickly and to remain permanently altered. Changes in glomerular function were only detected after 30 weeks following the higher drug dose. X-rays alone caused measurable alterations in both glomerular and tubular function after 16 weeks. In the combined treatment the influence of time and sequence was significant. If cisplatin was given at 7 to 1 days before X-rays the effect of time was minimal. Administration of cisplatin 12 h to 15 min before irradiation resulted in an increase of radiation damage with decreasing time interval. Total damage sharply decreased when both modalities were given at the same time, and decreased further with increasing time between irradiation and drug administration. It is suggested that in the tubular cells free cisplatin or one of its hydrolysis products may interact with radiation-induced damage, e.g. by interference with repair of sublethal or potentially lethal damage.

Treatment of 29 patients with bulky squamous cell carcinoma of the cervix with simultaneous cisplatin, 5-fluorouracil, and split-course hyperfractionated radiation therapy

Attempting to improve local disease control in bulky (greater than 8 cm) primary or recurrent pelvic tumors, 29 patients with squamous cell carcinoma of the cervix (stage II, 4; III, 10; IV, 6; recurrent, 9) were treated with concomitant chemotherapy and split-course hyperfractionated radiation therapy between April 1983 and August 1988. Cisplatin (CDDP) and 5-fluorouracil (5-FU) have been shown to be radiation enhancers; furthermore, CDDP, radiation therapy, and continuous-infusion 5-FU have elicited high local response rates in head and neck squamous cell carcinoma. A pilot study of cyclical week on/week off CDDP, continuous-infusion 5-FU, and hyperfractionated radiation therapy was developed. Radiation was administered at 116 cGy twice daily, Days 1-5, every other week for a median dose of 4600 cGy to a pelvic field, with paraaortic extension if indicated. Concomitant chemotherapy included CDDP 60 mg/m2 IV Day 1 and 5-FU 600 mg/m2 IV continuous infusion for 96 hr following CDDP infusion. Patients received a median of four cycles of combined treatment, and intracavitary or interstitial brachytherapy followed in 21 patients. Local pelvic response was achieved in 29 of 29 (100%): complete response (CR) in 19 of 29 (66%), partial response (PR) in 10 of 29 (34%). Among CR patients 10 of 19 (53%) were without evidence of disease at a mean follow-up of 29 (range 12-76) months. Five-year actuarial disease-free survival among complete responders was 65%. Of the 10 CR patients 2 failed in the pelvis, for a local control rate of 17/19 (89%). Chemotherapy-related and acute radiation morbidity was minimal but 2 patients required surgical correction of radiation injury. Aggressive combination of split-course hyperfractionated radiation therapy with radiation enhancers resulted in promising local control of bulky pelvic tumor, with an acceptable complication rate, in this otherwise very poor prognostic group of patients.

Concomitant cisplatin and radiotherapy in locally advanced cervical carcinoma

Patients with locally advanced cervical cancer have a poor prognosis. The efficacy of radiotherapy is limited by the presence of large tumor volume and nodal disease. As cisplatin is a documented radiosensitizer and has activity in squamous cell carcinomas, a prospective study was designed to evaluate the toxicity and potential synergism of concurrent cisplatin (20 mg/m2 x 5 d every 21 days) and radiotherapy in locally advanced cervical cancer. Forty-three patients were studied, of which 14 were stage IB/IIA (bulky disease) and 29 were stage IIB/IIIB/IVA. Of the 32 evaluable patients, there were 29 complete responders. Of these 29 patients, 27 remain without evidence of disease, with a median follow-up of 12 months. There were no treatment-related deaths. Cisplatin and radiotherapy appear to be a well-tolerated and highly effective regimen for locally advanced cervical cancer.

