Mechanism of Action
Cellular damage caused by photodynamic therapy (PDT) with PHOTOFRIN is a consequence
of the propagation of radical reactions. Radical initiation may occur after
porfimer sodium absorbs light to form a porphyrin excited state. Spin transfer
from porfimer sodium to molecular oxygen may then generate singlet oxygen. Subsequent
radical reactions can form superoxide and hydroxyl radicals. Tumor death also
occurs through ischemic necrosis secondary to vascular occlusion that appears
to be partly mediated by thromboxane A2 release. As opposed to a thermal effect,
the laser treatment with porfimer sodium induces a photochemical effect. The
necrotic reaction and associated inflammatory responses may evolve over several
days.
Pharmacodynamics
The cytotoxic and antitumor actions of PHOTOFRIN are light and oxygen dependent.
PDT with PHOTOFRIN is a two-stage process. The first stage is the intravenous
injection of PHOTOFRIN. Clearance from a variety of tissues occurs over 40-72
hours, but tumors, skin, and organs of the reticuloendothelial system (including
liver and spleen) retain PHOTOFRIN for a longer period. Illumination with 630
nm wavelength laser light constitutes the second stage of therapy. Tumor selectivity
in treatment occurs through a combination of selective retention of PHOTOFRIN
and selective delivery of light.
Pharmacokinetics
Following a 2 mg/kg dose of PHOTOFRIN to 4 male cancer patients, the average
peak plasma concentration was 15 ± 3 mcg/mL, the elimination half-life
was 250 ± 285 hours, the steady-state volume of distribution was 0.49 ±
0.28 L/kg, and the total plasma clearance was 0.051 ± 0.035 mL/min/kg.
The mean plasma concentration at 48 hours was 2.6 ± 0.4 mcg/mL. The influence
of impaired hepatic function on PHOTOFRIN disposition has not been evaluated.
PHOTOFRIN was approximately 90% protein bound in human serum, studied in vitro.
The binding was independent of concentration over the concentration range of
20100 mcg/mL.
The pharmacokinetics of PHOTOFRIN was also studied in 24 healthy subjects (12
men and 12 women) who received a single dose of 2 mg/kg PHOTOFRIN given via
the intravenous route. The serum decay was bi-exponential, with a slow distribution
phase and a very long elimination phase. The elimination half-life was 415 ±
104 hours (17 ± 4.3 days). The Cmax was determined to be 40 ±
11.6 mcg/mL and AUCinf was 2400 ± 552 mcg•hour/mL. Women had a lower
Cmax and a higher AUC. The clinical significance of these differences is unknown.
The Tmax was approximately 1.5 hours in women and 0.17 hours in men. At the
time of intended photoactivation 40-50 hours after injection, the pharmacokinetic
profiles of PHOTOFRIN in men and women were similar.
Clinical Studies
Clinical studies of photodynamic therapy (PDT) with PHOTOFRIN were conducted
in patients with obstructing esophageal and endobronchial non-small-cell lung
cancers, in patients with earlystage radiologically occult endobronchial cancer,
and in patients with high-grade dysplasia (HGD) in Barrett's esophagus (BE).
In all clinical studies, the method of PDT administration was essentially identical.
A course of therapy consisted of one injection of PHOTOFRIN (2 mg/kg administered
as a slow intravenous injection over 35 minutes) followed by up to two non-thermal
applications of 630 nm laser light. Light doses of 300 J/cm of diffuser length
were used in esophageal cancer. Light doses of 200 J/cm of diffuser length were
used in endobronchial cancer for both palliation of obstructing cancer and treatment
of superficial lesions. For the ablation of HGD in BE, the light dose administered
was 130 J/cm of diffuser length using a centering balloon for the first application
and 50 J/cm of diffuser length without a centering balloon for the second application
[see DOSAGE AND ADMINISTRATION]. In all cases, the first application
of light occurred 4050 hours after PHOTOFRIN injection.
