A Case of Adrenocortical Carcinoma With a Favorable Tumor Control by Radiofrequency Ablation for Liver Metastasis

Sage

Kensuke Kitsugi, MD’, Kazuhito Kawata, MD, PhD’, Keisuke Kakizawa, MD, PhD’, and Hidenao Noritake, MD, PhD’

Abstract

A 57-year-old woman was diagnosed with adrenocortical carcinoma. Following the adrenalectomy, she underwent adjuvant radiation and mitotane therapy; however, liver metastases were observed. Repeated radiofrequency ablation (RFA) was performed for liver metastases. In addition, a multidisciplinary approach combining systemic chemotherapy, radiotherapy, and surgery was used for lung and distant lymph node metastases that arose during the course of treatment. Notably, 49 months have passed since the adrenalectomy and 36 months since the recurrence of the liver metastases, and the patient remains on multidisciplinary therapy. Thus, RFA for liver metastasis of adrenocortical carcinoma may be an effective component of a multidisciplinary treatment.

Keywords

combined modality therapy, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid, lymphatic metastasis, mitotane

Introduction

Adrenocortical carcinoma (ACC) is a rare malignancy, with a prevalence of 0.72 million cases per year.1 Although the only curative treatment is complete surgical resection, its availability is limited because most patients are diagnosed at advanced stages of the disease.2 The frequency of metastasis to other organs at diagnosis is 60% to 70%,3 and the 5-year survival rate of ACC cases with metastasis to other organs is 0% to 17%.4 Moreover, ACC is associated with high recur- rence rates, despite complete resection of the primary tumor.5 The treatment options for metastatic ACC are limited. Complete resection of metastases is recommended in some cases; however, complete resection is difficult in many cases because the metastatic lesions are often multiple or large, and systemic chemotherapy is recommended.6 Nonetheless, options for systemic chemotherapy are limited. A regimen combining etoposide, doxorubicin, and cisplatin (EDP) with mitotane is commonly used; however, progression-free survival was 5.3 months and overall survival was 14.8 months, which were unsatisfactory results.7,8 Therefore, it is difficult to achieve the long-term prognosis with systemic chemotherapy alone.

Radiofrequency ablation (RFA) is a minimally invasive and highly curative treatment.9 Although the efficacy of RFA

on hepatocellular carcinoma is well established,1º its curative or cytoreductive effects on metastatic liver tumors have also been reported.11,12

We encountered a case in which aggressive RFA was per- formed for the recurrence of multiple liver metastases after resection of a primary ACC tumor, and favorable therapeutic effects were obtained. Systemic chemotherapy was effective for the subsequent concurrent lung and distant lymph node metastases. However, controlling liver metastasis is difficult with systemic chemotherapy, and the combination of RFA and systemic chemotherapy effectively prolongs prognosis. Multidisciplinary RFA therapy may be an effective treatment option for liver metastases of ACC.

‘Hamamatsu University School of Medicine, Japan

Received September 13, 2023. Revised November 13, 2023. Accepted November 16, 2023.

Corresponding Author:

Kensuke Kitsugi, MD, Department of Internal Medicine II, School

of Medicine, Hamamatsu University, 1-20-1 Handayama, Higashi-ku, Hamamatsu 431-3192, Shizuoka, Japan. Email: ken.kitsugi@gmail.com

Table 1. Laboratory Data at the First Visit.
Blood countBlood chemistryEndocrine
WBC7510/μLALB4.1 g/dLPAC297 pg/mL
RBC424 X 104/uLT.Bil0.9 mg/dLPRA0.4 ng/ml/h
Hb13.1 g/dLAST16 IU/LACTH<2.0 pg/mL
Ht38.5%ALT13 IU/LCortisol17.0 µg/dL
Plt38.5 X 104/µLALP86 IU/LUrine free cortisol102 µg/d
LDH215 IU/LDHEA-S9.0 µg/dL
CoagulationGGT23 IU/L
PT10.7 secondsChE220 mg/dL
PT%131%BUN15.7 mg/dL
APTT27.6 secondsCr0.52 mg/dL
APTT%100%Na141 mEq/L
Fibrinogen321 mg/dLK3.8 mEq/L
Cl104 mEq/L

