Schedule dependent effectiveness of CCNU and 5-fluorouracil in experimental chemotherapy

Adjuvant Chemotherapy with Fluorouracil and ccnu in Colon Cancer. Results of a Multicentric Randomized Study

To establish the effectiveness of adjuvant chemotherapy in patients with colon cancer after radical surgery, from 1980 to December 1983, 263 patients were randomized in a multicentric study to no further treatment (131 patients) or to a combination of fluorouracil (5-FU) (400 mg/m2 i.v., days 1–5) and lomustine (CCNU) (100 mg/m2 per os on day 5) every 6 weeks for 9 cycles (132 patients). The two groups were well balanced for age, sex, histology, tumor and nodal extent. Chemotherapy was not given to 30 of the 132 randomized patients, and of 98 treated patients only 38 completed the entire protocol. Analysis, as intention to treat, at 54 months did not show any significant difference between the two treatment groups in terms of relapse-free survival (surgery alone, 74.5%; surgery+adjuvant chemotherapy, 70.9%; p = 0.91). In contrast, a significant difference was observed in overall survival (surgery alone, 78.8%; surgery+adjuvant chemotherapy, 60.8%; p = 0.04). The sites of relapse were identical in the two treatment arms. In conclusion, from this study it appears that adjuvant chemotherapy with 5-FU and CCNU seems to have no efficacy in the cure rate of colon cancer patients.

Three tumor sensitivity tests evaluated with mouse tumors

The predictive value of three types of tumor sensitivity tests was evaluated using mouse tumors. Sensitivities of osteosarcoma C22LR, Lewis lung and M2661 carcinoma were determined for the following drugs: DNA interacting or alkylating agent (doxorubicin, cisplatin, 1,3-bis(2-chloroethyl)-1-nitrosourea, melphalan), antimetabolite (5-fluorouracil, methotrexate) and microtubule inhibitor (vinblastine, vincristine). Volume measurements of the subcutaneously growing tumors after treatment with the same drugs were considered to be the traditional reference system with which the results of the in vitro clonogenic assay, the labeled precursor incorporation assay and the subrenal capsule assay were compared. Results obtained with the in vitro clonogenic assay were highly reproducible. With the 1-h drug exposure technique the predictive accuracy was 71%. This result is in the same range as those found by others for human tumors. Predictive accuracy after continuous drug exposure was only 25%. Vinblastine, vincristine and cisplatin caused no inhibition of labeled precursor incorporation. However, the assay is too unreliable to use, due to the extreme variability when used with the other drugs. From 31 consecutively performed duplicate tests in the subrenal capsule assay, nine showed opposite results. This degree of disagreement between duplicate test results was considered too high to make reliable predictions of tumor sensitivity with this assay.

Temporal interactions in the Lewis lung tumour between cytotoxic drugs and acute or fractionated radiotherapy

The suggestion was examined, that acute irradiation might be combined with some cytotoxic drugs to produce a supra-additive antitumour effect by timing the second treatment to coincide with the period of repopulation by tumour cells that survived the first treatment. The possible interaction of fractionated irradiation with drugs was also studied. Lewis lung tumours were treated in vivo with acute radiation (20 Gy) and 1-(2-chloroethyl)-3-(4-methyl cyclohexyl)-1-nitrosourea (MeCCNU, 10 mg X kg-1), cyclophosphamide (CY, 120 mg X kg-1) or cis-dichlorodiammine platinum (cis-Pt, 10 mg X kg-1) with time intervals ranging from simultaneous to 9 days in either sequence. Tumour response was measured by regrowth delay and combination responses were evaluated relative to calculated "additivity envelopes". With CY and cis-Pt, tumour volume response was approximately additive, whether the drugs were administered simultaneously, or up to 7 days before or after radiation. However, with simultaneous administration, MeCCNU and radiation were supra-additive in terms of volume response, although only additive using a clonogenic cell survival assay. A transplantation experiment suggested that the supra-additive volume response may be due to retarded growth rate in regrowing tumours. In the fractionation studies, drugs were given either at the beginning or at the end of a regime of 5 daily 6 Gy doses. With CY and MeCCNU the drugs were more effective when given with the first radiation dose, but with cis-Pt either regime was equally effective. There was no evidence that repopulation could be exploited to improve therapeutic effect with any of the combination treatments used in this study.

