High-Dose Stereotactic Body Radiation Therapy Effective Treatment For Patients With Low Volume Lung or Liver Metastases

Libby’s H*O*P*E*™ previously reported on potential treatments for “oligometastasis,” which is defined as cancer that spreads to a few distant body sites, on June 23, 2008 and August 17, 2008.  Two related U.S. multi-institutional, phase I/II clinical studies and one Canadian Phase I clinical study reported recently results from an evaluation of the efficacy and tolerability of high-dose stereotactic body radiation therapy (SBRT) for the treatment of patients with liver or lung metastases.  A description of each study and its findings is provided below.  In addition, we have provided an excerpt from an editorial published in the Journal of Clinical Oncologythat comments upon the lessons learned from the three SBRT clinical studies described below, as well as other related studies.

Libby’s H*O*P*E*™ previously reported on potential treatments for “oligometastasis,” which is defined as cancer that spreads to a few distant body sites, on June 23, 2008 and August 17, 2008.  Two related U.S. multi-institutional, phase I/II clinical studies and one Canadian Phase I clinical study reported recently results from an evaluation of the efficacy and tolerability of high-dose stereotactic body radiation therapy (SBRT) for the treatment of patients with liver or lung metastases.  A description of each study and its findings are provided below.  In addition, we have provided an excerpt from an editorial published in the Journal of Clinical Oncology that comments upon the lessons learned from the three SBRT clinical studies described below, as well as other related studies.

sbrtU.S. SBRT Liver Metastases Study

In the first U.S. clinical study, patients with one to three hepatic lesions (with maximum individual tumor diameters less than 6 cm) were enrolled and treated on a multi-institutional, phase I/II clinical trial in which they received SBRT delivered in three fractions. During the phase I clinical study, the total radiation dose was safely escalated from 36 Gy to 60 Gy. During the phase II portion of the clinical study, the dose was 60 Gy. The study primary end point was local control of the hepatic metastases. Hepatic metastatic lesions with at least 6 months of radiographic follow-up were considered assessable for local control. The study secondary end points were toxicity and survival.

As part of this clinical study, 47 patients with 63 lesions were treated with SBRT. Among those patients, 69% had received at least one prior systemic therapy regimen for metastatic disease (range, 0 to 5 regimens), and 45% had extra-hepatic disease at study entry. Forty-nine discrete lesions were assessable for local control. Median follow-up for assessable lesions was 16 months (range, 6 to 54 months). The median maximal tumor diameter was 2.7 cm (range, 0.4 to 5.8 cm). Based upon this criteria, the researchers reported the following findings:

  • Only one patient experienced grade 3 or higher toxicity (2%);
  • Local progression occurred in only three lesions at a median of 7.5 months (range, 7 to 13 months) after SBRT;
  • Actuarial in-field local control rates at one and two years after SBRT were 95% and 92%, respectively;
  • Among lesions with maximal diameter of 3 cm or less, 2-year local control was 100%; and
  • Median survival was 20.5 months.

Based upon the foregoing, the U.S. researchers concluded that the multi-institutional, phase I/II clinical study demonstrates that high-dose liver SBRT is safe and effective for the treatment of patients with one to three liver metastases.

Canadian SBRT Liver Metastases Study

In the phase I Canadian clinical study, patients with liver metastases who were inoperable or medically unsuitable for resection, and were not candidates for standard therapies, were eligible for this individualized SBRT study. Individualized radiation doses were chosen to maintain the same nominal risk of radiation-induced liver disease (RILD) for three estimated risk levels (5%, 10%, and 20%).  Additional patients were treated at the maximal study dose (MSD) in an expanded cohort.  Median SBRT dose was 41.8 Gy (range, 27.7 to 60 Gy) in six fractions over 2 weeks.  Based upon this criteria, the Canadian researchers reported the following findings:

  • Sixty-eight patients with inoperable colorectal (n = 40), breast (n = 12), or other (n = 16) liver metastases were treated;
  • Median tumor volume was 75.2 mL (range, 1.19 to 3,090 mL);
  • The highest RILD risk level investigated was safe, with no dose-limiting toxicity;
  • Two patients experienced grade 3 liver enzyme changes, but no RILD or other grade 3 to 5 liver toxicity was seen, resulting in a low estimated risk of serious liver toxicity;
  • Six patients (9%) experienced acute grade 3 toxicities (two gastritis, two nausea, lethargy, and thrombocytopenia) and one (1%) patient experienced grade 4 toxicity (thrombocytopenia);
  • The 1-year local control rate was 71%; and
  • The median overall survival was 17.6 months.