Abbreviations: WBC, white blood cell; RBC, red blood cell; Hb, hemoglobin; Ht, hematocrit; Plt, platelet; PT, prothrombin time; APTT, activated partial thromboplastin time; ALB, albumin; T.Bil, total bilirubin; AST, aspartate aminotransferase; ALT, alanine aminotransferase; ALP, alkaline phosphatase; LDH, lactate dehydrogenase; GGT, gamma-glutamyl transpeptidase; ChE, choline esterase; BUN, blood urea nitrogen; Cr, creatinine; PAC, plasma aldosterone concentration; PRA, plasma renin activity; ACTH, adrenocorticotropic hormone; DHEA-S, dehydroepiandrosterone sulfate.

Case Presentation

A 57-year-old woman presented with muscle weakness, hypertension, and hypokalemia. She had a history of dyslip- idemia and osteoporosis. She reported no history of smok- ing or occasional alcohol consumption. The patient had no relevant family history. Typical features of Cushing’s syn- drome, such as a moon face, purple striae, or central obesity, were not observed. The laboratory data for the first visit are presented in Table 1. Hormone studies revealed high plasma aldosterone concentration (PAC, 297 pg/mL) and low plasma renin activity (PRA, 0.4 ng/mL/h). Captopril chal- lenge test revealed an increased aldosterone-to-renin ratio, suggesting primary aldosteronism. Basal adrenocortico- tropic hormone levels were <2.0 pg/mL, and cortisol levels were 17.0 µg/dL. The 24-hour urinary-free cortisol excre- tion rate increased to 102 ug/d. Serum cortisol levels were not suppressed by administration of 1 and 8 mg dexametha- sone, which were in concentrations of 15.3 and 17.7 µg/dL. The bedtime serum cortisol level was 17.4 µg/dL, greater than 5.0 µg/dL. All the results met the criteria of Cushing’s syndrome. Dehydroepiandrosterone sulfate concentration was not elevated (9.0 g/dL). Contrast-enhanced computed tomography (CT) revealed an irregular mass measuring 54 mm × 61 mm in the left adrenal gland with heterogeneous contrast enhancement (Figure 1A and B). Based on these findings, she was suspected to have aldosterone- and corti- sol-coproducing ACC and underwent left adrenalectomy.

Histological examination met all the Weiss criteria13 and confirmed the diagnosis of ACC (Figure 1C-E). The European Network for the Study of Adrenal Tumor staging was stage II (T2N0M0) and the Ki-67 index was 13%, suggesting a high risk of recurrence.6 In addition to

Figure 1. CT findings at the initial examination and pathological findings at primary tumor resection. Plain CT findings of the ACC at initial examination (A). The lesion (arrow) is a 54 mm × 61 mm heterogeneous mass in the left adrenal gland with heterogeneous enhancement (B). Macroscopic findings reveal a brownish solid tumor with internal hemorrhage and necrosis (C). Microscopic findings revealed alveolar growth of tumor cells, accompanied by high-grade nuclear atypia and multiple mitotic counts. Magnification 100X (D) and 400X (E). Abbreviations: CT, computed tomography; ACC, adrenocortical carcinoma.

A

B

C

D

E

Table 2. Laboratory Data at the Initial RFA.
Blood countBlood chemistryImmunochemistry
WBC3730/μLALB3.7 g/dLCRP0.1 mg/dL
RBC385 X 104/µLT.Bil0.6 mg/dL
Hb12.0 g/dLD.Bil<0.1 mg/dL
Ht35.3%AST21 IU/L
Plt30.6 × 104/µLALT11 IU/L
ALP52 IU/L
CoagulationLDH146 IU/LBlood concentration
PT11.6 secondsGGT1 15 IU/LMitotane7.8 µg/mL
PT%108%ChE241 mg/dL
APTT24.7 secondsBUN10.5 mg/dL
APTT%136%Cr0.44 mg/dL
Fibrinogen209 mg/dLNa141 mEq/L
K3.8 mEq/L
Cl106 mEq/L

Abbreviations: RFA, radiofrequency ablation; WBC, white blood cell; RBC, red blood cell; Hb, hemoglobin; Ht, hematocrit; Plt, platelet; PT, prothrombin time; APTT, activated partial thromboplastin time; ALB, albumin; T.Bil, total bilirubin; D.Bil, direct bilirubin; AST, aspartate aminotransferase; ALT, alanine aminotransferase; ALP, alkaline phosphatase; LDH, lactate dehydrogenase; GGT, gamma-glutamyl transpeptidase; ChE, choline esterase; BUN, blood urea nitrogen; Cr, creatinine; CRP, C-reactive protein.

