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Prone breast radiotherapy to optimally spare heart and lung
Significant strides continue to be made in the diagnosis
and treatment of breast cancer. Although access to
mammography has broadened, and the incidence of
estrogen-sensitive tumors has declined, breast cancer
remains the most commonly diagnosed cancer and the
second leading cause of cancer death among women
in the United States. Each year, approximately 200,000
A
new cases of breast cancer are diagnosed and 40,000
women die from it.1 This paper underscores the importance of radiation therapy in breast cancer survival and
supports the increasing evidence that the prone setup
position is advantageous in minimizing unwanted dose
to critical organs. The issues outlined here present an
exciting opportunity for additional study to optimize
tissue sparing techniques for breast cancer treatment.
FIGURE 1. SUPINE (A) AND PRONE (B) SCANS AT THE LEVEL OF LATERAL MARKERS SHOW
HOW THE SHAPE AND SITE OF THE POSTSEGMENTAL EXCISION SEROMA VARIES BASED
ON PATIENT’S POSITION. WHEN PRONE, THE CAVITY ELONGATES AND IS MORE DISTANT
FROM THE CHEST WALL. SAME PATIENT AS IN FIGURE 2, ONE MONTH FOLLOWING BREAST
SURGERY. FORMENTI, SILVIA. SEMINARS IN RADIATION ONCOLOGY, VOLUME 15, ISSUE 2,
APRIL 2005, PAGES 92-99.
the trials were conducted, the study underscored the importance
of excluding the lungs and especially the heart from the
treatment fields when irradiating the breast. All of these women
were treated in the supine position.
Radiation saves lives
Improvement with prone setup
In improving breast cancer survival, radiation has an important
role to play. Breast-conserving lumpectomy followed by radiation
to the whole breast has replaced mastectomy as the standard
of care for patients with small tumors.2 Post-operative radiation
therapy—after lumpectomy or mastectomy—significantly reduces
local recurrence of the cancer and improves survival rates. A large
meta-analysis published in the Lancet in 2005 analyzed 42,000
patients from 72 randomized trials conducted between 1958-1991,
demonstrating a 5 percent improved 15-year survival rate among
women who had received radiation treatment.3
Radiation treatment for breast cancer has traditionally been
planned and delivered with patients in the supine position.
However, there is increasing evidence that the prone treatment
position affords several potential advantages over supine
treatment. These include
Preventing heart and lung toxicity
Several trials investigated treating patients in the prone position
to provide better heart and lung sparing.5, 6, 7, 8 A 2007 trial of 91
patients, conducted at the New York University (NYU) Cancer
Institute, concluded that accelerated whole breast intensity
modulated radiotherapy in the prone position is feasible and can
drastically reduce the volume of lung and heart tissue exposed
to radiation.9 To determine when prone setup is optimal, a
Another study, however, also revealed a significantly higher
15-year mortality rate from heart disease and secondary lung
cancers among breast-cancer patients treated with radiation.
Furthermore, more patients treated for left breast cancer died
from heart disease than those treated for right breast cancer.4
While the precision of radiation techniques has improved since
• B etter normal tissue sparing with less delivered dose
to critical organs
• Improved dose homogeneity
• Less motion due to respiration
• Reduction in skin toxicity and fewer skin related effects
B
subsequent NYU prospective trial involved 200 left-breast and
200 right-breast cancer patients.10 All patients received 48 Gy in
15 fractions of IMRT. Each patient underwent two CT simulations
and planning in the supine and prone position. For patients with
left-breast cancer, the plan that minimized the volume of heart in
the field was chosen for treatment. For patients with right-breast
cancer, the plan with the least volume of lung in the field was
chosen. The prone position proved optimal for the majority of both
right and left breast patients, regardless of breast size. The prone
position spared lung volume in 98 percent of the right breast
patients, reducing the volume of lung in the treatment field by a
mean 107 cubic centimeters. The prone position was optimal for
85 percent of the left breast patients, reducing exposed lung volume
by a mean of 93 cubic centimeters (cc) and heart volume by a mean
of 11 cc. Figure 2, which was printed in the New York Times11, shows
a patient example of the better sparing of normal tissue that can
be achieved in the prone position.
Areas to explore
In the NYU study, breast size did not predict the optimum setup
position, since both large and small-breasted women benefited
from prone positioning. Selection parameters for prone versus
supine setup is an area that needs further investigation. While
prone set-up provided better heart sparing for the vast majority
(85 percent) of left-breast patients, the supine position was the
best in 15 percent of cases.
Techniques for prone setup need to be standardized. For example,
the NYU study10 found that turning a patient’s head to the left could
reduce heart volume in the treatment field when treating the left
breast. Differences in the results from trials of prone positioning may
be attributed to different positioning techniques and accessories.
Summary
Radiation after surgery improves survival from breast cancer,
but it can increase the risk of mortality from heart disease and
secondary lung cancer. There is growing evidence that special
care must be taken to spare lung and especially heart tissue.
Prone setup can drastically reduce the heart and lung volume in
the treatment field, compared to supine setup. Further study of
selection parameters for prone versus supine setup is needed.
Prone setup techniques to better spare normal tissue, and ultimately,
improve long term outcomes, are still in need of standardization.
References
A
B
FIGURE 2. (A,B) IMPROVED HEART AND LUNG SPARING IN THE PRONE POSITION
(A) SUPINE, HEAD FIRST (B) PRONE, HEAD FIRST
IMAGES COURTESY OF NYU
These reconstructed digital radiographs compare supine (A) and
prone (B) set up, showing the position of the lung (brown), heart
(blue), and tumor bed (red). The yellow frame represents the
beam’s eye view of the field. The insets above are the corresponding
supine and prone computed tomography cut, at the level of the
plane identified by radio-opaque markers. The prone set-up (B)
characteristically enables better sparing of normal tissue than the
supine set-up (A).12
A partner for life
1. Jemal A, et al. Cancer Statistics 2010, CA Cancer J Clin; 60(5): 277–300
2. NIH Consensus Development Conference statement: Adjuvant therapy for breast cancer,
November 1-3, 2000; J Natl Cancer Inst Monogr 30:5-15, 2001
3. Clarke M, et al. Effects of radiotherapy and of differences in the extent of surgery for early
breast cancer on local recurrence and 15-year survival: an overview of the randomized
trials, Lancet 2005 Dec 17;366(9503):2087-106.
4. Darby S et al, Lancet oncology 2005:6;(8)557-565
5. Formenti et al. IJROBP. 60(2):493-504.2004
6. Buijsen et al. IJRO. 82(1):337-340. 2007
7. Morrow et al. IJROBP. 69(3):910-917. 2007
8. Varga et al. IJROBP. 1-7. 2009
9. Formenti, S, et al. Phase I-II Trial of Prone Accelerated Intensity Modulated Radiation
Therapy to the Breast to Optimally Spare Normal Tissue, JCO 2007; 25(16): 2236-2242
10. Formenti S, et al. Results of NYU 05-181: A Prospective Trial to Determine Optimal Position
(Prone versus Supine) for Breast Radiotherapy, IJROBP 2009; 75(3): S203-S204
11. Grady. Shorter Radiation for Cancer of the Breast. New York Times 2008 Sep 22.
http://www.nytimes.com/2008/09/23/health/research/23canc.html?pagewanted=all
12. DeWyngaert et al. Accelerated Intensity-Modulated Radiotherapy to Breast in Prone
Position: Dosimetric Results, IJROBP 2007; 68(4):1251-1259. 2007
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