- Irinotecan hydrochloride injection is contraindicated in patients with a known hypersensitivity to the drug or its excipients.
Second-Line Single-Agent Therapy
Weekly Dosage Schedule
In three clinical studies evaluating the weekly dosage schedule, 304 patients with metastatic carcinoma of the colon or rectum that had recurred or progressed following 5-FU-based therapy were treated with Irinotecan hydrochloride. Seventeen of the patients died within 30 days of the administration of Irinotecan hydrochloride; in five cases (1.6%, 5/304), the deaths were potentially drug-related. One of the patients died of neutropenic sepsis without fever. Neutropenic fever occurred in nine (3.0%) other patients; these patients recovered with supportive care.
One hundred nineteen (39.1%) of the 304 patients were hospitalized because of adverse events; 81 (26.6%) patients were hospitalized for events judged to be related to administration of Irinotecan hydrochloride. The primary reasons for drug-related hospitalization were diarrhea, with or without nausea and/or vomiting (18.4%); neutropenia/leukopenia, with or without diarrhea and/or fever (8.2%); and nausea and/or vomiting (4.9%).
The first dose of at least one cycle of Irinotecan hydrochloride was reduced for 67% of patients who began the studies at the 125-mg/m2 starting dose. Within-cycle dose reductions were required for 32% of the cycles initiated at the 125-mg/m2 dose level. The most common reasons for dose reduction were late diarrhea, neutropenia, and leukopenia. Thirteen (4.3%) patients discontinued treatment with Irinotecan hydrochloride because of adverse events. The adverse events in Table 7 are based on the experience of the 304 patients enrolled in the three studies described in Clinical Studies (14.1).
Table 7. Adverse Events Occurring in >10% of 304 Previously Treated Patients with Metastatic Carcinoma of the Colon or Rectuma| a Severity of adverse events based on NCI CTC (version 1.0) |
| b Occurring >24 hours after administration of Irinotecan hydrochloride |
| c Occurring ≤24 hours after administration of Irinotecan hydrochloride |
| d Primarily upper respiratory infections |
| e Not applicable; complete hair loss = NCI grade 2 |
Body System & Event | % of Patients Reporting |
| NCI Grades 1-4 | NCI Grades 3 & 4 |
GASTROINTESTINAL | | |
Diarrhea (late)b | 88 | 31 |
7–9 stools/day (grade 3) | — | (16) |
≥10 stools/day (grade 4) | — | (14) |
Nausea | 86 | 17 |
Vomiting | 67 | 12 |
Anorexia | 55 | 6 |
Diarrhea (early)c | 51 | 8 |
Constipation | 30 | 2 |
Flatulence | 12 | 0 |
Stomatitis | 12 | 1 |
Dyspepsia | 10 | 0 |
HEMATOLOGIC | | |
Leukopenia | 63 | 28 |
Anemia | 60 | 7 |
Neutropenia | 54 | 26 |
500 to <1000/mm3 (grade 3) | — | (15) |
<500/mm3 (grade 4) | — | (12) |
BODY AS A WHOLE | | |
Asthenia | 76 | 12 |
Abdominal cramping/pain | 57 | 16 |
Fever | 45 | 1 |
Pain | 24 | 2 |
Headache | 17 | 1 |
Back pain | 14 | 2 |
Chills | 14 | 0 |
Minor infectiond | 14 | 0 |
Edema | 10 | 1 |
Abdominal enlargement | 10 | 0 |
METABOLIC AND NUTRITIONAL | | |
↓ Body weight | 30 | 1 |
Dehydration | 15 | 4 |
↑ Alkaline phosphatase | 13 | 4 |
↑ SGOT | 10 | 1 |
DERMATOLOGIC | | |
Alopecia | 60 | NAe |
Sweating | 16 | 0 |
Rash | 13 | 1 |
RESPIRATORY | | |
Dyspnea | 22 | 4 |
↑ Coughing | 17 | 0 |
Rhinitis | 16 | 0 |
NEUROLOGIC | | |
Insomnia | 19 | 0 |
Dizziness | 15 | 0 |
CARDIOVASCULAR | | |
Vasodilation (flushing) | 11 | 0 |
Once-Every-3-Week Dosage Schedule
A total of 535 patients with metastatic colorectal cancer whose disease had recurred or progressed following prior 5-FU therapy participated in the two phase 3 studies: 316 received irinotecan, 129 received 5-FU, and 90 received best supportive care. Eleven (3.5%) patients treated with irinotecan died within 30 days of treatment. In three cases (1%, 3/316), the deaths were potentially related to irinotecan treatment and were attributed to neutropenic infection, grade 4 diarrhea, and asthenia, respectively. One (0.8%, 1/129) patient treated with 5-FU died within 30 days of treatment; this death was attributed to grade 4 diarrhea.