hydrocortisone supplementation, she received adjuvant radiotherapy (54 Gy in 30 fractions) and mitotane; however, multiple liver metastases were observed 13 months postop- eratively. Systemic chemotherapy was considered; however, metastatic lesions were limited to the liver. Therefore, more curative treatment options were sought. Owing to the large number of liver metastases, complete surgical resection of these tumors is considered difficult and highly invasive. Furthermore, the liver metastases were not highly vascular- ized, and transarterial chemoembolization (TACE) was con- sidered less effective. Therefore, RFA was selected as the local therapy for liver metastases because it is highly curable and less invasive. The laboratory data at the initial RFA are presented in Table 2. Hepatic and biliary enzyme levels, blood counts, and coagulation test results were normal. However, as the blood concentration of mitotane was as low as 7.8 µg/mL, the mitotane dosage was increased from 3000 to 4500 mg per day. Imaging using plain CT revealed the presence of multiple low-density nodules in the periphery of the liver (Figure 2A and B), and contrast-enhanced CT revealed lesions with a lower density than the surrounding normal liver tissue (Figure 2C and D). Gadolinium ethoxy- benzyl diethylenetriamine pentaacetic acid magnetic reso- nance imaging (Gd-EOB-DTPA MRI) revealed low-intensity lesions in the hepatobiliary phase (Figure 2E and F). While CT revealed 4 lesions, Gd-EOB-DTPA MRI detected 11 met- astatic tumors in both liver lobes. Ultrasonography detected only 4 lesions that were identifiable on CT.

Radiofrequency ablation was performed percutaneously under ultrasonographic guidance using an Arfa RF ablation system (Japan Lifeline, Tokyo, Japan). Post-RFA CT revealed a sufficient ablation area without complications. Four months

after the initial RFA, lesions that could only be detected on MRI became apparent on CT, and local recurrence was observed near the initial ablation site (Figure 3A and B). At this time, the blood concentration of mitotane was 14.9 ug/mL, which was the optimal concentration. We thought that RFA would be more effective than systemic chemotherapy while the metastatic lesions were limited to the liver, and the patient also wished to continue RFA. Therefore, we decided to con- tinue RFA. A second RFA was performed (Figure 3C and D). Lung metastases appeared 6 months after the initial RFA (Figure 3E and F). Systemic chemotherapy with EDP plus mitotane was initiated. After 4 courses of EDP plus mitotane therapy, the lung metastases were stable, but the liver metas- tases became apparent and recurred. Radiofrequency abla- tion was repeatedly performed during the washout period of EDP plus mitotane therapy. During the 28-day cycle of EDP therapy, RFA was performed on day 14. Oral administration of mitotane was continued, even on the day of the RFA. Partial pneumonectomy and radiotherapy were performed as curative treatments for lung metastases 30 months after the initial RFA. Furthermore, the EDP therapy was discontinued because the cumulative dose of doxorubicin was almost maximal. Computed tomography revealed local recurrence of liver metastases and distant lymph node metastases 33 months after the initial RFA (Figure 4A-C). Systemic che- motherapy with a combination of etoposide and cisplatin (EP) was resumed, and distant lymph node metastases showed a partial response (Figure 4D). However, as there was no effect on the liver metastases, the seventh and eighth RFA sessions were performed (Figure 4E and F).

Currently, 49 months have passed since the adrenalec- tomy, 36 months have passed since the initial RFA, and EP

Figure 2. CT and MRI findings of the liver metastases at the initial RFA. Representative CT and Gd-EOB-DTPA MRI findings of liver metastases of ACC at the initial RFA. Plane CT reveals multiple low-density areas (arrows) in the periphery of the liver (A and B). These lesions were of relatively low density compared to the surrounding normal liver with indistinct borders on contrast-enhanced CT (C and D). In addition, a total of 11 lesions (arrows) were observed in the hepatobiliary phase of GdEOB- DTPA MRI (E and F). Abbreviations: CT, computed tomography; MRI, magnetic resonance imaging; Gd-EOB-DTPA, gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid; ACC, adrenocortical carcinoma; RFA, radiofrequency ablation.