For treatment of esophageal cancer debridement of residua via endoscopy is
optional 96120 hours after injection, after which any residual tumor could
be retreated with a second laser light application at the same light dose used
for the initial treatment. Additional courses of PDT with PHOTOFRIN were allowed
after one month, up to a maximum of three courses.
For treatment of endobronchial cancer, debridement of residua was performed
via bronchoscopy 96120 hours after injection, after which any residual tumor
could be retreated with a second laser light application at the same light dose
used for the initial treatment. Additional courses of PDT with PHOTOFRIN were
allowed after one month, up to a maximum of three courses.
For ablation of HGD in BE, a second laser light application of 50 J/cm of diffuser
length without a centering balloon could be given 96-120 hours after the PHOTOFRIN
injection for untreated areas (“skip” areas). Additional courses
of PDT with PHOTOFRIN were allowed after three months, up to a maximum of three
courses.
Esophageal Cancer
PDT with PHOTOFRIN was utilized in a multicenter, singlearm study in 17 patients
with completely obstructing esophageal carcinoma. Assessments were made at 1
week and 1 month after the last treatment procedure. As shown in Table 10,
after a single course of therapy, 94% of patients obtained an objective tumor
response and 76% of patients experienced some palliation of their dysphagia.
On average, before treatment these patients had difficulty swallowing liquids,
even saliva. After one course of therapy, there was a statistically significant
improvement in mean dysphagia grade (1.5 units, p < 0.05) and 13 of 17 patients
could swallow liquids without difficulty 1 week and/or 1 month after treatment.
Based on all courses, three patients achieved a complete tumor response (CR).
In two of these patients, the CR was documented only at Week 1 as they had no
further assessments. The third patient achieved a CR after a second course of
therapy, which was supported by negative histopathology and maintained for the
entire follow-up of 6 months.
Of the 17 treated patients, 11 (65%) received clinically important benefit
from PDT. Clinically important benefit was defined hierarchically as a complete
tumor response (3 patients), achievement of normal swallowing (2 patients went
from Grade 5 dysphagia to Grade 1), or achievement of a marked improvement of
two or more grades of dysphagia with minimal adverse reactions (6 patients).
The median duration of benefit in these patients was 69 days. Duration of benefit
was calculated only for the period with documented evidence of improvement.
All of these patients were still in response at their last assessment and, therefore,
the estimate of 69 days is conservative. The median survival for these 11 patients
was 115 days.
Endobronchial Cancer
Two randomized multicenter Phase III studies were conducted to compare the
safety and efficacy of PHOTOFRIN PDT versus Nd:YAG laser therapy for reduction
of obstruction and palliation of symptomatic patients with partially or completely
obstructing endobronchial non-small-cell lung cancer. Assessments were made
at 1 week and at monthly intervals after treatment. Table 11 shows the
results from all randomized patients in the two studies combined. Objective
tumor response rates (CR + PR), which demonstrate reduction of obstruction,
were 59% for PDT and 58% for Nd:YAG at Week 1. The response rate at 1 month
or later was 60% for PDT and 41% for Nd:YAG.
Patient symptoms were evaluated using a 5- or 6-grade pulmonary symptom severity
rating scale for dyspnoea, cough, and hemoptysis. Patients with moderate to
severe symptoms are those most in need of palliation. Improvements of 2 or more
grades are considered to be clinically significant. Table 12 shows the
percentages of patients with moderate to severe symptoms at baseline who demonstrated
a 2grade improvement at any time during the interval evaluated.