Hospitalizations due to serious adverse events occurred at least once in 60% (188/316) of patients who received irinotecan, 63% (57/90) who received best supportive care, and 39% (50/129) who received 5-FU-based therapy. Eight percent of patients treated with irinotecan and 7% treated with 5-FU-based therapy discontinued treatment due to adverse events.
Of the 316 patients treated with irinotecan, the most clinically significant adverse events (all grades, 1-4) were diarrhea (84%), alopecia (72%), nausea (70%), vomiting (62%), cholinergic symptoms (47%), and neutropenia (30%). Table 8 lists the grade 3 and 4 adverse events reported in the patients enrolled to all treatment arms of the two studies described in Clinical Studies (14.1).
Table 8: Percent of Patients Experiencing Grade 3 & 4 Adverse Events in Comparative Studies of Once-Every-3-Week Irinotecan Therapya| a Severity of adverse events based on NCI CTC (version 1.0) |
| b BSC = best supportive care |
| c Hepatic includes events such as ascites and jaundice |
| d Cutaneous signs include events such as rash |
| e Respiratory includes events such as dyspnea and cough |
| f Neurologic includes events such as somnolence |
| g Cardiovascular includes events such as dysrhythmias, ischemia, and mechanical cardiac dysfunction |
| h Other includes events such as accidental injury, hepatomegaly, syncope, vertigo, and weight loss |
Adverse Event | Study 1 | Study 2 |
| Irinotecan N=189 | BSCb N=90 | Irinotecan N=127 | 5-FU N=129 |
TOTAL Grade 3/4 Adverse Events | 79 | 67 | 69 | 54 |
GASTROINTESTINAL | | | | |
Diarrhea | 22 | 6 | 22 | 11 |
Vomiting | 14 | 8 | 14 | 5 |
Nausea | 14 | 3 | 11 | 4 |
Abdominal pain | 14 | 16 | 9 | 8 |
Constipation | 10 | 8 | 8 | 6 |
Anorexia | 5 | 7 | 6 | 4 |
Mucositis | 2 | 1 | 2 | 5 |
HEMATOLOGIC | | | | |
Leukopenia/Neutropenia | 22 | 0 | 14 | 2 |
Anemia | 7 | 6 | 6 | 3 |
Hemorrhage | 5 | 3 | 1 | 3 |
Thrombocytopenia | 1 | 0 | 4 | 2 |
Infection | | | | |
without grade 3/4 neutropenia | 8 | 3 | 1 | 4 |
with grade 3/4 neutropenia | 1 | 0 | 2 | 0 |
Fever | | | | |
without grade 3/4 neutropenia | 2 | 1 | 2 | 0 |
with grade 3/4 neutropenia | 2 | 0 | 4 | 2 |
BODY AS A WHOLE | | | | |
Pain | 19 | 22 | 17 | 13 |
Asthenia | 15 | 19 | 13 | 12 |
METABOLIC AND NUTRITIONAL | | | | |
Hepaticc | 9 | 7 | 9 | 6 |
DERMATOLOGIC | | | | |
Hand and foot syndrome | 0 | 0 | 0 | 5 |
Cutaneous signs d | 2 | 0 | 1 | 3 |
RESPIRATORYe | 10 | 8 | 5 | 7 |
NEUROLOGICf | 12 | 13 | 9 | 4 |
CARDIOVASCULARg | 9 | 3 | 4 | 2 |
OTHERh | 32 | 28 | 12 | 14 |
The incidence of akathisia in clinical trials of the weekly dosage schedule was greater (8.5%, 4/47 patients) when prochlorperazine was administered on the same day as Irinotecan hydrochloride than when these drugs were given on separate days (1.3%, 1/80 patients). The 8.5% incidence of akathisia, however, is within the range reported for use of prochlorperazine when given as a premedication for other chemotherapies.
Distribution
Irinotecan exhibits moderate plasma protein binding (30% to 68% bound). SN-38 is highly bound to human plasma proteins (approximately 95% bound). The plasma protein to which irinotecan and SN-38 predominantly binds is albumin.