Carboplatin (JM8), etoposide (VP16) and thoracic irradiation for small cell lung cancer (S.C.L.C.): an evaluation of lung toxicity

Carboplatin (JM8) and etoposide (VP16) have demonstrated activity against a range of solid tumours. A retrospective study has looked for evidence of enhanced radiation pneumonitis when these drugs are employed in conjunction with irradiation. Twenty-nine patients with limited disease small cell lung cancer (S.C.L.C.) received JM8 (300 mg/m2) and VP16 (300 mg/m2) at intervals of 3-4 weeks for 4 cycles followed by thoracic irradiation. Twenty-one were evaluated and compared with 21 matched non-S.C.L.C. patients treated by radiotherapy alone. Patients were stratified into three groups according to the radiation dose schedule normalised using Wara's modification of Ellis' formula (n = 0.38, t = 0.06) [28]. Group 1 received less than 1014 rets, Group 2 1015-1250 rets and Group 3 greater than 1250 rets. Radiological pneumonitis was observed in 57% (12/21) of patients receiving combined modality treatment compared to 71% (15/21) of patients receiving radiation alone with evidence of a radiation dose-response relationship for the appearance of pneumonitis in both groups of patients (p greater than 0.1). In conclusion, no enhancement of radiation pneumonitis by carboplatin (JM8) or etoposide (VP16) has been observed.

5-Fluorouracil/folinic acid/cisplatin-combination and simultaneous accelerated split-course radiotherapy in advanced head and neck cancer

In advanced inoperable head and neck cancer radiotherapy alone is unsatisfying. Better results can be obtained by simultaneous 5-Fluorouracil/Cisplatin-chemotherapy and irradiation. The cytotoxicity of 5-Fluorouracil can be enhanced synergistically by adding Folinic Acid in excess. In a clinical phase II trial 62 previously untreated patients suffering from unresectable AJCC-stage III (4 pts.) and IV (58 pts.) squamous cell carcinoma of the head and neck were treated with a simultaneous chemoradiotherapy consisting of high-dose Folinic Acid in addition to a 5-Fluorouracil/Cisplatin combination and of accelerated split-course radiotherapy. As results, three pts. died from tumor arrosion bleeding during the treatment. Median follow up time of the surviving pts. is 27 + months (range 18-44 months). 48/62 pts. (77%) achieved complete remission, 11/62 pts. (18%) partial remission. Presently, 32 pts. (52%) are without evidence of disease. Actuarial three years overall survival rate (Kaplan-Meier method) out of 62 pts. in 53%. Actuarial disease free survival and local tumor control rates at three years are 58% and 72%. Mucositis was severe but tolerable, bone marrow depression was moderate to marked. In conclusion, this combined simultaneous modality approach is highly effective in locally advanced head and neck cancer. It seems to provide superior survival and local control rates as compared to conventional radiotherapy or sequential chemo-radiotherapy or as compared to simultaneous 5-Fluorouracil/Cisplatin and non-fractionated radiotherapy. A comparative phase III study is required.

Improved response and survival to combined cisplatin and radiation in non-keratinizing squamous cell carcinomas of the head and neck. An RTOG study of 114 advanced stage tumors

Effective treatment modalities for Stage III and IV squamous cell carcinomas (SCC) of the head and neck are limited and seldom result in long term survival. The improved results with cisplatin containing chemotherapy have been encouraging and represent an additional therapeutic modality for head and neck cancer. To estimate the effectiveness of concomitant radiation and cisplatin chemotherapy, the Radiation Therapy Oncology Group (RTOG) initiated a Phase II study for patients with advanced nonresectable SCC of the head and neck. In addition, the diagnostic biopsy specimens were collected. Two pathologists reviewed and scored the biopsy specimens for a number of histologic parameters, including degree of keratinization, nuclear pleomorphism, frequency of mitoses, inflammatory and stromal reaction, pattern of invasion and vascular involvement in order to identify potential prognostically important patient subgroups. A total of 114 patients were evaluated for complete clinical responses (CR). These were achieved in 76% for all head and neck sites (ALL), and in 72% of the patients excluding nasopharyngeal and sinus cancers (REST). Evaluation of histopathologic parameters through multivariate analysis identified the presence of keratin as the most significant in predicting CR. Non-keratinizing SCC had CRs of 98% (ALL), and 94% (REST), as compared with 64% and 67% in the patients with keratin producing neoplasms (P less than 0.001 and 0.05) respectively. Survival at 24 months was found to be improved in the non-keratinizing SCC (P = 0.002). Multivariate analysis also identified the frequency of mitoses as being important in predicting for CR in patients with keratin in the biopsy findings. Biopsy specimens from ALL patients with two or more mitotic figures per high-power microscopic field had 76% CRs, in comparison with 46% when none or one mitotic figure was observed (P = 0.02). In the restricted group of patients (REST), the CR was 77% in the high mitotic figure group as opposed to 45% in the lower rate group (P = 0.03). However, this significant difference in CR rates did not translate into improved survival for the high CR subset.