TABLE 10. Course 1 Efficacy Results in Patients with Completely
Obstructing Esophageal Cancer
| EFFICACY PARAMETER |
PDT
N=17 |
| OBJECTIVE TUMOR RESPONSEa (% of patients) |
| Week 1 |
82% |
| Month 1 |
35%b |
| Any assessment c |
94% |
| IMPROVEMENTd IN DYSPHAGIA (% of patients) |
| Week 1 |
71% |
| Month 1 |
47% |
| Any assessment c |
76% |
| MEAN DYSPHAGIA GRADEe AT BASELINE (units) |
4.6 |
| MEAN IMPROVEMENTe IN DYSPHAGIA
GRADE (units) |
| Week 1 |
1.4 |
| Month 1 |
1.5 |
| MEAN NUMBER OF LASER APPLICATIONS (units) |
1.4 |
a CR+PR, CR = complete response
(absence of endoscopically visible tumor), PR = partial response (appearance
of a visible lumen).
b Eight of the 17 treated patients did not have assessments
at Month 1.
c Week 1 or Month 1.
d Patients with at least a one-grade improvement in dysphagia
grade.
e Dysphagia Scale: Grade 1 = normal swallowing; Grade 2 = difficulty
swallowing some hard solids, can swallow semisolids; Grade 3 = unable
to swallow any solids, can swallow liquids; Grade 4 = difficulty swallowing
liquids; Grade 5 = unable to swallow saliva. |
TABLE 11. Efficacy Results from Studies in Late-stage Obstructing
Endobronchial Cancer All Randomized Patientsa
| EFFICACY PARAMETER |
PDT
N=102
% Patients |
Nd:YAG
N=109
% Patients |
| OBJECTIVE TUMOR RESPONSEb |
| Week 1 |
59% |
58% |
| Month 1 or later |
60% |
41%a |
| ATELECTASIS IMPROVEMENTc |
n=60 |
N=71 |
| Week 1 |
35% |
18% |
| Month 1 or later |
35% |
20% |
a Statistical comparisons were
precluded by the amount of missing data at Month 1 or later (e.g., for
tumor response, PDT 28% missing, Nd:YAG 38%).
b CR+PR where CR = complete response (absence of bronchoscopically
visible tumor) and PR = partial response (increase of ≥ 50% in the smallest
luminal diameter; or any appearance of a lumen for completely obstructing
tumors).
c In patients with atelectasis at baseline. |
TABLE 12. Efficacy Results from Studies in Late-stage Obstructing
Endobronchial Cancer Clinically Significant Improvements in Patients with
Moderate to Severe Symptoms at Baselinea
CLINICALLY SIGNIFICANT
SYMPTOM IMPROVEMENTb |
PDT
N=102
% Patients |
Nd:YAG
N=109
% Patients |
| ANY SYMPTOM |
n=89 |
n=89 |
| Week 1 |
25% |
29% |
| Month 1 or later |
40% |
27%a |
| DYSPNOEA |
n=60 |
n=68 |
| Week 1 |
15% |
18% |
| Month 1 or later |
23% |
13% |
| COUGH |
n=63 |
n=65 |
| Week 1 |
6% |
9% |
| Month 1 or later |
24% |
8% |
| HEMOPTYSIS |
n=24 |
n=31 |
| Week 1 |
58% |
29% |
| Month 1 or later |
79% |
35% |
a Statistical comparisons were
precluded by the amount of missing data at Month 1 or later.
b Dyspnoea was graded on a 6-point severity rating scale; cough
and hemoptysis on a 5-point scale. Clinically significant improvement
was defined as a change of at least two grades from baseline. |
In a separate retrospective analysis, patients were individually evaluated
to identify those patients whose benefit to risk ratio was most favorable, i.e.,
those who obtained clinically important benefit with minimal adverse reactions.
Clinically important benefit was defined as one of the following:
A substantial improvement in pulmonary symptoms at Month 1 or later (dyspnoea
≥ 2 grades, hemoptysis ≥ 3 grades, cough ≥ 3 grades or increase in FEV1
> 40%);
A moderate improvement in symptoms at Month 2 or later (dyspnoea 1 grade, cough
2 grades, hemoptysis 2 grades or increase in FEV1 ≥ 20%); or
A durable objective tumor response (CR or PR maintained to Month 2 or longer).