Metabolism
Irinotecan is subject to extensive metabolic conversion by various enzyme systems, including esterases to form the active metabolite SN-38, and UGT1A1 mediating glucuronidation of SN-38 to form the inactive glucuronide metabolite SN-38G. Irinotecan can also undergo CYP3A4- mediated oxidative metabolism to several inactive oxidation products, one of which can be hydrolyzed by carboxylesterase to release SN-38. In vitro studies indicate that irinotecan, SN-38 and another metabolite aminopentane carboxylic acid (APC), do not inhibit cytochrome P-450 isozymes. UGT1A1 activity is reduced in individuals with genetic polymorphisms that lead to reduced enzyme activity such as the UGT1A1*28 polymorphism. Approximately 10% of the North American population is homozygous for the UGT1A1*28 allele (also referred to as UGT1A1 7/7 genotype). In a prospective study, in which irinotecan was administered as a single-agent (350 mg/m2) on a once-every-3-week schedule, patients with the UGT1A1 7/7 genotype had a higher exposure to SN-38 than patients with the wild-type UGT1A1 allele (UGT1A1 6/6 genotype) [see Warnings and Precautions (5.3) and Dosage and Administration (2.3) ]. SN-38 glucuronide had 1/50 to 1/100 the activity of SN-38 in cytotoxicity assays using two cell lines in vitro.
Excretion
The disposition of irinotecan has not been fully elucidated in humans. The urinary excretion of irinotecan is 11% to 20%; SN-38, <1%; and SN-38 glucuronide, 3%. The cumulative biliary and urinary excretion of irinotecan and its metabolites (SN-38 and SN-38 glucuronide) over a period of 48 hours following administration of irinotecan in two patients ranged from approximately 25% (100 mg/m2) to 50% (300 mg/m2).
Effect of Age
The pharmacokinetics of irinotecan administered using the weekly schedule was evaluated in a study of 183 patients that was prospectively designed to investigate the effect of age on irinotecan toxicity. Results from this trial indicate that there are no differences in the pharmacokinetics of irinotecan, SN-38, and SN-38 glucuronide in patients <65 years of age compared with patients ≥ 65 years of age. In a study of 162 patients that was not prospectively designed to investigate the effect of age, small (less than 18%) but statistically significant differences in dose-normalized irinotecan pharmacokinetic parameters in patients <65 years of age compared to patients ≥65 years of age were observed. Although dose-normalized AUC0-24 for SN-38 in patients ≥ 65 years of age was 11% higher than in patients <65 years of age, this difference was not statistically significant. No change in the starting dose is recommended for geriatric patients receiving the weekly dosage schedule of irinotecan [see Dosage and Administration (2)].
Effect of Gender
The pharmacokinetics of irinotecan do not appear to be influenced by gender.
Effect of Race
The influence of race on the pharmacokinetics of irinotecan has not been evaluated.
Effect of Hepatic Impairment
Irinotecan clearance is diminished in patients with hepatic impairment while exposure to the active metabolite SN-38 is increased relative to that in patients with normal hepatic function. The magnitude of these effects is proportional to the degree of liver impairment as measured by elevations in total bilirubin and transaminase concentrations. However, the tolerability of irinotecan in patients with hepatic dysfunction (bilirubin greater than 2 mg/dl) has not been assessed sufficiently, and no recommendations for dosing can be made [see Dosage and Administration (2), Warnings and Precautions (5.10) and Use in Specific Populations (8.7)].
Effect of Renal Impairment
The influence of renal impairment on the pharmacokinetics of irinotecan has not been evaluated. Therefore, caution should be undertaken in patients with impaired renal function. Irinotecan hydrochloride is not recommended for use in patients on dialysis [see Use in Specific Populations (8.6)].
Drug Interactions
Dexamethasone, a moderate CYP3A4 inducer, does not appear to alter the pharmacokinetics of irinotecan.
In the intent-to-treat analysis of the pooled data across all three studies, 193 of the 304 patients began therapy at the recommended starting dose of 125 mg/m2. Among these 193 patients, 2 complete and 27 partial responses were observed, for an overall response rate of 15.0% (95% Confidence Interval [CI], 10.0% to 20.1%) at this starting dose. A considerably lower response rate was seen with a starting dose of 100 mg/m2. The majority of responses were observed within the first two cycles of therapy, but responses did occur in later cycles of treatment (one response was observed after the eighth cycle). The median response duration for patients beginning therapy at 125 mg/m2 was 5.8 months (range, 2.6 to 15.1 months). Of the 304 patients treated in the three studies, response rates to irinotecan hydrochloride were similar in males and females and among patients older and younger than 65 years. Rates were also similar in patients with cancer of the colon or cancer of the rectum and in patients with single and multiple metastatic sites. The response rate was 18.5% in patients with a performance status of 0 and 8.2% in patients with a performance status of 1 or 2. Patients with a performance status of 3 or 4 have not been studied. Over half of the patients responding to irinotecan hydrochloride had not responded to prior 5-FU. Patients who had received previous irradiation to the pelvis responded to irinotecan hydrochloride at approximately the same rate as those who had not previously received irradiation.