Combined treatment of radiation and cisdiamminedichloroplatinum (II): a review of experimental and clinical data

Cis-diamminedichloroplatinum (II) (c-DDP), a highly effective cytostatic drug, is increasingly used in combination with irradiation both in the laboratory and in patients. This review aims at a critical reassessment of the potential role of this drug as a "radiosensitizer." The opinion about c-DDP being an effective hypoxic cell radiosensitizer in bacteria was substantiated in some studies on mammalian cells in culture but not in others. More powerful mechanisms of radiation enhancement, which are not yet fully explored, may be depletion of endogenous thiols, inhibition of cellular repair processes, and proliferation inhibition. The effects of c-DDP in combination with irradiation in experimental tumors seem to vary between different investigators and between different tumor systems. Occasionally, supra-additive effects have been observed in some animal tumors. This stresses the need for testing this combination treatment in various tumor types, preferentially of human origin. In normal tissues, the effects are, to a large extent, explained by independent cell killing by each agent. A substantial number of clinical pilot studies have shown that the combination treatment is feasible, but the results of ongoing phase III trials will be needed to assess the potential therapeutic benefit of this combined treatment modality.

Concurrent radiotherapy and chemotherapy with cisplatin in inoperable squamous cell carcinoma of the head and neck. An RTOG Study

In patients who have locally advanced and inoperable head and neck cancer, the achievement of initial local control (complete response) of the disease with initial definitive treatment with radiotherapy (RT) with or without chemotherapy, is an important prognostic factor for overall survival. Cisplatin 100 mg/M2-intravenously (IV) with hydration and mannitol diuresis was given every 3 weeks for three doses concurrently with definitive radiotherapy (followed by salvage surgery [if possible] for persistent disease) was activated by the Radiation Therapy Oncology Group (RTOG) in 1981. One hundred thirty-four patients were initially registered and 124 were eligible and analyzed for this report. Eighty-two percent of the patients had Stage IV disease and greater than 50% of the primary sites were in oropharynx (39%), nasopharynx (22%), and oral cavity (18%). Eighty-seven percent of the patients are known to have finished the planned RT greater than 6450 cGy and 60% received three courses of cisplatin. Overall, 60% finished the planned combined treatment. Complete response to initial treatment occurred in 69% and an additional one patient (1%) was rendered disease-free after radical node dissection. Severe toxicities were as follows: leukopenia, 11%; anemia, 8%; nausea and vomiting, 6%; stomatitis, 31%; and renal, 6%. One toxic death occurred when a nephrotoxic antibiotic was administered at the same time. All patients were evaluated for total disease and survival regardless of compliance to the treatment or the cause of death. At 1 year, an estimated 51% of the patients had their disease totally controlled and an estimated 66% were alive. Incidence of initial complete response by various patient characteristics also were analyzed. The authors concluded that the combination of cisplatin and radiotherapy is an effective and safe treatment in patients with advanced head and neck cancer and needs to be tested against radiotherapy alone.

The effect of combined treatment with platinum complexes and ionizing radiation on DNA in vitro

The conformation of isolated calf-thymus DNA treated with cis-diamminedichloroplatinum(II) (cis-DDP) or its trans-isomer (trans-DDP) and gamma radiation in combination was investigated by means of differential pulse polarography and circular dichroism spectroscopy. The results revealed that combined treatment with antitumour active cis-DDP enhanced the extent of double-stranded distorted regions in DNA molecules. If irradiation preceded the platination, the combined effect was purely additive, while the reverse order of application of the two agents resulted in an increased effect over and above what may be expected from using the two modalities separately. These results were explained on the basis of the hypothesis that favours as a major mechanism of this combined effect the fixation by the binding of cis-DDP of DNA lesions introduced during radiation. Combined treatment with antitumour inactive trans-DDP resulted in the enhancement of single-stranded, denatured DNA yield. However, more extensive alterations in DNA conformation were observed if DNA was platinated after irradiation. The different effects of the combined treatments with cis- and trans-DDP were thought to be connected with the different destabilizing effects resulting from distinct conformational distortions induced by the two isomers.

