Concurrent use of multiple low dose chemotherapy agents with differing mechanisms of action as a strategy vs passive resistance: A pilot study

Resistance may be classified as active (or competitive) (due to excess amou nt of a factor) vs passive (or non-competitive) (due to a deficiency of a f actor). Passive resistance may be important in human solid tumors. In passi ve resistance, the dose-response curve may be shallow, or may flatten at a relatively low dose. We hypothesized that, if passive resistance were impor tant, it might be advantageous to use low doses of multiple concurrent chem otherapy agents with differing mechanisms of action, rather than using high doses of 2 or 3 drugs. We combined single day cisplatin 60 mg/m(2), cyclop hosphamide 250 mg/m(2), epirubicin 40 mg/m(2), paclitaxel 60 mg/m(2), and v inblastine 2.5 mg/m(2), with 5 days of 5-fluorouracil 200 mg/m(2), folinic acid 20 mg/m(2) and dexamethasone 4 mg orally q.i.d. every 3 weeks. In late r cohorts, doses were escalated, and tamoxifen and verapamil were added. Tw enty-three patients were entered. ECOG performance status was 1 in 15 patie nts and 2 in 8. Number of prior chemotherapy regimens was 0 in 4 patients, 1 in 4, 2 in 8, 3 in 4, 4 in 2, and 7 in 1. Sixteen patients had prior radi otherapy, and 3 had no prior therapy. Myelosuppression and febrile neutrope nia were frequent, and 4 heavily pretreated patients died of pneumonia cont racted while neutropenic. Diarrhea, nausea and vomiting, and fatigue were a lso prominent. Among 9 patients with non-small cell lung cancer, one had a partial remission, 4 had stable disease (including 3 with minor objective r esponses). Two additional non-small cell lung cancer patients also had obje ctive tumor regression, but were coded as failures, since one had tumor pro gression in <6 weeks and the other died of respiratory failure (thought to be due to severe mucous plugging) one week after his first course of treatm ent. Among 14 patients with other tumor types, there was one partial respon se (esophageal carcinoma), 6 patients with stable disease for >6 weeks (inc luding minor responses in one patient each with adenocarcinomas of kidney a nd breast), and 7 failures (including one patient with adenocarcinoma unkno wn primary who had minor tumor regression lasting 4 weeks). Despite the una cceptably high toxic death rate, median survival time was 24 weeks (range, 1 week to >104 weeks). This regimen is toxic, but survival duration is long er than would be expected in this heavily pre-treated population. Doses rec ommended for further study are those used in the first treatment cohort las described above). Since myelosuppression is the major toxic effect, hemopo ietic growth factors might prove helpful with this regimen.