Once-Every-3-Week Dosage Schedule
Single Arm Study: Study 6
Data from an open-label, single-agent, single-arm, multicenter, clinical study involving a total of 132 patients support a once every-3-week dosage schedule of irinotecan in the treatment of patients with metastatic cancer of the colon or rectum that recurred or progressed following treatment with 5-FU. Patients received a starting dose of 350 mg/m2 given by 30-minute intravenous infusion once every 3 weeks. Among the 132 previously treated patients in this trial, the intent-to-treat response rate was 12.1% (95% CI, 7.0% to 18.1%).
Randomized Studies: Studies 7 and 8
Two multicenter, randomized, clinical studies further support the use of irinotecan given by the once-every-3-week dosage schedule in patients with metastatic colorectal cancer whose disease has recurred or progressed following prior 5-FU therapy. In Study 7, second-line irinotecan therapy plus best supportive care was compared with best supportive care alone. In Study 8, second-line irinotecan therapy was compared with infusional 5-FU-based therapy. In both studies, irinotecan was administered intravenously at a starting dose of 350 mg/m2 over 90 minutes once every 3 weeks. The starting dose was 300 mg/m2 for patients who were 70 years and older or who had a performance status of 2. The highest total dose permitted was 700 mg. Dose reductions and/or administration delays were permitted in the event of severe hematologic and/or nonhematologic toxicities while on treatment. Best supportive care was provided to patients in both arms of Study 7 and included antibiotics, analgesics, corticosteroids, transfusions, psychotherapy, or any other symptomatic therapy as clinically indicated. In both studies, concomitant medications such as antiemetics, atropine, and loperamide were given to patients for prophylaxis and/or management of symptoms from treatment. If late diarrhea persisted for greater than 24 hours despite loperamide, a 7-day course of fluoroquinolone antibiotic prophylaxis was given. Patients in the control arm of the Study 8 received one of the following 5-FU regimens: (1) LV, 200 mg/m2 IV over 2 hours; followed by 5-FU, 400 mg/m2 IV bolus; followed by 5-FU, 600 mg/m2 continuous IV infusion over 22 hours on days 1 and 2 every 2 weeks; (2) 5-FU, 250 to 300 mg/m2/day protracted continuous IV infusion until toxicity; (3) 5-FU, 2.6 to 3 g/m2 IV over 24 hours every week for 6 weeks with or without LV, 20 to 500 mg/m2/day every week IV for 6 weeks with 2-week rest between cycles. Patients were to be followed every 3 to 6 weeks for 1 year.
A total of 535 patients were randomized in the two studies at 94 centers. The primary endpoint in both studies was survival. The studies demonstrated a significant overall survival advantage for irinotecan compared with best supportive care (p=0.0001) and infusional 5-FU-based therapy (p=0.035) as shown in Figures 3 and 4. In Study 7, median survival for patients treated with irinotecan was 9.2 months compared with 6.5 months for patients receiving best supportive care. In Study 8, median survival for patients treated with irinotecan was 10.8 months compared with 8.5 months for patients receiving infusional 5-FU-based therapy. Multiple regression analyses determined that patients' baseline characteristics also had a significant effect on survival. When adjusted for performance status and other baseline prognostic factors, survival among patients treated with irinotecan remained significantly longer than in the control populations (p=0.001 for Study 7 and p=0.017 for Study 8). Measurements of pain, performance status, and weight loss were collected prospectively in the two studies; however, the plan for the analysis of these data was defined retrospectively. When comparing irinotecan with best supportive care in Study 7, this analysis showed a statistically significant advantage for irinotecan, with longer time to development of pain (6.9 months versus 2.0 months), time to performance status deterioration (5.7 months versus 3.3 months), and time to > 5% weight loss (6.4 months versus 4.2 months). Additionally, 33.3% (33/99) of patients with a baseline performance status of 1 or 2 showed an improvement in performance status when treated with irinotecan versus 11.3% (7/62) of patients receiving best supportive care (p=0.002). Because of the inclusion of patients with non-measurable disease, intent-to-treat response rates could not be assessed.
