Keywords:
Radiotherapy - Cancer - SABR - Oligometastasis.
Descritores:
Radioterapia - Câncer - REA - Oligometástases.
INTRODUCTION
Occult primary tumors (OPT) can be defined as malignant neoplasms, whose primary site
cannot be identified. Despite the technological advances in the pathological analysis
with the incorporation of molecular and immunohistochemical studies in the last decades,
the incidence of OPT remains stable, with about 5% of diagnosed cancers.([1]) Traditionally, the OPT is treated with chemotherapy of broad-spectrum, which generally
produces a clinical response and prolongs survival.([2]) Among the therapeutic arsenal to the management of the OPT, radiotherapy has a
reduced role. It is considered as a palliative treatment commonly after several chemotherapy
lines when the tumor is not responding, and the chances of controlling the disease
are reduced.([3])
Stereotactic ablative radiotherapy (SABR) is a radiation technique that allows delivering
a high-dose per fraction, with a strict margin and a deep fall-off the dose, sparing
the surrounding healthy tissues of an excessive dose.([4]) Recently, SABR has gained notability and widespread use in the oligometastatic
scenario. Several studies have reported a significant increase in the local control
and improvement of survival with SABR.([4]
[5]
[6]
[7]) However, SABR is commonly employed to treat small tumors (<5cm) with limited experience
of its use in large tumors (>10cm). The importance of tumor size reduces SABR considerably
as a treatment option in palliative care. To the best of our knowledge, there is no
case report describing the role of SABR in the palliative care of a giant mass of
an OPT. The intent in describing this case report is to show an outstanding clinical
response of a giant axillary mass achieved with SABR in a patient with the OPT refractory
to the chemotherapy treatment who required palliative radiotherapy.
CASE REPORT
In this case report, we present a 67-year-old male patient with a massive left axillary
metastasis of 13cm on the major axis ([Figure 1]). The immunohistochemistry panel from biopsy suggested a clear cell carcinoma. In
the additional workup, no renal tumor or other primary site was found. At the diagnostic,
the patient had complaints such as severe pain (10/10 points) and constant bleeding
by the axillary mass. Chemotherapy with carboplatin and paclitaxel was initiated without
any clinical response after 2 cycles.
Figure 1 Complete response after 3 months from SABR.
The patient was simulated in computerized tomography (CT) on the supine position with
the arm slightly elevated and open. A vac-loc cushion was molded to guarantee positioning
and daily reproduction. The CT slices of 1mm were acquired from the top of the cranium
until the second lumbar spinal vertebra. The gross tumor volume (GTV) was considered
the axillary mass, and no clinical target volume was adopted. The planning volume
treatment (PTV) was generated from GTV with a margin of 5mm in all directions. A dose
equivalent to 60Gy with a 2Gy fraction was chosen. Thus, a single dose fraction of
16Gy was delivered to cover 95% of PTV, respect all the restriction doses of the organs
at risk: lung (V520%), brachial plexus (Dmax<16Gy), and chest wall (Dmax<16Gy). The
intensity-modulated radiotherapy (IMRT) with xx fields was used. The patient tolerated
the treatment very well without any intercurrence. After treatment, the patient was
followed one week, 1, 3, and 6 months later, with clinical exam and CT. In the follow-up,
the only toxicity observed was grade 2-skin toxicity. The tumor had an extraordinary
response disappearing entirely after 3 months from SABR ([Figure 2]). Currently, the patient is found pain-free, with no opioid, analgesic consumption,
or bleeding, and sleeping well. The complete sustained response at the irradiated
site remains, and the patient report significantly better quality of life after 6
months from the SABR.
Figure 2 massive metastatic axillary lesion pretreatment.
DISCUSSION
Stereotactic ablative radiotherapy (SABR) proved to be an effective therapeutic modality.
It is capable of producing a high-rate of local control independently of the tumor
histology, while it is incredibly convenient due to the short treatment course. Toxicities
found in this approach do not differ from conventional treatment, with the majority
of patients having mild symptoms.([4])
Ablative radiotherapy alone as definitive treatment has been poorly investigated in
palliative care. The use of radiotherapy for the OPT available in the literature is
limited to traditional radiotherapy with palliative doses. The motivation to employ
SABR in a chemotherapy-refractory patient with a giant axillary mass was based on
the high probability of controlling the disease and improving the symptoms. Our case
report shows that ablative radiotherapy (SABR) should be a tool considered in palliative
cancer management, once it brings several advantages such as: effective symptom control,
sustained clinical response, short treatment time, and greater compliance.
Another peculiarity with the present case is the use of SABR in a large tumor. Generally,
the use of SABR is limited to tumors around 5cm due to the excessive risk of a large
volume of normal tissue to be exposed to high radiation doses. Keeping this risk in
mind, the SABR dose was calculated to respect the dose limit of the organs at risk
around the tumor. A dose of 16Gy in a single fraction using a/b=3, would be equivalent
to 60Gy in 2Gy fraction, which is a dose tolerable by the lung, skin, and chest wall.
Metastases, in any place, can generate pain and decrease the patients' quality of
life.([8]) In such a situation, the tumor and symptoms control are vitally important, and
SABR has considerable potential in producing a sustained clinical response. The sustained
local control is a desirable endpoint even in a palliative scenario because it increases
the chances of patients receiving more chemotherapy cycles without the inconvenience
of chemotherapy interruptions or delays due to tumor complications as bleeding or
infection.
In conclusion, this case report shows that SABR should be considered a treatment option
in palliative care of selected patients with a large symptomatic tumor. The benefit
observed here should be explored in further studies before SABR be adopted as the
standard of care in this scenario.
Bibliographical Record
Fernando Kojo Matsuura, Gustavo Viani Arruda, Leonardo Vicente Fay Neves, Alexandre
Ciuffi Faustino, Ana Carolina Hamamura, Anielle Freitas Bendo Danelichen. A spectacular
tumor response of a giant axillary mass treated with SABR in a palliative scenario.
Brazilian Journal of Oncology 2021; 17: e-20210018.
DOI: 10.5935/2526-8732.20210018