The effects of cis-diamminedichloroplatinum (II) and radiation on the proliferation kinetics of mouse duodenal crypt cells and on a partially synchronized crypt cell population

The effects of c-DDP and radiation, given alone or in combination, on the proliferation kinetics of mouse duodenal crypt cells were investigated by repeated labelling with 3H-thymidine. Crypt cells surviving a single dose of X-rays or c-DDP alone, appeared to proliferate faster than untreated controls. When both agents were given in combination, the proliferation rate of surviving crypt cells was markedly reduced as a result of a significant increase in the DNA synthesis time. The influence of the proliferation rate of crypt cells on the effects of c-DDP and X rays was analyzed using the crypt microcolony assay. Mice were given single doses or 2 fractions of X rays with 2 different time intervals (4 and 48 hours) either alone or in combination with c-DDP given 30 minutes before the second fraction. The lethal effect of the drug was approximately the same in cells that were in accelerated proliferation after the first irradiation as in unstimulated cells. A tendency for less cell killing by the drug was observed 3.5 hours after the first irradiation. To rule out cell age dependent effects of c-DDP, crypt cell survival was assessed after irradiation was given alone or in combination with the drug on a partially synchronized crypt cell population, obtained by repeated injections of hydroxyurea. A predominant lethal effect of c-DDP was found in cells in the late G1-phase. These findings are important to consider both from a mechanistic point of view as for clinical application of the agents.

Enhancement of radiation-induced cell kill by platinum complexes (carboplatin and iproplatin) in V79 cells

Two second generation platinum complexes currently undergoing clinical chemotherapeutic trials, carboplatin (CBDCA) and iproplatin (CHIP), were evaluated for their ability to alter the survival of cultured Chinese hamster V79 cells following irradiation. Two protocols were employed. In the first, the drug was added to preplated cells, some of which were subsequently made hypoxic with nitrogen gas. These hypoxic cells were irradiated following 1 hour exposure to drug and survival was assessed by standard colony forming unit (CFU) methods. Enhancement ratios (ER) of approximately 1.4 were obtained for irradiation under hypoxic conditions, if the cells were exposed to equitoxic doses of CBDCA (500 microM) CHIP (50 microM). In the second series of experiments, cells were treated with 10 Gy in air and then incubated for various times prior to trypsinization and serial dilution of single cell suspensions. Six hours after irradiation, cells treated with X rays alone had recovered to produce a surviving fraction twice that of cells trypsinized immediately after irradiation (not held). Post-irradiation administration of CBDCA (50 microM) or CHIP (20 microM), at a time when free radical-mediated radiosensitization would not be possible, operationally inhibited this recovery from radiation-induced potentially lethal damage (PLD). Inhibition, expressed as recovery inhibition factor (RIF) after 6 hr with drug, was 2.0 for CBDCA and 1.2 for CHIP. These results suggest that the rationale for designing clinical trials to exploit interactions between cisplatin and radiation might also extend to include combined modality therapy using radiation with either of these two platinum complexes.

Rhodium(III) as a potentiator of the effects of X-rays on cells

A rhodium compound, Rh(NH3)3Cl3, does not sensitize the spores of Bacillus megaterium to X-rays. However, it is a very effective sensitizer of vegetative cells of Staphylococcus aureus, raising the sensitivity four times in O2 and over 100 times in anoxia. The inhibition by oxygen of the sensitizing action of Rh(III), which operates over a wide range of [O2], is noteworthy. These experiments were performed in saline-phosphate buffer using 50 kVp X-rays. The results are discussed in terms of the known radiation chemistry of this compound.