Table 12. Once-Every-3-Week Dosage Schedule: Study Results| a BSC = best supportive care |
| b Relative dose intensity for irinotecan based on planned dose intensity of 116.7 and 100 mg/m2/wk corresponding with 350 and 300 mg/m2 starting doses, respectively. |
| Study 7 | Study 8 |
| Irinotecan | BSCa | Irinotecan | 5-FU |
Number of patients | 189 | 90 | 127 | 129 |
Demographics and treatment administration |
Female/Male (%) | 32/68 | 42/58 | 43/57 | 35/65 |
Median age in years (range) | 59 (22–75) | 62 (34–75) | 58 (30–75) | 58 (25–75) |
Performance status (%) | | | | |
0 | 47 | 31 | 58 | 54 |
1 | 39 | 46 | 35 | 43 |
2 | 14 | 23 | 8 | 3 |
Primary tumor (%) | | | | |
Colon | 55 | 52 | 57 | 62 |
Rectum | 45 | 48 | 43 | 38 |
Prior 5-FU therapy (%) | | | | |
For metastatic disease | 70 | 63 | 58 | 68 |
As adjuvant treatment | 30 | 37 | 42 | 32 |
Prior irradiation (%) | 26 | 27 | 18 | 20 |
Duration of study treatment (median, months) (Log-rank test) | 4.1 | -- | 4.2 (p=0.02) | 2.8 |
Relative dose intensity (median %) b | 94 | -- | 95 | 81–99 |
Survival |
Survival (median, months) (Log-rank test) | 9.2 (p=0.0001) | 6.5 | 10.8 (p=0.035) | 8.5 |
In the two randomized studies, the EORTC QLQ-C30 instrument was utilized. At the start of each cycle of therapy, patients completed a questionnaire consisting of 30 questions, such as "Did pain interfere with daily activities?" (1 = Not at All, to 4 = Very Much) and "Do you have any trouble taking a long walk?" (Yes or No). The answers from the 30 questions were converted into 15 subscales, that were scored from 0 to 100, and the global health status subscale that was derived from two questions about the patient's sense of general well being in the past week. The results as summarized in Table 13 are based on patients' worst post-baseline scores. In Study 7, a multivariate analysis and univariate analyses of the individual subscales were performed and corrected for multivariate testing. Patients receiving irinotecan reported significantly better results for the global health status, on two of five functional subscales, and on four of nine symptom subscales. As expected, patients receiving irinotecan noted significantly more diarrhea than those receiving best supportive care. In Study 8, the multivariate analysis on all 15 subscales did not indicate a statistically significant difference between irinotecan and infusional 5-FU.
Table 13. EORTC QLQ-C30: Mean Worst Post-Baseline Scorea| a For the five functional subscales and global health status subscale, higher scores imply better functioning, whereas, on the nine symptom subscales, higher scores imply more severe symptoms. The subscale scores of each patient were collected at each visit until the patient dropped out of the study. |
QLD-C30 Subscale | Study 7 | Study 8 |
| Irinotecan | BSC | p-value | Irinotecan | 5-FU | p-value |
Global health status | 47 | 37 | 0.03 | 53 | 52 | 0.9 |
Functional scales | | | | | | |
Cognitive | 77 | 68 | 0.07 | 79 | 83 | 0.9 |
Emotional | 68 | 64 | 0.4 | 64 | 68 | 0.9 |
Social | 58 | 47 | 0.06 | 65 | 67 | 0.9 |
Physical | 60 | 40 | 0.0003 | 66 | 66 | 0.9 |
Role | 53 | 35 | 0.02 | 54 | 57 | 0.9 |
| Symptom Scales | | | | | | |
Fatigue | 51 | 63 | 0.03 | 47 | 46 | 0.9 |
Appetite loss | 37 | 57 | 0.0007 | 35 | 38 | 0.9 |
Pain assessment | 41 | 56 | 0.009 | 38 | 34 | 0.9 |
Insomnia | 39 | 47 | 0.3 | 39 | 33 | 0.9 |
Constipation | 28 | 41 | 0.03 | 25 | 19 | 0.9 |
Dyspnea | 31 | 40 | 0.2 | 25 | 24 | 0.9 |
Nausea/Vomiting | 27 | 29 | 0.5 | 25 | 16 | 0.09 |
Financial impact | 22 | 26 | 0.5 | 24 | 15 | 0.3 |
Diarrhea | 32 | 19 | 0.01 | 32 | 22 | 0.2 |