A

B

C

D

E

F

therapy continues. Liver metastasis was not observed, and we will continue to monitor distant metastases and consider a ninth RFA when another liver metastasis becomes appar- ent. In the present case, 8 sessions of RFA were performed on 21 lesions. There were no complications, such as bleeding or infection, and each treatment required hospitalization for several days. Furthermore, the patient’s general condition and liver function did not worsen. The progress from diagno- sis to the present is shown in Figure 5.

Discussion

Liver metastasis is strongly associated with prognosis in ACC, and the control of liver metastasis is associated with a prolonged prognosis.14 A multidisciplinary therapy that

Figure 3. CT findings of the liver metastases at the second and third RFA. Representative CT findings at 4 months (A-D) and 6 months (E and F) after the initial RFA. New metastatic lesions (arrows) are observed in the liver (A and B). The lesions were treated with RFA (C and D). Metastatic lesions (arrows) were observed in the lungs (E, F). Abbreviations: CT, computed tomography; RFA, radiofrequency ablation.

A

B

C

D

E

F

combines systemic chemotherapy with local treatment of metastatic lesions is important.15 Surgical resection alone is often reported to be useful for the treatment of liver metasta- ses.16,17 If complete resection is possible, a long-term progno- sis can be expected. Moreover, Datrice et al16 reported that patients with ACC with recurrence >12 months after adrenal- ectomy had favorable outcomes. In our case, liver metastasis recurred 13 months after adrenalectomy. However, EOB- MRI revealed 11 metastases in both liver lobes, suggesting that surgical resection was challenging. In addition to surgical resection, RFA and TACE are considered local treatments for liver metastases. Soga et al18 reported the efficacy of TACE for the treatment of ACC. However, we selected RFA because it is generally more curative than TACE,19 and the vascularity of the liver metastases was not high in our case.

Radiofrequency ablation is a minimally invasive and curative local treatment for primary hepatocellular carci- noma, and it has also been reported to be effective for various metastatic liver tumors.20 Most reports on RFA for liver metastases in ACC have examined both surgical resection

Figure 4. Latest CT findings of liver and distant metastases. Representative CT findings at 33 months (A-C) and 36 months (D-F) after the initial RFA. Recurrence of liver metastases (A and B) and appearance of distant lymph node metastases (C) are observed (arrows). A reduction in the size of the distant lymph node metastasis was observed upon resumption of chemotherapy (D), and RFA was performed for liver metastases (E and F). Abbreviations: CT, computed tomography; RFA, radiofrequency ablation.

A

B

C

D

E

F

and RFA, with few reports on RFA alone.21,22 Veltri et al23 reported that RFA for liver metastasis in ACC was a safe and effective treatment option in the multidisciplinary manage- ment. They reported a high local recurrence rate of 66%, and the size of the metastatic liver tumor in the ACC significantly correlated with the local recurrence rate.23 Bauditz et al24 also reported a high local recurrence rate after RFA for liver metastases of ACC. They speculated that ACC tends to recur early owing to the heat sink effect due to the high vascular- ization in the liver metastases of ACC.24 The fact that high local recurrence rate in lesions with large tumor sizes in our case is consistent with these reports. Metastatic liver tumors should be ablated with a wider safety margin because of stromal infiltration and the lack of a capsule, which makes it difficult for the ablation heat to remain within the tumor.11 Considering our cases and previous reports, it is crucial to ensure a reliable safety margin to prevent the local recur- rence of liver metastasis of ACC. No large clinical trials have compared RFA with surgical resection for liver metastases from ACC. Although there have been cases of long-term survival with surgical resection for liver metastasis in ACC,16 the recurrence rate is as high as 80%.21 Radiofrequency ablation has the advantage of being less invasive and is supe- rior to surgical resection in this respect. Currently, surgical resection of metastatic liver lesions is the first treatment option; however, RFA is the next treatment option if surgical resection is difficult due to tumor and patient factors. Future studies are warranted to compare the outcomes of RFA and surgical resection for ACC with liver metastasis.