Potentiation of radiotherapy by cis-dichlorodiammine platinum (II) in advanced cervical carcinoma

Forty-five patients with Stages II and III cervical carcinoma were randomized to receive either radiation or cis-dichlorodiammine platinum (II) (cis-DPP) with radiation. Cis-DPP was administered in bolus injections of 25 mg/m2 at weekly intervals until completion of radium application. Complete response was noted in 11/20 (55%) patients in the radiochemotherapy group compared to 5/25 (20%) patients in the radiation group (P less than 0.025). No enhanced toxicities were observed with the addition of cis-DPP to radiation. The combined use of cis-DPP and radiotherapy offers promising potential in improving local-regional control of advanced cervical carcinoma.

Influence of cis-diamminedichloroplatinum (II) on mouse duodenal crypt stem cell survival after multifraction X ray treatment

The mechanism of interaction of cis-platinum and X rays was investigated in mouse duodenal crypts using the microcolony assay. Mice were exposed to 1, 2, 5, 10, or 15 fractions of X rays, either alone or preceded by a single i.p. injection of cis-platinum, 8 mg/kg, one-half hour before the first fraction. In all fractionation regimens, cisplatinum caused a shift of the X ray survival curve for crypt cells towards lower doses. The vertical distances between the survival curves after X rays and those in combination with cis-platinum were about the same, giving a mean value of 0.89 +/- 0.12 log10 cells. After cis-platinum treatment alone, a crypt cell survival curve was established in the high dose range. The estimated cell kill by 8 mg/kg of cis-platinum, obtained by extrapolation of this curve, was 1 log10 cell number. These data imply independent cell killing mechanisms for cis-platinum and X rays. However, even after correction for cell kill by the drug, cis-platinum tended to inhibit slightly sublethal damage repair after X rays. This was supported by linear quadratic analyses, in which the alpha/beta value after combined treatment was found to be slightly higher than after X rays alone (20 +/- 4 Gy versus 13.0 +/- 1.7 Gy).

Radiation and platinum drug interaction

Platinum drugs have chemical as well as biochemical and biological effects on cells, all of which may interact with radiation effects. They inhibit recovery from sublethal and potentially lethal radiation damage. They produce a pattern of chromosome aberrations analogous to that from alkylating agents. Cellular sensitivity to platinum is increased when glutathione levels are reduced, just as is radiosensitivity. There is a pattern of drug sensitivity throughout the phases of the cell cycle which is different from that for radiosensitivity. The ideal platinum drug-radiation interaction would achieve radiosensitization of hypoxic tumour cells with the use of a dose of drug which is completely non-toxic to normal tissues. Electron-affinic agents are employed with this aim, but the commoner platinum drugs are only weakly electron-affinic. They do have a quasi-alkylating action however, and this DNA targeting may account for the radiosensitizing effect which occurs with both pre- and post-radiation treatments. Because toxic drug dosage is usually required for this, the evidence of the biological responses to the drug and to the radiation, as well as to the combination, requires critical analysis before any claim of true enhancement, rather than simple additivity, can be accepted. The amount of enhancement will vary with both the platinum drug dose and the time interval between drug administration and radiation. Clinical schedules may produce an increase in tumour response and/or morbidity, depending upon such dose and time relationships.

Carboplatin as a potentiator of radiation therapy

A rationale for coordinating the administration of carboplatin with radiation to achieve enhancement of cancer therapy is developed. This approach is based upon a review of the reports of effects in a variety of systems, effects attributed to interactions between cisplatin or other platinum analogs and radiation. Two major effects include radiosensitization (RS) of hypoxic cells with platinum present during irradiation and potentiation of cell kill with platinum complexes administered after irradiation. Both these effects are expected to result in an improved therapeutic ratio. The latter effect may include inhibition of recovery from radiation-induced potentially lethal damage (PLD) and sublethal damage (SLD). Evidence for RS by carboplatin with an enhancement ratio (ER) of 1.8 is presented in Chinese hamster lung cells (V79) irradiated in culture under hypoxic conditions. Potentiation of radiation therapy in mice bearing a transplanted mouse mammary tumor (MTG-B) is reported as a supra-additive tumor growth delay when 60 mg/kg carboplatin is administered either 30 minutes before or immediately after 20 Gy of X-irradiation. Improved efficacy resulting from ongoing clinical trials coordinating cisplatin with radiation should support the role for carboplatin as a potentiator of radiation therapy since this second generation complex of platinum also interacts with radiation and larger concentrations of platinum should be attainable in tumors using the new drug.

