Inclusion Criteria:

- Voluntary written informed consent before performance of any study-related procedure
not part of normal medical care, with the understanding that consent may be withdrawn
by the subject at any time without prejudice to future medical care.

- Female subject is either post-menopausal or surgically sterilized or willing to use
an acceptable method of birth control (ie, a hormonal contraceptive, intra-uterine
device, diaphragm with spermicide, condom with spermicide, or abstinence) for the
duration of the study.

- Male subject agrees to use an acceptable method for contraception for the duration of
the study.

- Histologic Documentation: Histologically confirmed Primary Mediastinal Large B-cell
Lymphoma with confirmatory immunoperoxidase stains including TRAF-1, and nuclear
c-rel. All cases must be reviewed at Brigham and Women's Hospital.

- Previously untreated patients with the exception of limited radiotherapy or steroids
for SVC syndrome

- Age > 18 years of age

- Measurable Disease defined as lesions that can be accurately measured in at least one
dimension (longest diameter to be recorded) as ≥20 mm with conventional techniques or
as ≥10 mm with spiral CT scan.

Exclusion Criteria:

- Patient has a platelet count of < 100,000/uL within 14 days before enrollment.

- Patient has an absolute neutrophil count of < 1500/uL within 14 days before
enrollment.

- Patient has a calculated or measured creatinine clearance of <30 mL/minute within 14
days before enrollment.

- Patient has ³Grade 2 peripheral neuropathy within 14 days before enrollment.

- Myocardial infarction within 6 months prior to enrollment or has New York Hospital
Association (NYHA) Class III or IV heart failure (see section 8.4), uncontrolled
angina, severe uncontrolled ventricular arrhythmias, or electrocardiographic evidence
of acute ischemia or active conduction system abnormalities. Prior to study entry,
any ECG abnormality at Screening has to be documented by the investigator as not
medically relevant.

- Patient has hypersensitivity to bortezomib, boron or mannitol.

- Female subject is pregnant or breast-feeding. Confirmation that the subject is not
pregnant must be established by a negative serum b-human chorionic gonadotropin
(b-hCG) pregnancy test result obtained during screening. Pregnancy testing is not
required for post-menopausal or surgically sterilized women.

- Patient has received other investigational drugs with 14 days before enrollment

- Serious medical or psychiatric illness likely to interfere with participation in this
clinical study.

- Patient has a cardiac ejection fraction < 50% by echocardiogram or MUGA scan