Surgery, RFA, and systemic chemotherapy alone are insufficient to improve the prognosis of ACC metastases; therefore, multidisciplinary therapy is important. 15 Ou et al25 reported that RFA should be combined with systemic che- motherapy to achieve effects on microlesions that are unde- tected by imaging when attempting to treat liver cancer.

Figure 5. The progress from diagnosis to the present of the patient. Abbreviations: RFA, radiofrequency ablation; EDP, a combination of etoposide, doxorubicin, and cisplatin; EP, a combination of etoposide and cisplatin.

Liver metastases

Lung metastases

Distant lymph node metastasis

Months from initial RFA -13

0

6

13

18

27

36

RFA

Surgery

Hormone therapy (Mitotane)

3000mg/day

4500mg/day

5000mg/day

4500mg/day

Systemic chemotherapy

EDP

EP

Radiotherapy

Reports on the combination of RFA and systemic chemo- therapy for ACC are scarce. The EDP therapy is a 4-week course of chemotherapy. We were able to perform RFA safely and efficiently without delaying EDP therapy by using a washout period. This approach enabled the efficient treatment of liver metastases, as well as metastases to other organs. However, the efficacy and safety of the combination of RFA and chemotherapy should be further investigated in a large number of cases.

Lung and distant lymph node metastases also appeared during treatment of liver metastases. Lung metastases were well controlled by surgical resection and radiotherapy after a certain period of chemotherapy. Aggressive local treat- ments for lung and liver metastases are expected to improve ACC prognosis.26 Distant lymph node metastases and lung metastases were controlled by systemic chemotherapy, whereas liver metastases clearly increased. The doubling times of primary and metastatic solid tumors are often dif- ferent. One reason for this is thought to be the acquisition of resistance to the immune system and the induction of new vascularization due to increased tumor volume.27 Lung and distant lymph node metastases were smaller than liver metastases, which may have contributed to differences in doubling time and response to systemic chemotherapy. Therefore, aggressive RFA for fast-growing liver metastases may improve prognosis.

Our patient showed favorable tumor control with repeated RFA for ACC liver metastases and multidisciplinary therapy, including systemic chemotherapy, resection for lung meta- stasis, and radiotherapy. As part of a multidisciplinary ther- apy, RFA for liver metastasis is minimally invasive, may provide sufficient tumor control, and should be considered an effective treatment option for patients with ACC unsuit- able for surgical resection.

Conclusion

We encountered a case of ACC with liver metastases, in which aggressive RFA contributed to a favorable tumor con- trol. Radiofrequency ablation for liver metastasis from ACC is minimally invasive and can be performed with little effect on the patient’s general condition, even in combination with systemic chemotherapy. Further investigations with a larger number of cases, including comparisons with surgical resec- tion, are required.

Acknowledgments

We would like to thank Editage (http://www.editage.jp) for English language editing.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, author- ship, and/or publication of this article.

Ethics Approval

Our institution does not require ethical approval to report individual cases or a case series.

Written informed consent was obtained from the patient for the publication of anonymized information in this article.

References

1. Bilimoria KY, Shen WT, Elaraj D, et al. Adrenocortical carci- noma in the United States: treatment utilization and prognostic factors. Cancer. 2008;113:3130-3136.

2. Ayala-Ramirez M, Jasim S, Feng L, et al. Adrenocortical carcinoma: clinical outcomes and prognosis of 330 patients at a tertiary care center. Eur J Endocrinol. 2013;169(6):891- 899.

3. Berruti A, Baudin E, Gelderblom H, et al. Adrenal cancer: ESMO clinical practice guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2012;23(suppl 7):vii131-vii138.

4. Fassnacht M, Wittekind C, Allolio B. Current TNM classifica- tion systems for adrenocortical carcinoma. Pathologe. 2010; 31(5):374-378.

5. Glover AR, Ip JC, Zhao JT, Soon PS, Robinson BG, Sidhu SB. Current management options for recurrent adrenocortical carcinoma. Onco Targets Ther. 2013;6:635-643.

6. Fassnacht M, Dekkers OM, Else T, et al. European Society of Endocrinology Clinical Practice Guidelines on the manage- ment of adrenocortical carcinoma in adults, in collaboration with the European Network for the study of adrenal tumors. Eur J Endocrinol. 2018;179:G1-G46.