Platinum based combined modality approach for locally advanced head and neck carcinoma

Radiation therapy delivered soon after cisplatin administration is used for the treatment of advanced head and neck cancer. A radiation dose of 4800 cGy is given in standard fractions, followed by clinical evaluation and either surgical resection or an additional radiation dose of 2000 cGy. The histopathology of the surgical specimens from 21 patients undergoing resection in this protocol is compared with the corresponding clinical evaluation of tumor response. A significant number of both false negative and false positive clinical assessments are revealed by this comparison. In addition, it appears that local control of bulky head and neck cancer is approached by 4800 cGy combined soon after cisplatin. Discussion of the likely bases for this apparently favorable clinical interaction between cisplatin and radiation is presented.

Cell survival after the combined action of manganese (MnCl2) and X-rays in synchronized Chinese hamster cells

The interactions between the effects of manganese chloride and X-rays were studied in synchronized populations of V79 Chinese hamster fibroblasts. The cells were selected by shaking off asynchronous cultures for detachment of mitotic cells which were plated in petri dishes and exposed to various treatments. Irradiation was carried out with a Philips RT-100 X-ray unit. A final concentration of 0.25 mM MnCl2 was used. The main parameter was the colony forming ability of the surviving cell fraction. When MnCl2 was administered over 1 h, its toxicity was low regardless of the phase of the cell cycle. Administered separately, 2 Gy irradiation produced only a slight decrease in survival, less marked in the S phase. However, the two agents together induced a synergistic inhibition of the surviving fraction in the S phase when the metal was given immediately after irradiation. If manganese was administered 3 h after irradiation the two inhibitory effects apparently remained only additive. It seems that MnCl2 can impair some repair processes starting immediately after irradiation.

Enhancement of high intensity Iodine-125 brachytherapy by cis-platinum in a murine bladder tumor model

The interaction of cis-platinum chemotherapy and high-intensity Iodine-125 brachytherapy was studied in C3H/He mice with MBT-2 tumors growing in the thigh. Brachytherapy was delivered by 3 Iodine-125 seeds of 10 mCi each implanted into the tumor. Ninety-six animals were randomly divided into 8 groups of 12 animals each. Each group was given either no treatment (control), cis-platinum alone or brachytherapy of 20, 40 or 50 Gy either alone or combined with cis-platinum. Cis-platinum 3 mg. per kg. was given every 5 days for 3 doses. The addition of cis-platinum enhanced the effects of Iodine-125 brachytherapy as shown by the end-points of tumor regrowth delay, local tumor control and median survival times. The sensitization enhancement ratio ranged from 1.2 to 1.9. Further experiments are to be conducted to study the normal tissue effect, therapeutic gain factor, effects of altering the time of administration of cis-platinum and the clinical use of high-intensity Iodine-125 for removable brachytherapy.

Chemotherapy strategies in squamous cell carcinoma of the head and neck

Traditionally, chemotherapy has been utilized in the palliation of patients with recurrent or metastatic squamous cell carcinoma of the head and neck. The introduction of more effective agents has spawned many new multi-drug protocols as the initial therapy of patients with previously untreated advanced cancers (Stages III and IV). The combination of cis-platinum and other active agents given in two to three courses has produced overall response rates of 80 to 90% with clinically complete response rates of 20 to 54%. Many of the complete responders were histologically negative for cancer at the time of resection. The number of courses, stage (T and N), and tumor morphology influenced the complete response rate to combination chemotherapy. Responders to chemotherapy had statistically improved survival as compared to nonresponders. Response to chemotherapy was an excellent predictor for subsequent response to radiotherapy. Utilizing the same combination of chemotherapy, we improved the overall response rate in those patients with recurrent and systemic cancer. Although the median survival is still poor, there is improvement of survival at 25 percentile level. Some of the important factors that may influence the response rate and the survival of these patients are performance status, previous radiotherapy, and whether the recurrence is localized or systemic.