Based upon the foregoing, the Canadian researchers concluded that individualized six-fraction liver metastases SBRT is safe, with sustained local control observed in the majority of patients.

U.S. SBRT Lung Metastases Study

In the third study, patients with one to three lung metastases (with cumulative maximum tumor diameter smaller than 7 cm) were enrolled and treated as part of a U.S. multi-institutional phase I/II clinical study in which they received SBRT delivered in 3 fractions.  During the phase I clinical study, the total dose was safely escalated from 48 to 60 Gy. During the phase II portion of the clinical study, the phase II dose was 60 Gy.  The study primary end point was local control.  Metastatic lung lesions with at least 6 months of radiographic follow-up were considered assessable for local control.  The study secondary end points included toxicity and survival.

As part of this study, 38 patients with 63 lesions were enrolled and treated at three U.S. participating institutions. Among those patients, 71% received at least one prior systemic regimen for metastatic disease and 34% had received at least two prior regimens (range, 0 to 5 regimens). Two patients had local recurrence after prior surgical resection. Fifty lesions were assessable for local control.  Median follow-up for assessable lesions was 15.4 months (range, 6 to 48 months). The median gross tumor volume was 4.2 mL (range, 0.2 to 52.3 mL). Based upon this criteria, the researchers reported the following findings:

  • There was no grade 4 toxicity;
  • The incidence of any grade 3 toxicity was 8% (3 of 38 patients);
  • Symptomatic pneumonitis occurred in one patient (2.6%);
  • Actuarial local control at one and two years after SBRT was 100% and 96%, respectively;
  • Local progression occurred in one patient, 13 months after SBRT; and
  • Median survival was 19 months.

Based upon the foregoing, the U.S. researchers concluded that the multi-institutional phase I/II clinical study demonstrates that high-dose SBRT is safe and effective for the treatment of patients with one to three lung metastases.

Using a Bigger Hammer: The Role of Stereotactic Body Radiotherapy in the Management of Oligometastases Journal of Clinical Oncology Editorial

“… What can we learn from these three trials [described above]?

First, we have learned once again that it is possible to conduct prospective trials of new technological approaches. This is an important lesson. This is how future technologies, such as proton therapy, should be tested.

Second, although the poor overall survival of patients in these trials competes with the risk of local relapse, possibly leading to overestimation of the probability of local control at 2 years, it seems likely that SBRT is a good treatment for such patients. It would seem that a standardized dose/fractionation scheme, such as 60Gyin three fractions, works well for tumors smaller than 3 cm; larger ones may benefit from an individualized approach, such as described by Lee et al. [Canadian study decribed above, ftnote omitted]. However, we must continue to remember past experiences with hypofractionation of large volumes, which can produce severe late normal-tissue effects, especially fibrosis. Even if small volumes are irradiated, catastrophic complications can occur.  In the case of lung cancer, severe unacceptable complications (bronchial fibrosis or hemorrhage) have been associated with treatment of lesions within 2 cm of major airways.  A more protracted (five-fraction) regimen is about to be tested in a Radiation Therapy Oncology Group (RTOG) trial that will open in the coming months that will determine if these toxicities can be avoided.  Lesions close to the chest wall may also benefit from a more protracted fractionation to avoid rib fractures.  In the case of medial or central liver lesions, hypofractionation can cause intestinal obstruction or biliary fibrosis.

Finally, we should recognize that the methodology used in these trials applies to patients with relatively normal liver and lung functions.  At this time, it is not clear how to account for organ dysfunction in patients with lung cancer or primary liver tumors.  Certainly, differences in tolerance to radiation between patients with liver metastases and those with primary liver tumors have been observed before [ftnote omitted].  Therefore, although SBRT seems to have given us a bigger hammer, we still have much to learn about how and when to strike the nails.”

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