Thirty-six (36) of the 99 PDT-treated patients (36%) and 23 of the 99 Nd:YAG-treated
patients (23%) received clinically important benefit with only minimal or moderate
toxicities of short duration. Thirty-four (34) of 99 PDT-treated patients demonstrated
improvements in 2 or more efficacy endpoints (dyspnoea, cough, hemoptysis, sputum,
atelectasis, pulmonary function tests of FEV1 or FVC, Karnofsky Performance
Score or tumor response) and 29 patients had improvements in 3 or more.
The median duration of documented benefit in the 36 patients was 63 days. In
these patients with late-stage obstructing lung cancer, median survival was
174 days in PDT-treated patients and 161 days in Nd:YAG-treated patients.
The efficacy of PHOTOFRIN PDT was also evaluated in the treatment of microinvasive
endobronchial tumors in 62 inoperable patients in three noncomparative studies.
Microinvasive lung cancer is defined histologically as disease, which invades
beyond the basement membrane but not through or into the cartilage. For 11 of
the 62 patients, it was clearly documented that surgery and radiotherapy were
not indicated. These 11 patients were all inoperable for medical or technical
reasons. Radiotherapy was not indicated due to prior highdose radiotherapy (7
patients), poor pulmonary function (2 patients), multifocal multilobar disease
(1 patient), and poor medical condition (1 patient). As shown in Table 13,
the complete tumor response rate, biopsy-proven at least 3 months after treatment,
was 50%, median time to tumor recurrence was more than 2.7 years, median survival
was 2.9 years and disease-specific survival was 4.1 years.
TABLE 13. Overall Efficacy Results in Patients with Superficial
Endobronchial Tumors
| EFFICACY PARAMETER |
PDT |
| n=11 |
n=62 |
| COMPLETE TUMOR RESPONSE, BIOPSY PROVEN AT 3 MONTHS |
| Number of Patients (%) |
3 (27) |
31 (50)a |
| TIME TO TUMOR RECURRENCE IN PATIENTS WITH COMPLETE RESPONSE |
| Number of Patients (%) with Recurrences |
1 (33) |
11 (35) |
| Median Time to Tumor Recurrence |
|
>2.7 years |
| [95% Confidence Interval] |
|
[1.6, b] |
| SURVIVAL |
| Number of Patients (%) who Died of Any |
4 (36) |
32 (52) |
| Cause |
|
|
| Median Survival |
|
2.9 years |
| [95% Confidence Interval] |
|
[2.1, 5.7] |
| DISEASE-SPECIFIC SURVIVAL |
| Number of Patients (%) who Died of Lung |
3 (27) |
22 (35) |
| Cancer |
|
|
| Median Disease-Specific Survival |
|
4.1 years |
| [95% Confidence Interval] |
|
[2.5, b] |
a Not included are an additional
18 patients (6 patients not eligible for surgery or radiotherapy) who
had complete tumor responses which were documented earlier than 3 months
after treatment.
b The upper limit of the confidence interval could not be estimated
due to an insufficient number of patients whose tumors recurred (Time
to Tumor Recurrence) or who died (Survival). |
High-Grade Dysplasia in Barrett's Esophagus
The safety and efficacy of PDT with PHOTOFRIN in ablation of HGD in patients
with BE was assessed in one controlled randomized clinical study and two supportive
studies.
Controlled Randomized Study
A multicenter, pathology blinded, randomized, controlled study was conducted
in North America and Europe to assess the efficacy of PDT with PHOTOFRIN for
Injection plus omeprazole (PHOTOFRIN PDT + OM) in producing complete ablation
of HGD in patients with BE compared to control patients receiving omeprazole
alone (OM Only). A total of 485 patients with the diagnosis of HGD were screened
for the study; 208 (43%) were randomized to treatment, 237 (49%) were excluded
because the diagnosis of HGD was not confirmed and 40 (8%) did not meet other
screening criteria or declined to participate in the study. The high patient
exclusion rate re-enforces the recommendation by the American College of Gastroenterology
that the diagnosis of HGD in BE should be confirmed by an expert GI pathologist.