7. De Francia S, Ardito A, Daffara F, et al. Mitotane treatment for adrenocortical carcinoma: an overview. Minerva Endocrinol. 2012;37(1):9-23.

8. Fassnacht M, Terzolo M, Allolio B, et al. Combination chemo- therapy in advanced adrenocortical carcinoma. N Engl J Med. 2012;366:2189-2197.

9. Minami Y, Kudo M. Radiofrequency ablation of hepato- cellular carcinoma: current status. World J Radiol. 2010;2: 417-424.

10. Chen MS, Li JQ, Zheng Y, et al. A prospective randomized trial comparing percutaneous local ablative therapy and par- tial hepatectomy for small hepatocellular carcinoma. Ann Surg. 2006;243(3):321-328.

11. Minami Y, Kudo M. Radiofrequency ablation of liver metas- tases from colorectal cancer: a literature review. Gut Liver. 2013;7(1):1-6.

12. Lawes D, Chopada A, Gillams A, Lees W, Taylor I. Radio- frequency ablation (RFA) as a cytoreductive strategy for hepatic metastasis from breast cancer. Ann R Coll Surg Engl. 2006;88(7):639-642.

13. Weiss LM, Medeiros LJ, Vickery ALJ. Pathologic features of prognostic significance in adrenocortical carcinoma. Am J Surg Pathol. 1989;13:202-206.

14. Watanabe K, Kodama Y, Sakurai Y, et al. Adrenocortical carcinoma with multiple liver metastases controlled by bland transarterial embolization and surgery resulting in long-term survival. Radiol Case Rep. 2022;17(4):1095-1098.

15. Dy BM, Wise KB, Richards ML, et al. Operative intervention for recurrent adrenocortical cancer. Surgery. 2013;154(6):1292- 1299; discussion 1299.

16. Datrice NM, Langan RC, Ripley RT, et al. Operative manage- ment for recurrent and metastatic adrenocortical carcinoma. J Surg Oncol. 2012;105:709-713.

17. Nakano R, Satoh D, Nakajima H, et al. Repeated resections for liver metastasis from primary adrenocortical carcinoma: a case report. Int J Surg Case Rep. 2015;9:119-122.

18. Soga H, Takenaka A, Ooba T, et al. A twelve-year experience with adrenal cortical carcinoma in a single institution: long- term survival after surgical treatment and transcatheter arterial embolization. Urol Int. 2009;82(2):222-226.

19. Hsu CY, Huang YH, Chiou YY, et al. Comparison of radio- frequency ablation and transarterial chemoembolization for hepatocellular carcinoma within the Milan criteria: a propen- sity score analysis. Liver Transpl. 2011;17(5):556-566.

20. Izzo F, Granata V, Grassi R, et al. Radiofrequency ablation and microwave ablation in liver tumors: an update. Oncologist. 2019;24(10):e990-e1005.

21. Ayabe RI, Narayan RR, Ruff SM, et al. Disease-free inter- val and tumor functional status can be used to select patients for resection/ablation of liver metastases from adrenocorti- cal carcinoma: insights from a multi-institutional study. HPB (Oxford). 2020;22(1):169-175.

22. Ripley RT, Kemp CD, Davis JL, et al. Liver resection and abla- tion for metastatic adrenocortical carcinoma. Ann Surg Oncol. 2011;18(7):1972-1979.

23. Veltri A, Basile D, Calandri M, et al. Oligometastatic adreno- cortical carcinoma: the role of image-guided thermal ablation. Eur Radiol. 2020;30(12):6958-6964.

24. Bauditz J, Quinkler M, Wermke W. Radiofrequency thermal ablation of hepatic metastases of adrenocortical cancer-a case report and review of the literature. Exp Clin Endocrinol Diabetes. 2009;117(7):316-319.

25. Ou S, Xu R, Li K, et al. Radiofrequency ablation with sys- temic chemotherapy in the treatment of colorectal cancer liver metastasis: a 10-year single-center study. Cancer Manag Res. 2018;10:5227-5237.

26. Kemp CD, Ripley RT, Mathur A, et al. Pulmonary resection for metastatic adrenocortical carcinoma: the National Cancer Institute experience. Ann Thorac Surg. 2011;92(4):1195-1200.

27. Norton L. A Gompertzian model of human breast cancer growth. Cancer Res. 1988;48:7067-7071.