Hypoxic cell sensitization to radiation damage by a new radiosensitizer: cis-dichloro-bis(1-(2-hydroxyethyl)-2-methyl-5-nitroimidazole-N3)platinum(II) (flap)

A new, stable platinum coordination complex (FLAP) containing the 5-nitroimidazole, metronidazole, has been prepared and characterized. The square-planar platinum(II) complex has two metronidazole molecules and two chlorine atoms in the cis configuration. The properties of FLAP differ significantly from metronidazole alone or other platinum complexes tested in the same system. It has a low toxicity towards Chinese hamster ovary cells and is a very effective radiosensitizer toward hypoxic cells in vitro: a one-h pretreatment with a non-toxic dose of 50 microM gave an enhancement ratio of 2.4. No potentiation of aerated cells to X-irradiation damage was observed after a similar schedule of pretreatment at the higher dose of 100 microM FLAP.

Enhancement of the potentiation of radiotherapy by platinum drugs in a mouse tumor

This study examines two ways to enhance cisplatin-mediated potentiation of the radiotherapy of a mouse mammary tumor, MTG-B: a) the appropriate sequencing of the two modalities, and b) the use of platinum "rescue" at appropriate times relative to injection of cisplatin to ameliorate platinum toxicity and permit the use of larger concentrations of cisplatin. Reduced TCD50 values and potentiated tumor regression resulted when cisplatin preceded irradiation by 1 hr compared to injection of cisplatin post-irradiation. Cisplatin "rescue" was demonstrated by DDTC, WR-2721 and 5-TG, and enhanced effects on the inhibition of tumor growth resulted when 20 mg/kg cisplatin and 730 mg/kg DDTC were combined with radiotherapy.

Antimitotic and cytotoxic activity of cis-dichlorobis-(cyclohexylamine)platinum(II) on Chinese hamster ovary cells

The antimitotic and cytotoxic effects of cis-dichlorobis(cyclohexylamine)-platinum(II) (cis-HAD) which among Pt complexes used as antitumoral drugs shows the highest therapeutic index (TI) have been compared to those os cis-dichlorodiamine platinum(II) (cis-DDP), the most commonly used drug of this group, using Chinese hamster ovary cell cultures (CHO line). DNA synthesis inhibition, mitotic index, cell viability, chromosome aberrations and cell survival have been taken into account. The data indicates that the antimitotic agent cis-HAD is active only at doses causing high cell mortality and chromosome damage.

Isobologram analysis of the combined effects of anti-tumour platinum complexes and ionizing radiation on mammalian cells

Chinese hamster ovary cells have been treated in vitro with the platinum coordination complexes cis-PAD or CHIP and with radiation, either alone or in combination with different doses and time intervals. The isobologram method has been used to make a graphic comparison of these combined-modality data in terms of additivity and enhancement. The data showed enhancement of the radiation effect by these platinum complexes in many combinations, and a truly synergistic effect in one case. This method of analysis points to the limited usefulness of the parameter dose-modifying effect (DMF) since the most synergistic combination did not have the highest DMF.

Combination studies with misonidazole and a cis-platinum complex: cytotoxicity and radiosensitization in vitro

cis-Dichlorodiammineplatinum(II) (cis-Pt(II) can act as a radiosensitizer of hypoxic mammalian cells in vitro. Used in combination with misonidazole the level of sensitization achieved is greater than that seen with either drug alone, and it is suggested that these compounds sensitize by independent mechanisms. For cells held at 37 degrees C, cis-Pt(II) shows much greater toxicity to hypoxic cells than to aerobic cells. In combination with misonidazole, no additional cytotoxic effect is shown towards aerobic cells than that seen for cis-Pt(II) alone. However, there is additional killing of hypoxic cells when they are treated with both drugs.