Patients were centrally randomized in a 2:1 proportion to receive PHOTOFRIN
PDT + OM (138 patients) or OM Only (70 patients). All patients underwent rigorous
systematic quarterly endoscopic biopsy surveillance. Four-quadrant jumbo biopsies
at every 2 cm of the entire Barrett's mucosa were obtained at each follow-up
visit (every three months or six months if four consecutive quarterly follow-up
endoscopic biopsy results were negative for HGD). All histological assessments
were carried out at a central pathology laboratory and read by pathologists
blinded to the treatment administered.
A total of 208 patients who had biopsy-proven HGD in BE were enrolled in the
initial 2-year phase of the study. Of those, 199 patients were considered evaluable:
130 of 138 (94%) patients randomized to the PHOTOFRIN PDT + OM group and 69
of 70 (99%) randomized to the OM Only group had no esophageal invasive cancer,
suspicion of esophageal invasive cancer, lymph node involvement, or metastases,
and had received at least one PHOTOFRIN PDT course or one week of OM treatment,
respectively. A disproportionate percentage of patients were discontinued from
the OM Only group during the initial 2-year phase leaving 81 (59%) patients
in the PHOTOFRIN PDT + OM group and 21 (30%) patients in the OM Only group at
the end of the 2-year phase. Consequently, a total of 102 patients who completed
the initial 2-year phase were eligible for continuation into the long-term phase
until completion of 5 years; of those, 48 (59%) patients from the PHOTOFRIN
PDT + OM group and 13 (62%) patients from the OM Only group consented to pursue
the long-term phase until completion of 5 years. The mean age was 66 years (38
to 89 years) in the PHOTOFRIN PDT + OM group, and 67 (36 to 88 years) in the
OM Only group. The patients in both treatment groups were predominantly male
(85%), Caucasian (99%), and former smokers (64%). These characteristics are
typical of patients with HGD in BE. Patients randomized to the PHOTOFRIN PDT
+ OM treatment received up to three courses of treatment separated by at least
90 days. Each course consisted of intravenous administration of 2.0 mg/kg of
PHOTOFRIN followed 40-50 hours later by a 630 nm laser light dose of 130 J/cm
of diffuser length delivered using a centering balloon. A second laser light
dose of 50 J/cm of diffuser length could be administered without a centering
balloon 96-120 hours after the injection of PHOTOFRIN for treatment of “skip”
areas. Since centering balloons are up to 7 cm in length, patients with more
extensive HGD were treated with two or three courses. Both the PHOTOFRIN PDT
treatment group and the control group received 20 mg of omeprazole BID to decrease
reflux esophagitis. The mean duration of the follow-up period was 34 months
(0-67 months) for the PHOTOFRIN PDT + OM group and 25 months (0-65 months) for
the OM Only group.
The primary efficacy endpoint was the Complete Response rate (CR3 or better)
at any one of the endoscopic assessment time points. The CR3 or better response
was defined as the complete ablation of HGD and referred to as a composite of
the following three response levels.
- CR1 Complete replacement of all Barrett's metaplasia and dysplasia with
normal squamous cell epithelium;
- CR2 Ablation of all histological grades of dysplasia, including patients
with indefinite grade of dysplasia, but some areas of Barrett's epithelium
still remain; and
- CR3 Ablation of all areas of HGD but with some areas of low-grade dysplasia
with or without areas which are indefinite for dysplasia, or areas of Barrett's
metaplastic epithelium.
Additional efficacy endpoints included:
- Quality of Complete Response, which consisted of CR1 and CR2 or better.
- Duration of CR;
- Time to Progression to Cancer.