Etoposide prior to cis-diamminedichloroplatinum in combination chemotherapy: in vitro and in vivo studies

Antitumor effect and toxicity of etoposide (VP 16) in combination with cis-diamminedichloroplatinum (DDP) were studied on the in vitro C108 line and its in vivo counterpart, the M1087 line, both deriving from Lewis lung carcinoma. A colony-forming assay was used to assess the in vitro cytotoxicity of each drug and, on the basis of survival curve shape indications, different drug sequences were analyzed in order to find the optimal combination. Tumor growth inhibition, growth delay, metastasis reduction and percentage increase in lifespan were considered as parameters of therapeutic effect. From the present work it can be derived that the VP 16-DDP combination produces a poor antitumour effect against the Lewis lung carcinoma lines, otherwise associated with a highly acute toxicity. The sequence in which VP 16 is given before DDP induces a significant antimetastatic effect together with acceptable toxicity.

Comparison of metastatic disease after local tumour treatment with radiotherapy or surgery in various tumour models

Spontaneous metastases in lymph nodes and/or the lung were obtained after tumour cell inoculation of four mouse tumours and one rat tumour into the foot-pads of syngeneic animals or their F1 hybrids. Following local radiotherapy with doses of 45-80 Gy, significantly more mice died with metastases than following local amputation of the tumour-bearing foot when the 2661 carcinoma was involved. No significant difference was observed after these treatments for the other tumours. The enhancement of metastastic growth after local radiotherapy in the 2661 carcinoma seems not to be due to incomplete killing of tumour cells in the foot. The presence of irradiated normal structures and tumour tissue after radiotherapy promoted the outgrowth of 261 carcinoma cells which were outside the radiation field at the time of treatment. Evidently, even under similar experimental conditions, radiotherapy may enhance the growth of metastases from some tumours and not from others.

Cell kinetic factors, single drugs and combination

This communication focuses on the problems that exist in the application of cell kinetic information in cancer chemotherapy. From selected historical work, the following conclusions can be drawn. 1) Theoretically optimal drug sequences may fail to show the expected effect. 2) Similar drug sequences cause different effects in different tumors, even when the tumors have similar proliferation characteristics. The unpredictability and the heterogeneity in response make the extrapolation to clinical cancer chemotherapy very difficult. Better prediction may be made from the integration of results from studies combining cell kinetic factors, cellular pharmacokinetics, and biochemistry of drug exposure.

Adjuvant chemotherapy: theoretical considerations and model studies

Comparison of response of experimental tumors to adjuvant chemotherapy for minimal disease with the response of solid large tumors to similar drug regimens has indicated that for many tumors the small microscopic foci are more responsive. There are, however, a number of model tumors that respond far less to chemotherapy when applied to minimal disease than when applied to large tumors. The response of these tumors to adjuvant treatment shows similarities with the clinically observed response. The data do not support the hypothesis that the success of a drug combination given as adjuvant chemotherapy may be predicted from the success of the same treatment when applied for manifest disease.

Variation in response of xenografts of colo-rectal carcinoma to chemotherapy

Ten xenograft lines of human colonic and rectal carcinomas have been established in immune-suppressed mice. Mice bearing tumours in the 2nd to 6th passage were treated with maximum tolerated doses of 8 chemotherapeutic agents and tumour growth delay was estimated in terms of the number of volume doubling times gained by the treatment. The average response corresponded to a delay of only about 0.5 doubling times, but some tumour lines showed a good response to some agents. Twenty-three out of about 700 treated tumours failed to regrow. Statistical analysis showed no consistent difference in sensitivity among the tumour lines, but melphalan, 5-fluorouracil and hexamethylmelamine stood out as the most effective agents. A study of two-drug combinations showed that their order of administration had little effect on response. Only 4 of the patients who donated the xenografts were treated with chemotherapy, but among these there was some evidence that response in the xenografts correlated with response in the patient.