Cardiac side-effects of adjuvant radiotherapy for early breast cancer
Author: Gyenes, Gábor
Date: 1997-12-11
Location: Aulan, plan 6 Södersjukhuset
Time: 9.00
Abstract
It is well established that adjuvant radiotherapy (RT) reduces
loco-regional recurrences in breast cancer. The effect on overall
survival on the other hand is much debated. Some randomized radiation
therapy trials with more than 10 years follow-up as well as an overview
of all unconfounded randomized trials show, in fact, a reduced survival
among irradiated patients compared to the surgical controls. In an
updated overview the increased mortatlity was suggested to be due to
cardiac deaths. This excess mortality was balanced by a decreased
mortality from breast cancer.
Since the introduction of the term ,,radiation-induced heart disease (
RlHD)" the existence of radiation-induced coronary artery disease has
been a debated question. The papers in this thesis all investigate the
possible connection between RT and cardiac diseases, particularly
coronary artery disease.
In a prospective study the incidence of pericardial irritation-signs was
found to be about 40% in symptom-free patients mostly after
postmastectomy RT including the ipsilateral internal mammary nodes. Thus,
it was shown that the effect of adjuvant RT on the heart was detectalble
in a number of breast cancer patients.
In another study, survivors from the first Stockholm Breast Cancer Trial
were examined for signs of ischemic heart disease (IHD). In 25% of the
survivors treated for a left sided breast cancer with tangential 60Co
fields, scintigraphy signs of HID were found, while none of the controls
exhibited such findings. All defects affected the anterior wall of the
left ventricle, which indicated a possible correlation between the former
radiotherapy and the observed findings.
Mortality of patients from the first Stockholm Breast Cancer Trial from
ischemic heart diseease, from cardiovascular disease, together with
mortality and morbidity from acute myocardial infarction were analyzed in
the next study. Data after a median of 20 years follow-up showed that mor
tality from ischemic heart disease may be positively correlated wilh the
cardiac dose-volume. The lack of a significant increase of the incidence
of myocardial infarction in the highest dose-volume group indicated that
another form of radiation-induced cardiac disease may also be involved.
The difference in cardiovascular mortality between the subgroups with
different cardiac dose-volume was established after 4-5 years of
randomization The curves continued to diverce up to about 10 years, when
there appeared no further divergence. No excess risk was observed among
patients who had received intermediate or low dose-volumes.
From 1993 onwards, signs of cardiac damage were assessed in 31 selected
patients in whom it was impossible lo exelude the heart completely from
the significantly irradiated volurne. The results show that of the 19
patientls who underwent both a base-line and a conlrol examination, 12
developed new, significant, irreversible, anteriorly located defects on
scintigraphy. Almost all of the partially mastectomized. Stage I breast
cancer patients (9/10), but only a few of those operated with modified
radical mastectomy for more locally advanced cancer (3/9) developed such
defects. The defects correlated well with the irradiated area of the left
ventricle, and are likely to represent radiation-induced microvascular
perfusion damage of the myocardium.
Based on the above findings, an estimation was made of the proportion of
l patients at risk of significant cardiac irradiation among 100
node-negative left-sided breast cancer patients treated with
breast-conserving surgery and irradiated to the breast only. Data were
compared with the irradiated heart volumes estimated for patients treated
with left-sided deep tangential 60Co fields in the first Stockholm Breast
Cancer Trial. This technique was found to be associated with a signifcant
increase of cardiac mortality. The majority of the patients wilh T1N0M0
breast cancer were not found to receive irradiation to a heart volume
large enough to seem potentially harmful. Six percent of the patients
however, received at least 25 Gy to 15-21% of the volume of the heart,
which is close to the mean irradiated heart volume (25%) received by the
mentioned patients in the Stockholm Trial.
In conclusion, these studies illustrate that RlHD may be clinically
significant problem in subgroups of breast cancer patients, mainly for
those with left-sided disease also wilh modern radiation therapy
techniques in the postmastectomy as well as the conservative surgery
setting.
Issue date: 1997-11-20
Publication year: 1997
ISBN: 963-9106-04-6
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