Table 14 presents the overall clinical response for both treatment groups
in the intent-to-treat (ITT) population whose response was CR3 or better at
any one of the evaluation time points. Overall, PHOTOFRIN PDT + OM was effective
in eliminating HGD in patients with BE. The proportion of responders was significantly
higher in the PHOTOFRIN PDT + OM group than in the OM Only group (77% vs. 39%,
respectively; p < 0.0001).
The quality of response in the PHOTOFRIN PDT + OM group was significantly better
than that measured in the OM Only group at all response levels (p < 0.0001).
Seventy-two (52%) patients in the PHOTOFRIN PDT + OM group achieved a CR1 response
as compared to only five (7%) patients in the OM Only group. Eighty-one (59%)
patients in the PHOTOFRIN PDT + OM group achieved a CR2 or better response as
compared to ten (14%) patients in the OM Only group.
TABLE 14. Complete Response Rates After a Minimum Follow-
Up of 24 Months in the ITT Population
| |
Treatment Groups |
| Responders |
|
PHOTOFRIN
PDT + OM |
OM Only |
p-valuea |
| Numbers of patients |
N |
138 |
70 |
|
| CR3 or betterb |
n |
106 |
27 |
|
| |
Proportion |
|
|
|
| (%) |
0.768 (76.8) |
0.386 (38.6) |
< 0.0001 |
| 95% CI |
(0.689, 0.836) |
(0.272, 0.510) |
|
a Fisher's Exact test.
b CR3 or better: Ablation of all areas of HGD.
NOTE: Six patients in the PHOTOFRIN PDT + OM group and three patients
in the OM Only group without post-baseline biopsy data are considered
as non-responders. |
At the end of the long-term phase, the median response duration was 44.6 months
(95% CI: 15.0-not reached, months) in the PHOTOFRIN PDT + OM group compared
to 3.2 months (95% CI: 3.03.4, months) in the OM Only group.
At the end of the initial 2 year phase, the time to progression to cancer was
significantly longer in the PHOTOFRIN PDT + OM group compared to the OM Only
group (HR=0.36 (95% CI: 0.19-0.69), a hazard ratio less than 1 favors the PHOTOFRIN
PDT + OM group). The proportion of patients' progression to cancer was lower
in the PHOTOFRIN PDT + OM group than in the OM Only group: 13% (18 of 138 patients)
vs. 28% (20 of 70 patients).
Complete response was influenced by the following factors: treatment with PHOTOFRIN
PDT + OM (vs. OM Only), single focus of HGD (vs. multiple foci), and prior omeprazole
intake of at least 3 months (yes vs. no). Complete response was not influenced
by the duration of HGD, length of BE, nodular conditions, gender, age, smoking
history, and study center's size.
Supportive Studies
Two uncontrolled, supportive studies were conducted that were physician-sponsored,
single center Phase II trials. Both studies included patients that had low-grade
dysplasia (LGD), HGD and early adenocarcinoma. All HGD in BE patients were treated
with PHOTOFRIN PDT and omeprazole.
The first study enrolled 99 patients (44 with HGD); the purpose of this study
was to determine the required light dose to produce effective results. The second
study enrolled 86 patients (42 with HGD), who were randomized to receive either
PHOTOFRIN PDT with prednisone or PHOTOFRIN PDT without prednisone to determine
whether steroid treatment would reduce the incidence and severity of esophageal
strictures.
A CR3 or better response was demonstrated in 93% of 44 patients with HGD in
the first study and in 95% of 42 patients with HGD in the second study after
a minimum follow-up of 12 months. A CR2 or better response was achieved in 82%
of patients in the first study and in 91% of patients in the second study. A
CR1 response occurred in 57% of patients in the first study and in 60% of the
second study. Progression to cancer during the above follow-up period occurred
in 18% of patients in the first study and in 7% of patients in the second study.
No reduction in the incidence or severity of esophageal strictures was found
in the prednisone group in the second study.
Last updated on RxList: 12/5/2008