Radiation Oncology: A Question-Based Review

Transplant/Total Body Irradiation

Bronwyn R. Stall and Deborah E. Citrin

image Background

Define hematopoietic stem cell transplantation (HSCT).

HSCT is a procedure to infuse hematopoietic cells in order to restore normal hematopoiesis and/or to treat cancer.

What is the difference between allogeneic and autologous?

1.     Allogeneic: stem cells from another person

2.     Autologous: stem cells from the affected pt

What is a syngeneic transplant?

A syngeneic transplant uses an identical twin as the donor.

Name 3 sources of stem cells.

Umbilical cord blood, BM, and peripheral blood are 3 sources of stem cells.

What source of stem cells is most often used for transplant?

Most stem cells for transplant are obtained from peripheral blood.

What is a mini-transplant?

A mini-transplant, also known as nonmyeloablative or reduced-intensity transplant, employs less toxic preparatory regimens, targeted to host T cells to facilitate engraftment.

Name 4 malignancies routinely treated with autologous transplant.

Malignancies routinely treated with autologous transplant:

1.     Recurrent Hodgkin Dz

2.     Multiple myeloma

3.     Chemosensitive aggressive non-Hodgkin lymphoma

4.     Refractory testicular cancer

Which type of transplant is associated with a graft vs. tumor effect?

Allogeneic transplants may have graft vs. tumor effect.

Why is there decreased mortality with an autologous transplant in comparison to an allogeneic transplant?

The mortality rate with autologous transplant is lower due to the absence of graft-versus-host disease (GVHD).

What limits the use of allogeneic transplant?

The use of allogeneic transplant is limited by availability of donors.

What is the most important risk associated with autologous transplant?

The major risk of autologous transplant is relapse.

Allogeneic transplant is used most commonly in what type of malignancy?

Allogeneic transplant is most commonly used to treat acute leukemias.

What is a conditioning regimen?

A conditioning regimen is a Tx used to prepare pts for infusion of hematopoietic cells, which may be chemo alone or CRT.

image Workup/Staging

What evaluations should be done prior to total body irradiation (TBI)?

TBI evaluation: complete H&P, PFTs, LFTs, serum Cr, and fertility counseling to include potential cryopreservation. A dental evaluation should also be done.

image Treatment/Prognosis

What randomized data supports the use of fractionated rather than single-Tx TBI?

French (Institut Gustave Roussy) study of single vs. hyperfractionated TBI randomized 160 pts with various hematologic malignancies to 10 Gy single dose or 14.85 Gy/11 fx. OS at 8 yrs was nonsignificantly higher in the hyperfractionated arm (45% vs. 38%) as well as CSS (77% vs. 63.5%). The rate of interstitial pneumonitis was similar between the 2 arms (14% and 19%); however, the rate of liver veno-occlusive Dz was significantly higher with a single fx (4% vs. 14%). (Girinsky T et al., J Clin Oncol 2000)

What is the main site of recurrence after transplant for lymphoma?

Following transplant for lymphoma, local tumor recurrence is the main cause of failure.

In pts receiving BMT for refractory lymphoma, is it safe to give local RT prior to transplant?

Yes. In the Johns Hopkins Hospital dose-escalation study of locoregional RT prior to Cytoxan/TBI for pts with refractory lymphoma, 21 pts with chemorefractory Dz rcv RT to current or previous sites of Dz to total doses from 1,000–2,000 cGy (all in 5 fx at an LDR of 10–20 cGy/minute) → TBI to 1,200 cGy in 4 daily fx. 3 of 6 pts at the 2,000-cGy level had acute grade 3 toxicity. It was concluded that LDR locoregional RT has acceptable toxicity up to 1,500 cGy/5 fx → Cytoxan/TBI. (Song D et al., IJROBP 2003)

What 2 pt positions are used for TBI?

TBI pt Tx positions include supine, lateral recumbent or standing.

Why are beam spoilers used for TBI?

Beam spoilers are used to ensure adequate dose buildup in the skin; a screen of tissue-equivalent material is positioned between the pt and the beam.

What variation in homogeneity is considered acceptable for TBI?

Homogeneity +/ − 5% is considered ideal for TBI.

Why is the dose rate lowered in TBI?

A lower dose rate is used in TBI to decrease the incidence of interstitial pneumonitis.

What compensators are often used in TBI?

H&N compensators are often used in TBI to improve homogeneity.

What organs are most frequently blocked in TBI?

The lungs are most frequently blocked in TBI.

What areas may be boosted in TBI?

When using TBI for lymphomas, the site of residual Dz may be boosted to decrease the chance of LR.

image Toxicity

What is the major complication of allogeneic transplants?

The major complication of allogeneic transplants is GVHD.

What is acute GVHD?

Acute GVHD is the syndrome of hepatitis, enteritis, and dermatitis occurring secondary to allogeneic transplant.

What predicts the risk of GVHD and graft rejection?

GVHD and graft rejection risk increase with human leukocyte antigen disparity.

What is chronic GVHD?

The chronic form of GVHD occurs >3 mos after transplant and can affect many organs such as the GI tract, skin, liver, lungs, and eyes.

Name acute toxicities from TBI.

Most common acute toxicities from TBI:

1.     N/v

2.     Diarrhea

3.     Xerostomia

4.     Parotitis

5.     Mucositis

6.     Fatigue

What is the most common acute side effect?

The most common acute side effects from TBI are n/v.

Name 9 chronic toxicities from TBI.

Chronic toxicities from TBI:

1.     Cataracts

2.     Change in cognitive function

3.     Endocrinopathies

4.     Interstitial penumonitis

5.     Hepatic dysfunction

6.     Renal dysfunction

7.     Growth retardation

8.     Infertility

9.     2nd malignancies